Tag Archives: Columbia University

A biocompatible (implantable) micromachine (microrobot)

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I appreciate the detail and information in this well written Jan. 4, 2017 Columbia University news release (h/t Jan. 4, 2016 Nanowerk; Note: Links have been removed),

A team of researchers led by Biomedical Engineering Professor Sam Sia has developed a way to manufacture microscale-sized machines from biomaterials that can safely be implanted in the body. Working with hydrogels, which are biocompatible materials that engineers have been studying for decades, Sia has invented a new technique that stacks the soft material in layers to make devices that have three-dimensional, freely moving parts. The study, published online January 4, 2017, in Science Robotics, demonstrates a fast manufacturing method Sia calls “implantable microelectromechanical systems” (iMEMS).

By exploiting the unique mechanical properties of hydrogels, the researchers developed a “locking mechanism” for precise actuation and movement of freely moving parts, which can provide functions such as valves, manifolds, rotors, pumps, and drug delivery. They were able to tune the biomaterials within a wide range of mechanical and diffusive properties and to control them after implantation without a sustained power supply such as a toxic battery. They then tested the “payload” delivery in a bone cancer model and found that the triggering of release of doxorubicin from the device over 10 days showed high treatment efficacy and low toxicity, at 1/10 of the standard systemic chemotherapy dose.

“Overall, our iMEMS platform enables development of biocompatible implantable microdevices with a wide range of intricate moving components that can be wirelessly controlled on demand and solves issues of device powering and biocompatibility,” says Sia, also a member of the Data Science Institute. “We’re really excited about this because we’ve been able to connect the world of biomaterials with that of complex, elaborate medical devices. Our platform has a large number of potential applications, including the drug delivery system demonstrated in our paper which is linked to providing tailored drug doses for precision medicine.”

I particularly like this bit about hydrogels being a challenge to work with and the difficulties of integrating both rigid and soft materials,

Most current implantable microdevices have static components rather than moving parts and, because they require batteries or other toxic electronics, have limited biocompatibility. Sia’s team spent more than eight years working on how to solve this problem. “Hydrogels are difficult to work with, as they are soft and not compatible with traditional machining techniques,” says Sau Yin Chin, lead author of the study who worked with Sia. “We have tuned the mechanical properties and carefully matched the stiffness of structures that come in contact with each other within the device. Gears that interlock have to be stiff in order to allow for force transmission and to withstand repeated actuation. Conversely, structures that form locking mechanisms have to be soft and flexible to allow for the gears to slip by them during actuation, while at the same time they have to be stiff enough to hold the gears in place when the device is not actuated. We also studied the diffusive properties of the hydrogels to ensure that the loaded drugs do not easily diffuse through the hydrogel layers.”

The team used light to polymerize sheets of gel and incorporated a stepper mechanization to control the z-axis and pattern the sheets layer by layer, giving them three-dimensionality. Controlling the z-axis enabled the researchers to create composite structures within one layer of the hydrogel while managing the thickness of each layer throughout the fabrication process. They were able to stack multiple layers that are precisely aligned and, because they could polymerize a layer at a time, one right after the other, the complex structure was built in under 30 minutes.

Sia’s iMEMS technique addresses several fundamental considerations in building biocompatible microdevices, micromachines, and microrobots: how to power small robotic devices without using toxic batteries, how to make small biocompatible moveable components that are not silicon which has limited biocompatibility, and how to communicate wirelessly once implanted (radio frequency microelectronics require power, are relatively large, and are not biocompatible). The researchers were able to trigger the iMEMS device to release additional payloads over days to weeks after implantation. They were also able to achieve precise actuation by using magnetic forces to induce gear movements that, in turn, bend structural beams made of hydrogels with highly tunable properties. (Magnetic iron particles are commonly used and FDA-approved for human use as contrast agents.)

In collaboration with Francis Lee, an orthopedic surgeon at Columbia University Medical Center at the time of the study, the team tested the drug delivery system on mice with bone cancer. The iMEMS system delivered chemotherapy adjacent to the cancer, and limited tumor growth while showing less toxicity than chemotherapy administered throughout the body.

“These microscale components can be used for microelectromechanical systems, for larger devices ranging from drug delivery to catheters to cardiac pacemakers, and soft robotics,” notes Sia. “People are already making replacement tissues and now we can make small implantable devices, sensors, or robots that we can talk to wirelessly. Our iMEMS system could bring the field a step closer in developing soft miniaturized robots that can safely interact with humans and other living systems.”

Here’s a link to and a citation for the paper,

Additive manufacturing of hydrogel-based materials for next-generation implantable medical devices by Sau Yin Chin, Yukkee Cheung Poh, Anne-Céline Kohler, Jocelyn T. Compton, Lauren L. Hsu, Kathryn M. Lau, Sohyun Kim, Benjamin W. Lee, Francis Y. Lee, and Samuel K. Sia. Science Robotics  04 Jan 2017: Vol. 2, Issue 2, DOI: 10.1126/scirobotics.aah6451

This paper appears to be open access.

The researchers have provided a video demonstrating their work (you may want to read the caption below before watching),

Magnetic actuation of the Geneva drive device. A magnet is placed about 1cm below and without contact with the device. The rotating magnet results in the rotational movement of the smaller driving gear. With each full rotation of this driving gear, the larger driven gear is engaged and rotates by 60º, exposing the next reservoir to the aperture on the top layer of the device.

—Video courtesy of Sau Yin Chin/Columbia Engineering

You can hear some background conversation but it doesn’t seem to have been included for informational purposes.

Montreal Neuro creates a new paradigm for technology transfer?

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It’s one heck of a Christmas present. Canadian businessmen Larry Tannenbaum and his wife Judy have given the Montreal Neurological Institute (Montreal Neuro), which is affiliated with McGill University, a $20M donation. From a Dec. 16, 2016 McGill University news release,

The Prime Minister of Canada, Justin Trudeau, was present today at the Montreal Neurological Institute and Hospital (MNI) for the announcement of an important donation of $20 million by the Larry and Judy Tanenbaum family. This transformative gift will help to establish the Tanenbaum Open Science Institute, a bold initiative that will facilitate the sharing of neuroscience findings worldwide to accelerate the discovery of leading edge therapeutics to treat patients suffering from neurological diseases.

‟Today, we take an important step forward in opening up new horizons in neuroscience research and discovery,” said Mr. Larry Tanenbaum. ‟Our digital world provides for unprecedented opportunities to leverage advances in technology to the benefit of science.  That is what we are celebrating here today: the transformation of research, the removal of barriers, the breaking of silos and, most of all, the courage of researchers to put patients and progress ahead of all other considerations.”

Neuroscience has reached a new frontier, and advances in technology now allow scientists to better understand the brain and all its complexities in ways that were previously deemed impossible. The sharing of research findings amongst scientists is critical, not only due to the sheer scale of data involved, but also because diseases of the brain and the nervous system are amongst the most compelling unmet medical needs of our time.

Neurological diseases, mental illnesses, addictions, and brain and spinal cord injuries directly impact 1 in 3 Canadians, representing approximately 11 million people across the country.

“As internationally-recognized leaders in the field of brain research, we are uniquely placed to deliver on this ambitious initiative and reinforce our reputation as an institution that drives innovation, discovery and advanced patient care,” said Dr. Guy Rouleau, Director of the Montreal Neurological Institute and Hospital and Chair of McGill University’s Department of Neurology and Neurosurgery. “Part of the Tanenbaum family’s donation will be used to incentivize other Canadian researchers and institutions to adopt an Open Science model, thus strengthening the network of like-minded institutes working in this field.”

What they don’t mention in the news release is that they will not be pursuing any patents (for five years according to one of the people in the video but I can’t find text to substantiate that time limit*; there are no time limits noted elsewhere) on their work. For this detail and others, you have to listen to the video they’ve created,

The CBC (Canadian Broadcasting Corporation) news online Dec. 16, 2016 posting (with files from Sarah Leavitt and Justin Hayward) adds a few personal details about Tannenbaum,

“Our goal is simple: to accelerate brain research and discovery to relieve suffering,” said Tanenbaum.

Tanenbaum, a Canadian businessman and chairman of Maple Leaf Sports and Entertainment, said many of his loved ones suffered from neurological disorders.

“I lost my mother to Alzheimer’s, my father to a stroke, three dear friends to brain cancer, and a brilliant friend and scientist to clinical depression,” said Tanenbaum.

He hopes the institute will serve as the template for science research across the world, a thought that Trudeau echoed.

“This vision around open science, recognizing the role that Canada can and should play, the leadership that Canadians can have in this initiative is truly, truly exciting,” said Trudeau.

The Neurological Institute says the pharmaceutical industry is supportive of the open science concept because it will provide crucial base research that can later be used to develop drugs to fight an array of neurological conditions.

Jack Stilgoe in a Dec. 16, 2016 posting on the Guardian blogs explains what this donation could mean (Note: Links have been removed),

With the help of Tanenbaum’s gift of 20 million Canadian dollars (£12million) the ‘Neuro’, the Montreal Neurological Institute and Hospital, is setting up an experiment in experimentation, an Open Science Initiative with the express purpose of finding out the best way to realise the potential of scientific research.

…

Governments in science-rich countries are increasingly concerned that they do not appear to reaping the economic returns they feel they deserve from investments in scientific research. Their favoured response has been to try to bridge what they see as a ‘valley of death’ between basic scientific research and industrial applications. This has meant more funding for ‘translational research’ and the flowering of technology transfer offices within universities.

… There are some success stories, particularly in the life sciences. Patents from the work of Richard Axel at Columbia University at one point brought the university almost $100 million per year. The University of Florida received more than $150 million for inventing Gatorade in the 1960s. The stakes are high in the current battle between Berkely and MIT/Harvard over who owns the rights to the CRISPR/Cas9 system that has revolutionised genetic engineering and could be worth billions.

Policymakers imagine a world in which universities pay for themselves just as a pharmaceutical research lab does. However, for critics of technology transfer, such stories blind us to the reality of university’s entrepreneurial abilities.

For most universities, evidence of their money-making prowess is, to put it charitably, mixed. A recent Bloomberg report shows how quickly university patent incomes plunge once we look beyond the megastars. In 2014, just 15 US universities earned 70% of all patent royalties. British science policy researchers Paul Nightingale and Alex Coad conclude that ‘Roughly 9/10 US universities lose money on their technology transfer offices… MIT makes more money from selling T-shirts than it does from licensing’. A report from the Brookings institute concluded that the model of technology transfer ‘is unprofitable for most universities and sometimes even risks alienating the private sector’. In the UK, the situation is even worse. Businesses who have dealings with universities report that their technology transfer offices are often unrealistic in negotiations. In many cases, academics are, like a small child who refuses to let others play with a brand new football, unable to make the most of their gifts. And areas of science outside the life sciences are harder to patent than medicines, sports drinks and genetic engineering techniques. Trying too hard to force science towards the market may be, to use the phrase of science policy professor Keith Pavitt, like pushing a piece of string.

Science policy is slowly waking up to the realisation that the value of science may lie in people and places rather than papers and patents. It’s an idea that the Neuro, with the help of Tanenbaum’s gift, is going to test. By sharing data and giving away intellectual property, the initiative aims to attract new private partners to the institute and build Montreal as a hub for knowledge and innovation. The hypothesis is that this will be more lucrative than hoarding patents.

This experiment is not wishful thinking. It will be scientifically measured. It is the job of Richard Gold, a McGill University law professor, to see whether it works. He told me that his first task is ‘to figure out what to counts… There’s going to be a gap between what we would like to measure and what we can measure’. However, he sees an open-mindedness among his colleagues that is unusual. Some are evangelists for open science; some are sceptics. But they share a curiosity about new approaches and a recognition of a problem in neuroscience: ‘We haven’t come up with a new drug for Parkinson’s in 30 years. We don’t even understand the biological basis for many of these diseases. So whatever we’re doing at the moment doesn’t work’. …

Montreal Neuro made news on the ‘open science’ front in January 2016 when it formally announced its research would be freely available and that researchers would not be pursuing patents (see my January 22, 2016 posting).

I recommend reading Stilgoe’s posting in its entirety and for those who don’t know or have forgotten, Prime Minister’s Trudeau’s family has some experience with mental illness. His mother has been very open about her travails. This makes his presence at the announcement perhaps a bit more meaningful than the usual political presence at a major funding announcement.

*The five-year time limit is confirmed in a Feb. 17, 2017 McGill University news release about their presentations at the AAAS (American Association for the Advancement of Science) 2017 annual meeting) on EurekAlert,

umpstarting Neurological Research through Open Science – MNI & McGill University

Friday, February 17, 2017, 1:30-2:30 PM/ Room 208

Neurological research is advancing too slowly according to Dr. Guy Rouleau, director of the Montreal Neurological Institute (MNI) of McGill University. To speed up discovery, MNI has become the first ever Open Science academic institution in the world. In a five-year experiment, MNI is opening its books and making itself transparent to an international group of social scientists, policymakers, industrial partners, and members of civil society. They hope, by doing so, to accelerate research and the discovery of new treatments for patients with neurological diseases, and to encourage other leading institutions around the world to consider a similar model. A team led by McGill Faculty of Law’s Professor Richard Gold will monitor and evaluate how well the MNI Open Science experiment works and provide the scientific and policy worlds with insight into 21st century university-industry partnerships. At this workshop, Rouleau and Gold will discuss the benefits and challenges of this open-science initiative.

The dangers of metaphors when applied to science

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Metaphors can be powerful in both good ways and bad. I once read that there was a ‘lighthouse’ metaphor used to explain a scientific concept to high school students which later caused problems for them when they were studying the biological sciences as university students.  It seems there’s research now to back up the assertion about metaphors and their powers. From an Oct. 7, 2016 news item on phys.org,

Whether ideas are “like a light bulb” or come forth as “nurtured seeds,” how we describe discovery shapes people’s perceptions of both inventions and inventors. Notably, Kristen Elmore (Bronfenbrenner Center for Translational Research at Cornell University) and Myra Luna-Lucero (Teachers College, Columbia University) have shown that discovery metaphors influence our perceptions of the quality of an idea and of the ability of the idea’s creator. The research appears in the journal Social Psychological and Personality Science.

While the metaphor that ideas appear “like light bulbs” is popular and appealing, new research shows that discovery metaphors influence our understanding of the scientific process and perceptions of the ability of inventors based on their gender. [downloaded from http://www.spsp.org/news-center/press-release/metaphors-bias-perception]

While the metaphor that ideas appear “like light bulbs” is popular and appealing, new research shows that discovery metaphors influence our understanding of the scientific process and perceptions of the ability of inventors based on their gender. [downloaded from http://www.spsp.org/news-center/press-release/metaphors-bias-perception]

An Oct. 7, 2016  Society for Personality and Social Psychology news release (also on EurekAlert), which originated the news item, provides more insight into the work,

While those involved in research know there are many trials and errors and years of work before something is understood, discovered or invented, our use of words for inspiration may have an unintended and underappreciated effect of portraying good ideas as a sudden and exceptional occurrence.

In a series of experiments, Elmore and Luna-Lucero tested how people responded to ideas that were described as being “like a light bulb,” “nurtured like a seed,” or a neutral description. 

According the authors, the “light bulb metaphor implies that ‘brilliant’ ideas result from sudden and spontaneous inspiration, bestowed upon a chosen few (geniuses) while the seed metaphor implies that ideas are nurtured over time, ‘cultivated’ by anyone willing to invest effort.”

The first study looked at how people reacted to a description of Alan Turing’s invention of a precursor to the modern computer. It turns out light bulbs are more remarkable than seeds.

“We found that an idea was seen as more exceptional when described as appearing like a light bulb rather than nurtured like a seed,” said Elmore.

But this pattern changed when they used these metaphors to describe a female inventor’s ideas. When using the “like a light bulb” and “nurtured seed” metaphors, the researchers found “women were judged as better idea creators than men when ideas were described as nurtured over time like seeds.”

The results suggest gender stereotypes play a role in how people perceived the inventors.

In the third study, the researchers presented participants with descriptions of the work of either a female (Hedy Lamarr) or a male (George Antheil) inventor, who together created the idea for spread-spectrum technology (a precursor to modern wireless communications). Indeed, the seed metaphor “increased perceptions that a female inventor was a genius, while the light bulb metaphor was more consistent with stereotypical views of male genius,” stated Elmore.

Elmore plans to expand upon their research on metaphors by examining the interactions of teachers and students in real world classroom settings.

“The ways that teachers and students talk about ideas may impact students’ beliefs about how good ideas are created and who is likely to have them,” said Elmore. “Having good ideas is relevant across subjects—whether students are creating a hypothesis in science or generating a thesis for their English paper—and language that stresses the role of effort rather than inspiration in creating ideas may have real benefits for students’ motivation.”

Here’s a link to and a citation for the paper,

Light Bulbs or Seeds? How Metaphors for Ideas Influence Judgments About Genius by Kristen C. Elmore and Myra Luna-Lucero. Social Psychological and Personality Science doi: 10.1177/1948550616667611 Published online before print October 7, 2016

This paper is behind a paywall.

While Elmore and Luna-Lucero are focused on a nuanced analysis of specific metaphors, Richard Holmes’s book, ‘The Age of Wonder: How the Romantic Generation Discovered the Beauty and Terror of Science’, notes that the ‘Eureka’  (light bulb) moment for scientific discovery and the notion of a ‘single great man’ (a singular genius) as the discoverer has its roots in romantic (Shelley, Keats, etc.) poetry.

How might artificial intelligence affect urban life in 2030? A study

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Peering into the future is always a chancy business as anyone who’s seen those film shorts from the 1950’s and 60’s which speculate exuberantly as to what the future will bring knows.

A sober approach (appropriate to our times) has been taken in a study about the impact that artificial intelligence might have by 2030. From a Sept. 1, 2016 Stanford University news release (also on EurekAlert) by Tom Abate (Note: Links have been removed),

A panel of academic and industrial thinkers has looked ahead to 2030 to forecast how advances in artificial intelligence (AI) might affect life in a typical North American city – in areas as diverse as transportation, health care and education ­– and to spur discussion about how to ensure the safe, fair and beneficial development of these rapidly emerging technologies.

Titled “Artificial Intelligence and Life in 2030,” this year-long investigation is the first product of the One Hundred Year Study on Artificial Intelligence (AI100), an ongoing project hosted by Stanford to inform societal deliberation and provide guidance on the ethical development of smart software, sensors and machines.

“We believe specialized AI applications will become both increasingly common and more useful by 2030, improving our economy and quality of life,” said Peter Stone, a computer scientist at the University of Texas at Austin and chair of the 17-member panel of international experts. “But this technology will also create profound challenges, affecting jobs and incomes and other issues that we should begin addressing now to ensure that the benefits of AI are broadly shared.”

The new report traces its roots to a 2009 study that brought AI scientists together in a process of introspection that became ongoing in 2014, when Eric and Mary Horvitz created the AI100 endowment through Stanford. AI100 formed a standing committee of scientists and charged this body with commissioning periodic reports on different aspects of AI over the ensuing century.

“This process will be a marathon, not a sprint, but today we’ve made a good start,” said Russ Altman, a professor of bioengineering and the Stanford faculty director of AI100. “Stanford is excited to host this process of introspection. This work makes practical contribution to the public debate on the roles and implications of artificial intelligence.”

The AI100 standing committee first met in 2015, led by chairwoman and Harvard computer scientist Barbara Grosz. It sought to convene a panel of scientists with diverse professional and personal backgrounds and enlist their expertise to assess the technological, economic and policy implications of potential AI applications in a societally relevant setting.

“AI technologies can be reliable and broadly beneficial,” Grosz said. “Being transparent about their design and deployment challenges will build trust and avert unjustified fear and suspicion.”

The report investigates eight domains of human activity in which AI technologies are beginning to affect urban life in ways that will become increasingly pervasive and profound by 2030.

The 28,000-word report includes a glossary to help nontechnical readers understand how AI applications such as computer vision might help screen tissue samples for cancers or how natural language processing will allow computerized systems to grasp not simply the literal definitions, but the connotations and intent, behind words.

The report is broken into eight sections focusing on applications of AI. Five examine application arenas such as transportation where there is already buzz about self-driving cars. Three other sections treat technological impacts, like the section on employment and workplace trends which touches on the likelihood of rapid changes in jobs and incomes.

“It is not too soon for social debate on how the fruits of an AI-dominated economy should be shared,” the researchers write in the report, noting also the need for public discourse.

“Currently in the United States, at least sixteen separate agencies govern sectors of the economy related to AI technologies,” the researchers write, highlighting issues raised by AI applications: “Who is responsible when a self-driven car crashes or an intelligent medical device fails? How can AI applications be prevented from [being used for] racial discrimination or financial cheating?”

The eight sections discuss:

Transportation: Autonomous cars, trucks and, possibly, aerial delivery vehicles may alter how we commute, work and shop and create new patterns of life and leisure in cities.

Home/service robots: Like the robotic vacuum cleaners already in some homes, specialized robots will clean and provide security in live/work spaces that will be equipped with sensors and remote controls.

Health care: Devices to monitor personal health and robot-assisted surgery are hints of things to come if AI is developed in ways that gain the trust of doctors, nurses, patients and regulators.

Education: Interactive tutoring systems already help students learn languages, math and other skills. More is possible if technologies like natural language processing platforms develop to augment instruction by humans.

Entertainment: The conjunction of content creation tools, social networks and AI will lead to new ways to gather, organize and deliver media in engaging, personalized and interactive ways.

Low-resource communities: Investments in uplifting technologies like predictive models to prevent lead poisoning or improve food distributions could spread AI benefits to the underserved.

Public safety and security: Cameras, drones and software to analyze crime patterns should use AI in ways that reduce human bias and enhance safety without loss of liberty or dignity.

Employment and workplace: Work should start now on how to help people adapt as the economy undergoes rapid changes as many existing jobs are lost and new ones are created.

“Until now, most of what is known about AI comes from science fiction books and movies,” Stone said. “This study provides a realistic foundation to discuss how AI technologies are likely to affect society.”

Grosz said she hopes the AI 100 report “initiates a century-long conversation about ways AI-enhanced technologies might be shaped to improve life and societies.”

You can find the A100 website here, and the group’s first paper: “Artificial Intelligence and Life in 2030” here. Unfortunately, I don’t have time to read the report but I hope to do so soon.

The AI100 website’s About page offered a surprise,

This effort, called the One Hundred Year Study on Artificial Intelligence, or AI100, is the brainchild of computer scientist and Stanford alumnus Eric Horvitz who, among other credits, is a former president of the Association for the Advancement of Artificial Intelligence.

In that capacity Horvitz convened a conference in 2009 at which top researchers considered advances in artificial intelligence and its influences on people and society, a discussion that illuminated the need for continuing study of AI’s long-term implications.

Now, together with Russ Altman, a professor of bioengineering and computer science at Stanford, Horvitz has formed a committee that will select a panel to begin a series of periodic studies on how AI will affect automation, national security, psychology, ethics, law, privacy, democracy and other issues.

“Artificial intelligence is one of the most profound undertakings in science, and one that will affect every aspect of human life,” said Stanford President John Hennessy, who helped initiate the project. “Given’s Stanford’s pioneering role in AI and our interdisciplinary mindset, we feel obliged and qualified to host a conversation about how artificial intelligence will affect our children and our children’s children.”

Five leading academicians with diverse interests will join Horvitz and Altman in launching this effort. They are:

  • Barbara Grosz, the Higgins Professor of Natural Sciences at HarvardUniversity and an expert on multi-agent collaborative systems;
  • Deirdre K. Mulligan, a lawyer and a professor in the School of Information at the University of California, Berkeley, who collaborates with technologists to advance privacy and other democratic values through technical design and policy;

    This effort, called the One Hundred Year Study on Artificial Intelligence, or AI100, is the brainchild of computer scientist and Stanford alumnus Eric Horvitz who, among other credits, is a former president of the Association for the Advancement of Artificial Intelligence.

    In that capacity Horvitz convened a conference in 2009 at which top researchers considered advances in artificial intelligence and its influences on people and society, a discussion that illuminated the need for continuing study of AI’s long-term implications.

    Now, together with Russ Altman, a professor of bioengineering and computer science at Stanford, Horvitz has formed a committee that will select a panel to begin a series of periodic studies on how AI will affect automation, national security, psychology, ethics, law, privacy, democracy and other issues.

    “Artificial intelligence is one of the most profound undertakings in science, and one that will affect every aspect of human life,” said Stanford President John Hennessy, who helped initiate the project. “Given’s Stanford’s pioneering role in AI and our interdisciplinary mindset, we feel obliged and qualified to host a conversation about how artificial intelligence will affect our children and our children’s children.”

    Five leading academicians with diverse interests will join Horvitz and Altman in launching this effort. They are:

    • Barbara Grosz, the Higgins Professor of Natural Sciences at HarvardUniversity and an expert on multi-agent collaborative systems;
    • Deirdre K. Mulligan, a lawyer and a professor in the School of Information at the University of California, Berkeley, who collaborates with technologists to advance privacy and other democratic values through technical design and policy;
    • Yoav Shoham, a professor of computer science at Stanford, who seeks to incorporate common sense into AI;
    • Tom Mitchell, the E. Fredkin University Professor and chair of the machine learning department at Carnegie Mellon University, whose studies include how computers might learn to read the Web;
    • and Alan Mackworth, a professor of computer science at the University of British Columbia [emphases mine] and the Canada Research Chair in Artificial Intelligence, who built the world’s first soccer-playing robot.

    I wasn’t expecting to see a Canadian listed as a member of the AI100 standing committee and then I got another surprise (from the AI100 People webpage),

    Study Panels

    Study Panels are planned to convene every 5 years to examine some aspect of AI and its influences on society and the world. The first study panel was convened in late 2015 to study the likely impacts of AI on urban life by the year 2030, with a focus on typical North American cities.

    2015 Study Panel Members

    • Peter Stone, UT Austin, Chair
    • Rodney Brooks, Rethink Robotics
    • Erik Brynjolfsson, MIT
    • Ryan Calo, University of Washington
    • Oren Etzioni, Allen Institute for AI
    • Greg Hager, Johns Hopkins University
    • Julia Hirschberg, Columbia University
    • Shivaram Kalyanakrishnan, IIT Bombay
    • Ece Kamar, Microsoft
    • Sarit Kraus, Bar Ilan University
    • Kevin Leyton-Brown, [emphasis mine] UBC [University of British Columbia]
    • David Parkes, Harvard
    • Bill Press, UT Austin
    • AnnaLee (Anno) Saxenian, Berkeley
    • Julie Shah, MIT
    • Milind Tambe, USC
    • Astro Teller, Google[X]
  • [emphases mine] and the Canada Research Chair in Artificial Intelligence, who built the world’s first soccer-playing robot.

I wasn’t expecting to see a Canadian listed as a member of the AI100 standing committee and then I got another surprise (from the AI100 People webpage),

Study Panels

Study Panels are planned to convene every 5 years to examine some aspect of AI and its influences on society and the world. The first study panel was convened in late 2015 to study the likely impacts of AI on urban life by the year 2030, with a focus on typical North American cities.

2015 Study Panel Members

  • Peter Stone, UT Austin, Chair
  • Rodney Brooks, Rethink Robotics
  • Erik Brynjolfsson, MIT
  • Ryan Calo, University of Washington
  • Oren Etzioni, Allen Institute for AI
  • Greg Hager, Johns Hopkins University
  • Julia Hirschberg, Columbia University
  • Shivaram Kalyanakrishnan, IIT Bombay
  • Ece Kamar, Microsoft
  • Sarit Kraus, Bar Ilan University
  • Kevin Leyton-Brown, [emphasis mine] UBC [University of British Columbia]
  • David Parkes, Harvard
  • Bill Press, UT Austin
  • AnnaLee (Anno) Saxenian, Berkeley
  • Julie Shah, MIT
  • Milind Tambe, USC
  • Astro Teller, Google[X]

I see they have representation from Israel, India, and the private sector as well. Refreshingly, there’s more than one woman on the standing committee and in this first study group. It’s good to see these efforts at inclusiveness and I’m particularly delighted with the inclusion of an organization from Asia. All too often inclusiveness means Europe, especially the UK. So, it’s good (and I think important) to see a different range of representation.

As for the content of report, should anyone have opinions about it, please do let me know your thoughts in the blog comments.

Gold-144 is a polymorph

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Au-144 (also known as Gold-144) is an iconic gold nanocluster according to a June 14, 2016 news item announcing its polymorphic nature on ScienceDaily,

Chemically the same, graphite and diamonds are as physically distinct as two minerals can be, one opaque and soft, the other translucent and hard. What makes them unique is their differing arrangement of carbon atoms.

Polymorphs, or materials with the same composition but different structures, are common in bulk materials, and now a new study in Nature Communications confirms they exist in nanomaterials, too. Researchers describe two unique structures for the iconic gold nanocluster Au144(SR)60, better known as Gold-144, including a version never seen before. Their discovery gives engineers a new material to explore, along with the possibility of finding other polymorphic nanoparticles.

A June 14, 2016 Columbia University news release (also on EurekAlert), which originated the news item, provides more insight into the work,

“This took four years to unravel,” said Simon Billinge, a physics professor at Columbia Engineering and a member of the Data Science Institute. “We weren’t expecting the clusters to take on more than one atomic arrangement. But this discovery gives us more handles to turn when trying to design clusters with new and useful properties.”

Gold has been used in coins and jewelry for thousands of years for its durability, but shrink it to a size 10,000 times smaller than a human hair [at one time one billionth of a meter or a nanometer was said to be 1/50,000, 1/60,000 or 1/100,000 of the diameter of a human hair], and it becomes wildly unstable and unpredictable. At the nanoscale, gold likes to split apart other particles and molecules, making it a useful material for purifying water, imaging and killing tumors, and making solar panels more efficient, among other applications.

Though a variety of nanogold particles and molecules have been made in the lab, very few have had their secret atomic arrangement revealed. But recently, new technologies are bringing these miniscule structures into focus.

Under one approach, high-energy x-ray beams are fired at a sample of nanoparticles. Advanced data analytics are used to interpret the x-ray scattering data and infer the sample’s structure, which is key to understanding how strong, reactive or durable the particles might be.

Billinge and his lab have pioneered a method, the atomic Pair Distribution Function (PDF) analysis, for interpreting this scattering data. To test the PDF method, Billinge asked chemists at the Colorado State University to make tiny samples of Gold-144, a molecule-sized nanogold cluster first isolated in 1995. Its structure had been theoretically predicted in 2009, and though never confirmed, Gold-144 has found numerous applications, including in tissue-imaging.

Hoping the test would confirm Gold-144’s structure, they analyzed the clusters at the European Synchrotron Radiation Source in Grenoble, and used the PDF method to infer their structure. To their surprise, they found an angular core, and not the sphere-like icosahedral core predicted. When they made a new sample and tried the experiment again, this time using synchrotrons at Brookhaven and Argonne national laboratories, the structure came back spherical.

“We didn’t understand what was going on, but digging deeper, we realized we had a polymorph,” said study coauthor Kirsten Jensen, formerly a postdoctoral researcher at Columbia, now a chemistry professor at the University of Copenhagen.

Further experiments confirmed the cluster had two versions, sometimes found together, each with a unique structure indicating they behave differently. The researchers are still unsure if Gold-144 can switch from one version to the other or, what exactly, differentiates the two forms.

To make their discovery, the researchers solved what physicists call the nanostructure inverse problem. How can the structure of a tiny nanoparticle in a sample be inferred from an x-ray signal that has been averaged over millions of particles, each with different orientations?

“The signal is noisy and highly degraded,” said Billinge. “It’s the equivalent of trying to recognize if the bird in the tree is a robin or a cardinal, but the image in your binoculars is too blurry and distorted to tell.”

“Our results demonstrate the power of PDF analysis to reveal the structure of very tiny particles,” added study coauthor Christopher Ackerson, a chemistry professor at Colorado State. “I’ve been trying, off and on, for more than 10 years to get the single-crystal x-ray structure of Gold-144. The presence of polymorphs helps to explain why this molecule has been so resistant to traditional methods.”

The PDF approach is one of several rival methods being developed to bring nanoparticle structure into focus. Now that it has proven itself, it could help speed up the work of describing other nanostructures.

The eventual goal is to design nanoparticles by their desired properties, rather than through trial and error, by understanding how form and function relate. Databases of known and predicted structures could make it possible to design new materials with a few clicks of a mouse.

The study is a first step.

“We’ve had a structure model for this iconic gold molecule for years and then this study comes along and says the structure is basically right but it’s got a doppelgänger,” said Robert Whetten, a professor of chemical physics at the University of Texas, San Antonio, who led the team that first isolated Gold-144. “It seemed preposterous, to have two distinct structures that underlie its ubiquity, but this is a beautiful paper that will persuade a lot of people.”

Here’s an image illustrating the two shapes,

Setting out to confirm the predicted structure of Gold-144, researchers discovered an entirely unexpected atomic arrangement (right). The two structures, described in detail for the first time, each have 144 gold atoms, but are uniquely shaped, suggesting they also behave differently. (Courtesy of Kirsten Ørnsbjerg Jensen)

Setting out to confirm the predicted structure of Gold-144, researchers discovered an entirely unexpected atomic arrangement (right). The two structures, described in detail for the first time, each have 144 gold atoms, but are uniquely shaped, suggesting they also behave differently. (Courtesy of Kirsten Ørnsbjerg Jensen)

Here’s a link to and a citation for the paper,

Polymorphism in magic-sized Au144(SR)60 clusters by Kirsten M.Ø. Jensen, Pavol Juhas, Marcus A. Tofanelli, Christine L. Heinecke, Gavin Vaughan, Christopher J. Ackerson, & Simon J. L. Billinge.  Nature Communications 7, Article number: 11859  doi:10.1038/ncomms11859 Published 14 June 2016

This is an open access paper.

Saharan silver ants: the nano of it all (science and technology)

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Researchers at Columbia University (US) are on quite a publishing binge lately. The latest is a biomimicry story where researchers (from Columbia amongst other universities and including Brookhaven National Laboratory, which has issued its own news release) have taken a very close look at Saharan silver ants to determine how they stay cool in one of the hottest climates in the world. From a June 18, 2015 Columbia University news release (also on EurekAlert), Note: Links have been removed,

Nanfang Yu, assistant professor of applied physics at Columbia Engineering, and colleagues from the University of Zürich and the University of Washington, have discovered two key strategies that enable Saharan silver ants to stay cool in one of the hottest terrestrial environments on Earth. Yu’s team is the first to demonstrate that the ants use a coat of uniquely shaped hairs to control electromagnetic waves over an extremely broad range from the solar spectrum (visible and near-infrared) to the thermal radiation spectrum (mid-infrared), and that different physical mechanisms are used in different spectral bands to realize the same biological function of reducing body temperature. Their research, “Saharan silver ants keep cool by combining enhanced optical reflection and radiative heat dissipation,” is published June 18 [2015] in Science magazine.

The Columbia University news release expands on the theme,

“This is a telling example of how evolution has triggered the adaptation of physical attributes to accomplish a physiological task and ensure survival, in this case to prevent Saharan silver ants from getting overheated,” Yu says. “While there have been many studies of the physical optics of living systems in the ultraviolet and visible range of the spectrum, our understanding of the role of infrared light in their lives is much less advanced. Our study shows that light invisible to the human eye does not necessarily mean that it does not play a crucial role for living organisms.”

The project was initially triggered by wondering whether the ants’ conspicuous silvery coats were important in keeping them cool in blistering heat. Yu’s team found that the answer to this question was much broader once they realized the important role of infrared light. Their discovery that there is a biological solution to a thermoregulatory problem could lead to the development of novel flat optical components that exhibit optimal cooling properties.

“Such biologically inspired cooling surfaces will have high reflectivity in the solar spectrum and high radiative efficiency in the thermal radiation spectrum,” Yu explains. “So this may generate useful applications such as a cooling surface for vehicles, buildings, instruments, and even clothing.”

Saharan silver ants (Cataglyphis bombycina) forage in the Saharan Desert in the full midday sun when surface temperatures reach up to 70°C (158°F), and they must keep their body temperature below their critical thermal maximum of 53.6°C (128.48°F) most of the time. In their wide-ranging foraging journeys, the ants search for corpses of insects and other arthropods that have succumbed to the thermally harsh desert conditions, which they are able to endure more successfully. Being most active during the hottest moment of the day also allows these ants to avoid predatory desert lizards. Researchers have long wondered how these tiny insects (about 10 mm, or 3/8” long) can survive under such thermally extreme and stressful conditions.

Using electron microscopy and ion beam milling, Yu’s group discovered that the ants are covered on the top and sides of their bodies with a coating of uniquely shaped hairs with triangular cross-sections that keep them cool in two ways. These hairs are highly reflective under the visible and near-infrared light, i.e., in the region of maximal solar radiation (the ants run at a speed of up to 0.7 meters per second and look like droplets of mercury on the desert surface). The hairs are also highly emissive in the mid-infrared portion of the electromagnetic spectrum, where they serve as an antireflection layer that enhances the ants’ ability to offload excess heat via thermal radiation, which is emitted from the hot body of the ants to the cold sky. This passive cooling effect works under the full sun whenever the insects are exposed to the clear sky.

“To appreciate the effect of thermal radiation, think of the chilly feeling when you get out of bed in the morning,” says Yu. “Half of the energy loss at that moment is due to thermal radiation since your skin temperature is temporarily much higher than that of the surrounding environment.”

The researchers found that the enhanced reflectivity in the solar spectrum and enhanced thermal radiative efficiency have comparable contributions to reducing the body temperature of silver ants by 5 to 10 degrees compared to if the ants were without the hair cover. “The fact that these silver ants can manipulate electromagnetic waves over such a broad range of spectrum shows us just how complex the function of these seemingly simple biological organs of an insect can be,” observes Norman Nan Shi, lead author of the study and PhD student who works with Yu at Columbia Engineering.

Yu and Shi collaborated on the project with Rüdiger Wehner, professor at the Brain Research Institute, University of Zürich, Switzerland, and Gary Bernard, electrical engineering professor at the University of Washington, Seattle, who are renowned experts in the study of insect physiology and ecology. The Columbia Engineering team designed and conducted all experimental work, including optical and infrared microscopy and spectroscopy experiments, thermodynamic experiments, and computer simulation and modeling. They are currently working on adapting the engineering lessons learned from the study of Saharan silver ants to create flat optical components, or “metasurfaces,” that consist of a planar array of nanophotonic elements and provide designer optical and thermal radiative properties.

Yu and his team plan next to extend their research to other animals and organisms living in extreme environments, trying to learn the strategies these creatures have developed to cope with harsh environmental conditions.

“Animals have evolved diverse strategies to perceive and utilize electromagnetic waves: deep sea fish have eyes that enable them to maneuver and prey in dark waters, butterflies create colors from nanostructures in their wings, honey bees can see and respond to ultraviolet signals, and fireflies use flash communication systems,” Yu adds. “Organs evolved for perceiving or controlling electromagnetic waves often surpass analogous man-made devices in both sophistication and efficiency. Understanding and harnessing natural design concepts deepens our knowledge of complex biological systems and inspires ideas for creating novel technologies.”

Next, there’s the perspective provided by Brookhaven National Laboratory in a June 18, 2015 news item on Nanowerk (Note: It is very similar to the Columbia University news release but it takes a turn towards the technical challenges as you’ll see if you keep reading),

The paper, published by Columbia Engineering researchers and collaborators—including researchers from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory—describes how the nanoscale structure of the hairs helps increase the reflectivity of the ant’s body in both visible and near-infrared wavelengths, allowing the insects to deflect solar radiation their bodies would otherwise absorb. The hairs also enhance emissivity in the mid-infrared spectrum, allowing heat to dissipate efficiently from the hot body of the ants to the cool, clear sky.

A June 18, 2015 BNL news release by Alasdair Wilkins, which originated the Nanowerk news item, describes the collaboration between the researchers and the special adjustments made to the equipment in service of this project (Note: A link has been removed),

In a typical experiment involving biological material such as nanoscale hairs, it would usually be sufficient to use an electron microscope to create an image of the surface of the specimen. This research, however, required Yu’s group to look inside the ant hairs and produce a cross-section of the structure’s interior. The relatively weak beam of electrons from a standard electron microscope would not be able to penetrate the surface of the sample.

The CFN’s dual beam system solves the problem by combining the imaging of an electron microscope with a much more powerful beam of gallium ions.  With 31 protons and 38 neutrons, each gallium ion is about 125,000 times more massive than an electron, and massive enough to create dents in the nanoscale structure – like throwing a stone against a wall. The researchers used these powerful beams to drill precise cuts into the hairs, revealing the crucial information hidden beneath the surface. Indeed, this particular application, in which the system was used to investigate a biological problem, was new for the team at CFN.

“Conventionally, this tool is used to produce cross-sections of microelectronic circuits,” said Camino. “The focused ion beam is like an etching tool. You can think of it like a milling tool in a machine shop, but at the nanoscale. It can remove material at specific places because you can see these locations with the SEM. So locally you remove material and you look at the under layers, because the cuts give you access to the cross section of whatever you want to look at.”

The ant hair research challenged the CFN team to come up with novel solutions to investigate the internal structures without damaging the more delicate biological samples.

“These hairs are very soft compared to, say, semiconductors or crystalline materials. And there’s a lot of local heat that can damage biological samples. So the parameters have to be carefully tuned not to do much damage to it,” he said. “We had to adapt our technique to find the right conditions.”

Another challenge lay in dealing with the so-called charging effect. When the dual beam system is trained on a non-conducting material, electrons can build up at the point where the beams hit the specimen, distorting the resulting image. The team at CFN was able to solve this problem by placing thin layers of gold over the biological material, making the sample just conductive enough to avoid the charging effect.

Revealing Reflectivity

While Camino’s team focused on helping Yu’s group investigate the structure of the ant hairs, Matthew Sfeir’s work with high-brightness Fourier transform optical spectroscopy helped to reveal how the reflectivity of the hairs helped Saharan silver ants regulate temperature. Sfeir’s spectrometer revealed precisely how much those biological structures reflect light across multiple wavelengths, including both visible and near-infrared light.

“It’s a multiplexed measurement,” Sfeir said, explaining his team’s spectrometer. “Instead of tuning through this wavelength and this wavelength, that wavelength, you do them all in one swoop to get all the spectral information in one shot. It gives you very fast measurements and very good resolution spectrally. Then we optimize it for very small samples. It’s a rather unique capability of CFN.”

Sfeir’s spectroscopy work draws on knowledge gained from his work at another key Brookhaven facility: the original National Synchrotron Light Source, where he did much of his postdoc work. His experience was particularly useful in analyzing the reflectivity of the biological structures across many different wavelengths of the electromagnetic spectrum.

“This technique was developed from my experience working with the infrared synchrotron beamlines,” said Sfeir. “Synchrotron beamlines are optimized for exactly this kind of thing. I thought, ‘Hey, wouldn’t it be great if we could develop a similar measurement for the type of solar devices we make at CFN?’ So we built a bench-top version to use here.”

Fascinating, non? At last, here’s a link to and a citation for the paper,

Keeping cool: Enhanced optical reflection and heat dissipation in silver ants by Norman Nan Shi, Cheng-Chia Tsai, Fernando Camino, Gary D. Bernard, Nanfang Yu, and Rüdiger Wehner. Science DOI: 10.1126/science.aab3564 Published online June 18, 2015

This paper is behind a paywall.

Courtesy of graphene: world’s thinnest light bulb

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Columbia University’s (US) School of Engineering and Applied Science is trumpeting an achievement with graphene, i.e., the world’s thinnest light bulb. From a June 15, 2015 Columbia Engineering news release (also on EurekAlert),

Led by Young Duck Kim, a postdoctoral research scientist in James Hone’s group at Columbia Engineering, a team of scientists from Columbia, Seoul National University (SNU), and Korea Research Institute of Standards and Science (KRISS) reported today that they have demonstrated — for the first time — an on-chip visible light source using graphene, an atomically thin and perfectly crystalline form of carbon, as a filament. They attached small strips of graphene to metal electrodes, suspended the strips above the substrate, and passed a current through the filaments to cause them to heat up.

“We’ve created what is essentially the world’s thinnest light bulb,” says Hone, Wang Fon-Jen Professor of Mechanical Engineering at Columbia Engineering and coauthor of the study. “This new type of ‘broadband’ light emitter can be integrated into chips and will pave the way towards the realization of atomically thin, flexible, and transparent displays, and graphene-based on-chip optical communications.”

The news release goes on to describe some of the issues associated with generating light on a chip and how the researchers approached the problems (quick answer: they used graphene as the filament),

Creating light in small structures on the surface of a chip is crucial for developing fully integrated “photonic” circuits that do with light what is now done with electric currents in semiconductor integrated circuits. Researchers have developed many approaches to do this, but have not yet been able to put the oldest and simplest artificial light source—the incandescent light bulb—onto a chip. This is primarily because light bulb filaments must be extremely hot—thousands of degrees Celsius—in order to glow in the visible range and micro-scale metal wires cannot withstand such temperatures. In addition, heat transfer from the hot filament to its surroundings is extremely efficient at the microscale, making such structures impractical and leading to damage of the surrounding chip.

By measuring the spectrum of the light emitted from the graphene, the team was able to show that the graphene was reaching temperatures of above 2500 degrees Celsius, hot enough to glow brightly. “The visible light from atomically thin graphene is so intense that it is visible even to the naked eye, without any additional magnification,” explains Kim, first and co-lead author on the paper.

Interestingly, the spectrum of the emitted light showed peaks at specific wavelengths, which the team discovered was due to interference between the light emitted directly from the graphene and light reflecting off the silicon substrate and passing back through the graphene. Kim notes, “This is only possible because graphene is transparent, unlike any conventional filament, and allows us to tune the emission spectrum by changing the distance to the substrate.”

The ability of graphene to achieve such high temperatures without melting the substrate or the metal electrodes is due to another interesting property: as it heats up, graphene becomes a much poorer conductor of heat. This means that the high temperatures stay confined to a small “hot spot” in the center.

“At the highest temperatures, the electron temperature is much higher than that of acoustic vibrational modes of the graphene lattice, so that less energy is needed to attain temperatures needed for visible light emission,” Myung-Ho Bae, a senior researcher at KRISS and co-lead author, observes. “These unique thermal properties allow us to heat the suspended graphene up to half of the temperature of the sun, and improve efficiency 1000 times, as compared to graphene on a solid substrate.”

The team also demonstrated the scalability of their technique by realizing large-scale of arrays of chemical-vapor-deposited (CVD) graphene light emitters.

Yun Daniel Park, professor in the Department of Physics and Astronomy at Seoul National University and co-lead author, notes that they are working with the same material that Thomas Edison used when he invented the incandescent light bulb: “Edison originally used carbon as a filament for his light bulb and here we are going back to the same element, but using it in its pure form—graphene—and at its ultimate size limit—one atom thick.”

The group is currently working to further characterize the performance of these devices—for example, how fast they can be turned on and off to create “bits” for optical communications—and to develop techniques for integrating them into flexible substrates.

Hone adds, “We are just starting to dream about other uses for these structures—for example, as micro-hotplates that can be heated to thousands of degrees in a fraction of a second to study high-temperature chemical reactions or catalysis.”

Here’s a link to and a citation for the paper,

Bright visible light emission from graphene by Young Duck Kim, Hakseong Kim, Yujin Cho, Ji Hoon Ryoo, Cheol-Hwan Park, Pilkwang Kim, Yong Seung Kim, Sunwoo Lee, Yilei Li, Seung-Nam Park, Yong Shim Yoo, Duhee Yoon, Vincent E. Dorgan, Eric Pop, Tony F. Heinz, James Hone, Seung-Hyun Chun, Hyeonsik Cheong, Sang Wook Lee,    Myung-Ho Bae, & Yun Daniel Park. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.118 Published online 15 June 2015

This paper is behind a paywall.

Two final notes: there was an announcement earlier this year (mentioned in my March 30, 2015 post) that a graphene light bulb would be in stores this year. Dexter Johnson notes in his June 15, 2015 post (Nanoclast blog on the IEEE [International Institute of Electrical and Electronics Engineers] website) that the earlier light bulb has a graphene coating. You may want to check out Dexter’s posting about the latest light bulb achievement as he also includes an embedded video illustrating how Columbia Engineering’s graphene filament works.

Good enough for the real world? A new device consisting of a singular molecule

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While molecular diodes (a diode consisting of a single molecule) have been developed before, Columbia University’s Latha Venkataraman and her team have developed a new technique which may take these devices from the lab to real life. From a May 25, 2015 news item on Nanotechnology Now,

Under the direction of Latha Venkataraman, associate professor of applied physics at Columbia Engineering, researchers have designed a new technique to create a single-molecule diode, and, in doing so, they have developed molecular diodes that perform 50 times better than all prior designs. Venkataraman’s group is the first to develop a single-molecule diode that may have real-world technological applications for nanoscale devices.

A May 25, 2015 Columbia University news release on EurekAlert, which originated the news item, describes the new technique in greater detail,

“Our new approach created a single-molecule diode that has a high (>250) rectification and a high “on” current (~ 0.1 micro Amps),” says Venkataraman. “Constructing a device where the active elements are only a single molecule has long been a tantalizing dream in nanoscience. This goal, which has been the ‘holy grail’ of molecular electronics ever since its inception with Aviram and Ratner’s 1974 seminal paper, represents the ultimate in functional miniaturization that can be achieved for an electronic device.”

With electronic devices becoming smaller every day, the field of molecular electronics has become ever more critical in solving the problem of further miniaturization, and single molecules represent the limit of miniaturization. The idea of creating a single-molecule diode was suggested by Arieh Aviram and Mark Ratner who theorized in 1974 that a molecule could act as a rectifier, a one-way conductor of electric current. Researchers have since been exploring the charge-transport properties of molecules. They have shown that single-molecules attached to metal electrodes (single-molecule junctions) can be made to act as a variety of circuit elements, including resistors, switches, transistors, and, indeed, diodes. They have learned that it is possible to see quantum mechanical effects, such as interference, manifest in the conductance properties of molecular junctions.

Since a diode acts as an electricity valve, its structure needs to be asymmetric so that electricity flowing in one direction experiences a different environment than electricity flowing in the other direction. In order to develop a single-molecule diode, researchers have simply designed molecules that have asymmetric structures.

“While such asymmetric molecules do indeed display some diode-like properties, they are not effective,” explains Brian Capozzi, a PhD student working with Venkataraman and lead author of the paper. “A well-designed diode should only allow current to flow in one direction–the ‘on’ direction–and it should allow a lot of current to flow in that direction. Asymmetric molecular designs have typically suffered from very low current flow in both ‘on’ and ‘off’ directions, and the ratio of current flow in the two has typically been low. Ideally, the ratio of ‘on’ current to ‘off’ current, the rectification ratio, should be very high.”

In order to overcome the issues associated with asymmetric molecular design, Venkataraman and her colleagues–Chemistry Assistant Professor Luis Campos’ group at Columbia and Jeffrey Neaton’s group at the Molecular Foundry at UC Berkeley–focused on developing an asymmetry in the environment around the molecular junction. They created an environmental asymmetry through a rather simple method–they surrounded the active molecule with an ionic solution and used gold metal electrodes of different sizes to contact the molecule.

Their results achieved rectification ratios as high as 250: 50 times higher than earlier designs. The “on” current flow in their devices can be more than 0.1 microamps, which, Venkataraman notes, is a lot of current to be passing through a single-molecule. And, because this new technique is so easily implemented, it can be applied to all nanoscale devices of all types, including those that are made with graphene electrodes.

“It’s amazing to be able to design a molecular circuit, using concepts from chemistry and physics, and have it do something functional,” Venkataraman says. “The length scale is so small that quantum mechanical effects are absolutely a crucial aspect of the device. So it is truly a triumph to be able to create something that you will never be able to physically see and that behaves as intended.”

She and her team are now working on understanding the fundamental physics behind their discovery, and trying to increase the rectification ratios they observed, using new molecular systems.

Here’s a link to and a citation for the paper,

Single-molecule diodes with high rectification ratios through environmental control by Brian Capozzi, Jianlong Xia, Olgun Adak, Emma J. Dell, Zhen-Fei Liu, Jeffrey C. Taylor, Jeffrey B. Neaton, Luis M. Campos, & Latha Venkataraman. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.97 Published online 25 May 2015

This paper is behind a paywall but a free preview is available via ReadCube Access.

Multi-walled carbon nanotubes and blood clotting

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There’s been a lot of interest in using carbon nanotubes (CNTs) for biomedical applications such as drug delivery. New research from Trinity College Dublin (TCD) suggests that multi-walled carbon nanotubes (MWCNTs) may have some limitations when applied to biomedical uses. From a Jan. 20, 2014 news item on Nanowerk (Note: A link has been removed),

Scientists in the School of Pharmacy and Pharmaceutical Sciences in Trinity College Dublin, have made an important discovery about the safety issues of using carbon nanotubes as biomaterials which come into contact with blood. The significance of their findings is reflected in their paper being published as the feature story and front page cover of the international, peer-reviewed journal Nanomedicine (“Blood biocompatibility of surface-bound multi-walled carbon nanotubes”).

A Jan. 19, 2015 TCD press release, which originated the news item, offers a good description of the issues around blood clotting and the research problem (nonfunctionalized CNTs and blood compartibility) the scientists were addressing (Note: Links have been removed),

When blood comes into contact with foreign surfaces the blood’s platelets are activated which in turn leads to blood clots being formed. This can be catastrophic in clinical settings where extracorporeal circulation technologies are used such as during heart-lung bypass, in which the blood is circulated in PVC tubing outside the body. More than one million cardiothoracic surgeries are performed each year and while new circulation surfaces that prevent platelet activation are urgently needed, effective technologies have remained elusive.

One hope has been that carbon nanotubes, which are enormously important as potentially useful biomedical materials, might provide a solution to this challenge and this led the scientists from the School of Pharmacy and Pharmaceutical Sciences in collaboration with Trinity’s School of Chemistry and with colleagues from UCD and the University of Michigan in Ann Arbour to test the blood biocompatibility of carbon nanotubes. They found that the carbon nanotubes did actually stimulate blood platelet activation, subsequently leading to serious and devastating blood clotting. The findings have implications for the design of medical devices which contain nanoparticles and which are used in conjunction with flowing blood.

Speaking about their findings, Professor Marek Radomski, Chair of Pharmacology, Trinity and the paper’s senior author said: “Our results bear significance for the design of blood-facing medical devices, surface-functionalised with nanoparticles or containing surface-shedding nanoparticles. We feel that the risk/benefit ratio with particular attention to blood compatibility should be carefully evaluated during the development of such devices. Furthermore, it is clear that non-functionalised carbon nanotubes both soluble and surface-bound are not blood-compatible”.

The press release also quotes a TCD graduate,

Speaking about the significance of these findings for Nanomedicine research, the paper’s first author Dr Alan Gaffney, a Trinity PhD graduate who is now Assistant Professor of Anaesthesiology in Columbia University Medical Centre, New York said: “When new and exciting technologies with enormous potential benefits for medicine are being studied, there is often a bias towards the publication of positive findings. [emphasis mine] The ultimate successful and safe application of nanotechnology in medicine requires a complete understanding of the negative as well as positive effects so that un-intended side effects can be prevented. Our study is an important contribution to the field of nanomedicine and nanotoxicology research and will help to ensure that nanomaterials that come in contact with blood are thoroughly tested for their interaction with blood platelets before they are used in patients.”

Point well taken Dr. Gaffney. Too often there’s an almost euphoric quality to the nanomedicine discussion where nanoscale treatments are described as if they are perfectly benign in advance of any real testing. For example, I wrote about surgical nanobots being used in a human clinical trial in a Jan. 7, 2015 post which features a video of the researcher ‘selling’ his idea. The enthusiasm is laudable and necessary (researchers work for years trying to develop new treatments) but as Gaffney notes there needs to be some counter-ballast and recognition of the ‘positive bias’ issue.

Getting back to the TCD research, here’s a link to and a citation for the paper (or counter-ballast),

Blood biocompatibility of surface-bound multi-walled carbon nanotubes by Alan M. Gaffney, MD, PhD, Maria J. Santos-Martinez, MD, Amro Satti, Terry C. Major, Kieran J. Wynne, Yurii K. Gun’ko, PhD, Gail M. Annich, Giuliano Elia, Marek W. Radomski, MD. January 2015 Volume 11, Issue 1, Pages 39–46 DOI: http://dx.doi.org/10.1016/j.nano.2014.07.005 Published Online: July 26, 2014

This paper is open access.

Bendable, stretchable, light-weight, and transparent: a new competitor in the competition for ‘thinnest electric generator’

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An Oct. 15, 2014 Columbia University (New York, US) press release (also on EurekAlert), describes another contender for the title of the world’s thinnest electric generator,

Researchers from Columbia Engineering and the Georgia Institute of Technology [US] report today [Oct. 15, 2014] that they have made the first experimental observation of piezoelectricity and the piezotronic effect in an atomically thin material, molybdenum disulfide (MoS2), resulting in a unique electric generator and mechanosensation devices that are optically transparent, extremely light, and very bendable and stretchable.

In a paper published online October 15, 2014, in Nature, research groups from the two institutions demonstrate the mechanical generation of electricity from the two-dimensional (2D) MoS2 material. The piezoelectric effect in this material had previously been predicted theoretically.

Here’s a link to and a citation for the paper,

Piezoelectricity of single-atomic-layer MoS2 for energy conversion and piezotronics by Wenzhuo Wu, Lei Wang, Yilei Li, Fan Zhang, Long Lin, Simiao Niu, Daniel Chenet, Xian Zhang, Yufeng Hao, Tony F. Heinz, James Hone, & Zhong Lin Wang. Nature (2014) doi:10.1038/nature13792 Published online 15 October 2014

This paper is behind a paywall. There is a free preview available with ReadCube Access.

Getting back to the Columbia University press release, it offers a general description of piezoelectricity and some insight into this new research on molybdenum disulfide,

Piezoelectricity is a well-known effect in which stretching or compressing a material causes it to generate an electrical voltage (or the reverse, in which an applied voltage causes it to expand or contract). But for materials of only a few atomic thicknesses, no experimental observation of piezoelectricity has been made, until now. The observation reported today provides a new property for two-dimensional materials such as molybdenum disulfide, opening the potential for new types of mechanically controlled electronic devices.

“This material—just a single layer of atoms—could be made as a wearable device, perhaps integrated into clothing, to convert energy from your body movement to electricity and power wearable sensors or medical devices, or perhaps supply enough energy to charge your cell phone in your pocket,” says James Hone, professor of mechanical engineering at Columbia and co-leader of the research.

“Proof of the piezoelectric effect and piezotronic effect adds new functionalities to these two-dimensional materials,” says Zhong Lin Wang, Regents’ Professor in Georgia Tech’s School of Materials Science and Engineering and a co-leader of the research. “The materials community is excited about molybdenum disulfide, and demonstrating the piezoelectric effect in it adds a new facet to the material.”

Hone and his research group demonstrated in 2008 that graphene, a 2D form of carbon, is the strongest material. He and Lei Wang, a postdoctoral fellow in Hone’s group, have been actively exploring the novel properties of 2D materials like graphene and MoS2 as they are stretched and compressed.

Zhong Lin Wang and his research group pioneered the field of piezoelectric nanogenerators for converting mechanical energy into electricity. He and postdoctoral fellow Wenzhuo Wu are also developing piezotronic devices, which use piezoelectric charges to control the flow of current through the material just as gate voltages do in conventional three-terminal transistors.

There are two keys to using molybdenum disulfide for generating current: using an odd number of layers and flexing it in the proper direction. The material is highly polar, but, Zhong Lin Wang notes, so an even number of layers cancels out the piezoelectric effect. The material’s crystalline structure also is piezoelectric in only certain crystalline orientations.

For the Nature study, Hone’s team placed thin flakes of MoS2 on flexible plastic substrates and determined how their crystal lattices were oriented using optical techniques. They then patterned metal electrodes onto the flakes. In research done at Georgia Tech, Wang’s group installed measurement electrodes on samples provided by Hone’s group, then measured current flows as the samples were mechanically deformed. They monitored the conversion of mechanical to electrical energy, and observed voltage and current outputs.

The researchers also noted that the output voltage reversed sign when they changed the direction of applied strain, and that it disappeared in samples with an even number of atomic layers, confirming theoretical predictions published last year. The presence of piezotronic effect in odd layer MoS2 was also observed for the first time.

“What’s really interesting is we’ve now found that a material like MoS2, which is not piezoelectric in bulk form, can become piezoelectric when it is thinned down to a single atomic layer,” says Lei Wang.

To be piezoelectric, a material must break central symmetry. A single atomic layer of MoS2 has such a structure, and should be piezoelectric. However, in bulk MoS2, successive layers are oriented in opposite directions, and generate positive and negative voltages that cancel each other out and give zero net piezoelectric effect.

“This adds another member to the family of piezoelectric materials for functional devices,” says Wenzhuo Wu.

In fact, MoS2 is just one of a group of 2D semiconducting materials known as transition metal dichalcogenides, all of which are predicted to have similar piezoelectric properties. These are part of an even larger family of 2D materials whose piezoelectric materials remain unexplored. Importantly, as has been shown by Hone and his colleagues, 2D materials can be stretched much farther than conventional materials, particularly traditional ceramic piezoelectrics, which are quite brittle.

The research could open the door to development of new applications for the material and its unique properties.

“This is the first experimental work in this area and is an elegant example of how the world becomes different when the size of material shrinks to the scale of a single atom,” Hone adds. “With what we’re learning, we’re eager to build useful devices for all kinds of applications.”

Ultimately, Zhong Lin Wang notes, the research could lead to complete atomic-thick nanosystems that are self-powered by harvesting mechanical energy from the environment. This study also reveals the piezotronic effect in two-dimensional materials for the first time, which greatly expands the application of layered materials for human-machine interfacing, robotics, MEMS, and active flexible electronics.

I see there’s a reference in that last paragraph to “harvesting mechanical energy from  the environment.” I’m not sure what they mean by that but I have written a few times about harvesting biomechanical energy. One of my earliest pieces is a July 12, 2010 post which features work by Zhong Lin Wang on harvesting energy from heart beats, blood flow, muscle stretching, or even irregular vibrations. One of my latest pieces is a Sept. 17, 2014 post about some work in Canada on harvesting energy from the jaw as you chew.

A final note, Dexter Johnson discusses this work in an Oct. 16, 2014 post on the Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website).