How To Harness Heat To Power Computers

One of the biggest problems with computers, dating to the invention of the first one, has been finding ways to keep them cool so that they don’t overheat or shut down. Instead of combating the heat, two University of Nebraska–Lincoln engineers have embraced it as an alternative energy source that would allow computing at ultra-high temperatures. Sidy Ndao, assistant professor of mechanical and materials engineering, said his research group’s development of a nano-thermal-mechanical device, or thermal diode, came after flipping around the question of how to better cool computers.

thermal diode

If you think about it, whatever you do with electricity you should (also) be able to do with heat, because they are similar in many ways,” Ndao said. “In principle, they are both energy carriers. If you could control heat, you could use it to do computing and avoid the problem of overheating.”

A paper Ndao co-authored with Mahmoud Elzouka, a graduate student in mechanical and materials engineering, was published in the March edition of Scientific Reports. In it, they documented their device working in temperatures that approached 630 degrees Fahrenheit (332 degrees Celsius).


How To Turn Sunlight, Heat and Movement Into Electricity — All at Once

Many forms of energy surround you: sunlight, the heat in your room and even your own movements. All that energy — normally wasted — can potentially help power your portable and wearable gadgets, from biometric sensors to smart watches. Now, researchers from the University of Oulu in Finland have found that a mineral with the perovskite crystal structure has the right properties to extract energy from multiple sources at the same time.

perovskite solar panel

Perovskites are a family of minerals, many of which have shown promise for harvesting one or two types of energy at a time — but not simultaneously. One family member may be good for solar cells, with the right properties for efficiently converting solar energy into electricity. Meanwhile, another is adept at harnessing energy from changes in temperature and pressure, which can arise from motion, making them so-called pyroelectric and piezoelectric materials, respectively.

Sometimes, however, just one type of energy isn’t enough. A given form of energy isn’t always available — maybe it’s cloudy or you’re in a meeting and can’t get up to move around. Other researchers have developed devices that can harness multiple forms of energy, but they require multiple materials, adding bulk to what’s supposed to be a small and portable device.

This week in Applied Physics Letters, Yang Bai and his colleagues at the University of Oulu explain their research on a specific type of perovskite called KBNNO, which may be able to harness many forms of energy. Like all perovskites, KBNNO is a ferroelectric material, filled with tiny electric dipoles analogous to tiny compass needles in a magnet. Within the next year, Bai said, he hopes to build a prototype multi-energy-harvesting device. The fabrication process is straightforward, so commercialization could come in just a few years once researchers identify the best material. “This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable,” he said.

This kind of material would likely supplement the batteries on your devices, improving energy efficiency and reducing how often you need to recharge. One day, Bai said, multi-energy harvesting may mean you won’t have to plug in your gadgets anymore. Batteries for small devices may even become obsolete.


Electronics: How To Dissipate Heat in A Nanocomputer

Controlling the flow of heat through semiconductor materials is an important challenge in developing smaller and faster computer chips, high-performance solar panels, and better lasers and biomedical devices. For the first time, an international team of scientists led by a researcher at the University of California, Riverside has modified the energy spectrum of acoustic phononselemental excitations, also referred to as quasi-particles, that spread heat through crystalline materials like a wave—by confining them to nanometer-scale semiconductor structures. The results have important implications in the thermal management of electronic devices. Led by Alexander Balandin, Professor of Electrical and Computing Engineering and UC Presidential Chair Professor in UCR’s Bourns College of Engineering, the research is described in a paper published in the journal Nature Communications.


The team used semiconductor nanowires from Gallium Arsenide (GaAs), synthesized by researchers in Finland, and an imaging technique called Brillouin-Mandelstam light scattering spectroscopy (BMS) to study the movement of phonons through the crystalline nanostructures. By changing the size and the shape of the GaAs nanostructures, the researchers were able to alter the energy spectrum, or dispersion, of acoustic phonons. The BMS instrument used for this study was built at UCR’s Phonon Optimized Engineered Materials (POEM) Center, which is directed by Balandin.

Controlling phonon dispersion is crucial for improving heat removal from nanoscale electronic devices, which has become the major roadblock in allowing engineers to continue to reduce their size. It can also be used to improve the efficiency of thermoelectric energy generation, Balandin said. In that case, decreasing thermal conductivity by phonons is beneficial for thermoelectric devices that generate energy by applying a temperature gradient to semiconductors.

For years, the only envisioned method of changing the thermal conductivity of nanostructures was via acoustic phonon scattering with nanostructure boundaries and interfaces. We demonstrated experimentally that by spatially confining acoustic phonons in nanowires one can change their velocity, and the way they interact with electrons, magnons, and how they carry heat. Our work creates new opportunities for tuning thermal and electronic properties of semiconductor materials,” Balandin said.


How To Safely Use Graphene Implants Into Tissues

In the future, our health may be monitored and maintained by tiny sensors and drug dispensers, deployed within the body and made from grapheneone of the strongest, lightest materials in the world. Graphene is composed of a single sheet of carbon atoms, linked together like razor-thin chicken wire, and its properties may be tuned in countless ways, making it a versatile material for tiny, next-generation implants. But graphene is incredibly stiff, whereas biological tissue is soft. Because of this, any power applied to operate a graphene implant could precipitously heat up and fry surrounding cells.

Now, engineers from MIT and Tsinghua University in Beijing have precisely simulated how electrical power may generate heat between a single layer of graphene and a simple cell membrane. While direct contact between the two layers inevitably overheats and kills the cell, the researchers found they could prevent this effect with a very thin, in-between layer of water. By tuning the thickness of this intermediate water layer, the researchers could carefully control the amount of heat transferred between graphene and biological tissue. They also identified the critical power to apply to the graphene layer, without frying the cell membrane.

Co-author Zhao Qin, a research scientist in MIT’s Department of Civil and Environmental Engineering (CEE), says the team’s simulations may help guide the development of graphene implants and their optimal power requirements.


We’ve provided a lot of insight, like what’s the critical power we can accept that will not fry the cell,” Qin says. “But sometimes we might want to intentionally increase the temperature, because for some biomedical applications, we want to kill cells like cancer cells. This work can also be used as guidance [for those efforts.

Qin’s co-authors include Markus Buehler, head of CEE and the McAfee Professor of Engineering, along with Yanlei Wang and Zhiping Xu of Tsinghua University.
The results are published today in the journal Nature Communications.


How To Break The Brain Barrier To Kill Cancer

Using a laser probe, neurosurgeons at Washington University School of Medicine in St. Louis have opened the brain’s protective cover, enabling them to deliver chemotherapy drugs to patients with a form of deadly brain cancer. In a pilot study, 14 patients with glioblastoma – the most common and aggressive type of brain cancer – underwent minimally invasive laser surgery to treat a recurrence of their tumors. Heat from the laser is known to kill brain tumor cells but, unexpectedly, the researchers found that the technology can penetrate the blood-brain barrier.

laser breaks brain barrierCLICK ON THE IMAGE TO ENJOY THE VIDEO

The laser treatment kept the blood-brain barrier open for four to six weeks, providing us with a therapeutic window of opportunity to deliver chemotherapy drugs to the patients,” said co-corresponding author Eric C. Leuthardt, MD, a Washington University professor of neurosurgery who treats patients at Barnes-Jewish Hospital. “This is crucial because most chemotherapy drugs can’t get past the protective barrier, greatly limiting treatment options for patients with brain tumors. We are closely following patients in the trial,” said Leuthardt, who also is a Siteman Cancer Center member. “Our early results indicate that the patients are doing much better on average, in terms of survival and clinical outcomes, than what we would expect. We are encouraged but very cautious because additional patients need to be evaluated before we can draw firm conclusions.

The study is published online Feb. 24 in the journal PLOS ONE.


How To Harvest Heat In The Dark To Produce Electricity

Physicists have discovered radical new properties in a nanomaterial, opening new possibilities for highly efficient thermophotovoltaic cells that could one day harvest heat in the dark and turn it into electricity. The research team from the Australian National University (ANU/ARC Centre of Excellence CUDOS) and the University of California Berkeley demonstrated a new artificial material, or metamaterial, that glows in an unusual way when heated.

The findings could drive a revolution in the development of cells which convert radiated heat into electricity, known as thermophotovoltaic cells. “Thermophotovoltaic cells have the potential to be much more efficient than solar cells,” said Dr Sergey Kruk from the ANU Research School of Physics and Engineering.


Our metamaterial overcomes several obstacles and could help to unlock the potential of thermophotovoltaic cells.”

Thermophotovoltaic cells have been predicted to be more than twice as efficient as conventional solar cells. They do not need direct sunlight to generate electricity, and instead can harvest heat from their surroundings in the form of infrared radiation. They can also be combined with a burner to produce on-demand power or can recycle heat radiated by hot engines. The team’s metamaterial, made of tiny nanoscopic structures of gold and magnesium fluoride, radiates heat in specific directions. The geometry of the metamaterial can also be tweaked to give off radiation in specific spectral range, in contrast to standard materials that emit their heat in all directions as a broad range of infrared wavelengths. This makes the new material ideal for use as an emitter paired with a thermophotovoltaic cell.

The project started when Dr Kruk predicted the new metamaterial would have these surprising properties. The ANU team then worked with scientists at the University of California Berkeley, who have unique expertise in manufacturing such materials.

To fabricate this material the Berkeley team were operating at the cutting edge of technological possibilities,” Dr Kruk said. “The size of an individual building block of the metamaterial is so small that we could fit more than 12,000 of them on the cross-section of a human hair.

The research is published in Nature Communications.


Hybrid Solar Cells 20% More Efficient

Scientists have developed a new hybrid, solar-energy system that harnesses the full spectrum of the sun’s radiation by pairing a photovoltaic cell with polymer films. The films convert the light that goes unused by the solar cell into heat and then converts the heat into electricity. The device produces a voltage more than five times higher than other hybrid systems.

Solar cells today are getting better at converting sunlight to electricity, but commercial panels still harvest only part of the radiation they’re exposed to. Scientists are working to change this using various methods. One approach is to hybridize solar cells with different materials to capture more of the sun’s energy. Professor Eunkyoung Kim, from Seoul’s Yonsei University (Korea), and colleagues turned to a clear, conductive polymer known as PEDOT to try to accomplish this.

hybrid solar cells

A display changes colors, powered solely by a new hybrid solar-energy device

The researchers layered a dye-sensitized solar cell on top of a PEDOT film, which heats up in response to light. Below that, they added a pyroelectric thin film and a thermoelectric device, both of which convert heat into electricity. The efficiency of all components working together was more than 20 percent higher than the solar cell alone. With that boost, the system could operate an LED lamp and an electrochromic display.

A report has been published in the journal ACS Nano.


How To Heat Your House At Night With Sun’s Energy

It’s an obvious truism, but one that may soon be outdated: The problem with solar power is that sometimes the sun doesn’t shine. Now a team at the Massachusetts Institute of Technology ( MIT) and Harvard University has come up with an ingenious workaround — a material that can absorb the sun’s heat and store that energy in chemical form, ready to be released again on demand. This solution is no solar-energy panacea: While it could produce electricity, it would be inefficient at doing so. But for applications where heat is the desired output — whether for heating buildings, cooking, or powering heat-based industrial processes — this could provide an opportunity for the expansion of solar power into new realms.

It could change the game, since it makes the sun’s energy, in the form of heat, storable and distributable,” says Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering at MIT, who is a co-author of a paper describing the new process in the journal Nature Chemistry. Timothy Kucharski, a postdoc at MIT and Harvard, is the paper’s lead author.

How To Triple Service Life Of Aircraft Engines

Researchers at University West in Sweden have started using nanoparticles in the heat-insulating surface layer that protects aircraft engines from heat. In tests, this increased the service life of the coating by 300%. This is something that interests the aircraft industry to a very great degree, and the hope is that motors with the new layers will be in production within two years.

To increase the service life of aircraft engines, a heat-insulating surface layer is sprayed on top of the metal components. Thanks to this extra layer, the engine is shielded from heat. The temperature can also be raised, which leads to increased efficiency, reduced emissions, and decreased fuel consumption.

The goal of the University West research group is to be able to control the structure of the surface layer in order to increase its service life and insulating capability. They have used different materials in their work.

The ceramic layer is subjected to great stress when the enormous changes in temperature make the material alternately expand and contract. Making the layer elastic is therefore important. Over the last few years, the researchers have focused on further refining the microstructure, all so that the layer will be of interest for the industry to use

The base is a ceramic powder, but we have also tested adding plastic to generate pores that make the material more elastic,” says Nicholas Curry, who has just presented his doctoral thesis on the subject.

We have tested the use of a layer that is formed from nanoparticles. The particles are so fine that we aren’t able to spray the powder directly onto a surface. Instead, we first mix the powder with a liquid that is then sprayed. This is called suspension plasma spray application“.


How To Cool Fusion In Nuclear Reactors

Particles suspended in cooling water could prevent hotspots in nuclear plant cooling systems and electronics. Cooling systems generally rely on water pumped through pipes to remove unwanted heat. Now, researchers at MIT and in Australia have found a way of enhancing heat transfer in such systems by using magnetic fields, a method that could prevent hotspots that can lead to system failures. The system could also be applied to cooling everything from electronic devices to advanced fusion reactors, they say. Hu, associate director of MIT’s Nuclear Reactor Laboratory, says the new results are the culmination of several years of research on nanofluids — nanoparticles dissolved in water.

“The magnets attract the particles closer to the heated surface” of the tube, greatly enhancing the transfer of heat from the fluid, through the walls of the tube, and into the outside air, says Hu.

Without the magnets in place, the fluid behaves just like water, with no change in its cooling properties. But with the magnets, the heat transfer coefficient is higher, she says — in the best case, about 300 percent better than with plain water. “We were very surprised” by the magnitude of the improvement, Hu says.
The system, which relies on a slurry of tiny particles of magnetite, a form of iron oxide, is described in the International Journal of Heat and Mass Transfer, in a paper co-authored by MIT researchers Jacopo Buongiorno and Lin-Wen Hu, and four others.

New Polymer Nanoparticles Kill 95 % of Cancer Cells

Researchers at Wake Forest Baptist Medical Center have modified electrically-conductive polymers, commonly used in solar energy applications, to develop revolutionary polymer nanoparticles (PNs) for a medical application. When the nanoparticles are exposed to infrared light, they generate heat that can be used to kill colorectal cancer cells.

Levi-Polyachenko and her team discovered a novel formulation that gives the polymers two important capabilities for medical applications: the polymers can be made into nanoparticles that are easily dispersed in water and generate a lot of heat when exposed to infrared light.Results of this study showed that when colorectal cancer cells incubated with the PNs were exposed to five minutes of infrared light, the treatment killed up to 95 percent of cells. “The results of this study demonstrate how new medical advancements are being developed from materials science research,” said Levi-Polyachenko.
The study was directed by Assistant Professor of Plastic and Reconstructive Surgery, Nicole H. Levi-Polyachenko, Ph.D., and done in collaboration with colleagues at the Center for Nanotechnology and Molecular Materials at Wake Forest University. This study was recently published online, ahead of print, in the journal, Macromolecular Bioscience (DOI: 10.1002/mabi.201200241)