Engineering and Technology Updates
Developing a sustainable concrete substitute
Worcester Polytechnic Institute (WPI) researchers from the National Science Foundation (NSF) are working on how to improve and develop new functions for their Enzymatic Construction Material (ECM), a “living” low-cost negative-emission construction material they created to address one of the largest contributors to climate change — concrete — by providing what they refer to as “a pathway to repair or even replace [traditional] concrete in the future.” They have already made their research available for commercial use through a start-up called Enzymatic, Inc.; this new funding will also allow them to: explore new avenues for ECM’s use, including repairing cracks in different types of glass, such as eyeglass lenses, cell phone screens, and car windshields. In addition to their efforts to help mitigate the massive climate change impacts created by concrete, they plan to use the new funding to refine and optimize ECM and the processes to create it and expand its use to different materials. Biological enzymes are catalysts that drive chemical reactions. ECM is made through a process involving an enzyme known as carbonic anhydrase — found in all living cells — that has the unique ability to react with CO2 to rapidly remove the greenhouse gas from the atmosphere. This reaction creates calcium carbonate crystals, which serve as ECM’s main ingredient. A sand slurry is also added, as well as a polymer, which holds the ECM together during its early stages, much like scaffolding does during the construction of a building. Through this process, ECM can “heal itself” and fix cracks or other imperfections that may develop over time, retaining its strength through as many as six self-healing cycles. Through extensive testing and experimentation, the research team found that ECM has “outstanding” compression strength, rivaling traditional mortar, making it strong enough to be used in the construction of buildings as compressive elements. It also does not require baking at high temperatures like a traditional brick does, and it can be made quickly, unlike the 28 days needed to cure concrete. ECM can also be produced at a low cost as the percentage of the enzymes is minute. This new NSF funding will help the team improve the processes that will allow for EMC to move more swiftly from the lab to construction sites. A new pathway for the material could also be used to fix cracked or fractured glass. The researchers plan to partner with organizations in Worcester, to create summer programs and after-school programs in which students will design a six-inch model building, make a mould for it using 3D printing, and build the structure out of ECM.
Key element for a scalable quantum computer
Millions of quantum bits are required for quantum computers to prove useful in practical applications. The scalability is one of the greatest challenges in the development of future devices. One problem is that the qubits have to be very close to each other on the chip in order to couple them together. Researchers at Forschungszentrum Jülich and RWTH Aachen University have now come a significant step closer to solving the problem. They succeeded in transferring electrons, the carriers of quantum information, over several micrometres on a quantum chip. Their “quantum bus” could be the key component to master the leap to millions of qubits. Quantum computers have the potential to vastly exceed the capabilities of conventional computers for certain tasks. But there is still a long way to go before they can help to solve real-world problems. Many applications require quantum processors with millions of quantum bits. Today’s prototypes merely come up with a few of these compute units. At some point, the number of signal lines becomes a bottleneck. The lines take up too much space compared to the size of the tiny qubits. And a quantum chip cannot have millions of inputs and outputs — a modern classical chip only contains about 2000 of these. The overall goal of researchers is to integrate parts of the control electronics directly on the chip. The approach is based on so-called semiconductor spin qubits made of silicon and germanium. This type of qubit is comparatively tiny. The manufacturing processes largely match those of conventional silicon processors. This is considered to be advantageous when it comes to realising very many qubits. But first, some fundamental barriers have to be overcome. “The natural entanglement that is caused by the proximity of the particles alone is limited to a very small range, about 100 nanometres. To couple the qubits, they currently have to be placed very close to each other. There is simply no space for additional control electronics that we would like to install there,” says a researcher Schreiber. To set the qubits apart, the JARA Institute for Quantum Information (IQI) came up with the idea of a quantum shuttle. This special component should help to exchange quantum information between the qubits over greater distances. An important step has now been achieved by Lars Schreiber and his team. They succeeded in transporting an electron 5000 times over a distance of 560 nanometres without any significant errors. This corresponds to a distance of 2.8 millimetres. One essential improvement: the electrons are driven by means of four simple control signals, which — in contrast to previous approaches — do not become more complex over longer distances. This is important because otherwise extensive control electronics would be required, which would take up too much space — or could not be integrated on the chip at all. This achievement is based on a new way of transporting electrons. “Until now, people have tried to steer the electrons specifically around individual disturbances on their path. Or they created a series of so-called quantum dots and let the electrons hop from one of these dots to another. Both approaches require precise signal adjustment, which results in too complex control electronics,” explains Lars Schreiber. “In contrast, we generate a potential wave on which the electrons simply surf over various sources of interference. A few control signals are sufficient for such a uniform wave; four sinusoidal pulses are all it takes.” As a next step, the physicists now want to show that the qubit information encoded in the electron spin is not lost during transportation. Theoretical calculations have already shown that this is possible in silicon in certain speed ranges. The quantum bus thus paves the way to a scalable quantum computer architecture that can also serve as a basis for several million qubits.
Converting 3D-printed polymer into a 100-times stronger, ductile hybrid carbon microlattice material
Developing a lightweight material that is both strong and highly ductile has been regarded as a long-desired goal in the field of structural materials, but these properties are generally mutually exclusive. Researchers at City University of Hong Kong (CityU) recently discovered a low-cost, direct method to turn commonly used 3D printable polymers into lightweight, ultra-tough, biocompatible hybrid carbon microlattices, which can be in any shape or size, and are 100 times stronger than the original polymers. The research team believes that this innovative approach can be used to create sophisticated 3D parts with tailored mechanical properties for a wide range of applications, including coronary stents and bio-implants. Metamaterials are materials engineered to have properties that are not found in naturally occurring materials. 3D architected metamaterials, such as microlattices, combine the benefits of lightweight structural design principles with the intrinsic properties of their constituent materials. Making these microlattices often requires advanced fabrication technologies, such as additive manufacturing (commonly referred to as 3D printing), but the range of materials available for 3D printing is still fairly limited. So far, the most effective approach for increasing the strength of these 3D printable polymer lattices is pyrolysis, a thermal treatment that transforms the entire polymers into ultra-strong carbon. However, this process deprives the original polymer lattice of almost all its deformability and produces an extremely brittle material, like glass. Other methods to increase the strength of the polymers also typically result in compromising their ductility. The team led by Professor Lu found a “magic-like” condition in the pyrolysis of the 3D-printed photopolymer microlattices, which resulted in a 100-fold increase in strength and doubled the ductility of the original material. They discovered that by carefully controlling the heating rate, temperature, duration and gas environment, it is possible to simultaneously enhance the stiffness, strength and ductility of a 3D-printed polymer microlattice drastically in a single step. Through various characterization techniques, the team found that simultaneous improvement in strength and ductility is possible only when the polymeric chains are “partially carbonized” by slow heating, where incomplete conversion of the polymer chains to pyrolytic carbon occurs, producing a hybrid material in which both loosely cross-linked polymer chains and carbon fragments synergistically coexist. The carbon fragments serve as reinforcing agents that strengthen the material, while the polymer chains restrict the fracture of the composite. The ratio of polymer to carbon fragments is also crucial to obtaining optimal strength and ductility. If there are too many carbon fragments, the material becomes brittle, and if there are too few, the material lacks strength. During the experiments, the team successfully created an optimally carbonized polymer lattice that was over 100 times stronger and over two times more ductile than the original polymer lattice. The research team also found that these “hybrid carbon” microlattices showed improved biocompatibility compared to the original polymer. Through cytotoxicity and cell behaviour monitoring experiments, they proved that the cells cultured on the hybrid carbon microlattices were more viable than cells seeded on the polymer microlattices. The enhanced biocompatibility of the hybrid-carbon lattices implies that the benefits of partial carbonization may go beyond enhancement in mechanical performance and potentially improve other functionalities as well. “Our work provides a low-cost, simple and scalable route for making lightweight, strong and ductile mechanical metamaterials with virtually any geometry,” said Professor Lu. He envisions that the newly invented approach can be applied to other types of functional polymers, and that the geometrical flexibility of these architected hybrid-carbon metamaterials will allow their mechanical properties to be tailored for a wide range of applications, such as biomedical implants, mechanically robust scaffolds for micro-robots, energy harvesting and storage devices.
Simple method destroys dangerous ‘forever chemicals,’ making water safe
If you’re despairing at recent reports that Earth’s water sources have been thoroughly infested with hazardous human-made chemicals called PFAS that can last for thousands of years, making even rainwater unsafe to drink, there’s a spot of good news. Chemists at UCLA and Northwestern University have developed a simple way to break down almost a dozen types of these nearly indestructible “forever chemicals” at relatively low temperatures with no harmful byproducts. The researchers show that in water heated to just 176 to 248 degrees Fahrenheit, common, inexpensive solvents and reagents severed molecular bonds in PFAS that are among the strongest known and initiated a chemical reaction that “gradually nibbled away at the molecule” until it was gone, said UCLA distinguished research professor and co-corresponding author Kendall Houk. The simple technology, the comparatively low temperatures and the lack of harmful byproducts mean there is no limit to how much water can be processed at once, Houk added. The technology could eventually make it easier for water treatment plants to remove PFAS from drinking water. Per- and polyfluoroalkyl substances — PFAS for short — are a class of around 12,000 synthetic chemicals that have been used since the 1940s in nonstick cookware, waterproof makeup, shampoos, electronics, food packaging and countless other products. They contain a bond between carbon and fluorine atoms that nothing in nature can break. When these chemicals leach into the environment through manufacturing or everyday product use, they become part of the Earth’s water cycle. Over the past 70 years, PFAS have contaminated virtually every drop of water on the planet, and their strong carbon-fluorine bond allows them to pass through most water treatment systems completely unharmed. They can accumulate in the tissues of people and animals over time and cause harm in ways that scientists are just beginning to understand. Certain cancers and thyroid diseases, for example, are associated with PFAS. For these reasons, finding ways to remove PFAS from water has become particularly urgent. Scientists are experimenting with many remediation technologies, but most of them require extremely high temperatures, special chemicals or ultraviolet light and sometimes produce byproducts that are also harmful and require additional steps to remove. Northwestern chemistry professor William Dichtel and his team noticed that while PFAS molecules contain a long “tail” of stubborn carbon-fluorine bonds, their “head” group often contains charged oxygen atoms, which react strongly with other molecules. Dichtel’s team built a chemical guillotine by heating the PFAS in water with dimethyl sulfoxide, also known as DMSO, and sodium hydroxide, or lye, which lopped off the head and left behind an exposed, reactive tail. “That triggered all these reactions, and it started spitting out fluorine atoms from these compounds to form fluoride, which is the safest form of fluorine,” Dichtel said. “Although carbon-fluorine bonds are super-strong, that charged head group is the Achilles’ heel.” But the experiments revealed another surprise: The molecules didn’t seem to be falling apart the way conventional wisdom said they should. The researchers had expected the PFAS molecules would disintegrate one carbon atom at a time, but researchers ran computer simulations that showed two or three carbon molecules peeled off the molecules simultaneously, just as they had observed experimentally. The simulations also showed the only byproducts should be fluoride — often added to drinking water to prevent tooth decay — carbon dioxide and formic acid, which is not harmful. Dichtel confirmed these predicted byproducts in further experiments. The current work degraded 10 types of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl ether carboxylic acids (PFECAs), including perfluorooctanoic acid (PFOA). The researchers believe their method will work for most PFAS that contain carboxylic acids and hope it will help identify weak spots in other classes of PFAS. They hope these encouraging results will lead to further research that tests methods for eradicating the thousands of other types of PFAS.
Cobalt-free cathode for lithium-ion batteries
Researchers at the University of California, Irvine and four national laboratories have devised a way to make lithium-ion battery cathodes without using cobalt, a mineral plagued by price volatility and geopolitical complications. The scientists describe how they overcame thermal and chemical-mechanical instabilities of cathodes composed substantially of nickel — a common substitute for cobalt — by mixing in several other metallic elements. “Through a technique we refer to as ‘high-entropy doping,’ we were able to successfully fabricate a cobalt-free layered cathode with extremely high heat tolerance and stability over repeated charge and discharge cycles,” said corresponding author Huolin Xin, UCI professor of physics & astronomy. “This achievement resolves long-standing safety and stability concerns around high-nickel battery materials, paving the way for broad-based commercial applications.” Cobalt is one of the most significant supply chain risks threatening widespread adoption of electric cars, trucks and other electronic devices requiring batteries, according to the researchers. However, nickel-based cathodes come with their own problems, such as poor heat tolerance, which can lead to oxidization of battery materials, thermal runaway and even explosion. Although high-nickel cathodes accommodate larger capacities, volume strain from repeated expansion and contraction can result in poor stability and safety concerns. The researchers sought to address these issues through compositionally complex high-entropy doping using HE-LMNO, an amalgamation of transition metals magnesium, titanium, manganese, molybdenum and niobium in the structure’s interior, with a subset of these minerals used on its surface and interface with other battery materials. Xin and his colleagues employed an array of synchrotron X-ray diffraction, transmission electron microscopy and 3D nanotomography instruments to determine that their zero-cobalt cathode exhibited an unprecedented volumetric change of zero during repeated use. The highly stable structure is capable of withstanding more than 1,000 cycles and high temperatures, which makes it comparable to cathodes with much lower nickel content. “The combination of the different methods at NSLS II beamlines enabled the discovery of a trapping effect of oxygen vacancies and defects inside the material, which effectively prevents the crack formation in the HE-LMNO secondary particle, making this structure extremely stable during cycling,” said co-author Mingyuan Ge, a scientist at NSLS-II.Added Xin: “Using these advanced tools, we were able to observe the dramatically increased thermal stability and zero-volumetric-change characteristics of the cathode, and we’ve been able to demonstrate extraordinarily improved capacity retention and cycle life. This research could set the stage for the development of an energy-dense alternative to existing batteries.” He said the work represents a step toward achieving the dual goal of spurring the proliferation of clean transportation and energy storage while addressing environmental justice issues around the extraction of minerals used in batteries.
Smart microrobots walk autonomously with electronic ‘brains’
Cornell University researchers have installed electronic “brains” on solar-powered robots that are 100 to 250 micrometers in size — smaller than an ant’s head — so that they can walk autonomously without being externally controlled. While Cornell researchers and others have previously developed microscopic machines that can crawl, swim, walk and fold themselves up, there were always “strings” attached; to generate motion, wires were used to provide electrical current or laser beams had to be focused directly onto specific locations on the robots. “Before, we literally had to manipulate these ‘strings’ in order to get any kind of response from the robot,” said Itai Cohen, professor of physics. “But now that we have these brains on board, it’s like taking the strings off the marionette. It’s like when Pinocchio gains consciousness.” The innovation sets the stage for a new generation of microscopic devices that can track bacteria, sniff out chemicals, destroy pollutants, conduct microsurgery and scrub the plaque out of arteries. The “brain” in the new robots is a complementary metal-oxide-semiconductor (CMOS) clock circuit that contains a thousand transistors, plus an array of diodes, resistors and capacitors. The integrated CMOS circuit generates a signal that produces a series of phase-shifted square wave frequencies that in turn set the gait of the robot. The robot legs are platinum-based actuators. Both the circuit and the legs are powered by photovoltaics. “Eventually, the ability to communicate a command will allow us to give the robot instructions, and the internal brain will figure out how to carry them out,” researcher Cohen said. “Then we’re having a conversation with the robot. The robot might tell us something about its environment, and then we might react by telling it, ‘OK, go over there and try to suss out what’s happening.'” The new robots are approximately 10,000 times smaller than macroscale robots that feature onboard CMOS electronics, and they can walk at speeds faster than 10 micrometers per second. The fabrication process that Reynolds designed, basically customizing foundry-built electronics, has resulted in a platform that can enable other researchers to outfit microscopic robots with their own apps — from chemical detectors to photovoltaic “eyes” that help robots navigate by sensing changes in light. “What this lets you imagine is really complex, highly functional microscopic robots that have a high degree of programmability, integrated with not only actuators, but also sensors,” another researcher Reynolds said. “We’re excited about the applications in medicine — something that could move around in tissue and identify good cells and kill bad cells — and in environmental remediation, like if you had a robot that knew how to break down pollutants or sense a dangerous chemical and get rid of it.”
ISRO successfully tests hybrid motor, eyes new propulsion system for rockets
The Indian Space Research Organisation (ISRO) has recently successfully tested a hybrid motor, potentially paving the way for a new propulsion system for the forthcoming launch vehicles. The 30 kN hybrid motor tested at ISRO Propulsion Complex (IPRC) at Mahendragiri in Tamil Nadu is scalable and stackable, the Bengaluru-headquartered space agency said. Unlike solid-solid or liquid-liquid combinations, a hybrid motor uses solid fuel and liquid oxidiser, it was noted. “Today’s (Tuesday’s) September 20, 2022 test of a flight equivalent 30 kN hybrid motor demonstrated ignition and sustained combustion for the intended duration of 15 seconds. The motor performance was satisfactory”, an ISRO statement said. The use of liquids facilitates throttling, and the control over the flow rate of LOX enables the re-start capability, it was explained. While both HTPB and LOX are green, LOX is safer to handle, ISRO noted. “The hybrid motor tested today (Tuesday) is scalable and stackable, potentially paving the way for a new propulsion system for the forthcoming launch vehicles”, it said.
A swarm of 3D printing drones for construction and repair
An international research team led by drone expert Mirko Kovac of Empa and Imperial College London has taken bees as a model to develop a swarm of cooperative, 3D-printing drones. Under human control, these flying robots work as a team to print 3D materials for building or repairing structures while flying. 3D printing is gaining momentum in the construction industry. Both on-site and in the factory, static and mobile robots print materials for use in construction projects, such as steel and concrete structures. A new approach to 3D printing — led in its development by Imperial College London and Empa, the Swiss Federal Laboratories of Materials Science and Technology — uses flying robots, known as drones, that use collective building methods inspired by natural builders like bees and wasps. The system, called Aerial Additive Manufacturing (Aerial-AM), involves a fleet of drones working together from a single blueprint. It consists of BuilDrones, which deposit materials during flight, and quality-controlling ScanDrones, which continually measure the BuilDrones’ output and inform their next manufacturing steps. The researchers say that in contrast to alternative methods, in-flight 3D printing unlocks doors that will lead to on-site manufacturing and building in difficult-to-access or dangerous locations such as post-disaster relief construction and tall buildings or infrastructure. The research was Led by Professor Mirko Kovac of Imperial’s Department of Aeronautics and Empa’s Materials and Technology Center of Robotics. Professor Kovac said: “We’ve proved the concept that drones can work autonomously and in tandem to construct and repair buildings, at least in the lab. This scalable solution could help construction and repair in difficult-to-reach areas, like tall buildings.” Aerial-AM uses both a 3D printing and path-planning framework so the drones can adapt to variations in geometry of the structure as a build progresses. The drones are fully autonomous in flight, but there is a human controller in the loop can monitor progress and intervene if necessary, based on the information provided by the drones. To test the concept, the researchers developed four cement-like mixtures for the drones to build with. Throughout the build, the drones assess the printed geometry in real time and adapt their behaviour to ensure they meet the build specifications, with manufacturing accuracy of five millimetres. The proof-of-concept prints included a 2.05-metre cylinder (72 layers) with a polyurethane-based foam material, and an 18-centimetre cylinder (28 layers) with a custom designed structural cement-like material. The technology offers future possibilities for building and repairing structures in unbounded, high or other hard-to-access locations. Next the researchers will work with construction companies to validate the solutions and provide repair and manufacturing capabilities. They believe the technology will provide significant cost savings and reduce access risks compared to traditional manual methods.
Paving the way for large-scale, efficient organic solar cells with water treatment
Organic solar cells (OSCs) are attractive owing to their lightweight, flexibility, and high-power conversion efficiency. However, a lack of morphology control of the active layer makes it challenging to develop OSCs with large active areas. Now, researchers from Gwangju Institute of Science and Technology, Korea take things to the next level by using water treatment for morphology control in the fabrication of active layer thin films, improving the performance and stability of large-area OSCs. Organic solar cells (OSCs), which use organic polymers to convert sunlight into electricity, have received considerable attention in recent times for their desirable properties as next-generation energy sources. These include lightweight, flexibility, scalability, and a high-power conversion efficiency (>19%). Currently, several strategies exist for enhancing the performance and stability of OSCs. However, a problem that lingers on is the difficulty of controlling the morphology of the active layer in OSCs when scaling up to large areas. This makes it challenging to obtain high-quality active layer thin films and, in turn, fine-tune the device efficiency. A team of researchers from the Gwangju Institute of Science and Technology, Korea set out to address this issue. In their work, they suggested a solution that appears rather counterintuitive at first glance: using water treatment to control the active layer morphology. “Water is known to hinder the performance of organic electronic devices, since it remains in the ‘trap states’ of the organic material, blocking the charge flow and degrading the device performance. However, we figured that using water rather than an organic solvent-based active solution as a medium of treatment method would enable necessary physical changes without causing chemical reactions,” explains Professor Dong-Yu Kim, who headed the study. The researchers chose the polymers PTB7-Th and PM6 as donor materials and PC61BM and EH-IDTBR and Y6 as acceptor materials for the active layer. They noticed that inducing a vortex to mix the donor and acceptor materials in the active solution could lead to a well-mixed active solution, yet it was not enough on its own. The active solution was hydrophobic and, accordingly, the researchers decided to use deionized (DI) water and vortices to stir the solution. They let the donor and acceptor materials sit in chlorobenzene (host active solution) overnight, and then added DI water in the solution and stirred it, creating tiny vortices. Due to the hydrophobic nature of the solution, the water pushed on the donor and acceptor molecules, causing them to dissolve more finely into the solution. They then let the solution rest, which caused the water to separate from the solution. This water was then removed, and the water-treated active solution was used to prepare thin films of PTB7-Th: PC61BM (F, fullerene), PTB7-Th: EH-IDTBR (NF, fullerene), and PM6: Y6 (H-NF, high-efficiency non-fullerene). The researchers then examined the photovoltaic performance of these thin films in a slot-die-coated inverted OSC configuration and compared them with those for OSCs without water treatment. “We observed that the water-treated active solution led to a more uniform active layer thin films, which showed higher power conversion efficiencies compared to those not treated with water. Moreover, we fabricated large-area OSC modules with an active area of 10 cm2, which showed a conversion efficiency as high as 11.92% for water-treated H-NF films,” highlights Prof Kim. Overall, this study provides a guideline for developing large-scale, efficient OSCs using a remarkably easy, economical, and eco-friendly method, which can open doors to their realization and commercialization.
Wearable sensors styled into T-shirts and face masks
Imperial researchers have embedded new low-cost sensors that monitor breathing, heart rate, and ammonia into t-shirts and face masks. Potential applications range from monitoring exercise, sleep, and stress to diagnosing and monitoring disease through breath and vital signs. Spun from a new Imperial-developed cotton-based conductive thread called PECOTEX, the sensors cost little to manufacture. Just $0.15 produces a metre of thread to seamlessly integrate more than ten sensors into clothing, and PECOTEX is compatible with industry-standard computerised embroidery machines. First author of the research Fahad Alshabouna, PhD candidate at Imperial’s Department of Bioengineering, said: “The flexible medium of clothing means our sensors have a wide range of applications. They’re also relatively easy to produce which means we could scale up manufacturing and usher in a new generation of wearables in clothing.” The research team embroidered the sensors into a face mask to monitor breathing, a t-shirt to monitor heart activity, and textiles to monitor gases like ammonia, a component of the breath that can be used to track liver and kidney function. The ammonia sensors were developed to test whether gas sensors could also be manufactured using embroidery. Fahad added: “We demonstrated applications in monitoring cardiac activity and breathing, and sensing gases. Future potential applications include diagnosing and monitoring disease and treatment, monitoring the body during exercise, sleep, and stress, and use in batteries, heaters, anti-static clothing.” Wearable sensors, like those on smartwatches, let us continuously monitor our health and wellbeing non-invasively. Until now, however, there has been a lack of suitable conductive threads, which explains why wearable sensors seamlessly integrated into in clothing aren’t yet widely available. Enter PECOTEX. Developed and spun into sensors by Imperial researchers, the material is machine washable, and is less breakable and more electrically conductive than commercially available silver-based conductive threads, meaning more layers can be added for to create complex types of sensor. Lead author Dr Firat Guder, also of the Department of Bioengineering, said: “PECOTEX is high-performing, strong, and adaptable to different needs. It’s readily scalable, meaning we can produce large volumes inexpensively using both domestic and industrial computerised embroidery machines. “Our research opens up exciting possibilities for wearable sensors in everyday clothing. By monitoring breathing, heart rate, and gases, they can already be seamlessly integrated, and might even be able to help diagnose and monitor treatments of disease in the future.” Next, the researchers will explore new application areas like energy storage, energy harvesting and biochemical sensing, as well as finding partners for commercialisation.