‘Nano-Spidey senses’ could help autonomous machines (EV’s, Drones) see better

Researchers are building spider-inspired sensors into the shells of autonomous drones and cars so that they can detect objects better. Credit: Taylor Callery

What if drones and self-driving cars had the tingling “spidey senses” of Spider-Man?

They might actually detect and avoid objects better, says Andres Arrieta, an assistant professor of mechanical engineering at Purdue University, because they would process sensory information faster.

Better sensing capabilities would make it possible for drones to navigate in dangerous environments and for cars to prevent accidents caused by human error. Current state-of-the-art sensor technology doesn’t process data fast enough—but nature does.

And researchers wouldn’t have to create a radioactive spider to give autonomous machines superhero sensing abilities.

Instead, Purdue researchers have built sensors inspired by spiders, bats, birds and other animals, whose actual spidey senses are nerve endings linked to special neurons called mechanoreceptors.

The nerve endings—mechanosensors—only detect and process information essential to an animal’s survival. They come in the form of hair, cilia or feathers.

“There is already an explosion of data that intelligent systems can collect—and this rate is increasing faster than what conventional computing would be able to process,” said Arrieta, whose lab applies principles of nature to the design of structures, ranging from robots to aircraft wings.

“Nature doesn’t have to collect every piece of data; it filters out what it needs,” he said.

Many biological mechanosensors filter data—the information they receive from an environment—according to a threshold, such as changes in pressure or temperature.

In nature, ‘spidey-senses’ are activated by a force associated with an approaching object. Researchers are giving autonomous machines the same ability through sensors that change shape when prompted by a predetermined level of force. Credit: ETH Zürich images/Hortense Le Ferrand

A spider’s hairy mechanosensors, for example, are located on its legs. When a spider’s web vibrates at a frequency associated with prey or a mate, the mechanosensors detect it, generating a reflex in the spider that then reacts very quickly. The mechanosensors wouldn’t detect a lower frequency, such as that of dust on the web, because it’s unimportant to the spider’s survival.

The idea would be to integrate similar sensors straight into the shell of an autonomous machine, such as an airplane wing or the body of a car. The researchers demonstrated in a paper published in ACS Nano that engineered mechanosensors inspired by the hairs of spiders could be customized to detect predetermined forces. In real life, these forces would be associated with a certain object that an autonomous machine needs to avoid.

But the sensors they developed don’t just sense and filter at a very fast rate—they also compute, and without needing a power supply.

“There’s no distinction between hardware and software in nature; it’s all interconnected,” Arrieta said. “A sensor is meant to interpret data, as well as collect and filter it.”

In nature, once a particular level of force activates the mechanoreceptors associated with the hairy mechanosensor, these mechanoreceptors compute information by switching from one state to another.

Purdue researchers, in collaboration with Nanyang Technology University in Singapore and ETH Zürich, designed their sensors to do the same, and to use these on/off states to interpret signals. An intelligent machine would then react according to what these sensors compute.

These artificial mechanosensors are capable of sensing, filtering and computing very quickly because they are stiff, Arrieta said. The sensor material is designed to rapidly change shape when activated by an external force. Changing shape makes conductive particles within the material move closer to each other, which then allows electricity to flow through the sensor and carry a signal. This signal informs how the autonomous system should respond.

“With the help of machine learning algorithms, we could train these sensors to function autonomously with minimum energy consumption,” Arrieta said. “There are also no barriers to manufacturing these sensors to be in a variety of sizes.”

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More information: Hortense Le Ferrand et al, Filtered Mechanosensing Using Snapping Composites with Embedded Mechano-Electrical Transduction, ACS Nano (2019). DOI: 10.1021/acsnano.9b01095

Journal information: ACS Nano

Provided by Purdue University

Purdue University: A New hybrid energy method with Highly Porous Graphene Foams – Could Fuel the Future of Rockets, Space Exploration

Purdue University researchers have developed a new propellant formulation method to use graphene foams to power spacecraft. Credit: Purdue University

Graphene, a new material with applications in biomedical technology, electronics, composites, energy and sensors, may soon help send rockets to space.

A new propellant formulation method to use graphene foams – material used in electronics, optics and energy devices – to power spacecraft is being developed in Purdue University’s Maurice J. Zucrow Laboratories, which is the largest academic propulsion lab in the world. The research is showing success at increasing burn rate of solid propellants that are used to fuel rockets and spacecraft.

“Our propulsion and physics researchers came together to focus on a material that has not previously been used in rocket propulsion, and it is demonstrating strong results,” said Li Qiao, an associate professor of aeronautics and astronautics in Purdue’s College of Engineering.

The research team, led by Qiao, developed methods of making and using compositions with solid fuel loaded on highly conductive, highly porous graphene foams for enhanced burn rates for the loaded solid fuel. They wanted to maximize the catalytic effect of metal oxide additives commonly used in solid propellant to enhance decomposition.

The graphene foam structures are also thermally stable, even at high temperatures, and can be reused. The developed compositions provide significantly improved burn rate and reusability.

A new propellant formulation method to use porous graphene foams to power spacecraft is being developed at Purdue University. Credit: Purdue University

Qiao said the graphene foam works well for solid propellants because it is super lightweight and highly porous, which means it has many holes in which scientists can pour fuel to help ignite a rocket launch.

The graphene foam has a 3-D, interconnected structure to allow a more efficient thermal transport pathway for heat to quickly spread and ignite the propellant.

“Our patented technology provides higher performance that is especially important when looking at areas such as hypersonics,” Qiao said. “Our tests showed a burn rate enhancement of nine times the normal, using functionalized graphene foam structures.”

Qiao said the Purdue graphene foam discovery has applications for energy conversion devices and missile defense systems, along with other areas where tailoring nanomaterials for specific outcomes may be useful.

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New technologies could solve rocket challenges 800 years in the making

Purdue University: New chemical conversion process turns plastic waste into fuel

One of the biggest problems facing the Earth’s environment right now is the abundance of plastic waste. An estimated 5 billion tons of plastic is collecting in landfills or filling the oceans, and if not addressed, it will plague the decades to come by degrading into toxic chemicals, polluting the land and sea and destroying the habitats of wildlife. As scientific research looks for a solution, one possible option is trying to turn the waste into a usable fuel source.

A groups of chemists from Purdue University have developed a new process that can convert common types of plastic into a fuel similar to gasoline and diesel. Their research, recently published in ACS Sustainable Chemistry and Engineering, details how polypropylene, which is often found in toys, medical devices, and food packaging, can be converted into a fuel pure enough to be used in motor vehicles.

The researchers explain that their conversion process uses supercritical water, or water that has the characteristics of both a liquid and a gas based on pressure and temperature conditions. Specifically, they heated water until it was between 716 and 932 degrees Fahrenheit, with pressures that were 2,300 times that found at sea level. It was discovered that purified polypropylene would turn into oil when added to this mix, with the conversion process taking less than an hour at 850 degrees Fahrenheit.

Polypropylene is said to make up roughly a quarter of the world’s 5 billion tons of plastic waste, but lead researcher Linda Wang believes their new process could convert 90% of polypropylene into fuel. There’s no word on how or when this conversion process might be widely implemented, but Wang says the recycling industry should be motivated to move quickly, as the fuel it produces can be sold for a profit.

New “Instantly Rechargeable” Flow Battery could Dramatically Change EV Market

IN BRIEF

Purdue researchers have developed a flow battery that would allow electric cars to be recharged instantly at stations like conventional cars are. The technology is clean, safe, and cheap.

GO WITH THE FLOW

Purdue researchers have developed technology for an “instantly rechargeable” battery that is affordable, environmentally friendly, and safe. Currently, electric vehicles need charging ports in convenient locations to be viable, but this battery technology would allow drivers of hybrid and electric vehicles to charge up much like drivers of conventional cars refill quickly and easily at gas stations.

This breakthrough would not only speed the switch to electric vehicles by making them more convenient to drive, but also reduce the amount of new supportive infrastructure needed for electric cars dramatically. 

Purdue University professors John Cushman and Eric Nauman teamed up with doctoral student Mike Mueterthies to co-found Ifbattery LLC (IF-battery) for commercializing and developing the technology.
Image Credit: John Cushman/Purdue

The new model is a flow battery, which does not require an electric charging station to be recharged. Instead, all the users have to do is replace the battery’s fluid electrolytes — rather like filling up a tank. 

This battery’s fluids from used batteries, all clean, inexpensive, and safe, could be collected and recharged at any solar, wind, or hydroelectric plant. Electric cars using this technology would arrive at the refueling station, deposit spent fluids for recharging, and “fill up” like a traditional car might.

CLEANER, FASTER BATTERY TECHNOLOGY

This flow battery system is unique because, unlike other versions of the flow battery, this one lacks the membranes which are both costly and vulnerable to fouling. 

“Membrane fouling can limit the number of recharge cycles and is a known contributor to many battery fires,” Cushman said in a press release. “Ifbattery’s components are safe enough to be stored in a family home, are stable enough to meet major production and distribution requirements, and are cost effective.”

What’s My Range? Electric Vehicles (Click to View Full Infographic)

Transitioning existing infrastructure to accommodate cars using these batteries would be far simpler than designing and building a host of new charging stations — which is Tesla’s current strategy. Existing pumps could even be used for these battery chemicals, which are very safe.

“Electric and hybrid vehicle sales are growing worldwide and the popularity of companies like Tesla is incredible, but there continues to be strong challenges for industry and consumers of electric or hybrid cars,” Cushman said in the press release. “The biggest challenge for industry is to extend the life of a battery’s charge and the infrastructure needed to actually charge the vehicle.”

When can we expect to see these batteries in use? 
The biggest hurdle isn’t the materials, which are cheap and plentiful, but person power. The researchers still need more financing to complete research and development to put the batteries into mass production.

 To overcome this problem, they’re working to publicize the innovation in the hopes of drawing interest from investors.

References: Purdue, Purdue Research Park

Replacing Silicon in Solar Cells with Hybrid perovskite material could double efficiency

A new material has been shown to have the capability to double the efficiency of solar cells by researchers at Purdue University and the National Renewable Energy Laboratory.

Hybrid perovskite

The material, called a hybrid perovskite, has an inorganic crystal “cage” which contains an organic molecule, methyl-ammonium. (Image: Libai Huang)

Conventional solar cells are at most one-third efficient, a limit known to scientists as the Shockley-Queisser Limit. The new material, a crystalline structure that contains both inorganic materials (iodine and lead) and an organic material (methyl-ammonium), boosts the efficiency so that it can carry two-thirds of the energy from light without losing as much energy to heat.

In less technical terms, this material could double the amount of electricity produced without a significant cost increase.

Enough solar energy reaches the earth to supply all of the planet’s energy needs multiple times over, but capturing that energy has been difficult – as of 2013, only about 1 percent of the world’s grid electricity was produced from solar panels.
Libai Huang, assistant professor of chemistry at Purdue, says the new material, called a hybrid perovskites, would create solar cells thinner than conventional silicon solar cells, and is also flexible, cheap and easy to make.

“My graduate students learn how to make it in a few days,” she says.

The breakthrough is published this week in the journal Science (“Long-range hot-carrier transport in hybrid perovskites visualized by ultrafast microscopy”).

The most common solar cells use silicon as a semiconductor, which can transmit only one-third of the energy because of the band gap, which is the amount of energy needed to boost an electron from a bound state to a conducting state, in which the electrons are able to move, creating electricity.

How electrons move in hybrid perovskite

Scientists at Purdue University and the National Renewable Energy Laboratory have discovered how electrons move in a new crystalline material and this discovery could lead to doubling the efficiency of solar cells. Ultrafast microscope images, such as these, show that the electrons in material is able to move over 200 nanometers with minimal energy loss to heat. (Image: Libai Huang) (click on image to enlarge)

Incoming photons can have more energy than the band gap, and for a very short time – so short it’s difficult to imagine – the electrons exist with extra energy. These electrons are called “hot carriers,” and in silicon they exist for only one picosecond (which is 10-12 seconds) and only travel a maximum distance of 10 nanometers. At this point the hot carrier electrons give up their energy as heat. This is one of the main reasons for the inefficiency of solar cells.

Huang and her colleagues have developed a new technique that can track the range of the motion and the speed of the hot carriers by using fast lasers and microscopes.

“The distance hot carriers need to migrate is at least the thickness of a solar cell, or about 200 nanometers, which this new perovskite material can achieve,” Huang says. “Also these carriers can live for about 100 picoseconds, two orders of magnitude longer than silicon.”

Kai Zhu, senior scientist at the National Renewable Energy Laboratory in Golden, Colorado, and one of the journal paper’s co-authors, says that these are critical factors for creating a commercial hot-carrier solar cell.

“This study demonstrated that hot carriers in a standard polycrystalline perovskite thin film can travel for a distance that is similar to or longer than the film thickness required to build an efficient perovskite solar cell,” he says. “This indicates that the potential for developing hot carrier perovskite solar cell is good.”

However, before a commercial product is developed, researchers are trying to use the same techniques developed at Purdue by replacing lead in the material with other, less toxic, metals.

“The next step is to find or develop suitable contact materials or structures with proper energy levels to extract these hot carriers to generate power in the external circuit,” Zhu says. “This may not be easy.”

Source: Purdue University 

‘On-Demand ‘ Nanotube Forests’ for Electronics Fabrication

A system that uses a laser and electrical current to precisely position and align carbon nanotubes represents a potential new tool for creating electronic devices out of the tiny fibers.

Because carbon nanotubes have unique thermal and electrical properties, they may have future applications in electronic cooling and as devices in microchips, sensors and circuits. Being able to orient the carbon nanotubes in the same direction and precisely position them could allow these nanostructures to be used in such applications.

However, it is difficult to manipulate something so small that thousands of them would fit within the diameter of a single strand of hair, said Steven T. Wereley, a professor of mechanical engineering at Purdue University.

“One of the things we can do with this technique is assemble carbon nanotubes, put them where we want and make them into complicated structures,” he said.

This graphic illustrates a system that uses a laser and electrical field to precisely position and align carbon nanotubes, representing a potential new tool for assembling sensors and devices out of the tiny nanotubes and nanowires. The two microscope images at the bottom show the nanotubes aligned (left) and returning to their random orientation after the electric field and laser were turned off. (Image: Avanish Mishra and Steven Wereley)

New findings from research led by Purdue doctoral student Avanish Mishra are detailed in a paper that has appeared online March 24 in the journal Microsystems and Nanoengineering (“Dynamic optoelectric trapping and deposition of multiwalled carbon nanotubes”).

The technique, called rapid electrokinetic patterning (REP), uses two parallel electrodes made of indium tin oxide, a transparent and electrically conductive material. The nanotubes are arranged randomly while suspended in deionized water. Applying an electric field causes them to orient vertically. Then an infrared laser heats the fluid, producing a doughnut-shaped vortex of circulating liquid between the two electrodes. This vortex enables the researchers to move the nanotubes and reposition them.

“When we apply the electric field, they are immediately oriented vertically, and then when we apply the laser, it starts a vortex, that sweeps them into little nanotube forests,” Wereley said.

The research paper was authored by Mishra; Purdue graduate student Katherine Clayton; University of Louisville student Vanessa Velasco; Stuart J. Williams, an assistant professor of mechanical engineering at the University of Louisville and director of the Integrated Microfluidic Systems Laboratory; and Wereley. Williams is a former doctoral student at Purdue.

The technique overcomes limitations of other methods for manipulating particles measured on the scale of nanometers, or billionths of a meter. In this study, the procedure was used for multiwalled carbon nanotubes, which are rolled-up ultrathin sheets of carbon called graphene. However, according to the researchers, using this technique other nanoparticles such as nanowires and nanorods can be similarly positioned and fixed in vertical orientation.

The researchers have received a U.S. patent on the system.

The experimental work was performed at the Birck Nanotechnology Center in Purdue’s Discovery Park. Future research will explore using the technique to create devices.

Source: By Emil Venere, Purdue University

 

Purdue University: Nanowire Implants offer Remote-Controlled Drug Delivery: Applications: Spinal Cord Injuries; Chemotherapy

A team of researchers has created a new implantable drug-delivery system using nanowires that can be wirelessly controlled.

The nanowires respond to an electromagnetic field generated by a separate device, which can be used to control the release of a preloaded drug. The system eliminates tubes and wires required by other implantable devices that can lead to infection and other complications, said team leader Richard Borgens, Purdue University’s Mari Hulman George Professor of Applied Neuroscience and director of Purdue’s Center for Paralysis Research.

“This tool allows us to apply drugs as needed directly to the site of injury, which could have broad medical applications,” Borgens said. “The technology is in the early stages of testing, but it is our hope that this could one day be used to deliver drugs directly to spinal cord injuries, ulcerations, deep bone injuries or tumors, and avoid the terrible side effects of systemic treatment with steroids or chemotherapy.”

The team tested the drug-delivery system in mice with compression injuries to their spinal cords and administered the corticosteroid dexamethasone. The study measured a molecular marker of inflammation and scar formation in the central nervous system and found that it was reduced after one week of treatment. A paper detailing the results will be published in an upcoming issue of the Journal of Controlled Release and is currently available online.

IMAGE: An image of a field of polypyrrole nanowires captured by a scanning electron microscope is shown. A team of Purdue University researchers developed a new implantable drug-delivery system using the… view more

Credit: (Purdue University image/courtesy of Richard Borgens)

The nanowires are made of polypyrrole, a conductive polymer material that responds to electromagnetic fields. Wen Gao, a postdoctoral researcher in the Center for Paralysis Research who worked on the project with Borgens, grew the nanowires vertically over a thin gold base, like tiny fibers making up a piece of shag carpet hundreds of times smaller than a human cell. The nanowires can be loaded with a drug and, when the correct electromagnetic field is applied, the nanowires release small amounts of the payload. This process can be started and stopped at will, like flipping a switch, by using the corresponding electromagnetic field stimulating device, Borgens said.

The researchers captured and transported a patch of the nanowire carpet on water droplets that were used used to deliver it to the site of injury. The nanowire patches adhere to the site of injury through surface tension, Gao said.

The magnitude and wave form of the electromagnetic field must be tuned to obtain the optimum release of the drug, and the precise mechanisms that release the drug are not yet well understood, she said. The team is investigating the release process.

The electromagnetic field is likely affecting the interaction between the nanomaterial and the drug molecules, Borgens said.

“We think it is a combination of charge effects and the shape change of the polymer that allows it to store and release drugs,” he said. “It is a reversible process. Once the electromagnetic field is removed, the polymer snaps back to the initial architecture and retains the remaining drug molecules.”

For each different drug the team would need to find the corresponding optimal electromagnetic field for its release, Gao said.

This study builds on previous work by Borgens and Gao. Gao first had to figure out how to grow polypyrrole in a long vertical architecture, which allows it to hold larger amounts of a drug and extends the potential treatment period. The team then demonstrated it could be manipulated to release dexamethasone on demand. A paper detailing the work, titled “Action at a Distance: Functional Drug Delivery Using Electromagnetic-Field-Responsive Polypyrrole Nanowires,” was published in the journal Langmuir.

Other team members involved in the research include John Cirillo, who designed and constructed the electromagnetic field stimulating system; Youngnam Cho, a former faculty member at Purdue’s Center for Paralysis Research; and Jianming Li, a research assistant professor at the center.

For the most recent study the team used mice that had been genetically modified such that the protein Glial Fibrillary Acidic Protein, or GFAP, is luminescent. GFAP is expressed in cells called astrocytes that gather in high numbers at central nervous system injuries. Astrocytes are a part of the inflammatory process and form a scar tissue, Borgens said.

A 1-2 millimeter patch of the nanowires doped with dexamethasone was placed onto spinal cord lesions that had been surgically exposed, Borgens said. The lesions were then closed and an electromagnetic field was applied for two hours a day for one week. By the end of the week the treated mice had a weaker GFAP signal than the control groups, which included mice that were not treated and those that received a nanowire patch but were not exposed to the electromagnetic field. In some cases, treated mice had no detectable GFAP signal.

Whether the reduction in astrocytes had any significant impact on spinal cord healing or functional outcomes was not studied. In addition, the concentration of drug maintained during treatment is not known because it is below the limits of systemic detection, Borgens said.

“This method allows a very, very small dose of a drug to effectively serve as a big dose right where you need it,” Borgens said. “By the time the drug diffuses from the site out into the rest of the body it is in amounts that are undetectable in the usual tests to monitor the concentration of drugs in the bloodstream.”

Polypyrrole is an inert and biocompatable material, but the team is working to create a biodegradeable form that would dissolve after the treatment period ended, he said.

The team also is trying to increase the depth at which the drug delivery device will work. The current system appears to be limited to a depth in tissue of less than 3 centimeters, Gao said.

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Story Source:

The above post is reprinted from materials provided by Purdue University. The original item was written by Elizabeth K. Gardner. Note: Materials may be edited for content and length.

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Journal Reference:

1. Wen Gao, Richard Ben Borgens. Remote-controlled eradication of astrogliosis in spinal cord injury via electromagnetically-induced dexamethasone release from “smart” nanowires. Journal of Controlled Release, 2015; 211: 22 DOI: 10.1016/j.jconrel.2015.05.266

Inkjet-printed nanoparticle liquid metal could bring wearable tech, soft robotics

New research shows how inkjet-printing technology can be used to mass-produce electronic circuits made of liquid-metal alloys for “soft robots” and flexible electronics.

Elastic technologies could make possible a new class of pliable robots and stretchable garments that people might wear to interact with computers or for therapeutic purposes. However, new manufacturing techniques must be developed before soft machines become commercially feasible, said Rebecca Kramer, an assistant professor of mechanical engineering at Purdue University.

“We want to create stretchable electronics that might be compatible with soft machines, such as robots that need to squeeze through small spaces, or wearable technologies that aren’t restrictive of motion,” she said. “Conductors made from liquid metal can stretch and deform without breaking.”

A new potential manufacturing approach focuses on harnessing inkjet printing to create devices made of liquid alloys.

“This process now allows us to print flexible and stretchable conductors onto anything, including elastic materials and fabrics,” Kramer said.

A research paper about the method will appear on April 18 in the journal Advanced Materials (“Mechanically Sintered Gallium–Indium Nanoparticles”). The paper generally introduces the method, called mechanically sintered gallium-indium nanoparticles, and describes research leading up to the project. It was authored by postdoctoral researcher John William Boley, graduate student Edward L. White and Kramer.

This artistic rendering depicts electronic devices created using a new inkjet-printing technology to produce circuits made of liquid-metal alloys for “soft robots” and flexible electronics. Elastic technologies could make possible a new class of pliable robots and stretchable garments that people might wear to interact with computers or for therapeutic purposes. (Image: Alex Bottiglio/Purdue University)

A printable ink is made by dispersing the liquid metal in a non-metallic solvent using ultrasound, which breaks up the bulk liquid metal into nanoparticles. This nanoparticle-filled ink is compatible with inkjet printing.

“Liquid metal in its native form is not inkjet-able,” Kramer said. “So what we do is create liquid metal nanoparticles that are small enough to pass through an inkjet nozzle. Sonicating liquid metal in a carrier solvent, such as ethanol, both creates the nanoparticles and disperses them in the solvent. Then we can print the ink onto any substrate. The ethanol evaporates away so we are just left with liquid metal nanoparticles on a surface.”

After printing, the nanoparticles must be rejoined by applying light pressure, which renders the material conductive. This step is necessary because the liquid-metal nanoparticles are initially coated with oxidized gallium, which acts as a skin that prevents electrical conductivity.

“But it’s a fragile skin, so when you apply pressure it breaks the skin and everything coalesces into one uniform film,” Kramer said. “We can do this either by stamping or by dragging something across the surface, such as the sharp edge of a silicon tip.”

The approach makes it possible to select which portions to activate depending on particular designs, suggesting that a blank film might be manufactured for a multitude of potential applications.

“We selectively activate what electronics we want to turn on by applying pressure to just those areas,” said Kramer, who this year was awarded an Early Career Development award from the National Science Foundation, which supports research to determine how to best develop the liquid-metal ink.

The process could make it possible to rapidly mass-produce large quantities of the film.

Future research will explore how the interaction between the ink and the surface being printed on might be conducive to the production of specific types of devices.

“For example, how do the nanoparticles orient themselves on hydrophobic versus hydrophilic surfaces? How can we formulate the ink and exploit its interaction with a surface to enable self-assembly of the particles?” she said.

The researchers also will study and model how individual particles rupture when pressure is applied, providing information that could allow the manufacture of ultrathin traces and new types of sensors.

Source: By Emil Venere, Purdue University

Read more: Inkjet-printed nanoparticle liquid metal could bring wearable tech, soft robotics

Nanoparticle network could bring fast-charging batteries

WEST LAFAYETTE, Ind. – A new electrode design for lithium-ion batteries has been shown to potentially reduce the charging time from hours to minutes by replacing the conventional graphite electrode with a network of tin-oxide nanoparticles.

Batteries have two electrodes, called an anode and a cathode. The anodes in most of today’s lithium-ion batteries are made of graphite.

The theoretical maximum storage capacity of graphite is very limited, at 372 milliamp hours per gram, hindering significant advances in battery technology, said Vilas Pol, an associate professor of chemical engineering at Purdue University.

The researchers have performed experiments with a “porous interconnected” tin-oxide based anode, which has nearly twice the theoretical charging capacity of graphite. The researchers demonstrated that the experimental anode can be charged in 30 minutes and still have a capacity of 430 milliamp hours per gram (mAh g−1), which is greater than the theoretical maximum capacity for graphite when charged slowly over 10 hours.

This schematic diagram depicts the concept for a new electrode design for lithium-ion batteries that has been shown to potentially reduce the charging time from hours to minutes by replacing the conventional graphite electrode with a network of tin-oxide nanoparticles. (Purdue University image/Vinodkumar Etacheri)

The anode consists of an “ordered network” of interconnected tin oxide nanoparticles that would be practical for commercial manufacture because they are synthesized by adding the tin alkoxide precursor into boiling water followed by heat treatment, Pol said.

“We are not using any sophisticated chemistry here,” Pol said. “This is very straightforward rapid ‘cooking’ of a metal-organic precursor in boiling water. The precursor compound is a solid tin alkoxide – a material analogous to cost-efficient and broadly available titanium alkoxides. It will certainly become fully affordable in the perspective of broad scale application mentioned by collaborators Vadim G. Kessler and Gulaim A. Seisenbaeva from the Swedish University of Agricultural Sciences.”

Findings are detailed in a paper published in November in the journal Advanced Energy Materials.

When tin oxide nanoparticles are heated at 400 degrees Celsius they “self-assemble” into a network containing pores that allow the material to expand and contract, or breathe, during the charge-discharge battery cycle.

“These spaces are very important for this architecture,” said Purdue postdoctoral research associate Vinodkumar Etacheri. “Without the proper pore size, and interconnection between individual tin oxide nanoparticles, the battery fails.”

The research paper was authored by Etacheri; Swedish University of Agricultural Sciences researchers Gulaim A. Seisenbaeva, Geoffrey Daniel and Vadim G. Kessler; James Caruthers, Purdue’s Gerald and Sarah Skidmore Professor of Chemical Engineering; Jeàn-Marie Nedelec, a researcher from Clermont Université in France; and Pol.

Electron microscopy studies were performed at the Birck Nanotechnology Center in Purdue’s Discovery Park. Future research will include work to test the battery’s s ability to operate over many charge-discharge cycles in fully functioning batteries.

ABSTRACT

Ordered Network of Interconnected SnO₂ Nanoparticles for Excellent Lithium-Ion Storage

Vinodkumar Etacheri, Gulaim A. Seisenbaeva, James Caruthers, Geoffrey Daniel, Jean-Marie Nedelec, Vadim G. Kessler, and Vilas G. Pol*

*E-mail: vpol@purdue.edu 

An ordered network of interconnected tin oxide (Tin oxide) nanoparticles with a unique 3D architecture and an excellent lithium-ion (Li-ion) storage performance is derived for the first time through hydrolysis and thermal self assembly of the solid alkoxide precursor. Mesoporous anodes composed of these ~9 nm-sized Tin oxide particles exhibit substantially higher specific capacities, rate performance, coulombic efficiency, and cycling stabilities compared with disordered nanoparticles and commercial Tin oxide. A discharge capacity of 778 mAh g^–1, which is very close to the theoretical limit of 781 mAh g^–1, is achieved at a current density of 0.1 C. Even at high rates of 2 C (1.5 A g^–1) and 6 C (4.7 A g^–1), these ordered Tin oxide nanoparticles retain stable specific capacities of 430 and 300 mAh g^–1, respectively, after 100 cycles. Interconnection between individual nanoparticles and structural integrity of the Tin oxide electrodes are preserved through numerous charge–discharge process cycles. The significantly better electrochemical performance of ordered Tin oxide nanoparticles with a tap density of 1.60 g cm^–3 is attributed to the superior electrode/electrolyte contact, Li-ion diffusion, absence of particle agglomeration, and improved strain relaxation (due to tiny space available for the local expansion). This comprehensive study demonstrates the necessity of mesoporosity and interconnection between individual nanoparticles for improving the Li-ion storage electrochemical performance of Tin oxide anodes.

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Purdue Engineering names 2014 pre-eminent teams: “Nanomanufacturing” – Agriculture and Textiles

WEST LAFAYETTE, Ind. – Purdue University’s College of Engineering has named four pre-eminent teams to focus on research ranging from drug delivery to nanomanufacturing.

The effort is part of the college’s strategic growth plan that will add as many as 107 faculty over five years.

“The pre-eminent teams process helps us make informed faculty hiring decisions based on research strengths and with a focus on the potential for impact,” said Leah Jamieson, the John A. Edwardson Dean of Engineering. “This approach emphasizes the power of team-based research.”

It is the second annual competition, which brings the total number of teams to eight. The teams are building on strengths that are already part of the college. To become pre-eminent teams, they went through a process similar to a pitch entrepreneurs would give to venture capitalists. This year 27 teams, comprising more than 150 faculty members, participated in the competition.

“The panelists were unanimous in their compliments to all of the teams for the evidence of strength, teamwork, and the impressive array of ideas,” Jamieson said.

The strategic growth plan is part of Purdue Moves, a range of initiatives designed to broaden Purdue’s global impact and enhance educational opportunities for its students.

The four pre-eminent teams chosen will focus on:

* A research center for the manufacture of particulate products including foods and feed, consumer goods, specialty chemicals, agricultural chemicals, pharmaceuticals and energetic materials. The team is led by Jim Litster, a Professor of Chemical Engineering and Industrial and Physical Pharmacy. The work will focus on a model-based process design to produce engineered particles and structured particulate products, develop the understanding of process-structure-function relationships for these products, and build capacity through a highly qualified workforce in particulate science and engineering. The research could impact applications in areas including drug delivery and agriculture. Particle products contribute more than $1 trillion to the U.S. economy annually, and a number of companies are headquartered in the Midwest.

* Nanomanufacturing research aimed at creating “aware-responsive” films with applications in pharmacy, agriculture, food packaging, and functional non-woven materials for uses including wound dressings and diapers. The team is led by Ali Shakouri, a professor of electrical and computer engineering and the Mary Jo and Robert L. Kirk Director of the Birck Nanotechnology Center. Nanomanufacturing can bring advances such as: smart pharmaceuticals that release medications differently for specific patients; food packaging that contains sensors to monitor food quality; and cheap sensors for health monitoring.

* Research into development of new types of computer memory and electronic devices based on “spintronics.” The team is led by Supriyo Datta, the Thomas Duncan Distinguished Professor of Electrical and Computer Engineering. In 2006, the semiconductor industry and the National Science Foundation launched the Nanoelectronics Research Initiative (NRI) to look for “the next transistor.” Purdue researchers led by the Network for Computational Nanotechnology and the Birck Nanotechnology Center have been a visible and active part of the NRI since its inception. Conventional computers use the presence and absence of an electric charge to represent ones and zeroes in a binary code needed to carry out computations. Spintronics, however, uses the “spin state” of electrons to represent ones and zeros. Purdue could play a leading role in this new field emerging from the confluence of spintronics and nanomagnetics.

* Extreme density, low-temperature plasmas for electronics, aerospace, food science and biotechnology applications. The team is led by Sergey Macheret, a professor of aeronautics and astronautics. Low-temperature plasmas (LTP) are weakly ionized gases that are being extensively used in fluorescent lights and in microchip fabrication. New ways of generating and controlling LTP could lead to new applications ranging from medicine and food processing to enhancing aerodynamics and propulsion performance of existing and future airplanes. The ability of plasmas to interact with electromagnetic waves, combined with controllability and “tunability” of plasma characteristics, could enable novel radio-frequency devices.

Writer:  Emil Venere, 765-494-4709, venere@purdue.edu