Tag Archives: Northwestern University

The inside scoop on beetle exoskeletons

In the past I’ve covered work on the Namib beetle and its bumps which allow it to access condensation from the air in one of the hottest places on earth and work on jewel beetles and how their structural colo(u)r is derived. Now, there’s research into a beetle’s body armor from the University of Nebraska-Lincoln according to a Feb. 22, 2017 news item on ScienceDaily,

Beetles wear a body armor that should weigh them down — think medieval knights and turtles. In fact, those hard shells protecting delicate wings are surprisingly light, allowing even flight.

Better understanding the structure and properties of beetle exoskeletons could help scientists engineer lighter, stronger materials. Such materials could, for example, reduce gas-guzzling drag in vehicles and airplanes and reduce the weight of armor, lightening the load for the 21st-century knight.

But revealing exoskeleton architecture at the nanoscale has proven difficult. Nebraska’s Ruiguo Yang, assistant professor of mechanical and materials engineering, and his colleagues found a way to analyze the fibrous nanostructure. …

A Feb. 22, 2017 University of Nebraska-Lincoln news release by Gillian Klucas (also on EurekAlert), which originated the news item, describes skeletons and the work in more detail,

The lightweight exoskeleton is composed of chitin fibers just around 20 nanometers in diameter (a human hair measures approximately 75,000 nanometers in diameter) and packed and piled into layers that twist in a spiral, like a spiral staircase. The small diameter and helical twisting, known as Bouligand, make the structure difficult to analyze.

Yang and his team developed a method of slicing down the spiral to reveal a surface of cross-sections of fibers at different orientations. From that viewpoint, the researchers were able to analyze the fibers’ mechanical properties with the aid of an atomic force microscope. This type of microscope applies a tiny force to a test sample, deforms the sample and monitors the sample’s response. Combining the experimental procedure and theoretical analysis, the researchers were able to reveal the nanoscale architecture of the exoskeleton and the material properties of the nanofibers.

Yang holds a piece of the atomic force microscope used to measure the beetle's surface. A small wire can barely be seen in the middle of the piece. Unseen is a two-nano-size probe attached to the wire, which does the actual measuring.

Craig Chandler | University Communication

Yang holds a piece of the atomic force microscope used to measure the beetle’s surface. A small wire can barely be seen in the middle of the piece. Unseen is a two-nano-size probe attached to the wire, which does the actual measuring.

They made their discoveries in the common figeater beetle, Cotinis mutabilis, a metallic green native of the western United States. But the technique can be used on other beetles and hard-shelled creatures and might also extend to artificial materials with fibrous structures, Yang said.

Comparing beetles with differing demands on their exoskeletons, such as defending against predators or environmental damage, could lead to evolutionary insights as well as a better understanding of the relationship between structural features and their properties.

Yang’s co-authors are Alireza Zaheri and Horacio Espinosa of Northwestern University; Wei Gao of the University of Texas at San Antonio; and Cheryl Hayashi of the University of California, Riverside.

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

Exoskeletons: AFM Identification of Beetle Exocuticle: Bouligand Structure and Nanofiber Anisotropic Elastic Properties by Ruiguo Yang, Alireza Zaheri,Wei Gao, Charely Hayashi, Horacio D. Espinosa. Adv. Funct. Mater. vol. 27 (6) 2017 DOI: 10.1002/adfm.201770031 First published: 8 February 2017

This paper is behind a paywall.

A DNA switch for new electronic applications

I little dreamed when reading “The Double Helix : A Personal Account of the Discovery of the Structure of DNA” by James Watson that DNA (deoxyribonucleic acid) would one day become just another material for scientists to manipulate. A Feb. 20, 2017 news item on ScienceDaily describes the use of DNA as a material in electronics applications,

DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices.

Much like flipping your light switch at home — only on a scale 1,000 times smaller than a human hair — an ASU [Arizona State University]-led team has now developed the first controllable DNA switch to regulate the flow of electricity within a single, atomic-sized molecule. The new study, led by ASU Biodesign Institute researcher Nongjian Tao, was published in the advanced online journal Nature Communications.

DNA, the stuff of life, may very well also pack quite the jolt for engineers trying to advance the development of tiny, low-cost electronic devices. Courtesy: ASU

A Feb. 20, 2017 ASU news release (also on EurekAlert), which originated the news item, provides more detail,

“It has been established that charge transport is possible in DNA, but for a useful device, one wants to be able to turn the charge transport on and off. We achieved this goal by chemically modifying DNA,” said Tao, who directs the Biodesign Center for Bioelectronics and Biosensors and is a professor in the Fulton Schools of Engineering. “Not only that, but we can also adapt the modified DNA as a probe to measure reactions at the single-molecule level. This provides a unique way for studying important reactions implicated in disease, or photosynthesis reactions for novel renewable energy applications.”

Engineers often think of electricity like water, and the research team’s new DNA switch acts to control the flow of electrons on and off, just like water coming out of a faucet.

Previously, Tao’s research group had made several discoveries to understand and manipulate DNA to more finely tune the flow of electricity through it. They found they could make DNA behave in different ways — and could cajole electrons to flow like waves according to quantum mechanics, or “hop” like rabbits in the way electricity in a copper wire works —creating an exciting new avenue for DNA-based, nano-electronic applications.

Tao assembled a multidisciplinary team for the project, including ASU postdoctoral student Limin Xiang and Li Yueqi performing bench experiments, Julio Palma working on the theoretical framework, with further help and oversight from collaborators Vladimiro Mujica (ASU) and Mark Ratner (Northwestern University).

To accomplish their engineering feat, Tao’s group, modified just one of DNA’s iconic double helix chemical letters, abbreviated as A, C, T or G, with another chemical group, called anthraquinone (Aq). Anthraquinone is a three-ringed carbon structure that can be inserted in between DNA base pairs but contains what chemists call a redox group (short for reduction, or gaining electrons or oxidation, losing electrons).

These chemical groups are also the foundation for how our bodies’ convert chemical energy through switches that send all of the electrical pulses in our brains, our hearts and communicate signals within every cell that may be implicated in the most prevalent diseases.

The modified Aq-DNA helix could now help it perform the switch, slipping comfortably in between the rungs that make up the ladder of the DNA helix, and bestowing it with a new found ability to reversibly gain or lose electrons.

Through their studies, when they sandwiched the DNA between a pair of electrodes, they careful [sic] controlled their electrical field and measured the ability of the modified DNA to conduct electricity. This was performed using a staple of nano-electronics, a scanning tunneling microscope, which acts like the tip of an electrode to complete a connection, being repeatedly pulled in and out of contact with the DNA molecules in the solution like a finger touching a water droplet.

“We found the electron transport mechanism in the present anthraquinone-DNA system favors electron “hopping” via anthraquinone and stacked DNA bases,” said Tao. In addition, they found they could reversibly control the conductance states to make the DNA switch on (high-conductance) or switch-off (low conductance). When anthraquinone has gained the most electrons (its most-reduced state), it is far more conductive, and the team finely mapped out a 3-D picture to account for how anthraquinone controlled the electrical state of the DNA.

For their next project, they hope to extend their studies to get one step closer toward making DNA nano-devices a reality.

“We are particularly excited that the engineered DNA provides a nice tool to examine redox reaction kinetics, and thermodynamics the single molecule level,” said Tao.

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

I last featured Tao’s work with DNA in an April 20, 2015 posting.

Gate-controlled conductance switching in DNA by Limin Xiang, Julio L. Palma, Yueqi Li, Vladimiro Mujica, Mark A. Ratner, & Nongjian Tao.  Nature Communications 8, Article number: 14471 (2017)  doi:10.1038/ncomms14471 Published online: 20 February 2017

This paper is open access.

Nominations open for Kabiller Prizes in Nanoscience and Nanomedicine ($250,000 for visionary researcher and $10,000 for young investigator)

For a change I can publish something that doesn’t have a deadline in three days or less! Without more ado (from a Feb. 20, 2017 Northwestern University news release by Megan Fellman [h/t Nanowerk’s Feb. 20, 2017 news item]),

Northwestern University’s International Institute for Nanotechnology (IIN) is now accepting nominations for two prestigious international prizes: the $250,000 Kabiller Prize in Nanoscience and Nanomedicine and the $10,000 Kabiller Young Investigator Award in Nanoscience and Nanomedicine.

The deadline for nominations is May 15, 2017. Details are available on the IIN website.

“Our goal is to recognize the outstanding accomplishments in nanoscience and nanomedicine that have the potential to benefit all humankind,” said David G. Kabiller, a Northwestern trustee and alumnus. He is a co-founder of AQR Capital Management, a global investment management firm in Greenwich, Connecticut.

The two prizes, awarded every other year, were established in 2015 through a generous gift from Kabiller. Current Northwestern-affiliated researchers are not eligible for nomination until 2018 for the 2019 prizes.

The Kabiller Prize — the largest monetary award in the world for outstanding achievement in the field of nanomedicine — celebrates researchers who have made the most significant contributions to the field of nanotechnology and its application to medicine and biology.

The Kabiller Young Investigator Award recognizes young emerging researchers who have made recent groundbreaking discoveries with the potential to make a lasting impact in nanoscience and nanomedicine.

“The IIN at Northwestern University is a hub of excellence in the field of nanotechnology,” said Kabiller, chair of the IIN executive council and a graduate of Northwestern’s Weinberg College of Arts and Sciences and Kellogg School of Management. “As such, it is the ideal organization from which to launch these awards recognizing outstanding achievements that have the potential to substantially benefit society.”

Nanoparticles for medical use are typically no larger than 100 nanometers — comparable in size to the molecules in the body. At this scale, the essential properties (e.g., color, melting point, conductivity, etc.) of structures behave uniquely. Researchers are capitalizing on these unique properties in their quest to realize life-changing advances in the diagnosis, treatment and prevention of disease.

“Nanotechnology is one of the key areas of distinction at Northwestern,” said Chad A. Mirkin, IIN director and George B. Rathmann Professor of Chemistry in Weinberg. “We are very grateful for David’s ongoing support and are honored to be stewards of these prestigious awards.”

An international committee of experts in the field will select the winners of the 2017 Kabiller Prize and the 2017 Kabiller Young Investigator Award and announce them in September.

The recipients will be honored at an awards banquet Sept. 27 in Chicago. They also will be recognized at the 2017 IIN Symposium, which will include talks from prestigious speakers, including 2016 Nobel Laureate in Chemistry Ben Feringa, from the University of Groningen, the Netherlands.

2015 recipient of the Kabiller Prize

The winner of the inaugural Kabiller Prize, in 2015, was Joseph DeSimone the Chancellor’s Eminent Professor of Chemistry at the University of North Carolina at Chapel Hill and the William R. Kenan Jr. Distinguished Professor of Chemical Engineering at North Carolina State University and of Chemistry at UNC-Chapel Hill.

DeSimone was honored for his invention of particle replication in non-wetting templates (PRINT) technology that enables the fabrication of precisely defined, shape-specific nanoparticles for advances in disease treatment and prevention. Nanoparticles made with PRINT technology are being used to develop new cancer treatments, inhalable therapeutics for treating pulmonary diseases, such as cystic fibrosis and asthma, and next-generation vaccines for malaria, pneumonia and dengue.

2015 recipient of the Kabiller Young Investigator Award

Warren Chan, professor at the Institute of Biomaterials and Biomedical Engineering at the University of Toronto, was the recipient of the inaugural Kabiller Young Investigator Award, also in 2015. Chan and his research group have developed an infectious disease diagnostic device for a point-of-care use that can differentiate symptoms.

BTW, Warren Chan, winner of the ‘Young Investigator Award’, and/or his work have been featured here a few times, most recently in a Nov. 1, 2016 posting, which is mostly about another award he won but also includes links to some his work including my April 27, 2016 post about the discovery that fewer than 1% of nanoparticle-based drugs reach their destination.

Nanomechanics for deciphering beetle exoskeletons

Beetles carry remarkably light yet strong armor in the form of their exoskeletons and a research team at Northwestern University (US) is looking to those beetle exoskeletons for inspiration according to a Jan. 11, 2017 news item on ScienceDaily,

What can a beetle tell us about good design principles? Quite a lot, actually.

Many insects and crustaceans possess hard, armor-like exoskeletons that, in theory, should weigh the creatures down. But, instead, the exoskeletons are surprisingly light — even allowing the armor-wearing insects, like the beetle, to fly.

Northwestern Engineering’s Horacio D. Espinosa and his group are working to understand the underlying design principles and mechanical properties that result in structures with these unique, ideal properties. This work could ultimately uncover information that could guide the design and manufacturing of new and improved artificial materials by emulating these time-tested natural patterns, a process known as bio-mimicry.

Supported by the Air Force Office of Scientific Research’s Multidisciplinary University Research Initiative (MURI), the research was featured on the cover of Advanced Functional Materials. Postdoctoral fellows Ruiguo Yang and Wei Gao and graduate student Alireza Zaheri, all members of Espinosa’s laboratory, were co-first authors of the paper. Cheryl Hayashi, professor of biology at the University of California, Riverside, was also a co-author.

A Jan. 11, 2017 Northwestern University news release, which originated the news item, expands on the theme,

Though there are more than a million species of beetles, the team is first studying the exoskeleton of the Cotinis mutabilis, a field crop pest beetle native to the western United States. Like all insects and crustaceans, its exoskeleton is composed of twisted plywood structures, known as Bouligand structures, which help protect against predators. Fibers in this Bouligand structure are bundles of chitin polymer chains wrapped with proteins. In this chain structure, each fiber has a higher density along the length than along the transverse.

“It is very challenging to characterize the properties of such fibers given that they are directionally dependent and have a small diameter of just 20 nanometers,” said Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at Northwestern’s McCormick School of Engineering. “We had to develop a novel characterization method by taking advantage of the spatial distribution of fibers in the Bouligand structure.”

To meet this challenge, Espinosa and his team employed a creative way to identify the geometry and material properties of the fibers that comprise the exoskeleton. They cut the Bouligand structure along a plane, resulting in a surface composed of closely packed cross-sections of fibers with different orientations. They were then able to analyze the mechanics of the fibers.

“With more than a million species, which greatly vary from each other in taxomic relatedness, size, and ecology, the beetle is the largest group of insects,” Hayashi said. “What makes this research exciting is that the methods applied to the Cotinis mutabilis beetle exoskeleton can be extended to other beetle species.”

By correlating the mechanical properties with the exoskeleton geometries from diverse beetle species, Espinosa and his team plan to gain insight into natural selection and better understand structure-function-properties relationships.

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

AFM Identification of Beetle Exocuticle: Bouligand Structure and Nanofiber Anisotropic Elastic Properties by Ruiguo Yang, Alireza Zaheri, Wei Gao, Cheryl Hayashi, and Horacio D. Espinosa. Advanced Functional Materials DOI: 10.1002/adfm.201603993 Version of Record online: 27 DEC 2016

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

This paper is behind a paywall.

Nanorods as multistate switches

This research goes beyond the binary (0 or 1) and to an analog state that resembles quantum states. Fascinating, yes? An Oct. 10, 2016 news item on phys.org tells more,

Rice University scientists have discovered how to subtly change the interior structure of semi-hollow nanorods in a way that alters how they interact with light, and because the changes are reversible, the method could form the basis of a nanoscale switch with enormous potential.

“It’s not 0-1, it’s 1-2-3-4-5-6-7-8-9-10,” said Rice materials scientist Emilie Ringe, lead scientist on the project, which is detailed in the American Chemical Society journal Nano Letters. “You can differentiate between multiple plasmonic states in a single particle. That gives you a kind of analog version of quantum states, but on a larger, more accessible scale.”

Ringe and colleagues used an electron beam to move silver from one location to another inside gold-and-silver nanoparticles, something like a nanoscale Etch A Sketch. The result is a reconfigurable optical switch that may form the basis for a new type of multiple-state computer memory, sensor or catalyst.

An Oct. 10, 2016 Rice University news release, which originated the news item, describes the work in additional detail,

At about 200 nanometers long, 500 of the metal rods placed end-to-end would span the width of a human hair. However, they are large in comparison with modern integrated circuits. Their multistate capabilities make them more like reprogrammable bar codes than simple memory bits, she said.

“No one has been able to reversibly change the shape of a single particle with the level of control we have, so we’re really excited about this,” Ringe said.

Altering a nanoparticle’s internal structure also alters its external plasmonic response. Plasmons are the electrical ripples that propagate across the surface of metallic materials when excited by light, and their oscillations can be easily read with a spectrometer — or even the human eye — as they interact with visible light.

The Rice researchers found they could reconfigure nanoparticle cores with pinpoint precision. That means memories made of nanorods need not be merely on-off, Ringe said, because a particle can be programmed to emit many distinct plasmonic patterns.

The discovery came about when Ringe and her team, which manages Rice’s advanced electron microscopy lab, were asked by her colleague and co-author Denis Boudreau, a professor at Laval University in Quebec, to characterize hollow nanorods made primarily of gold but containing silver.

“Most nanoshells are leaky,” Ringe said. “They have pinholes. But we realized these nanorods were defect-free and contained pockets of water that were trapped inside when the particles were synthesized. We thought: We have something here.”

Ringe and the study’s lead author, Rice research scientist Sadegh Yazdi, quickly realized how they might manipulate the water. “Obviously, it’s difficult to do chemistry there, because you can’t put molecules into a sealed nanoshell. But we could put electrons in,” she said.

Focusing a subnanometer electron beam on the interior cavity split the water and inserted solvated electrons – free electrons that can exist in a solution. “The electrons reacted directly with silver ions in the water, drawing them to the beam to form silver,” Ringe said. The now-silver-poor liquid moved away from the beam, and its silver ions were replenished by a reaction of water-splitting byproducts with the solid silver in other parts of the rod.

“We actually were moving silver in the solution, reconfiguring it,” she said. “Because it’s a closed system, we weren’t losing anything and we weren’t gaining anything. We were just moving it around, and could do so as many times as we wished.”

The researchers were then able to map the plasmon-induced near-field properties without disturbing the internal structure — and that’s when they realized the implications of their discovery.

“We made different shapes inside the nanorods, and because we specialize in plasmonics, we mapped the plasmons and it turned out to have a very nice effect,” Ringe said. “We basically saw different electric-field distributions at different energies for different shapes.” Numerical results provided by collaborators Nicolas Large of the University of Texas at San Antonio and George Schatz of Northwestern University helped explain the origin of the modes and how the presence of a water-filled pocket created a multitude of plasmons, she said.

The next challenge is to test nanoshells of other shapes and sizes, and to see if there are other ways to activate their switching potentials. Ringe suspects electron beams may remain the best and perhaps only way to catalyze reactions inside particles, and she is hopeful.

“Using an electron beam is actually not as technologically irrelevant as you might think,” she said. “Electron beams are very easy to generate. And yes, things need to be in vacuum, but other than that, people have generated electron beams for nearly 100 years. I’m sure 40 years ago people were saying, ‘You’re going to put a laser in a disk reader? That’s crazy!’ But they managed to do it.

“I don’t think it’s unfeasible to miniaturize electron-beam technology. Humans are good at moving electrons and electricity around. We figured that out a long time ago,” Ringe said.

The research should trigger the imaginations of scientists working to create nanoscale machines and processes, she said.

“This is a reconfigurable unit that you can access with light,” she said. “Reading something with light is much faster than reading with electrons, so I think this is going to get attention from people who think about dynamic systems and people who think about how to go beyond current nanotechnology. This really opens up a new field.”

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

Reversible Shape and Plasmon Tuning in Hollow AgAu Nanorods by Sadegh Yazdi, Josée R. Daniel, Nicolas Large, George C. Schatz, Denis Boudreau, and Emilie Ringe. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.6b02946 Publication Date (Web): October 5, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

The researchers have made this video available for the public,

2016 Nobel Chemistry Prize for molecular machines

Wednesday, Oct. 5, 2016 was the day three scientists received the Nobel Prize in Chemistry for their work on molecular machines, according to an Oct. 5, 2016 news item on phys.org,

Three scientists won the Nobel Prize in chemistry on Wednesday [Oct. 5, 2016] for developing the world’s smallest machines, 1,000 times thinner than a human hair but with the potential to revolutionize computer and energy systems.

Frenchman Jean-Pierre Sauvage, Scottish-born Fraser Stoddart and Dutch scientist Bernard “Ben” Feringa share the 8 million kronor ($930,000) prize for the “design and synthesis of molecular machines,” the Royal Swedish Academy of Sciences said.

Machines at the molecular level have taken chemistry to a new dimension and “will most likely be used in the development of things such as new materials, sensors and energy storage systems,” the academy said.

Practical applications are still far away—the academy said molecular motors are at the same stage that electrical motors were in the first half of the 19th century—but the potential is huge.

Dexter Johnson in an Oct. 5, 2016 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) provides some insight into the matter (Note: A link has been removed),

In what seems to have come both as a shock to some of the recipients and a confirmation to all those who envision molecular nanotechnology as the true future of nanotechnology, Bernard Feringa, Jean-Pierre Sauvage, and Sir J. Fraser Stoddart have been awarded the 2016 Nobel Prize in Chemistry for their development of molecular machines.

The Nobel Prize was awarded to all three of the scientists based on their complementary work over nearly three decades. First, in 1983, Sauvage (currently at Strasbourg University in France) was able to link two ring-shaped molecules to form a chain. Then, eight years later, Stoddart, a professor at Northwestern University in Evanston, Ill., demonstrated that a molecular ring could turn on a thin molecular axle. Then, eight years after that, Feringa, a professor at the University of Groningen, in the Netherlands, built on Stoddardt’s work and fabricated a molecular rotor blade that could spin continually in the same direction.

Speaking of the Nobel committee’s selection, Donna Nelson, a chemist and president of the American Chemical Society told Scientific American: “I think this topic is going to be fabulous for science. When the Nobel Prize is given, it inspires a lot of interest in the topic by other researchers. It will also increase funding.” Nelson added that this line of research will be fascinating for kids. “They can visualize it, and imagine a nanocar. This comes at a great time, when we need to inspire the next generation of scientists.”

The Economist, which appears to be previewing an article about the 2016 Nobel prizes ahead of the print version, has this to say in its Oct. 8, 2016 article,

BIGGER is not always better. Anyone who doubts that has only to look at the explosion of computing power which has marked the past half-century. This was made possible by continual shrinkage of the components computers are made from. That success has, in turn, inspired a search for other areas where shrinkage might also yield dividends.

One such, which has been poised delicately between hype and hope since the 1990s, is nanotechnology. What people mean by this term has varied over the years—to the extent that cynics might be forgiven for wondering if it is more than just a fancy rebranding of the word “chemistry”—but nanotechnology did originally have a fairly clear definition. It was the idea that machines with moving parts could be made on a molecular scale. And in recognition of this goal Sweden’s Royal Academy of Science this week decided to award this year’s Nobel prize for chemistry to three researchers, Jean-Pierre Sauvage, Sir Fraser Stoddart and Bernard Feringa, who have never lost sight of nanotechnology’s original objective.

Optimists talk of manufacturing molecule-sized machines ranging from drug-delivery devices to miniature computers. Pessimists recall that nanotechnology is a field that has been puffed up repeatedly by both researchers and investors, only to deflate in the face of practical difficulties.

There is, though, reason to hope it will work in the end. This is because, as is often the case with human inventions, Mother Nature has got there first. One way to think of living cells is as assemblies of nanotechnological machines. For example, the enzyme that produces adenosine triphosphate (ATP)—a molecule used in almost all living cells to fuel biochemical reactions—includes a spinning molecular machine rather like Dr Feringa’s invention. This works well. The ATP generators in a human body turn out so much of the stuff that over the course of a day they create almost a body-weight’s-worth of it. Do something equivalent commercially, and the hype around nanotechnology might prove itself justified.

Congratulations to the three winners!

Not exactly ‘Prey’: self-organizing materials that can mimic swarm behaviour

Prey, a 2002 novel by Michael Crichton, focused on nanotechnology and other emerging technologies and how their development could lead to unleashing swarms of nanobots with agendas of their own. Crichton’s swarms had collective artificial intelligence, and could massive themselves together to take on different macroscale shapes to achieve their own ends. This latest development has nowhere near that potential—not yet and probably never. From a July 21, 2016 news item on ScienceDaily,

A new study by an international team of researchers, affiliated with Ulsan National Institute of Science and Technology (UNIST) [Korea] has announced that they have succeeded in demonstarting control over the interactions occurring among microscopic spheres, which cause them to self-propel into swarms, chains, and clusters.

The research published in the current online edition of Nature Materials takes lessons from cooperation in nature, including that observed in honey bee swarms and bacterial clusters. In the study, the team has successfully demonstrated the self-organizing pattern formation in active materials at microscale by modifying only one parameter.

A July 21, 2016 UNIST press release, which originated the news item, expands on the theme,

This breakthrough comes from a research, conducted by Dr. Steve Granick (School of Natural Science, UNIST) of IBS Center for Soft and Living Matter in collaboration with Dr. Erik Luijten from Northwestern University. Ming Han, a PhD student in Luijten’s laboratory, and Jing Yan, a former graduate student at the University of Illinois, served as co-first authors of the paper.

Researchers expect that such active particles could open a new class of technologies with applications in medicine, chemistry, and engineering as well as advance scientists’ fundamental understanding of collective, dynamic behavior in systems.

According to the research team, the significance of team work was stressed by both Dr. Luijten and Dr. Granick as this current breakthrough is part of a longtime partnership using a new class of soft-matter particles known as Janus colloids, which Dr. Granick had earlier created in his laboratory. The theoretical computer simulations were completed by the team, led by Dr. Luijten and Dr. Granick used these colloids to experimentally test the collective, dynamic behavior in the laboratory.

The micron-sized spheres, typically suspended in solution, were named after the Roman god with two faces as they have attractive interactions on one side and negative charges on the other side.

The electrostatic interactions between the two sides of the self-propelled spheres could be manipulated by subjecting the colloids to an electric field. Some experienced stronger repulsions between their forward-facing sides, while others went through the opposite. Along with them, another set remained completely neutral. This imbalance caused the self-propelled particles to swim and self-organize into one of the following patterns, which are swarms, chains, clusters and isotropic gases.

To avoid head-to-head collisions, head-repulsive particles swam side-by-side, forming into swarms. Depending on the electric-field frequency, tail-repulsive particles positioned their tails apart, thus encouraging them to face each other to form jammed clusters of high local density. Also, swimmers with equal-and-opposite charges attracted one another into connected chains.

Dr. Granick states, “This truly is a joint work of the technological know-how by the Korean IBS and the University of Illinois, as well as the computer simulations technology by Northwestern University.” He expects that this breakthrough has probable application in sensing, drug delivery, or even microrobotics.

With this discovery, a drug could be placed within particles, for instance, that cluster into the delivery spot. Moreover, alterations in the environment could be perceived if the system unexpectedly switches from swarming to forming chains.

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

Reconfiguring active particles by electrostatic imbalance by Jing Yan, Ming Han, Jie Zhang, Cong Xu, Erik Luijten, & Steve Granick. Nature Materials (2016)  doi:10.1038/nmat4696 Published online 11 July 2016

This paper is behind a paywall.

Ultimate discovery tool?

For anyone familiar with the US nanomedicine scene, Chad Mirkin’s appearance in this announcement from Northwestern University isn’t much of a surprise.  From a June 23, 2016 news item on ScienceDaily,

The discovery power of the gene chip is coming to nanotechnology. A Northwestern University research team is developing a tool to rapidly test millions and perhaps even billions or more different nanoparticles at one time to zero in on the best particle for a specific use.

When materials are miniaturized, their properties—optical, structural, electrical, mechanical and chemical—change, offering new possibilities. But determining what nanoparticle size and composition are best for a given application, such as catalysts, biodiagnostic labels, pharmaceuticals and electronic devices, is a daunting task.

“As scientists, we’ve only just begun to investigate what materials can be made on the nanoscale,” said Northwestern’s Chad A. Mirkin, a world leader in nanotechnology research and its application, who led the study. “Screening a million potentially useful nanoparticles, for example, could take several lifetimes. Once optimized, our tool will enable researchers to pick the winner much faster than conventional methods. We have the ultimate discovery tool.”

A June 23, 2016 Northwestern University news release (also on EurekAlert), which originated the news item, describes the work in more detail,

Using a Northwestern technique that deposits materials on a surface, Mirkin and his team figured out how to make combinatorial libraries of nanoparticles in a very controlled way. (A combinatorial library is a collection of systematically varied structures encoded at specific sites on a surface.) Their study will be published June 24 by the journal Science.

The nanoparticle libraries are much like a gene chip, Mirkin says, where thousands of different spots of DNA are used to identify the presence of a disease or toxin. Thousands of reactions can be done simultaneously, providing results in just a few hours. Similarly, Mirkin and his team’s libraries will enable scientists to rapidly make and screen millions to billions of nanoparticles of different compositions and sizes for desirable physical and chemical properties.

“The ability to make libraries of nanoparticles will open a new field of nanocombinatorics, where size — on a scale that matters — and composition become tunable parameters,” Mirkin said. “This is a powerful approach to discovery science.”

“I liken our combinatorial nanopatterning approach to providing a broad palette of bold colors to an artist who previously had been working with a handful of dull and pale black, white and grey pastels,” said co-author Vinayak P. Dravid, the Abraham Harris Professor of Materials Science and Engineering in the McCormick School of Engineering.

Using five metallic elements — gold, silver, cobalt, copper and nickel — Mirkin and his team developed an array of unique structures by varying every elemental combination. In previous work, the researchers had shown that particle diameter also can be varied deliberately on the 1- to 100-nanometer length scale.

Some of the compositions can be found in nature, but more than half of them have never existed before on Earth. And when pictured using high-powered imaging techniques, the nanoparticles appear like an array of colorful Easter eggs, each compositional element contributing to the palette.

To build the combinatorial libraries, Mirkin and his team used Dip-Pen Nanolithography, a technique developed at Northwestern in 1999, to deposit onto a surface individual polymer “dots,” each loaded with different metal salts of interest. The researchers then heated the polymer dots, reducing the salts to metal atoms and forming a single nanoparticle. The size of the polymer dot can be varied to change the size of the final nanoparticle.

This control of both size and composition of nanoparticles is very important, Mirkin stressed. Having demonstrated control, the researchers used the tool to systematically generate a library of 31 nanostructures using the five different metals.

To help analyze the complex elemental compositions and size/shape of the nanoparticles down to the sub-nanometer scale, the team turned to Dravid, Mirkin’s longtime friend and collaborator. Dravid, founding director of Northwestern’s NUANCE Center, contributed his expertise and the advanced electron microscopes of NUANCE to spatially map the compositional trajectories of the combinatorial nanoparticles.

Now, scientists can begin to study these nanoparticles as well as build other useful combinatorial libraries consisting of billions of structures that subtly differ in size and composition. These structures may become the next materials that power fuel cells, efficiently harvest solar energy and convert it into useful fuels, and catalyze reactions that take low-value feedstocks from the petroleum industry and turn them into high-value products useful in the chemical and pharmaceutical industries.

Here’s a diagram illustrating the work,

 Caption: A combinatorial library of polyelemental nanoparticles was developed using Dip-Pen Nanolithography. This novel nanoparticle library opens up a new field of nanocombinatorics for rapid screening of nanomaterials for a multitude of properties. Credit: Peng-Cheng Chen/James Hedrick

Caption: A combinatorial library of polyelemental nanoparticles was developed using Dip-Pen Nanolithography. This novel nanoparticle library opens up a new field of nanocombinatorics for rapid screening of nanomaterials for a multitude of properties. Credit: Peng-Cheng Chen/James Hedrick

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

Polyelemental nanoparticle libraries by Peng-Cheng Chen, Xiaolong Liu, James L. Hedrick, Zhuang Xie, Shunzhi Wang, Qing-Yuan Lin, Mark C. Hersam, Vinayak P. Dravid, Chad A. Mirkin. Science  24 Jun 2016: Vol. 352, Issue 6293, pp. 1565-1569 DOI: 10.1126/science.aaf8402

This paper is behind a paywall.

Congratulations to Markus Buehler on his Foresight Institute Feynman Prize for advances in nanotechnology

A May 24, 2016 Massachusetts Institute of Technology (MIT) news release celebrates Markus Buehler’s latest award,

On May 21 [2016], Department of Civil and Environmental Engineering head and McAfee Professor of Engineering Markus J. Buehler received the 2015 Foresight Institute Feynman Prize in Theoretical Molecular Nanotechnology. Buehler’s award was one of three prizes presented by the Foresight Institute, a leading think tank and public interest organization, at its annual conference in Palo Alto, California. …

The Foresight Institute recognized Buehler for his important contributions to making nanotechnology scalable for large-scale materials applications, enabled by bottom-up multiscale computational methods, and linking new manufacturing and characterization methods.

Focusing on mechanical properties — especially deformation and failure — and translation from biological materials and structures to bio-inspired synthetic materials, his work has led to the development and application of new modeling, design, and manufacturing approaches for advanced materials that offer greater resilience and a wide range of controllable properties from the nano- to the macroscale.

Buehler’s signature achievement, according to the Institute, is the application of molecular and chemical principles in the analysis of mechanical systems, with the aim to design devices and materials that provide a defined set of functions.

“It’s an incredible honor to receive such an esteemed award. I owe this to the outstanding students and postdocs whom I had a pleasure to work with over the years, my colleagues, as well my own mentors,” Buehler said. “Richard Feynman was a revolutionary scientist of his generation. It’s a privilege to share his goals of researching molecular technology at very small scale to create new, more efficient, and better lasting materials at much larger scale that will help transform lives and industries.”

The two other award winners are Professor Michelle Y. Simmons of the University of New South Wales [Australia], who won the Feynman Prize for Experimental Molecular Nanotechnology, and Northwestern University graduate student Chuyang Cheng, who won the Distinguished Student Award.

I have featured Buehler’s work here a number of times. The most recent appearance was in  a May 29, 2015 posting about synthesizing spider’s silk.

“One minus one equals zero” has been disproved

Two mirror-image molecules can be optically active according to an April 27, 2016 news item on ScienceDaily,

In 1848, Louis Pasteur showed that molecules that are mirror images of each other had exactly opposite rotations of light. When mixed in solution, they cancel the effects of the other, and no rotation of light is observed. Now, a research team has demonstrated that a mixture of mirror-image molecules crystallized in the solid state can be optically active.

An April 26, 2016 Northwestern University news release (also on EurekAlert), which originated the news item, expands on the theme,

In the world of chemistry, one minus one almost always equals zero.

But new research from Northwestern University and the Centre National de la Recherche Scientifique (CNRS) in France shows that is not always the case. And the discovery will change scientists’ understanding of mirror-image molecules and their optical activity.

Now, Northwestern’s Kenneth R. Poeppelmeier and his research team are the first to demonstrate that a mixture of mirror-image molecules crystallized in the solid state can be optically active. The scientists first designed and made the materials and then measured their optical properties.

“In our case, one minus one does not always equal zero,” said first author Romain Gautier of CNRS. “This discovery will change scientists’ understanding of these molecules, and new applications could emerge from this observation.”

The property of rotating light, which has been known for more than two centuries to exist in many molecules, already has many applications in medicine, electronics, lasers and display devices.

“The phenomenon of optical activity can occur in a mixture of mirror-image molecules, and now we’ve measured it,” said Poeppelmeier, a Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences. “This is an important experiment.”

Although this phenomenon has been predicted for a long time, no one — until now — had created such a racemic mixture (a combination of equal amounts of mirror-image molecules) and measured the optical activity.

“How do you deliberately create these materials?” Poeppelmeier said. “That’s what excites me as a chemist.” He and Gautier painstakingly designed the material, using one of four possible solid-state arrangements known to exhibit circular dichroism (the ability to absorb differently the “rotated” light).

Next, Richard P. Van Duyne, a Morrison Professor of Chemistry at Northwestern, and graduate student Jordan M. Klingsporn measured the material’s optical activity, finding that mirror-image molecules are active when arranged in specific orientations in the solid state.

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

Optical activity from racemates by Romain Gautier, Jordan M. Klingsporn, Richard P. Van Duyne, & Kenneth R. Poeppelmeier. Nature Materials (2016) doi:10.1038/nmat4628 Published online 18 April 2016

This paper is behind a paywall.