From Smart Materials To Genius Materials
28 November 2013, 13:05
Categories: smt-rheometry-smart-fluids smt-polymorphic-shape-shifters
Around the world, designers are working on other smart materials such as alloys that can change shape on demand, plastics that heal themselves when ruptured, and fluids that obey magnetic commands to flow or stiffen under computer control. Eric Furst of the University of Delaware wants to create a new class of materials, beyond smart. “We need ‘genius materials’—materials that arrange themselves,” he says.
Furst is the principal investigator of an experiment called InSPACE-3, which focuses on magnetorheological (MR) smart fluids. In the microgravity of Earth orbit, vials of fluid mixed with very small ‘colloidal’ particles (about a millionth of a meter in diameter) are exposed to magnetic fields. Magnetism is switched on and off again very rapidly. This jostles the particles, causing them to bump together and self-assemble into microscopic structures that currently no supercomputer can predict.
Recently, observers have seen the colloidal particles forming long fibrous chains. Furst speculates that these could lead to materials that conduct heat or electricity in one direction only. The experiment has also yielded crystalline structures that the team is just beginning to investigate.
If you own a sports car or a Cadillac, you might have MR fluids in your shock absorbers. The stiffness of magnetic shocks can be electronically adjusted thousands of times per second, providing a remarkably smooth ride. Similar but more powerful devices have been installed at Japan’s National Museum of Emerging Science and China’s Dong Ting Lake Bridge. They’re there to counteract vibrations caused by earthquakes and gusts of wind. Some researchers have speculated that MR fluids might one day flow through the veins of robots, moving artificial joints and limbs in lifelike fashion.
Furst and colleagues are using these fluids as a laboratory for studying self-assembly. MR fluids are, by definition, responsive to the magnetic nudging that sets self-assembly in motion. Furthermore, in space the particles don’t sediment out due to gravity. “We can study the full 3D evolution of the material,” he adds.
Varying the shape of the colloidal particles, the cadence of magnetic toggling, the temperature of the fluid and other factors will allow researchers and astronauts to further explore the frontiers of self-assembly.
3-D Printing Of Batteries
28 November 2013, 12:31
Categories: energy techniques
By making the basic building blocks of batteries out of ink, Harvard materials scientist Jennifer Lewis is laying the groundwork for lithium-ion batteries and other high-performing electronics that can be produced with 3-D printers. Although the technology is still at an early stage, the ability to print batteries and other electronics could make it possible to manufacture new kinds of devices.
Lewis has invented an arsenal of what she calls functional inks that can solidify into batteries and simple components, including electrodes, wires, and antennas. She has also developed nozzles and high-pressure extruders that squeeze out the batteries and other components from an industrial-grade 3-D printer. The inks use suspended nanoparticles of the desired materials, such as compounds of lithium for batteries and silver for wires.
These materials are mixed into a variety of solutions, and the resulting inks are nearly solid when unperturbed but flow when a certain amount of pressure is applied. Once printed, the materials return to solid form. Printing a battery from a single nozzle can take minutes, but Lewis’s custom 3-D printing technology can deposit inks from hundreds of nozzles at the same time.
Will 2-D Tin Be The Next Super Material?
27 November 2013, 17:48
A single layer of tin atoms could be the world’s first material to conduct electricity with 100 percent efficiency at the temperatures that computer chips operate, according to researchers from the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory, Tsinghua University in Beijing, the Max Planck Institute in Dresden, and Stanford University.
Researchers call the new material “stanene,” combining the Latin name for tin (sternum) with the suffix used in graphene, another single-layer material whose novel electrical properties hold promise for a wide range of applications.
Calculations indicated that a single layer of tin would be a topological insulator at and above room temperature, and that adding fluorine atoms to the tin would extend its operating range to at least 100 degrees Celsius (212 degrees Fahrenheit).
The first application for this stanene-fluorine combination could be in wiring that connects the many sections of a microprocessor, allowing electrons to flow as freely as cars on a highway. Traffic congestion would still occur at on- and off-ramps made of conventional conductors. Stanene wiring, however, should significantly reduce the power consumption and heat production of microprocessors.
Piezoelectric Nano-Foam Measures Football Helmet Impact
27 November 2013, 17:32
Categories: smt-energy-piezoelectric sensors
According to the CDC, over 1.6 million sports-related concussions happen annually, and football is the sport with the highest concussion risk. The NFL and helmet makers have recently put more resources into investigating concussions, but current technology only provides data through bulky accelerometers in the crown of a helmet.
Now, a new piezoelectric foam created by Brigham Young University student Jake Merrell can account for both force and acceleration to measure actual impact. When compressed, the foam generates electrical signals that are transmitted wirelessly to a tablet or computer in the hands of a coach or trainer. Merrell hopes this technology is able to transform any foam into an impact sensor for a wide range of applications, from law enforcement to automotive.
A Self-Healing, Super-Repellent, Nanocoated Fabric
22 November 2013, 16:43
Categories: superoleophobic-philic superhydrophobicphilic
Previous research on self-healing, superoleophobic or superamphiphobic coatings have demonstrated limited liquid repellency with single self-healing ability against either physical or chemical damage. Now, researchers at Deakin University in Australia have demonstrated a superamphiphobic fabric with remarkable multi self-healing ability against both physical and chemical damages, and exceptional liquid-repellency. The work provides new insights into development of durable, liquid repellent fabrics for various applications in practice.
“Our findings are based on our previous study on a unique coating system,” says Professor Tong Lin. “Previously, we found that when a hydrolyzed fluoroalkyl silane (FAS) containing well-dispersed fluorinated-decyl polyhedral oligomeric silsequioxane (FD-POSS) was applied to fabrics, the fabrics showed superamphiphobicity with remarkable self-healing ability against chemical damages. In our new work, we further find that a fabric after being treated with hydrophobic nanoparticles and the FAS/FD-POSS coating shows a novel multi self-healing ability against both physical damages – e.g. blade scratching, sandpapering, and abrasion – and chemical damages.”
The researchers submitted their coated fabric to a repeated standard machine laundry process. They found that the coating is durable to withstand 200 cycles of wash and 5000 cycles of Martindale abrasion without apparently changing the superamphiphobicity. Furthermore, the coating has self-healing ability against both chemical and physical damages. The researchers employed physical damages such as scratching with a sharp blade, abrasion with sandpaper, and Martindale abrasion to test durability and self-healing ability of the coated fabric.
Robust Superhydrophobicity In Large Nanostructured Surfaces
22 November 2013, 15:58
Scientists at Brookhaven National Laboratory have investigated the effects of differently shaped, nanoscale textures on a material’s ability to force water droplets to roll off without wetting its surface. The findings are highly relevant for a broad range of applications where water-resistance is important, including power generation and transportation.
“In principle, the high robustness required for several applications could be achieved with texture features as small as 10 nanometers because the pressure needed for liquid to infiltrate the texture and force the air out increases dramatically with shrinking texture size,” explained Antonio Checco. “But in practice, it is difficult to shrink the surface texture features while maintaining control over their shape.”
“For this work, we have developed a fabrication approach based on self assembly of nano structures, which lets us precisely control the surface texture geometry over as large an area as we want—in principle, even as large as square meters,” Checco said.
The procedure for creating the superhydrophobic nanostructured surfaces takes advantage of the tendency of “block copolymer” materials to spontaneously self-organize through a mechanism known as micro phase separation. The self-assembly process results in polymer thin films with highly uniform, tunable dimensions of 20 nanometers or smaller.
Intelligent Oil Droplets Dance
22 November 2013, 15:45
Back in 2009, researchers at Northwestern University caused a blob of oil to navigate its way from one side of a maze to the other, making seemingly intelligent decisions along the way. The maze was filled with a solution of potassium hydroxide which is strongly alkaline, and at the exit is a chunk of gel soaked in hydrochloric acid, which then diffuses into the maze setting up a pH gradient. This gradient causes a difference in surface tension around the blob that pushes it along. So the blob simply follows the pH gradient, eventually finding its way to the chunk of gel at the exit.
Now researchers at Stanford University have used a similar phenomenon to create blobs that push each other around. They even use the blobs to make simple machines that produce circular motion, oscillations or one machine that sorts blobs by surface tension. That has implications for technologies such as microfluidics in which chemicals are pumped through microscopic channels inside tiny laboratories.
21 November 2013, 12:49
Categories: nanoparticles nanocomposites
Researchers at the State University of New York (SUNY) Stony Brook have created a novel “nanogrid,” a large net consisting of metal grids made of a copper tungsten oxide, that, when activated by sunlight, can break down oil from a spill, leaving only biodegradable compounds behind. It is thought that the nanogrid might help during and after oil spills, which are extraordinarily difficult to clean up and do untold damage to the environment.
“We have made a new catalyst that can break down hydrocarbons in water, and it does not contaminate the water,” says Pelagia-Irene (Perena) Gouma. “It utilizes the whole solar spectrum and can work in water for a long time, which no existing photocatalyst can do now. Ours is a unique technology. When you shine light on these grids, they begin to work and can be used over and over again.
“Something like this would work fine for any oil spill,” Gouma adds. “Any ship can carry them, so if they have even a small amount of spill, they can take care of it.”
Initially, the grids, which resemble non-woven mats of miniaturized ceramic fishing nets, probably will be used for oil spills, although they potentially could prove valuable in other applications, such as cleaning contaminated water produced by “fracking,” the process of hydraulic fracturing to extract natural gas from shale, and as well as from other industrial processes.
“Fracking is a reality,” she says. “It is happening. If the science and engineering we produce in the lab can help alleviate environmental problems, we will be happy about that.”
Because they work well both in water and air, they also could be a chemical-free, possibly even water-free, method of cleaning clothes in the future. “The dry cleaning process that we now use involves a lot of contaminants that have to be remediated and treated, such as benzene,” she says. “This could be a dry cleaning substitute that would be more environmentally friendly than current dry cleaning approaches.”
Moreover, “imagine you lay this over your clothes, and expose them to light. You won’t need a washing machine, or chemicals, or even water,” she adds.
The photocatalytic nanogrids™ invented in her lab are made by a unique self-assembly process that occurs “during the nanomanufacturing on non-woven nanofibrous mats deposited on metal meshes,” according to Gouma. “Upon heating, metal clusters diffuse inside polymeric nanofibers, then turn into single crystal nanowires, then oxidize to form metal oxide—ceramic—nanoparticles that are interconnected, like links in a chain,” she says.
These form an unusual and “robust third architecture that allows for the highest surface area, providing maximum exposure to the contaminant to be remediated, while the nanoscale particle sizes enable fast catalytic action,” she adds. “The result is a self-supported water remediation targeted photocatalytic technology that has no precedent.”
She and her team are in the process of creating a startup business, with the hope of scaling up production and carrying out pilot studies. “We want to demonstrate feasibility in the real world, and then produce them in large quantities,” she says. “We have proof of principle that our technology can be useful. Our technique works in the lab. We now need to make sure that it works in the field.”
Perovskite Shines As New Solar Cell Material
21 November 2013, 12:48
Researchers from the University of Pennsylvania and Drexel University are reporting that a new solar cell material, perovskite, has properties that could lead to solar cells capable of converting over half of the energy in sunlight directly into electricity. That’s more than twice as efficient as conventional solar cells. Such high efficiency would cut in half the number of solar cells needed to produce a given amount of power. Besides reducing the cost of solar panels, this would greatly reduce installation costs, which now account for most of the cost of a new solar system.
Unlike conventional solar cell materials, the new material doesn’t require an electric field to produce an electrical current. This reduces the amount of material needed and produces higher voltages, which can help increase power output. While other materials have been shown to produce current without the aid of an electric field, the new material is the first to also respond well to visible light, making it relevant for solar cells.
Transport And Self-Organization Of Programmable DNA Nanobots
20 November 2013, 13:20
Categories: bionanotech--nanobiotech molecular-machines--devices
Tiny self-assembling transport networks, powered by nanoscale motors and controlled by DNA, have been developed by scientists at Oxford University and Warwick University. The system can construct its own network of tracks spanning tens of micrometers in length, transport cargo across the network and even dismantle the tracks. The researchers were inspired by melanophores (a subclass of chromatophores), which are used by fish cells to control their color.
Many species are able to translocate the pigment inside their chromatophores, resulting in an apparent change in body color. This process is most widely studied in melanophores. Tracks in the network all come from a central point, like the spokes of a bicycle wheel. Motor proteins transport pigment around the network, either concentrating it in the centre or spreading it throughout the network. Concentrating pigment in the centre makes the cells lighter, as the surrounding space is left empty and transparent.
The system developed by the Oxford University team is very similar, and is built from DNA and a motor protein called kinesin. Powered by ATP fuel, kinesins move along the micro-tracks carrying control modules made from short strands of DNA. ‘Assembler’ nanobots are made with two kinesin proteins, allowing them to move tracks around to assemble the network, whereas the ‘shuttles’ only need one kinesin protein to travel along the tracks. Green dye-carrying shuttles sit idle on the tracks before refuelling.
“DNA is an excellent building block for constructing synthetic molecular systems, as we can program it to do whatever we need,” says Adam Wollman, who conducted the research at Oxford. “We design the chemical structures of the DNA strands to control how they interact with each other. The shuttles can be used to either carry cargo or deliver signals to tell other shuttles what to do.”
“We first use assemblers to arrange the track into ‘spokes’, triggered by the introduction of ATP. We then send in shuttles with fluorescent green cargo which spread out across the track, covering it evenly. When we add more ATP, the shuttles all cluster in the centre of the track where the spokes meet. Next, we send signal shuttles along the tracks to tell the cargo-carrying shuttles to release the fluorescent cargo into the environment, where it disperses. We can also send shuttles programmed with ‘dismantle’ signals to the central hub, telling the tracks to break up.”
This demonstration used fluorescent green dyes as cargo, but the same methods could be applied to other compounds. As well as colour changes, spoke-like track systems could be used to speed up chemical reactions by bringing the necessary compounds together at the central hub. More broadly, using DNA to control motor proteins could enable the development of more sophisticated self-assembling systems for a wide variety of applications.
Textile Battery Can Be Recharged By Sunlight
20 November 2013, 12:54
Categories: energy nanocomposites
A research team at the Korea Advanced Institute of Science and Technology (KAIST) has developed wearable textile batteries that can be integrated with flexible solar cells and thus be recharged by solar energy. The team made a fully functional wearable textile battery by finding unconventional materials for all of the key battery components and integrating them systemically: nickel-coated polyester yarn as a current collector for efficient stress release, polyurethane binder for strong adhesion of active materials, and polyurethane separator with superior mechanical, electrochemical, and thermal properties.
“In developing wearable rechargeable batteries, the component requiring the most significant alteration from the conventional cell configuration is the current collector because the current collector largely dictates the mechanical properties of the entire cell,” says Jang Wook Choi, who led the work. “Along this direction, one of the most natural approaches would be to use textiles as current collectors after integration with conductive materials.”
Choi points out that the use of carbon nanomaterials for the fabrication of textile supercapacitors and paper batteries, as previously reported, has encountered limitations in increasing the cell size and rate performance. Also, the investigation of metal-incorporating current collectors, like silver-coated textiles, runs into cost issues as well as mechanical challenges with regard to fatigue failure.
“In contrast, our battery cells endure extremely severe mechanical tests while delivering comparable electrochemical properties to those of the conventional foil-based counterparts,” says Choi. “It is important that, for the wearable capability of the rechargeable battery, the binder and separator also support the mechanical endurance of the overall system.”
To this end, the researchers decided to investigate unconventional materials rather than modify existing ones; they found that polyurethane possesses various material properties that are suitable for both binder and separator in a wearable battery. Furthermore, flexible and lightweight solar cells based on plastic substrates were integrated onto the outer surface of the textile battery for recharging the textile battery without physical connection to power outlet.
Silver Nanoparticles Create Smart Textiles
20 November 2013, 12:21
Categories: nanoparticles nanofibers
Scientists at the National Physical Laboratory (NPL) have developed a way to print silver directly onto fibers. This new technique could make integrating electronics into all types of clothing simple and practical. This has many potential applications in sports, health, medicine, consumer electronics and fashion. Smart fabric connected to a power source conducting electrical charge through an LED.
Most current plans for wearable electronics require weaving conductive materials into fabrics, which offer limited flexibility and can only be achieved when integrated into the design of the clothing from the start. NPL’s technique could allow lightweight circuits to be printed directly onto complete garments.
Silver coated fibers created using this technique are flexible and stretchable, meaning circuits can be easily printed onto many different types of fabric, including wool which is knitted in tight loops.
The technique involves chemically bonding a nano-silver layer onto individual fibres to a thickness of 20 nm. The conductive silver layer fully encapsulates fibers and has good adhesion and excellent conductivity.
Chris Hunt, Project Leader, says: “The technique has many potential applications. One particularly exciting area is wearable sensors and antennas which could be used for monitoring, for example checking on patients and vulnerable people; data capture and feedback for soldiers in the field; and performance monitoring in sports. It offers particular benefits over the ‘weaving in’ approach, as the conductive pattern and flexibility ensures that sensors are always positioned in the same location on the body.”
The technique could also create opportunities in fashion and consumer technology, such as incorporating LED lighting into clothing or having touch-screens on shirt sleeves.
In addition, silver has antibacterial properties, opening up opportunities for medical applications such as wound dressings, face masks, long lasting anti-bacterial wipes, and military clothing.
Having successfully shown that the additive technique is viable in the lab, NPL is now looking for funding or collaborators to develop a full printed circuit on a textile, which can be tested for flexibility and robustness, for example by putting it through the wash. Once this has been successfully achieved, the scientists will then look to develop prototypes of practical applications.
Using Sound Waves For Bomb Detection
20 November 2013, 12:14
A remote acoustic detection system designed to identify homemade bombs can determine the difference between those that contain low-yield and high-yield explosives. That capability, never before reported in a remote bomb detection system, was recently described in a paper by Vanderbilt engineer Douglas Adams.
A number of different tools are currently used for explosives detection. These range from dogs and honeybees to mass spectrometry, gas chromatography and specially designed X-ray machines. “Existing methods require you to get quite close to the suspicious object,” said Adams. “The idea behind our project is to develop a system that will work from a distance to provide an additional degree of safety.”
Adams is developing the acoustic detection system with researchers at Purdue University and the Colorado School of Mines. The new system consists of a phased acoustic array that focuses an intense sonic beam at a suspected improvised explosive device. At the same time, an instrument called a laser vibrometer is aimed at the object’s casing and records how the casing is vibrating in response. The nature of the vibrations can reveal a great deal about what is inside the container.
“We are applying techniques of laser vibrometry that have been developed for non-destructive inspection of materials and structures to the problem of bomb detection and they are working quite well,” Adams said.
In the current experiments, the engineers created two targets. One used an inert material that simulates the physical properties of low-yield explosive. The other was made from a simulant of high-yield explosive. They were fastened to acrylic caps to simulate plastic containers. Mechanical actuators substituted for the acoustic array to supply the sonic vibrations. The laser vibrometer was focused on the top of the plastic cap, corresponding to the outside of the bomb casing. The tests clearly showed differences in the vibration patterns of the two caps that allow the researchers to distinguish between the two materials (hydroxyl-terminated polybutadiene polymer embedded with 50 percent and 75 percent by volume ammonium chloride crystals).
Adams has also conducted a test that demonstrates the acoustic technique can differentiate between an empty container, one filled with water and one filled with a clay-like substance. The test used one-gallon plastic milk containers. In this case, the acoustic waves were produced by a device called an air driver. The empty jug had the largest vibrations while the jug containing the clay-like material had the smallest vibrations. The vibrations of the water-filled jug were in between.
The researchers have established that the best way to detect the contents of devices made of rigid material like metal is to use short ultrasonic waves. On the other hand, longer subsonic and infrasonic waves can be used to penetrate softer materials like plastics. Adam’s colleagues at Purdue are studying frequencies that can penetrate other materials like cloth.
New Flexible Battery Made With Carbon Nanotubes
20 November 2013, 12:07
Categories: energy nanocomposites
Researchers at NJIT have developed a flexible battery made with carbon nanotubes that could potentially power electronic devices with flexible displays.
Electronic manufacturers are now making flexible organic light-emitting diode (OLED) displays, a pioneering technology that allow devices such as cell phones, tablet computers and TVs to literally fold up. The device, given its flexibility and components, can be used to power this new generation of bendable electronics.
Each battery is made up of a flexible plastic substrate, impregnated with electro-active ingredients consisting of carbon nanotubes and microparticles. Those particles can be zinc and manganese dioxide in the case of alkaline batteries, or lithium salts for lithium batteries. “The goal is to take existing systems and convert them to a flexible platform,” says Somenath Mitra, a professor whose research group invented the battery.
“This battery can be made as small as a pinhead or as large as a carpet in your living room,” says Mithra. “So its applications are endless. You can place a rolled-up battery in the trunk of your electric car and have it power the vehicle.”
Metamaterials Convert Microwaves Into Electrical Power
20 November 2013, 10:34
Categories: metamaterials energy
Using inexpensive materials that have been configured and tuned to capture microwave signals, researchers at Duke University have designed a power-harvesting device with efficiency similar to that of modern solar panels.
The device wirelessly converts the microwave signal to direct current voltage capable of recharging a cell phone battery or other small electronic device. The researchers say that the versatile energy harvester could also be tuned to harvest the signal from other energy sources, including satellite signals, sound signals or Wi-Fi signals.
The key to the power harvester lies in its application of metamaterials, engineered structures that can capture various forms of wave energy and tune them for useful applications.
With additional modifications, the researchers said the power-harvesting metamaterial could potentially be built into a cell phone, allowing the phone to recharge wirelessly while not in use. This feature could, in principle, allow people living in locations without ready access to a conventional power outlet to harvest energy from a nearby cell phone tower instead.
Star Path Glows In The Dark
18 November 2013, 10:33
Categories: smt-luminescent-light-emit designers
The Eindhoven region in The Netherlands will receive a new bicycle path that uses phosphors to glow in the dark. The 600 meter bicycle path runs where Vincent van Gogh lived from 1883 to 1885 and will have a unique design comprising thousands of sparkling stones designed by Studio Roosegaarde.
The light stones will be used to create patterns in the path that will charge with UV light during the day and emit light during the evening. It makes use of the same photoluminescent phenomenon that one can witness along a Christ’s Pieces Park pedestrian path in Cambridge, UK, which was created by ProTeq.
Writing With Light In A Polymer Mixture
17 November 2013, 19:47
Categories: smt-chromism-color-change smt-polymorphic-shape-shifters
Researchers from the University of Helsinki have manufactured photochemically active polymers which can be dissolved in water or certain alcohols. In the study, a laser was aimed at a solution into which the polymer was partially dissolved. When exposed to light, the polymer switched from its trans conformation to its cis conformation, dissolving completely and leaving a clear form which was visible in the cloudy solution.
The effect can last several hours depending, for example, on the concentration of the solution. According to the scientists, this discovery is particularly significant for the development of new materials for optics and electronics.
Strawscraper: An Urban Piezo Power Plant Proposal
17 November 2013, 19:30
Categories: smt-energy-piezoelectric designers
Belatchew Arkitekter has proposed an urban wind farm of the future. By using piezoelectric technology, a large number of thin straws can produce electricity merely through small movements generated by the wind. The result is a new kind of wind power plant that opens up possibilities of how buildings can produce energy. With the help of this technique surfaces on both old and new buildings can be transformed into energy producing entities.
Natural Compound Can Be Used For 3-D Printing of Medical Implants
17 November 2013, 19:17
Categories: bionanotech--nanobiotech nanocomposites
A team of scientists from North Carolina State University, the University of North Carolina at Chapel Hill, and Laser Zentrum Hannover have discovered that a naturally-occurring compound called riboflavin, which is better known as vitamin B2, can be incorporated into 3D printing processes to create medical implants out of non-toxic polymers.
The researchers used a 3D printing technique called two-photon polymerization, which can create small objects with detailed features, such as scaffolds for tissue engineering, microneedles, or other implantable drug-delivery devices. Two-photon polymerization can be used to make small solid structures from many types of photo-reactive liquid precursors.
The liquid precursors contain chemicals that react to light, turning the liquid into a solid polymer. By exposing the liquid precursor to targeted amounts of light, the technique allows users to “print” 3D objects. But, most chemicals mixed into the precursors to make them photo-reactive are also toxic, and should not be used in a medical implant or in direct contact with the body.
The researchers determined that mixing nontoxic and biocompatible riboflavin with a precursor material can make it photo-reactive, making it much more biocompatible to fabricate tissue engineering scaffolds for custom implants.
Shape Memory Polymers Enable 4D Printing
4 November 2013, 18:29
Categories: nanocomposites smt-polymorphic-shape-shifters
Researchers at the University of Colorado Boulder and Singapore University of Technology and Design have developed and tested a method for 4D printing. The researchers incorporated shape memory polymer fibers into the composite materials used in traditional 3D printing, which results in the production of an object fixed in one shape that can later be changed to take on a new shape.
“In this work, the initial configuration is created by 3D printing, and then the programmed action of the shape memory fibers creates time dependence of the configuration – the 4D aspect,” said Martin L. Dunn, who has studied the mechanics and physics of composite materials for more two decades.
The 4D printing concept, which allows materials to self-assemble into 3D structures, was initially proposed by Massachusetts Institute of Technology faculty member Skylar Tibbits in April of this year. Tibbits and his team combined a strand of plastic with a layer made out of smart material that could self-assemble in water.
“We advanced this concept by creating composite materials that can morph into several different, complicated shapes based on a different physical mechanism,” said Dunn. “The secret of using shape memory polymer fibers to generate desired shape changes of the composite material is how the architecture of the fibers is designed, including their location, orientation and other factors.”
“The fascinating thing is that these shapes are defined during the design stage, which was not achievable a few years ago,” said Qi Ge.
The CU-Boulder team demonstrated that the orientation and location of the fibers within the composite determines the degree of shape memory effects like folding, curling, stretching or twisting. The researchers also showed the ability to control those effects by heating or cooling the composite material.
Qi says 3D printing technology, which has existed for about three decades, has only recently advanced to the point that active fibers can be incorporated into the composites so their behavior can be predictably controlled when the object is subjected to thermal and mechanical forces.
The technology promises exciting new possibilities for a variety of applications. Qi said that a solar panel or similar product could be produced in a flat configuration onto which functional devices can be easily installed. It could then be changed to a compact shape for packing and shipping. After arriving at its destination, the product could be activated to form a different shape that optimizes its function.
As 3D printing technology matures with more printable materials and higher resolution at larger scales, the research should help provide a new approach to creating reversible or tunable 3D surfaces and solids in engineering like the composite shells of complex shapes used in automobiles, aircraft and antennas.