DNA origami as Van Gogh’s Starry Night

This glowing reproduction of "The Starry Night" contains 65,536 pixels and is the width of a dime across. Credit: Ashwin Gopinath/Caltech

This glowing reproduction of “The Starry Night” contains 65,536 pixels and is the width of a dime across.
Credit: Ashwin Gopinath/Caltech

It may take you a few seconds (it did me) but it’s possible to see Van Gogh’s Starry Night in this image. A July 12, 2016 news item on ScienceDaily reveals more,

Using folded DNA [deoxyribonucleic acid] to precisely place glowing molecules within microscopic light resonators, researchers at Caltech have created one of the world’s smallest reproductions of Vincent van Gogh’s The Starry Night.

A July 12, 2016 Caltech news release (also on EurekAlert) by Richard Perkins, which originated the news item, provides more information about the image, DNA origami, and this latest research on coupling light emitters to photonic crystal cavities (Note: Links have been removed),

The monochrome image—just the width of a dime across—was a proof-of-concept project that demonstrated, for the first time, how the precision placement of DNA origami can be used to build chip-based devices like computer circuits at smaller scales than ever before.

DNA origami, developed 10 years ago by Caltech’s Paul Rothemund (BS ’94), is a technique that allows researchers to fold a long strand of DNA into any desired shape. The folded DNA then acts as a scaffold onto which researchers can attach and organize all kinds of nanometer-scale components, from fluorescent molecules to electrically conductive carbon nanotubes to drugs.

“Think of it a bit like the pegboards people use to organize tools in their garages, only in this case, the pegboard assembles itself from DNA strands and the tools likewise find their own positions,” says Rothemund, research professor of bioengineering, computing and mathematical sciences, and computation and neural systems. “It all happens in a test tube without human intervention, which is important because all of the parts are too small to manipulate efficiently, and we want to make billions of devices.”

The process has the potential to influence a variety of applications from drug delivery to the construction of nanoscale computers. But for many applications, organizing nanoscale components to create devices on DNA pegboards is not enough; the devices have to be wired together into larger circuits and need to have a way of communicating with larger-scale devices.

One early approach was to make electrodes first, and then scatter devices randomly on a surface, with the expectation that at least a few would land where desired, a method Rothemund describes as “spray and pray.”

In 2009, Rothemund and colleagues at IBM Research first described a technique through which DNA origami can be positioned at precise locations on surfaces using electron-beam lithography to etch sticky binding sites that have the same shape as the origami. For example, triangular sticky patches bind triangularly folded DNA.

Over the last seven years, Rothemund and Ashwin Gopinath, senior postdoctoral scholar in bioengineering at Caltech, have refined and extended this technique so that DNA shapes can be precisely positioned on almost any surface used in the manufacture of computer chips. In the Nature paper, they report the first application of the technique—using DNA origami to install fluorescent molecules into microscopic light sources.

“It’s like using DNA origami to screw molecular light bulbs into microscopic lamps,” Rothemund says.

In this case, the lamps are microfabricated structures called photonic crystal cavities (PCCs), which are tuned to resonate at a particular wavelength of light, much like a tuning fork vibrates with a particular pitch. Created within a thin glass-like membrane, a PCC takes the form of a bacterium-shaped defect within an otherwise perfect honeycomb of holes.

“Depending on the exact size and spacing of the holes, a particular wavelength of light reflects off the edge of the cavity and gets trapped inside,” says Gopinath, the lead author of the study. He built PCCs that are tuned to resonate at around 660 nanometers, the wavelength corresponding to a deep shade of the color red. Fluorescent molecules tuned to glow at a similar wavelength light up the lamps—provided they stick to exactly the right place within the PCC.

“A fluorescent molecule tuned to the same color as a PCC actually glows more brightly inside the cavity, but the strength of this coupling effect depends strongly on the molecule’s position within the cavity. A few tens of nanometers is the difference between the molecule glowing brightly, or not at all,” Gopinath says.

By moving DNA origami through the PCCs in 20-nanometer steps, the researchers found that they could map out a checkerboard pattern of hot and cold spots, where the molecular light bulbs either glowed weakly or strongly. As a result, they were able to use DNA origami to position fluorescent molecules to make lamps of varying intensity. Similar structures have been proposed to power quantum computers and for use in other optical applications that require many tiny light sources integrated together on a single chip.

“All previous work coupling light emitters to PCCs only successfully created a handful of working lamps, owing to the extraordinary difficulty of reproducibly controlling the number and position of emitters in a cavity,” Gopinath says. To prove their new technology, the researchers decided to scale-up and provide a visually compelling demonstration. By creating PCCs with different numbers of binding sites, Gopinath was able to reliably install any number from zero to seven DNA origami, allowing him to digitally control the brightness of each lamp. He treated each lamp as a pixel with one of eight different intensities, and produced an array of 65,536 of the PCC pixels (a 256 x 256 pixel grid) to create a reproduction of Van Gogh’s “The Starry Night.”

Now that the team can reliably combine molecules with PCCs, they are working to improve the light emitters. Currently, the fluorescent molecules last about 45 seconds before reacting with oxygen and “burning out,” and they emit a few shades of red rather than a single pure color. Solving both these problems will help with applications such as quantum computers.

“Aside from applications, there’s a lot of fundamental science to be done,” Gopinath says.

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

Engineering and mapping nanocavity emission via precision placement of DNA origami by Ashwin Gopinath, Evan Miyazono, Andrei Faraon, & Paul W. K. Rothemund. Nature (2016) doi:10.1038/nature18287 Published online 11 July 2016

This paper is behind a paywall.

Drink your spinach juice—illuminate your guts

Contrast agents used for magnetic resonance imaging, x-ray imaging, ultrasounds, and other imaging technologies are not always kind to the humans ingesting them. So, scientists at the University at Buffalo (also known as the State University of New York at Buffalo) have developed a veggie juice that does the job according to a July 11, 2016 news item on Nanowerk (Note: A link has been removed),

The pigment that gives spinach and other plants their verdant color may improve doctors’ ability to examine the human gastrointestinal tract.

That’s according to a study, published in the journal Advanced Materials (“Surfactant-Stripped Frozen Pheophytin Micelles for Multimodal Gut Imaging”), which describes how chlorophyll-based nanoparticles suspended in liquid are an effective imaging agent for the gut.

The University of Buffalo has provided an illustration of the work,

A new UB-led study suggests that chlorophyll-based nanoparticles are an effective imaging agent for the gut. The medical imaging drink, developed to diagnose and treat gastrointestinal illnesses, is made of concentrated chlorophyll, the pigment that makes spinach green. Photo illustration credit: University at Buffalo.

A new UB-led study suggests that chlorophyll-based nanoparticles are an effective imaging agent for the gut. The medical imaging drink, developed to diagnose and treat gastrointestinal illnesses, is made of concentrated chlorophyll, the pigment that makes spinach green. Photo illustration credit: University at Buffalo.

A July 11, 2016 University at Buffalo (UB) news release (also on EurekAlert) by Cory Nealon, which originated the news item, expands on the theme,

“Our work suggests that this spinach-like, nanoparticle juice can help doctors get a better look at what’s happening inside the stomach, intestines and other areas of the GI tract,” says Jonathan Lovell, PhD, assistant professor in the Department of Biomedical Engineering, a joint program between UB’s School of Engineering and Applied Sciences and the Jacobs School of Medicine and Biomedical Sciences at UB, and the study’s corresponding author.

To examine the gastrointestinal tract, doctors typically use X-rays, magnetic resonance imaging or ultrasounds, but these techniques are limited with respect to safety, accessibility and lack of adequate contrast, respectively.

Doctors also perform endoscopies, in which a tiny camera attached to a thin tube is inserted into the patient’s body. While effective, this procedure is challenging to perform in the small intestine, and it can cause infections, tears and pose other risks.

The new study, which builds upon Lovell’s previous medical imaging research, is a collaboration between researchers at UB and the University of Wisconsin-Madison. It focuses on Chlorophyll a, a pigment found in spinach and other green vegetables that is essential to photosynthesis.

In the laboratory, researchers removed magnesium from Chlorophyll a, a process which alters the pigment’s chemical structure to form another edible compound called pheophytin. Pheophytin plays an important role in photosynthesis, acting as a gatekeeper that allows electrons from sunlight to enter plants.

Next, they dissolved pheophytin in a solution of soapy substances known as surfactants. The researchers were then able to remove nearly all of the surfactants, leaving nearly pure pheophytin nanoparticles.

The drink, when tested in mice, provided imaging of the gut in three modes: photoacoustic imaging, fluorescence imaging and positron emission tomography (PET). (For PET, the researchers added to the drink Copper-64, an isotope of the metal that, in small amounts, is harmless to the human body.)

Additional studies are needed, but the drink has commercial potential because it:

·         Works in different imaging techniques.

·         Moves stably through the gut.

·         And is naturally consumed in the human diet already.

In lab tests, mice excreted 100 percent of the drink in photoacoustic and fluorescence imaging, and nearly 93 percent after the PET test.

“The veggie juice allows for techniques that are not commonly used today by doctors for imaging the gut like photoacoustic, PET, and fluorescence,” Lovell says. “And part of the appeal is the safety of the juice.”

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

Surfactant-Stripped Frozen Pheophytin Micelles for Multimodal Gut Imaging by Yumiao Zhang, Depeng Wang, Shreya Goel, Boyang Sun, Upendra Chitgupi, Jumin Geng, Haiyan Sun, Todd E. Barnhart, Weibo Cai, Jun Xia, and Jonathan F. Lovell. Advanced Materials DOI: 10.1002/adma.201602373 Version of Record online: 11 JUL 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Nanotechnology-enabled electronic tattoo from Tel Aviv University (Israel)

This is the first stick-on, nanotechnology-enabled tattoo I’ve seen that’s designed for the face. From a July 11, 2016 news item on ScienceDaily,

A new temporary “electronic tattoo” developed by Tel Aviv University [TAU] that can measure the activity of muscle and nerve cells researchers is poised to revolutionize medicine, rehabilitation, and even business and marketing research.

A July 11, 2016 American Friends of Tel Aviv University news release (also on EurekAlert), which originated the news item, provides more detail (Note: Some formatting has been changed),

The tattoo consists of a carbon electrode, an adhesive surface that attaches to the skin, and a nanotechnology-based conductive polymer coating that enhances the electrode’s performance. It records a strong, steady signal for hours on end without irritating the skin.

The electrode, developed by Prof. Yael Hanein, head of TAU’s Center for Nanoscience and Nanotechnology, may improve the therapeutic restoration of damaged nerves and tissue — and may even lead to new insights into our emotional life.

Prof. Hanein’s research was published last month in Scientific Reports and presented at an international nanomedicine program held at TAU.

“Stick it on and forget about it”

One major application of the new electrode is the mapping of emotion by monitoring facial expressions through electric signals received from facial muscles. “The ability to identify and map people’s emotions has many potential uses,” said Prof. Hanein. “Advertisers, pollsters, media professionals, and others — all want to test people’s reactions to various products and situations. Today, with no accurate scientific tools available, they rely mostly on inevitably subjective questionnaires.

“Researchers worldwide are trying to develop methods for mapping emotions by analyzing facial expressions, mostly via photos and smart software,” Prof. Hanein continued. “But our skin electrode provides a more direct and convenient solution.”

The device was first developed as an alternative to electromyography, a test that assesses the health of muscles and nerve cells. It’s an uncomfortable and unpleasant medical procedure that requires patients to lie sedentary in the lab for hours on end. Often a needle is stuck into muscle tissue to record its electrical activity, or patients are swabbed with a cold, sticky gel and attached to unwieldy surface electrodes.

“Our tattoo permits patients to carry on with their daily routines, while the electrode monitors their muscle and nerve activity,” said Prof. Hanein. “The idea is: stick it on and forget about it.”

Applications for rehabilitation and more

According to Prof. Hanein, the new skin electrode has other important therapeutic applications. The tattoo will be used to monitor the muscle activity of patients with neurodegenerative diseases in a study at Tel Aviv Medical Center.

“But that’s not all,” said Prof. Hanein. “The physiological data measured in specific muscles may be used in the future to indicate the alertness of drivers on the road; patients in rehabilitation following stroke or brain injury may utilize the ‘tattoo’ to improve muscle control; and amputees may employ it to move artificial limbs with remaining muscles.”

As it often is, the funding sources prove to be interesting (from the news release),

The electrode is the product of a European Research Council (ERC) project and received support from the BSMT Consortium of Israel’s Ministry of Economy.

The involvement of the European Research Council underlines the very close relationship Israel has to the European Union even though it is not an official member.

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

Temporary-tattoo for long-term high fidelity biopotential recordings by Lilach Bareket, Lilah Inzelberg, David Rand, Moshe David-Pur, David Rabinovich, Barak Brandes & Yael Hanein. Scientific Reports 6, Article number: 25727 (2016)  doi:10.1038/srep25727 Published online: 12 May 2016

This paper is open access.

Making ordinary microscopes image objects at the nanoscale

The researchers believe this technique for making ordinary microscopes capable of nanoscale imaging will make research into diseases easier, especially in developing countries. A July 20, 2016 news item on phys.org announces the new technique,

Research completed through a collaboration with University of Missouri [MU] engineers, biologists, and chemists could transform how scientists study molecules and cells at sub-microscopic (nanoscale) levels. Shubra Gangopadhyay, an electrical and computer engineer and her team at MU recently published studies outlining a new, relatively inexpensive imaging platform that enables single molecule imaging. This patented method highlights Gangopadhyay’s more than 30 years of nanoscale research that has proven invaluable in biological research and battling diseases.

This diagram shows the difference between regular and plasmonic gratings in terms of fluorescent intensity. Credit: Shubhra Gangopadhyay/Nanoscale.

This diagram shows the difference between regular and plasmonic gratings in terms of fluorescent intensity. Credit: Shubhra Gangopadhyay/Nanoscale.

A July 19, 2016 University of Missouri news release (also received via email), which originated the news item, explains further,

“Usually, scientists have to use very expensive microscopes to image at the sub-microscopic level,” said Gangopadhyay, the C.W. LaPierre Endowed Chair of electrical and computer engineering in the MU College of Engineering. “The techniques we’ve established help to produce enhanced imaging results with ordinary microscopes. The relatively low production cost for the platform also means it could be used to detect a wide variety of diseases, particularly in developing countries.”

The team’s custom platform uses an interaction between light and the surface of the metal grating to generate surface plasmon resonance (SPR), a rapidly developing imaging technique that enables super-resolution imaging down to 65 nanometers—a resolution normally reserved for electron microscopes. Using HD-DVD and Blu-Ray discs as starting templates, a repeating grating pattern is transferred onto the microscope slides where the specimen will be placed. Since the patterns originate from a widely used technology, the manufacturing process remains relatively inexpensive.

“In previous studies, we’ve used plasmonic gratings to detect cortisol and even tuberculosis,” Gangopadhyay said. “Additionally, the relatively low production cost for the platform also means it could be used to further detect a wide variety of diseases, particularly in developing countries. Eventually, we might even be able to use smartphones to detect disease in the field.”

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

Plasmonic gratings with nano-protrusions made by glancing angle deposition for single-molecule super-resolution imaging by B. Chen, A. Wood, A. Pathak, J. Mathai, S. Bok, H. Zheng, S. Hamm, S. Basuray, S. Grant, K. Gangopadhyay, P. V. Cornish, and S. Gangopadhyay. Nanoscale, 2016,8, 12189-12201 DOI: 10.1039/C5NR09165A First published online 24 May 2016

This paper is behind a paywall.

ETA July 22, 2016: Dexter Johnson’s July 21, 2016 posting provides both a neat summary and added detail from an engineer’s perspective.

Inspiration from the sea for titanium implants (mussels) and adhesive panels for flexible sensors (octopuses/octopi/octopodes)

I have two sea-inspired news bits both of which concern adhesion.

Mussels and titanium implants

A July 8, 2016 news item on ScienceDaily features some mussel-inspired research from Japan into how to make better titanium implants,

Titanium is used medically in applications such as artificial joints and dental implants. While it is strong and is not harmful to tissues, the metal lacks some of the beneficial biological properties of natural tissues such as bones and natural teeth. Now, based on insights from mussels–which are able to attach themselves very tightly to even metallic surfaces due to special proteins found in their byssal threads–scientists from RIKEN have successfully attached a biologically active molecule to a titanium surface, paving the way for implants that can be more biologically beneficial.

A July 11, 2016 RIKEN press release (also on EurekAlert but dated July 8, 2016), which originated the news item, provides more information,

The work began from earlier discoveries that mussels can attach to smooth surfaces so effectively thanks to a protein, L-DOPA, which is known to be able to bind very strongly to smooth surfaces such as rocks, ceramics, or metals (…). Interestingly, the same protein functions in humans as a precursor to dopamine, and is used as a treatment for Parkinson’s disease.

According to Chen Zhang of the RIKEN Nano Medical Engineering Laboratory, the first author of the paper published in Angewandte Chemie, “We thought it would be interesting to try to use various techniques to attach a biologically active protein—in our case we chose insulin-like growth factor-1, a promoter of cell proliferation—to a titanium surface like those used in implants” (…).

Using a combination of recombinant DNA technology and treatment with tyrosinase, they were able to create a hybrid protein that contained active parts of both the growth factor and L-DOPA. Tests showed that the proteins were able to fold normally, and further experiments in cell cultures demonstrated that the IGF-1 was still functioning normally. Thanks to the incorporation of the L-DOPA, the team was able to confirm that the proteins bound strongly to the titanium surface, and remained attached even when the metal was washed with phosphate-buffered saline, a water-based solution. Zhang says, “This is similar to the powerful properties of mussel adhesive, which can remain fixed to metallic materials even underwater.”

According to Yoshihiro Ito, Team Leader of the Emergent Bioengineering Research Team of the RIKEN Center for Emergent Matter Science, “We are very excited by this finding, because the modification process is a universal one that could be used with other proteins. It could allow us to prepare new cell-growth enhancing materials, with potential applications in cell culture systems and regenerative medicine. And it is particularly interesting that this is an example of biomimetics, where nature can teach us new ways to do things. The mussel has given us insights that could be used to allow us to live healthier lives.”

The work was done by RIKEN researchers in collaboration with Professor Peibiao Zhang of the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, and Professor Yi Wang of the School of Pharmaceutical Sciences, Jilin University. The work was partially supported by the Japan Society for the Promotion of Science KAKENHI (Grant Number 15H01810 and 22220009), CAS-JSPS joint fund (GJHZ1519), and RIKEN MOST joint project.

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

A Bioorthogonal Approach for the Preparation of a Titanium-Binding Insulin-like Growth-Factor-1 Derivative by using Tyrosinase by Chen Zhang, Hideyuki Miyatake, Yu Wang, Takehiko Inaba, Yi Wang, Peibiao Zhang, and Prof. Yoshihiro Ito. Angewandte Chemie International Edition DOI: 10.1002/anie.201603155 Version of Record online: 6 JUL 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Octopuses/octopi/octopodes and adhesive panels

Before launching into the science part of this news bit, here’s some grammar (from the Octopus Wikipedia entry; Note: Links have been removed),

The standard pluralized form of “octopus” in the English language is “octopuses” /ˈɒktəpʊsɪz/,[10] although the Ancient Greek plural “octopodes” /ɒkˈtɒpədiːz/, has also been used historically.[9] The alternative plural “octopi” — which misguidedly assumes it is a Latin “-us”-word — is considered grammatically incorrect.[11][12][13][14] It is nevertheless used enough to make it notable, and was formally acknowledged by the descriptivist Merriam-Webster 11th Collegiate Dictionary and Webster’s New World College Dictionary. The Oxford English Dictionary (2008 Draft Revision)[15] lists “octopuses”, “octopi”, and “octopodes”, in that order, labelling “octopodes” as rare and noting that “octopi” derives from the apprehension that octōpus comes from Latin.[16] In contrast, New Oxford American Dictionary (3rd Edition 2010) lists “octopuses” as the only acceptable pluralization, with a usage note indicating “octopodes” as being still occasionally used but “octopi” as being incorrect.[17]

Now the news. A July 12, 2016 news item on Nanowerk highlights some research into adhesives and octopuses,

With increased study of bio-adhesives, a significant effort has been made in search for novel adhesives that will combine reversibility, repeated usage, stronger bonds and faster bonding time, non-toxic, and more importantly be effective in wet and other extreme conditions.

A team of Korean scientists-made up of scientists from Korea Institute of Science and Technology (KIST) and UNIST has recently found a way to make building flexible pressure sensors easier–by mimicking the suction cups on octopus’s tentacles.

A July 5, 2016 UNIST (Ulsan National Institute of Science and Technology) press release, which originated the news item, provides more information,

According to the research team, “Although flexible pressure sensors might give future prosthetics and robots a better sense of touch, building them requires a lot of laborious transferring of nano- and microribbons of inorganic semiconductor materials onto polymer sheets.”

In search of an easier way to process this transfer printing, Prof. Hyunhyub Ko (School of Energy and Chemical Engineering, UNIST) and his colleagues turned to the octopus suction cups for inspiration.

An octopus uses its tentacles to move to a new location and uses suction cups underneath each tentacle to grab onto something. Each suction cup contains a cavity whose pressure is controlled by surrounding muscles. These can be made thinner or thicker on demand, increasing or decreasing air pressure inside the cup, allowing for sucking and releasing as desired.

By mimicking muscle actuation to control cavity-pressure-induced adhesion of octopus suckers, Prof. Ko and his team engineered octopus-inspired smart adhesive pads. They used the rubbery material polydimethylsiloxane (PDMS) to create an array of microscale suckers, which included pores that are coated with a thermally responsive polymer to create sucker-like walls.

The team discovered that the best way to replicate organic nature of muscle contractions would be through applied heat. Indeed, at room temperature, the walls of each pit sit in an ‘open’ state, but when the mat is heated to 32°C, the walls contract, creating suction, therby allowing the entire mate to adhere to a material (mimicking the suction function of an octopus). The adhesive strength also spiked from .32 kilopascals to 94 kilopascals at high temperature.

The team reports that the mat worked as envisioned—they made some indium gallium arsenide transistors that sat on a flexible substrate and also used it to move some nanomaterials to a different type of flexible material.

Prof. Ko and his team expect that their smart adhesive pads can be used as the substrate for wearable health sensors, such as Band-Aids or sensors that stick to the skin at normal body temperatures but fall off when rinsed under cold water.

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

Octopus-Inspired Smart Adhesive Pads for Transfer Printing of Semiconducting Nanomembranes by Hochan Lee, Doo-Seung Um, Youngsu Lee, Seongdong Lim, Hyung-jun Kim,  and Hyunhyub Ko. Advanced Materials DOI: 10.1002/adma.201601407 Version of Record online: 20 JUN 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

NEC and its ‘carbon nanobrush’

Long associated with the discovery of carbon nanotubes (CNTs), NEC Corporation has announced another carbon material, carbon nanobrushes, in a July 7, 2016 news item on phys.org,

NEC Corporation today [June 30, 2016] announced the discovery of a new nano carbon material, the “carbon nanobrush,” a fibrous aggregate of single-walled carbon nanohorns. Moreover, NEC has become the first company in the world to manufacture the carbon nanobrush.

A June 30, 2016 NEC Corporation press release, which originated the news item, provides more detail (Note: This excerpt has been reformatted for clarity),

“The ‘carbon nanobrush’ is a new nano carbon material that, like existing carbon nanohorns, has high water and solvent dispersity, and high adsorptivity, including substance adsorption, but has more than 10 times the electrical conductivity than existing carbon nanohorns, an important characteristic for industrial applications,” said Dr. Sumio Iijima, Senior Research Fellow, NEC Corporation. “With these characteristics, it is anticipated that the carbon nanobrush will help to improve the basic functionality of a range of devices, including increasing the speed of sensor and actuator responses, improving the output properties of batteries and capacitors, while increasing the electrical conductivity of rubber and plastic composite materials, as well as having application in a wide range of industries.”

1. TEM images of the obtained samples

2. Tips of single-walled carbon nanohorn

3. Spherical-carbon nanohorn aggregates

Carbon nanohorns are horn-shaped (figure 2) nano carbon structures 2-5 nanometers (nm) in diameter and 40-50nm in length, which until now have been produced as radial spherical aggregates (figure 3). The newly discovered carbon nanobrush is a uniquely shaped material. It is fibrous aggregates composed of radially-assembled graphene-based single-walled nanotubules, named here as fibrous aggregates of single-walled carbon nanohorns, whose structure resembles that of a round brush (figure 1).

Features of the “carbon nanobrush” include the following:

    1. Structure
      (1)Single-walled carbon nanohorns of 2-5nm in diameter and 40-50nm in length radially gather and are connected fibrously in several micrometers.
      (2)The single-walled carbon nanohorn which is a horn-shaped nano carbon structure with a large surface area radially gather and are connected fibrously in several micrometers. So it has a large surface area per unit mass (up to 1700㎡/g).
    1. Characteristics
      (1)Dispersity
      Like carbon nanohorns, the carbon nanobrush has high dispersibility, dispersing in water and organic solvents, for example. This means that it can be easily mixed with a variety of materials, making it easy to improve its characteristics as a base material.(2)Adsorptivity
      Like spherical carbon nanohorns, the carbon nanobrush can contain various substances in the nano-sized spaces inside the tubular structure, so it can be utilized as a high-performance adsorbent. When holes are formed on the surface of the carbon nanohorns by oxidation treatments, the inner space can be used, expanding the surface area by a factor of approximately five and greatly increasing adsorptivity.

      (3)Electrical conductivity
      As carbon nanobrush is a fibrous aggregate of radially-assembled carbon nanohorns, it has more than 10 times the electrical conductivity compared with existing spherical carbon nanohorn aggregates. As a result, they are highly effective in increasing the speed of sensor and actuator responses, increasing output properties of batteries and capacitors, and increasing the electrical conductivity of rubber and plastic composite materials.

  1. Production process
    Carbon nanobrush can be produced at room temperature and under atmospheric pressure using the laser ablation method where an iron-containing carbon target (mass of carbon) is irradiated by a laser with high power density. The simple production process means that they can be produced efficiently and at a low cost when compared to the cost of other nano carbon materials.

This technology was developed in part through collaborative research with the National Institute of Advanced Industrial Science and Technology (AIST).

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

Preparation and Characterization of Newly Discovered Fibrous Aggregates of Single-Walled Carbon Nanohorns by Ryota Yuge, Fumiyuki Nihey, Kiyohiko Toyama, and Masako Yudasaka. Advanced Materials DOI: 10.1002/adma.201602022 Version of Record online: 25 MAY 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

For anyone interested in a history of carbon nanotubes, there’s my June 10, 2016 posting: The birth of carbon nanotubes (CNTs): a history, which includes a mention of NEC and its position as the discoverer of carbon nanotubes.

Getting one step closer to molecular robots

A July 5, 2016 news item on ScienceDaily announced research from Hokkaido University (Japan),

Scientists at Japan’s Hokkaido University have developed light-powered molecular motors that repetitively bend and unbend, bringing us closer to molecular robots.

A July 6, 2016 Hokkaido University press release (also on EurekAlert), which originated the news item, expands on the theme,

Researchers are working on mimicking cellular systems to develop molecular motors that can move or even deliver drugs to target tissues. Engineering such motors may ultimately lead to molecular robots that can execute more complex tasks. To this end, researchers must find ways to convert motion at the molecular level to motion at the macroscopic level. They also must find ways to cause chemical reactions to repeat autonomously and continuously.
Yoshiyuki Kageyama, Sadamu Takeda and colleagues at Hokkaido University’s Department of Chemistry have successfully created a chemical compound, or a crystalline assembly, which autonomously repeated flipping under blue light.

The team made crystals composed of an organic compound, called azobenzene, commonly used in dye manufacturing, and oleic acid, commonly found in cooking oil. Azobenzene molecules take two structurally different forms: cis and trans. They repetitively convert from one form to the other under blue right. The scientists tested if this would influence the structure of the azobenzene-oleic acid crystal, which contained unequal amounts of cis– and trans-azobenzene.

By applying blue light to the crystals in solution, the team observed, under a microscope, an oscillatory bending-unbending motion of the thin crystals, suggesting the existence of two stable structures, bent or unbent, depending on the cis/trans ratio. The frequency of the motion increased when the light intensity was increased. Some crystal complexes even exhibited ‘swimming-like’ motions in the water. Previously reported light-responsive materials have been limited in their ability to deform. The properties of the compounds in the Hokkaido University-developed crystals, however, allowed for a two-step switching mechanism, resulting in regular repetitive oscillations.

Schematic illustration of each step of the self-oscillatory motion. (Ikegami T. et. al., Angewandte Chemie International Edition, May 19, 2016)

Schematic illustration of each step of the self-oscillatory motion. (Ikegami T. et. al., Angewandte Chemie International Edition, May 19, 2016)

“The ability to self-organize rhythmic motions, such as the repetitive flipping motion we observed, is one of the fundamental characteristics of living organisms”, says Kageyama. “This mechanism can be used in the future to develop bio-inspired molecular motors and robots that will find applications in wide areas, including medicine”.

You can observe the flipping here in this video provided by Hokkaido University,

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

Dissipative and Autonomous Square-Wave Self-Oscillation of a Macroscopic Hybrid Self-Assembly under Continuous Light Irradiation by Tomonori Ikegami, Dr. Yoshiyuki Kageyama, Kazuma Obara, and Prof. Sadamu Takeda. Angewandte Chemie International Edition Volume 55, Issue 29, pages 8239–8243, July 11, 2016 DOI: 10.1002/anie.201600218 Version of Record online: 19 MAY 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Google Arts & Culture: an app for culture vultures

In its drive to take over single aspect of our lives in the most charming, helpful, and delightful ways possible, Google has developed its Arts & Culture app.

Here’s more from a July 19, 2016 article by John Brownlee for Fast Company (Note: Links have been removed),

… Google has just unveiled a new app that makes it as easy to find the opening times of your local museum as it is to figure out who painted that bright purple Impressionist masterpiece you saw five years ago at the Louvre.

It’s called Google Arts & Culture, and it’s a tool for discovering art “from more than a thousand museums across 70 countries,” Google writes on its blog. More than just an online display of art, though, it encourages viewers to parse the works and gather insight into the visual culture we rarely encounter outside the rarified world of brick-and-mortar museums.

For instance, you can browse all of Van Gogh’s paintings chronologically to see how much more vibrant his work became over time. Or you can sort Monet’s paintings by color for a glimpse at his nuanced use of gray.

You can also read daily stories about subjects such as stolen Nazi artworks or Bruegel’s Tower of Babel. …

A July 19, 2016 post announcing the Arts & Culture app on the Google blog by Duncan Osborn provides more details,

Just as the world’s precious artworks and monuments need a touch-up to look their best, the home we’ve built to host the world’s cultural treasures online needs a lick of paint every now and then. We’re ready to pull off the dust sheets and introduce the new Google Arts & Culture website and app, by the Google Cultural Institute. The app lets you explore anything from cats in art since 200 BCE to the color red in Abstract Expressionism, and everything in between.

• Search for anything, from shoes to all things gold • Scroll through art by time—see how Van Gogh’s works went from gloomy to vivid • Browse by color and learn about Monet’s 50 shades of gray • Find a new fascinating story to discover every day—today, it’s nine powerful men in heels

You can also use this app when visiting a real life museum. For the interested, you can download it for for iOS and Android.

Memory material with functions resembling synapses and neurons in the brain

This work comes from the University of Twente’s MESA+ Institute for Nanotechnology according to a July 8, 2016 news item on ScienceDaily,

Our brain does not work like a typical computer memory storing just ones and zeroes: thanks to a much larger variation in memory states, it can calculate faster consuming less energy. Scientists of the MESA+ Institute for Nanotechnology of the University of Twente (The Netherlands) now developed a ferro-electric material with a memory function resembling synapses and neurons in the brain, resulting in a multistate memory. …

A July 8, 2016 University of Twente press release, which originated the news item, provides more technical detail,

The material that could be the basic building block for ‘brain-inspired computing’ is lead-zirconium-titanate (PZT): a sandwich of materials with several attractive properties. One of them is that it is ferro-electric: you can switch it to a desired state, this state remains stable after the electric field is gone. This is called polarization: it leads to a fast memory function that is non-volatile. Combined with processor chips, a computer could be designed that starts much faster, for example. The UT scientists now added a thin layer of zinc oxide to the PZT, 25 nanometer thickness. They discovered that switching from one state to another not only happens from ‘zero’ to ‘one’ vice versa. It is possible to control smaller areas within the crystal: will they be polarized (‘flip’) or not?

In a PZT layer without zinc oxide (ZnO) there are basically two memorystates. Adding a nano layer of ZnO, every state in between is possible as well.

Multistate

By using variable writing times in those smaller areas, the result is that many states can be stored anywhere between zero and one. This resembles the way synapses and neurons ‘weigh’ signals in our brain. Multistate memories, coupled to transistors, could drastically improve the speed of pattern recognition, for example: our brain performs this kind of tasks consuming only a fraction of the energy a computer system needs. Looking at the graphs, the writing times seem quite long compared to nowaday’s processor speeds, but it is possible to create many memories in parallel. The function of the brain has already been mimicked in software like neurale networks, but in that case conventional digital hardware is still a limitation. The new material is a first step towards electronic hardware with a brain-like memory. Finding solutions for combining PZT with semiconductors, or even developing new kinds of semiconductors for this, is one of the next steps.

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

Multistability in Bistable Ferroelectric Materials toward Adaptive Applications by Anirban Ghosh, Gertjan Koster, and Guus Rijnders. Advanced Functional Materials DOI: 10.1002/adfm.201601353 Version of Record online: 4 JUL 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Using light to make gold crystal nanoparticles

Gold crystal nanoparticles? Courtesy: University of Florida

Gold crystal nanoparticles? Courtesy: University of Florida

A team from the University of Florida has used gold instead of silver in a process known as plasmon-driven synthesis. From a July 8, 2016 news item on phys.org,

A team of University of Florida researchers has figured out how gold can be used in crystals grown by light to create nanoparticles, a discovery that has major implications for industry and cancer treatment and could improve the function of pharmaceuticals, medical equipment and solar panels.

A July 6, 2016 University of Florida news release, which originated the news item, provides more detail,

Nanoparticles can be “grown” in crystal formations with special use of light, in a process called plasmon-driven synthesis. However, scientists have had limited control unless they used silver, but silver limits the uses for medical technology. The team is the first to successfully use gold, which works well within the human body, with this process.

“How does light actually play a role in the synthesis? [This knowledge] was not well developed,” said David Wei, an associate professor of chemistry who led the research team. “Gold was the model system to demonstrate this.”

Gold is highly desired for nanotechnology because it is malleable, does not react with oxygen and conducts heat well. Those properties make gold an ideal material for nanoparticles, especially those that will be placed in the body.

When polyvinylpyrrolidone, or PVP, a substance commonly found in pharmaceutical tablets, is used in the plasmon-driven synthesis, it enables scientists to better control the growth of crystals. In Wei’s research, PVP surprised the team by showing its potential to relay light-generated “hot” electrons to a gold surface to grow the crystals.

The research describes the first plasmonic synthesis strategy that can make high-yield gold nanoprisms. Even more exciting, the team has demonstrated that visible-range and low-power light can be used in the synthesis. Combined with nanoparticles being used in solar photovoltaic devices, this method can even harness solar energy for chemical synthesis, to make nanomaterials or for general applications in chemistry.

Wei has spent the last decade working in nanotechnology. He is intrigued by its applications in photochemistry and biomedicine, especially in targeted drug delivery and photothermal therapeutics, which is crucial to cancer treatment. His team includes collaborators from Pacific Northwest National Laboratory, where he has worked as a visiting scholar, and Brookhaven National Laboratory. In addition, the project has provided an educational opportunity for chemistry students: one high school student (through UF’s Student Science Training Program), two University scholars who also [sic] funded by the Howard Hughes Medical Institute, five graduate students and two postdocs.

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

Polyvinylpyrrolidone-induced anisotropic growth of gold nanoprisms in plasmon-driven synthesis by Yueming Zhai, Joseph S. DuChene, Yi-Chung Wang, Jingjing Qiu, Aaron C. Johnston-Peck, Bo You, Wenxiao Guo, Benedetto DiCiaccio, Kun Qian, Evan W. Zhao, Frances Ooi, Dehong Hu, Dong Su, Eric A. Stach, Zihua Zhu, & Wei David Wei. Nature Materials (2016) doi:10.1038/nmat4683 Published online 04 July 2016

This paper is behind a paywall.