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Nature inspires first artificial molecular pump

A blueprint for an artificial molecular pump that acts to organize rings in a high-energy state on a polymethylene chain. The flashing energy ratchet mechanism shows how redox chemistry can be used to prime the pump with rings (top) under reducing conditions and then have it pump the rings (bottom) under oxidative conditions into a high-energy state. Hypothetical distributions of the components of the pump on a simplified potential energy surface diagram are indicated by purple dots in the reduced state and blue dots in the oxidized state. A solid green arrow indicates a surmountable energy barrier. (credit: Chuyang Cheng et al./Nature Nanotechnology)

Northwestern University scientists have developed the first entirely artificial molecular pump, in which molecules pump other molecules. The pump might one day be used to power other molecular machines, such as artificial muscles.

The new machine mimics the pumping mechanism of proteins that move small molecules around living cells to metabolize and store energy from food. The artificial pump draws power from chemical reactions, driving molecules step-by-step from a low-energy state to a high-energy state — far away from equilibrium.

While nature has had billions of years to perfect its complex molecular machinery, modern science is now beginning to scratch the surface of what might be possible in tomorrow’s world.

Imitating how nature transfers energy

“Our molecular pump is radical chemistry — an ingenious way of transferring energy from molecule to molecule, the way nature does,” said Sir Fraser Stoddart, the senior author of the study. Stoddart is the Board of Trustees Professor of Chemistry in Northwestern’s Weinberg College of Arts and Sciences.

“All living organisms, including humans, must continuously transport and redistribute molecules around their cells, using vital carrier proteins,” he said. “We are trying to recreate the actions of these proteins using relatively simple small molecules we make in the laboratory.”

“In some respects, we are asking the molecules to behave in a way that they would not do normally,” Cheng said. “It is much like trying to push two magnets together. The ring-shaped molecules we work with repel one another under normal circumstances. The artificial pump is able to syphon off some of the energy that changes hands during a chemical reaction and uses it to push the rings together.”

The tiny molecular machine threads the rings around a nanoscopic chain — a sort of axle — and squeezes the rings together, with only a few nanometers separating them. At present, the artificial molecular pump is able to force only two rings together, but the researchers believe it won’t be long before they can extend its operation to tens of rings and store more energy.

Compared to nature’s system, the artificial pump is very simple, but it is a start, the researchers say. They have designed a novel system, using kinetic barriers, that allows molecules to flow “uphill” energetically.

Powering artificial muscles

“This is non-equilibrium chemistry, moving molecules far away from their minimum energy state, which is essential to life,” said Paul R. McGonigal, an author of the study. “Conducting non-equilibrium chemistry in this way, with simple artificial molecules, is one of the major challenges for science in the 21st century.”

Ultimately, they intend to use the energy stored in their pump to power artificial muscles and other molecular machines. The researchers also hope their design will inspire other chemists working in non-equilibrium chemistry.

“This is completely unlike the process of designing the machinery we are used to seeing in everyday life,” Stoddart said. “In a way, one must learn to see things from the molecules’ point of view, considering forces such as random thermal motion that one would never consider when building an agricultural water pump or any other mechanical device.”

The National Science Foundation supported the research, published May 18 in the journal Nature Nanotechnology.


Northwestern University | Artificial Molecular Pump Animation

Animation shows the steps of the pumping mechanism, which operates in response to redox cycling, with simplified illustrations of the corresponding energy profiles. The dumbbell and the ring repel each other initially, then reduction favors complexation both thermodynamically and kinetically. Oxidation restores the repulsion between the components and causes the ring to be trapped around the dumbbell during thermal relaxation. When another reduction step is performed, attraction of a second ring from the bulk solution is kinetically favored. After oxidation and thermal relaxation, the second ring falls into the same kinetic trap as the first, resulting in the mutually repulsive rings being held in close proximity to one another.

Abstract of An artificial molecular pump

Carrier proteins consume fuel in order to pump ions or molecules across cell membranes, creating concentration gradients. Their control over diffusion pathways, effected entirely through noncovalent bonding interactions, has inspired chemists to devise artificial systems that mimic their function. Here, we report a wholly artificial compound that acts on small molecules to create a gradient in their local concentration. It does so by using redox energy and precisely organized noncovalent bonding interactions to pump positively charged rings from solution and ensnare them around an oligomethylene chain, as part of a kinetically trapped entanglement. A redox-active viologen unit at the heart of a dumbbell-shaped molecular pump plays a dual role, first attracting and then repelling the rings during redox cycling, thereby enacting a flashing energy ratchet mechanism with a minimalistic design. Our artificial molecular pump performs work repetitively for two cycles of operation and drives rings away from equilibrium toward a higher local concentration.

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How to print stronger, bigger, conductive 3-D graphene structures for tissue engineering

3D graphene inks are produced by simple combination and mixing an elastomer solution with graphene powder in a graded solvent, followed by volume reduction and thickening, a process that can be scaled up to many liters at once (credit: Adam E. Jakus et al./ACS Nano)

Northwestern University researchers have developed a way to print large, robust 3-D structures with graphene-based ink.

The new method could allow for using graphene-printed scaffolds for regenerative medicine and other medical and electronic  applications.

“People have tried to print graphene before,” said Ramille Shah, assistant professor of materials science and engineering at the McCormick School of Engineering and of surgery in the Feinberg School of Medicine.  “But it’s been a mostly polymer composite with graphene making up less than 20 percent of the volume.”

Adding higher volumes of graphene flakes to the mix in these ink systems typically results in printed structures too brittle and fragile to manipulate. At 60–70 percent graphene, the new ink preserves the material’s unique properties, including its electrical conductivity. And it’s flexible and robust enough to print robust macroscopic structures.

The secret: graphene nanoflakes are mixed with a biocompatible elastomer and fast-evaporating solvents.

“After the ink is extruded, one of the solvents in the system evaporates right away, causing the structure to solidify nearly instantly,” Shah explained. “The presence of the other solvents and the interaction with the specific polymer binder chosen also has a significant contribution to its resulting flexibility and properties. Because it holds its shape, we are able to build larger, well-defined objects.”

Could allow neurons to grow and communicate

Shah said her team populated one of the scaffolds with stem cells to surprising results. Not only did the cells survive; they divided, proliferated, and morphed into neuron-like cells.

The printed graphene structure is also flexible and strong enough to be easily sutured to existing tissues, so it could be used for biodegradable sensors and medical implants. Shah said the biocompatible elastomer and graphene’s electrical conductivity most likely contributed to the scaffold’s biological success.

“Cells conduct electricity inherently — especially neurons,” Shah said. “So if they’re on a substrate that can help conduct that signal, they’re able to communicate over wider distances.”

Supported by a Google Gift and a McCormick Research Catalyst Award, the research is described in the paper published in the April 2015 issue of ACS Nano.

Abstract of Three-Dimensional Printing of High-Content Graphene Scaffolds for Electronic and Biomedical Applications

The exceptional properties of graphene enable applications in electronics, optoelectronics, energy storage, and structural composites. Here we demonstrate a 3D printable graphene (3DG) composite consisting of majority graphene and minority polylactide-co-glycolide, a biocompatible elastomer, 3D-printed from a liquid ink. This ink can be utilized under ambient conditions via extrusion-based 3D printing to create graphene structures with features as small as 100 μm composed of as few as two layers (<300 μm thick object) or many hundreds of layers (>10 cm thick object). The resulting 3DG material is mechanically robust and flexible while retaining electrical conductivities greater than 800 S/m, an order of magnitude increase over previously reported 3D-printed carbon materials. In vitro experiments in simple growth medium, in the absence of neurogenic stimuli, reveal that 3DG supports human mesenchymal stem cell (hMSC) adhesion, viability, proliferation, and neurogenic differentiation with significant upregulation of glial and neuronal genes. This coincides with hMSCs adopting highly elongated morphologies with features similar to axons and presynaptic terminals. In vivo experiments indicate that 3DG has promising biocompatibility over the course of at least 30 days. Surgical tests using a human cadaver nerve model also illustrate that 3DG has exceptional handling characteristics and can be intraoperatively manipulated and applied to fine surgical procedures. With this unique set of properties, combined with ease of fabrication, 3DG could be applied toward the design and fabrication of a wide range of functional electronic, biological, and bioelectronic medical and nonmedical devices.

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‘Natural’ sounds improve mood and productivity, study finds

(credit: iStock)

Playing natural sounds such as flowing water in offices could boost worker moods and improve cognitive abilities in addition to providing speech privacy, according to a new study from researchers at Rensselaer Polytechnic Institute.

An increasing number of modern open-plan offices employ sound masking systems such as “white noise” that raise the background sound of a room so that speech is rendered unintelligible beyond a certain distance and distractions are less annoying.

“If you’re close to someone, you can understand them. But once you move farther away, their speech is obscured by the masking signal,” said Jonas Braasch, an acoustician and musicologist at the Rensselaer Polytechnic Institute in New York.

Braasch and his team are currently testing whether masking signals inspired by natural sounds might work just as well, or better, than white noise. The idea was inspired by previous work by Braasch and his graduate student Mikhail Volf, which showed that people’s ability to regain focus improved when they were exposed to natural sounds versus silence or machine-based sounds.

Recently, Braasch and his graduate student Alana DeLoach built upon those results to start a new experiment.

They are exposing 12 human participants to three different sound stimuli while performing a task that requires them to pay close attention: typical office noises with the conventional random electronic signal; an office soundscape with a “natural” masker; and an office soundscape with no masker. The test subjects only encounter one of the three stimuli per visit.

The natural sound used in the experiment was designed to mimic the sound of flowing water in a mountain stream. “The mountain stream sound possessed enough randomness that it did not become a distraction,” DeLoach said. “This is a key attribute of a successful masking signal.”

They want to find out if workers who are listening to natural sounds are more productive and overall in better moods than the workers exposed to traditional masking signals.

Braasch said using natural sounds as a masking signal could have benefits beyond the office environment. “You could use it to improve the moods of hospital patients,” for example, Braasch said.

Abstract of Tuning the cognitive environment: sound masking with “natural” sounds in open-plan offices

With the gain in popularity of open-plan office design and the engineering efforts to achieve acoustical comfort for building occupants, a majority of workers still report dissatisfaction in their workplace environment. Office acoustics influence organizational effectiveness, efficiency, and satisfaction through meeting appropriate requirements for speech privacy and ambient sound levels. Implementing a sound masking system is one tried-and-true method of achieving privacy goals. Although each sound masking system is tuned for its specific environment, the signal – random steady state electronic noise, has remained the same for decades. This session explores how “natural” sounds may be used as an alternative to this standard masking signal employed so ubiquitously in sound masking systems in the contemporary office environment. As an unobtrusive background sound, possessing the appropriate spectral characteristics, this proposed use of “natural” sounds for masking challenges the convention that masking sounds should be as meaningless as possible. Based on psychophysical data and a sound-field analysis through an auditory model, we hypothesize that “natural” sounds as masking sounds have the ability (with equal success as conventional masking sounds) to meet standards and criteria for speech privacy while enhancing cognitive functioning, optimizing the ability to concentrate, and increasing overall worker satisfaction.

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Wearables and electric vehicles may get boost from boron-infused graphene

Rice University scientists made this supercapacitor with interlocked “fingers” using a laser and writing the pattern into a boron-infused sheet of polyimide. The device may be suitable for flexible, wearable electronics. (credit: Tour Group/Rice University)

Infusing the polymer in a laser-induced graphene supercapacitor (used to rapidly store and discharge electricity) with boric acid quadrupled the supercapacitor’s ability to store an electrical charge while greatly boosting its energy density (energy per unit volume), Rice University researchers have found.

The Rice lab of chemist James Tour uses commercial lasers to create thin, flexible supercapacitors by burning patterns into common polymers. The laser burns away everything but the carbon to a depth of 20 microns on the top layer, which becomes a foam-like matrix of interconnected graphene flakes.

Capacitors charge quickly and release their energy in a burst when needed, as in a camera flash. Supercapacitors add the high energy capacity of batteries and have potential for electric vehicles and other heavy-duty applications. But the potential to shrink them into a small, flexible, easily produced package could make them suitable for many more applications, including catalysts, field emission transistors, and components for solar cells and lithium-ion batteries, the researchers said.

In their earlier work, the team led by Rice graduate student Zhiwei Peng tried many polymers and discovered that a commercial polyimide was the best for the process. For the new work, the lab dissolved boric acid into polyamic acid and condensed it into a boron-infused polyimide sheet, which was then exposed to the laser.

Industrial-scale production

The two-step process produces microsupercapacitors with four times the ability to store an electrical charge and five to 10 times the energy density of the earlier, boron-free version.

The new devices proved highly stable over 12,000 charge-discharge cycles, retaining 90 percent of their capacitance. In stress tests, they handled 8,000 bending cycles with no loss of performance, the researchers reported.

Tour said the technique lends itself to industrial-scale, roll-to-roll production of microsupercapacitors. “What we’ve done shows that huge modulations and enhancements can be made by adding other elements and performing other chemistries within the polymer film prior to exposure to the laser,” he said.

Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of materials science and nanoengineering and of computer science and a member of Rice’s Richard E. Smalley Institute for Nanoscale Science and Technology.

The research is detailed in the journal ACS Nano.

The Air Force Office of Scientific Research and its Multidisciplinary University Research Initiative supported the research.

Abstract of Flexible Boron-Doped Laser Induced Graphene Microsupercapacitors

Heteroatom-doped graphene materials have been intensely studied as active electrodes in energy storage devices. Here, we demonstrate that boron-doped porous graphene can be prepared in ambient air using a facile laser induction process from boric acid containing polyimide sheets. At the same time, active electrodes can be patterned for flexible microsupercapacitors. As a result of boron doping, the highest areal capacitance of as-prepared devices reaches 16.5 mF/cm^2, three times higher than non-doped devices, with concomitant energy density increases of 5 to 10 times at various power densities. The superb cyclability and mechanical flexibility of the device is well-maintained, showing great potential for future microelectronics made from this boron-doped laser induced graphene material.

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The geometry of immune system cloaking

Cloaking materials: The sugar polymers that make up the spheres in this image are designed to package and protect specially engineered cells that work to produce drugs and fight disease and remain undetected by the body’s natural defense system. However, the reddish markers on the spheres’ surfaces indicate that immune cells (blue/green) have discovered these invaders and begun to block them off from the rest of the body. — credit | MIT researchers

A team of MIT researchers has come up with a way to reduce immune-system rejection of implantable devices used for for drug delivery, tissue engineering, or sensing.

Previous research found that smooth surfaces, especially spheres, are better — but counterintuively, larger spheres actually work better at reducing scar tissue, the researchers discovered.

“We were surprised by how much the size and shape of an implant can affect its triggering of an immune response. What it’s made of is still an important piece of the puzzle, but it turns out if you really want to have the least amount of scar tissue you need to pick the right size and shape,” says Daniel Anderson, the Samuel A. Goldblith Associate Professor in MIT’s Department of Chemical Engineering, a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES), and the paper’s senior author.

Tests of spheres

The study grew out of the researchers’ efforts to build an artificial pancreas. The goal is to deliver pancreatic islet cells encapsulated within a particle made of alginate — a polysaccharide (sugar) naturally found in algae — or another material. These implanted cells could replace patients’ pancreatic islet cells, which are nonfunctional in Type I diabetes.

Increasing the spherical diameter of a variety of materials including hydrogels, ceramics, metals and plastics (a) — scale bar: 2 millimeters — results in reduced foreign-body responses (b) — scale bar: 300 micrometers (credit: Omid Veiseh et al./Nature Materials)

The researchers tested spheres in two sizes — 0.5 and 1.5 millimeters in diameter. In tests of diabetic mice, the spheres were implanted within the abdominal cavity and the researchers tracked their ability to accurately respond to changes in glucose levels. The devices prepared with the smaller spheres were completely surrounded by scar tissue and failed after about a month, while the larger ones were not rejected and continued to function for more than six months.

The larger spheres also evaded the immune response in tests in nonhuman primates. Smaller spheres implanted under the skin were engulfed by scar tissue after only two weeks, while the larger ones remained clear for up to four weeks.

A universal size effect

This effect was seen not only with alginate, but also with spheres made of stainless steel, glass, polystyrene, and polycaprolactone, a type of polyester. “We realized that regardless of what the composition of the material is, this effect still persists, and that made it a lot more exciting because it’s a lot more generalizable,” said Koch Institute postdoc Omid Veiseh, one of the lead authors of a paper in the May 18 issue of Nature Materials.

The researchers believe this finding could also be applicable to any other type of implantable device, including drug-delivery vehicles and sensors for glucose and insulin, which could also help improve diabetes treatment. Optimizing particle size and shape could also help guide scientists in developing other types of implantable cells for treating diseases other than diabetes.

The research was funded by the Juvenile Diabetes Research Foundation, the Leona M. and Harry B. Helmsley Charitable Trust Foundation, the National Institutes of Health, the Koch Institute Support Grant from the National Cancer Institute, and the Tayebati Family Foundation. Veiseh was also supported by the Department of Defense.

Abstract of Size- and shape-dependent foreign body immune response to materials implanted in rodents and non-human primates

The efficacy of implanted biomedical devices is often compromised by host recognition and subsequent foreign body responses. Here, we demonstrate the role of the geometry of implanted materials on their biocompatibility in vivo. In rodent and non-human primate animal models, implanted spheres 1.5 mm and above in diameter across a broad spectrum of materials, including hydrogels, ceramics, metals and plastics, significantly abrogated foreign body reactions and fibrosis when compared with smaller spheres. We also show that for encapsulated rat pancreatic islet cells transplanted into streptozotocin-treated diabetic C57BL/6 mice, islets prepared in 1.5-mm alginate capsules were able to restore blood-glucose control for up to 180 days, a period more than five times longer than for transplanted grafts encapsulated within conventionally sized 0.5-mm alginate capsules. Our findings suggest that the in vivo biocompatibility of biomedical devices can be significantly improved simply by tuning their spherical dimensions.

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New graphene-like two-dimensional material could improve energy storage

Porous, layered structure of highly conductive powder Ni3(HITP)2 (credit: Mircea Dinca, MIT)

MIT and Harvard University researchers have created a graphene-like electrically conductive. porous, layered material as possible new tool for storing energy and investigating the physics of unusual materials.

They synthesized the material using an organic molecule called HITP and nickel ions, forming a new compound: Ni3(HITP)2.

The new porous material is a crystalline, structurally tunable electrical conductor with a high surface area — features that are ideal for supercapacitors, which could extend the range of electric vehicles by capturing and storing the energy that would normally be wasted when brakes slow down a vehicle.

The new material is composed of stacks of unlimited numbers of two-dimensional sheets resembling graphite, with a room temperature electrical conductivity of ~40 S/cm (Siemens per centimeter). The conductivity of this material is comparable to that of bulk graphite and among the highest for any conducting Metal-organic frameworks (MOFs)* reported to date.

Also, the temperature-dependence of its conductivity linear at temperatures between 100 K (Kelvin) and 500 K, suggesting an unusual charge transport mechanism that has not been previously observed in any organic semiconductors, and thus remains to be investigated.

In bulk form, the material could be used for electrocatalysis applications (modifying the rate of chemical reactions) similar to how platinum works (but at lower cost). Upon exfoliation (peeling off of successive layers), the material is expected to behave similar to graphene, but with tunable bandgap and electromagnetic properties, suggesting new uses in electronic circuits and new exotic quantum properties in solid-state physics.

* MOFs are hybrid organic-inorganic materials that have traditionally been studied for gas storage or separation applications owing to their high surface area. Making good electrical conductors out of these normally insulating materials has been a long-standing challenge, as highly porous intrinsic conductors could be used for a range of applications, including energy storage.

Abstract of High Electrical Conductivity in Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2, a Semiconducting Metal–Organic Graphene Analogue

Reaction of 2,3,6,7,10,11-hexaaminotriphenylene with Ni2+ in aqueous NH3 solution under aerobic conditions produces Ni3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene), a new two-dimensional metal–organic framework (MOF). The new material can be isolated as a highly conductive black powder or dark blue-violet films. Two-probe and van der Pauw electrical measurements reveal bulk (pellet) and surface (film) conductivity values of 2 and 40 S·cm–1, respectively, both records for MOFs and among the best for any coordination polymer.

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Unraveling the mysteries of spider-web strength and damage-resistant design

Scientists at MIT have developed a systematic approach to research the structure of spider silk, blending computational modeling and mechanical analysis to 3D-print synthetic spider webs (credit: Zhao Qin et al./Nature Communications)

MIT scientists have developed a systematic approach to research the structure of spider “silk” (which ounce for ounce, is stronger than steel) and how spiders optimize their own webs. The researchers are  blending computational modeling and mechanical analysis to 3D-print synthetic spider webs, with the goal of fabricating and testing synthetic spider-web structures.

“This is the first methodical exploration of its kind,” says Professor Markus Buehler, head of MIT’s Department of Civil and Environmental Engineering (CEE), and the lead author of an open-access paper appearing in Nature Communications. “We are looking to expand our knowledge of the function of natural webs in a systematic and repeatable manner.”

The lessons learned through this approach may help harness spider silk’s strength for other uses, and ultimately inspire engineers to digitally design new structures and composites that are lighter, more reliable, and damage-resistant.

Reverse-engineering the spider’s sophisticated architecture

The study explores the relationship between spider web structure, loading points, and failure mechanisms. By adjusting the material distribution throughout an entire web, a spider is able to optimize the web’s strength for its anticipated prey.

The team, adopting an experimental setup, used metal structures to 3D-print synthetic webs, and directly integrate their data into models. “Ultimately we merged the physical with the computational in our experiments,” Buehler says.

According to Buehler, spider webs employ a limited amount of material to capture prey of different sizes, with materials only a few micrometers (millionths of a meter) in diameter.

The 3D-printed models, Lewis says, open the door to studying the effects of spider-web architecture on strength and damage tolerance — a feat that would have been impossible to achieve using only natural spider webs.

Buehler’s team used orb-weaver spider webs as the inspiration for their 3-D designs. In each of their samples, they controlled the diameter of the thread as a method of comparing homogeneous and heterogeneous thread thickness.

The work revealed that spider webs consisting of uniform thread diameters are better suited to bear force applied at a single point, such as the impact coming from flies hitting webs, while a nonuniform diameter can withstand more widespread pressure, such as from wind, rain, or gravity.

The team now plans to examine the dynamic aspects of webs through controlled impact and vibration experiments, changing the printed material’s properties in real time and opening the door to printing optimized, multifunctional structures.

Abstract of Structural optimization of 3D-printed synthetic spider webs for high strength

Spiders spin intricate webs that serve as sophisticated prey-trapping architectures that simultaneously exhibit high strength, elasticity and graceful failure. To determine how web mechanics are controlled by their topological design and material distribution, here we create spider-web mimics composed of elastomeric filaments. Specifically, computational modelling and microscale 3D printing are combined to investigate the mechanical response of elastomeric webs under multiple loading conditions. We find the existence of an asymptotic prey size that leads to a saturated web strength. We identify pathways to design elastomeric material structures with maximum strength, low density and adaptability. We show that the loading type dictates the optimal material distribution, that is, a homogeneous distribution is better for localized loading, while stronger radial threads with weaker spiral threads is better for distributed loading. Our observations reveal that the material distribution within spider webs is dictated by the loading condition, shedding light on their observed architectural variations.

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NASA challenges ‘makers’ to design 3-D printed habitats for deep-space exploration

One concept for a 3D-printed Moon habitat (credit: NASA)

NASA and the National Additive Manufacturing Innovation Institute (America Makes) are holding a new $2.25 million competition, the 3-D Printed Habitat Challenge, to design and build a 3-D printed habitat for deep space exploration, including the agency’s journey to Mars.

The program is designed to advance the additive construction technology needed to create sustainable housing solutions for Earth and beyond. The idea is to avoid taking along materials and equipment for building a habitat on a distant planet, which would take up valuable cargo space.

The first phase of the competition calls on participants to develop state-of-the-art architectural concepts that take advantage of the unique capabilities 3-D printing offers. A prize purse of $50,000 will be awarded at the 2015 Maker Faire in New York.

“The future possibilities for 3-D printing are inspiring, and the technology is extremely important to deep space exploration,” said Sam Ortega, Centennial Challenges program manager. “This challenge definitely raises the bar from what we are currently capable of, and we are excited to see what the maker community does with it.”

Robot prints a road in front of a hangar for a lunar lander (credit: Behnaz Farahi/NASA)

The second phase of the competition is divided into two levels. The Structural Member Competition (Level 1) focuses on the fabrication technologies needed to manufacture structural components from a combination of indigenous materials (such as Moon regolith) and recyclables, or indigenous materials alone. The On-Site Habitat Competition (Level 2) challenges competitors to actually fabricate full-scale habitats using indigenous materials or indigenous materials combined with recyclables. Both levels are open for registration Sept. 26, and each carries a $1.1 million prize.

Winning concepts and products will help NASA build the technical expertise to send habitat-manufacturing machines to distant destinations, such as Mars, to build shelters for the human explorers who follow. On Earth, these capabilities may be used one day to construct affordable housing in remote locations with limited access to conventional building materials.

 

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3D-printed aerogels enable new energy-storage and nanoelectronic devices

Lawrence Livermore researchers have made graphene aerogel microlattices with an engineered architecture via a 3D printing technique known as direct ink writing (credit: Ryan Chen/LLNL)

Lawrence Livermore National Laboratory researchers have made novel graphene aerogel microlattices with an engineered architecture, using a 3D printing technique known as “direct ink writing.” The research, which could lead to better energy storage, sensors, nanoelectronics, catalysis, and separations, is described in an open-access paper in the April 22 edition of the journal Nature Communications.


Lawrence Livermore National Laboratory | How we 3D-print aerogel

The 3D printed graphene aerogels have high surface area, excellent electrical conductivity, are lightweight, have mechanical stiffness and exhibit supercompressibility (allowing for up to 90 percent compressive strain), and show a ten times improvement over bulk graphene materials and much better mass transport.

Aerogel is a synthetic porous, ultralight material derived from a gel, in which the liquid component of the gel has been replaced with a gas. It is often referred to as “liquid smoke.”

3D printing with graphene oxide (GO) inks

SEM image of a 3D printed graphene aerogel microlattice. Scale bar: 100nm. (credit: Cheng Zhu et al./Nature Communications)

The graphene oxide (GO) inks are prepared by combining an aqueous GO suspension and silica filler to form a homogenous, highly viscous ink. These GO inks are then loaded into a syringe barrel and extruded through a micronozzle to pattern 3D structures.

“Adapting the 3D printing technique to aerogels makes it possible to fabricate countless complex aerogel architectures for applications such as mechanical properties and compressibility, which has never been achieved before, ” said engineer Cheng Zhu, a co-author of the journal article.

Previous attempts at creating bulk graphene aerogels produced a largely random pore structure, excluding the ability to tailor transport and other mechanical properties of the material for specific applications such as separations, flow batteries, and pressure sensors. “Making graphene aerogels with tailored macro-architectures for specific applications with a controllable and scalable assembly method remains a significant challenge that we were able to tackle,” said engineer Marcus Worsley, a co-author of the paper.

In contrast, “3D printing allows for intelligently designing the pore structure of the aerogel, permitting control over mass transport (aerogels typically require high pressure gradients to drive mass transport through them due to small, tortuous pore structure) and optimization of physical properties, such as stiffness,” he said. “This development should open up the design space for using aerogels in novel and creative applications.”

The work is funded by the Laboratory Directed Research and Development Program.

Abstract of Highly compressible 3D periodic graphene aerogel microlattices

Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young’s moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.

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New evidence that electrical stimulation accelerates wound healing

An untreated wound (left) after 10 days is larger than an electrical-stimulation-treated wound (right) (credit: The University of Manchester)

The most detailed study to date of skin wound healing, conducted by University of Manchester scientists with 40 volunteers, has provided new evidence that electrical stimulation accelerates wound healing.

In the new research, half-centimeter harmless wounds were created on each upper arm of the volunteers.  One wound was left to heal normally, while the other was treated with electrical pulses* over a period of two weeks.  The pulses stimulated angiogenesis — the process by which new blood vessels form — increasing blood flow to the damaged area and resulting in wounds healing significantly faster.

Normal-healing tissues (top) vs. electrical-stimulation-treated healing tissues (bottom). Electrical-stimulation sample showed reorganization and accelerated granulation tissue stage development. ED is epidermis, DE is dermis, GT is granulation tissue, FT is fat/adipose tissue. (credit: Sara Ud-Din et al./PLoS ONE)

“The aim of this study was to further evaluate the role of electrical stimulation (ES) in affecting angiogenesis during the acute phase of cutaneous wound healing over multiple time points to identify if the enhanced effect occurred earlier than day 14,” the researchers note in a paper published in open-access PLoS ONE.

“This research has shown the effectiveness of electrical stimulation in wound healing,” said research leader Ardeshir Bayat of the University’s Institute of Inflammation and Repair. “We believe this technology has the potential to be applied to any situation where faster wound healing is particularly desirable, such as human or veterinary surgical wounds, accidents, military trauma, and sports injuries.”

Based on the findings, the researchers plan to work with Oxford BioElectronics Ltd. on a five-year project to develop and evaluate devices and dressings that use these experimental techniques to stimulate the body’s nervous system to generate nerve impulses directed to the site of skin repair.

How electrical stimulation enhances wound healing

The researchers explain in the paper that “ES in its various forms has been shown to enhance wound healing by promoting the migration of keratinocytes and macrophages, enhancing angiogenesis, stimulating fibroblasts, and influencing protein synthesis throughout the inflammatory, proliferative, and remodeling phases of healing.”

The researchers previously “investigated the in vitro effect of different types of ES on the expression of collagen in skin fibroblasts. Importantly, we highlighted the role of a novel waveform termed degenerate wave (DW is a degenerating sine wave, which deteriorates over time) and demonstrated its beneficial effects compared to other known waveforms such as direct and alternating currents.”

Skin wounds that are slow to heal are a clinical challenge to physicians all over the world. Every year, the NHS in the U.K. alone spends £1 billion on treating chronic wounds such as lower limb venous and diabetic ulcers. (Wounds become chronic when they fail to heal and remain open for longer than six weeks.)

* According to the researchers writing in the PLoS ONE paper, the electrical stimulation device used was the Fenzian system (Fenzian Ltd, Hungerford, UK), a transcutaneous low intensity device that  detects changes in skin impedance and adjusts the outgoing microcurrent electrical biofeedback impulses (20–80V, 6-millisecond “degenerate wave” pulses at 0.004 milliamps, with a frequency default of 60Hz).

Abstract of Angiogenesis Is Induced and Wound Size Is Reduced by Electrical Stimulation in an Acute Wound Healing Model in Human Skin

Angiogenesis is critical for wound healing. Insufficient angiogenesis can result in impaired wound healing and chronic wound formation. Electrical stimulation (ES) has been shown to enhance angiogenesis. We previously showed that ES enhanced angiogenesis in acute wounds at one time point (day 14). The aim of this study was to further evaluate the role of ES in affecting angiogenesis during the acute phase of cutaneous wound healing over multiple time points. We compared the angiogenic response to wounding in 40 healthy volunteers (divided into two groups and randomised), treated with ES (post-ES) and compared them to secondary intention wound healing (control). Biopsy time points monitored were days 0, 3, 7, 10, 14. Objective non-invasive measures and H&E analysis were performed in addition to immunohistochemistry (IHC) and Western blotting (WB). Wound volume was significantly reduced on D7, 10 and 14 post-ES (p = 0.003, p = 0.002, p<0.001 respectively), surface area was reduced on days 10 (p = 0.001) and 14 (p<0.001) and wound diameter reduced on days 10 (p = 0.009) and 14 (p = 0.002). Blood flow increased significantly post-ES on D10 (p = 0.002) and 14 (p = 0.001). Angiogenic markers were up-regulated following ES application; protein analysis by IHC showed an increase (p<0.05) in VEGF-A expression by ES treatment on days 7, 10 and 14 (39%, 27% and 35% respectively) and PLGF expression on days 3 and 7 (40% on both days), compared to normal healing. Similarly, WB demonstrated an increase (p<0.05) in PLGF on days 7 and 14 (51% and 35% respectively). WB studies showed a significant increase of 30% (p>0.05) on day 14 in VEGF-A expression post-ES compared to controls. Furthermore, organisation of granulation tissue was improved on day 14 post-ES. This randomised controlled trial has shown that ES enhanced wound healing by reduced wound dimensions and increased VEGF-A and PLGF expression in acute cutaneous wounds, which further substantiates the role of ES in up-regulating angiogenesis as observed over multiple time points. This therapeutic approach may have potential application for clinical management of delayed and chronic wounds.