Using Less to Cool More

As a part of the evening session of Symposium QN05 : Emerging Thermal Materials—From Nanoscale to Multiscale Thermal Transport, Energy Conversion, Storage and Thermal Management, Amin Nozariasbmarz, a PhD student at The Pennsylvania State University presented his research on optimizing the performance of thermoelectric (TE) coolers (TECs) and generators (TEGs), titled "Efficient Thermoelectric Materials and Module Design for Wearable Applications".

Amin started the talk by illustrating the basics of TE devices. These are solid state devices that take the advantage of the Seebeck effect to generate electricity from an applied temperature gradient or are capable to moving heat away from an area (refrigeration) by taking advantage of the Peltier effect. In this way, wearable applications of TEs can include both TECs and TEGs. However, it is important to note that unlike commercial applications of TE devices where the temperature gradients encountered are quite high, when it comes to wearable applications for the human body, the temperature gradients expected are quite low (between 1-3 degrees C, usually). 

Amin's analysis took into account that there are two ways to improve performance of TE devices: (i) improving the material's intrinsic thermoelectric properties and (ii) improving the device design. By focusing on the latter, Amin and his colleagues were able to posit that for low thermal gradient applications, optimizing the fill factor and aspect ratio of the TE module is a good way to improve overall TE module performance. The fill factor refers to the ratio of surface area of the TE legs to that of the module, whereas the aspect ratio refers to the ratio of the length of the leg to its width. In commercial devices, the fill factor is usually 20% or more, but using their analytical modelling, Amin was able to conclude that for wearable applications, the fill factor should be lower to about 10-15% to get the maximum cooling power in case of TECs, or maximum power generation in case of TEGs. In this way they were able to demonstrate the possibility of creating TECs with twice the cooling power and eight times more cooling compared to commercial TECs at the same applied voltages. This is great news for thermoelectrics researchers who are trying to use less material to create more conformable and lightweight wearable TECs and TEGs. 

To know more about this research work, please click here


Symposium X: The James Webb Space Telescope

Dr. Jonathan Arenberg, Chief Engineer for the Space Science Mission at Northrop Grumman Aerospace Systems gave a very interesting and engaging talk on the The James Webb Space Telescope (JWST) - Its Mission, Design and Development as a part of Symposium X - Frontiers of Materials Research. 

Dr. Arenberg highlighted the various missions of the JWST that range from getting information about the first light and reionization events after the creation of the universe, understanding the evolution and assembly of the galaxies, the birth of stars and protoplanetary systems, to understanding the planetary systems and fundamentals about the origin of life. The JWST will help scientists and researchers understand the origin of life, how galaxies evolve, and the most important question - are we alone in the universe. 

He went on to talk about the impressive design and engineering marvel that makes the JWST possible. The challenge in undertaking such a mission is to produce a telescope that can observe the earliest, faintest galaxies and nearby planetary systems in good detail with good resolution and the ability to separate foreground objects without confusion. The design of the JWST makes this possible by using large mirrors for light gathering and detail, infrared (IR) to see distant galaxies which are red shifted due to the expanding size of space (even though they emit in the visible and ultraviolet (UV) wavelengths), ensure that the telescope remains cold (between 25 - 90 K) so as to not obscure the IR data with its own temperature, and have high enough resolution to separate foreground objects. Additionally, the JWST needs a wide field of view, should be capable of imaging the sky in one year, have a stable optical system, be launchable (and transportable!) and have a reliable performance over its lifetime. These design constraints make selection of materials very important, and Dr. Arenberg stressed on the importance of picking the right materials and being able to predict their behavior not at room temperature, but at cold temperatures encountered in space. He stressed on how "confidence in performance is critical because uncertainty is expensive" which is especially true for a telescope that costs billions of dollars. 

The JWST is a very impressive design feat: consisting of a 6.5 m diameter telescope composed of Beryllium mirrors chosen due to their low coefficient of thermal expansion, a scientific successor to the Hubble and Spitzer telescopes, passively cooled to 45 K on the cool side, it will orbit around the Sun-Earth second Lagrange point (L2) to prevent the Sun, Earth, and Moon from blocking its view of space.  The hot side of the sunshield would go up to 340-370 K in space, which requires materials that have a stable performance in this temperature range and do not degrade over time. Compared to the 2.5 m diameter and 11,110 kg weight of the Hubble telescope, the JWST has a diameter of 6.5 m and weighs just 6400 kg. With 40 deployable structures and 178 release devices, the telescope has to be capable of being transported to the launch site via both land and water transportation, making it important not just to make the telescope robust while use, but also robust while transportation. 

From a materials science perspective, Dr. Arenberg highlighted the importance of various materials and their properties that are important in any space mission, including this one. These include selecting adhesives with long pot life that can cure completely, exploring adhesiveless bonding, selecting materials that do not creep, using low outgassing materials (silicone replacement), with stable indices of refraction over a wide range of temperatures, photopolymerizable materials, development of photocatalytic treatments or coatings, and UV enhanced material deposition. With all these avenues, it was truly amazing to see an intersection of materials science, optics, and physics to create such an amazing telescope and I'll be watching closely for its launch in 2021. 


Large Pressure Sensors for Human-Machine Interactions

Xiaodong Wu from Sichuan University presented his research on "Large-Area Compliant, Sensitive and Highly Tunable Pressure Sensors for Versatile Human-Machine Interaction" as a part of the Symposium EP04: Soft and Stretchable Electronics - From Fundamentals to Applications session today. This research was done in collaboration with Yasser Khan, Jonathan Ting, Juan Zhu, Seiya Ono, and Ana Arias from University of California, Berkeley. 

Wearable pressure sensors usually consist of an active layer that undergoes certain transformations that are translated to the electrodes which usually sandwich this active, deformable layer. As the dimensions of the layer change due to deformation, the electrodes can translate this into a capacitive or resistive response, depending on the change in electrical and/or mechanical properties of the deformable material. By incorporating microstructures into this sensing layer, the sensitivity and sensing range of the pressure sensor can be tuned. The most common method of incorporating microstructures is by using a microstructured silicon mold, pouring and curing silicone in this mold, and releasing this silicone layer to realize microstructures in the silicone. However, this method is limited by the high cost and low scalability, preventing the creation of large-area flexible pressure sensors. Wu and colleagues demonstrated a method of creating highly sensitive and large-area pressure sensors in a facile and scalable manner by using commercially available micro-meshes that can embed microstructural features on the silicone material. This mass-molding method was combined with the arrangement of side-by-side electrodes to form flexible pressure sensors with high sensitivity and a broad working range, capable of sensing pressure up to 1000 kPa. This was then shown to be applicable as a gait analyzer, by using it as a smart insole that can monitor both foot pressure and temperature. 

To know more about this research, please click here


Singing and Color Changing Robots

PhD student Do Yoon Kim from Seoul National University presented a very interesting talk with a great background score by Vivaldi, during the Symposium EP04: Soft and Stretchable Electronics - From Fundamentals to Applications session, titled "Electro-active Soft Photonic Devices for the Simultaneous Generation of Color and Sound". Kim carried this research out in collaboration with Sunglok Choi from Electronics and Telecommunications Research Institute and with his advisor Prof. Jeong-Yun Sun from Seoul National University as well. 

This research was based on an interesting application of dielectric electroactive polymers (DEAPs). DEAPs are interesting materials that are very soft and compliant, and demonstrate a Maxwell effect in the presence of an electric field. When an electric field is applied, the electrodes applied on a DEAP act as capacitors which can hold charges, thereby compressing the DEAP sandwich layer, creating an areal displacement or actuation. In this way, DEAP actuators are capable of areal actuation strains > 200% with actuation speeds between 10 Hz - 20kHz. Kim combined this performance of DEAPs with organogels containing photonic crystals (PCs). When subjected to either a stretching, swelling, or magnetic drive, PCs can show a change in color thereby acting as active pigments. When combined with DEAPs, on the application of an electric field, the DEAP would stretch, stretching the PC-laden organogel, creating colorful actuation. Moreover, these organogels are very soft (modulus 50kPa compared to 1MPa for silicone) and can sustain the their mechanical properties for a long time. Moreover, when this layered DEAP is subjected to an AC electrical input, it can vibrate and thereby generate a corresponding sound. The output signals' amplitudes and frequencies correlate well with the input signals. In this way Kim and colleagues were able to create an actuator that could produce sound with an AC input and change color with a DC input, which could also be decoupled depending on the frequency and corresponding areal strain. At high enough frequencies, the areal strain is low enough that the color change is imperceptible, thereby creating only a sound output. At lower frequencies, both colors and sounds can be changed and observed. 

This was an excellent application of DEAPs, and demonstrated the application of such a device for smart speakers and interactive video displays. To read more about this research work, please click here


Symposium ES09: Advanced Materials for the Water-Energy Nexus

Guihua Yu, The University of Texas at Austin

Hydrogels as an Emerging Material Platform for the Water-Energy Nexus

Written by Chiung-Wei Huang

The nanostructured materials have demonstrated versatile advantages which enables high-performance renewable energy devices. Guihua Yu showed that the nanostructured hydrogels, a cross-linked network, exhibit improved carrier transport and permeability. The conducting polymer hydrogels contributed to the enhanced conductivity. Based on the hydrogel, Yu devoted the second part of his talk on the realization of using solar energy to purify polluted or saline water for drinkable water. Because the conversion suffers from inefficient optical and heat loss, Yu’s group introduced the nanostructured polymers network to serve as a solar vapor generator. As a result, the converted energy from the generator can be used to vaporize water with an increased purification rate. The hydrogel-based solar-water harvesting system thus helps to reduce the energy demand.


Innovation in Materials Characterization Award

InnCharTalk_800x533Stig Helveg, Haldor Topsoe A/S

Electron Microscopy Advances in Catalysis

Written by Prachi Patel

Stig Helveg set the stage for his talk by emphasizing the importance of catalysis for a sustainable future. Catalysis is the backbone of chemical reactions to produce fertilizers, chemicals, and fuels. It will be critical for increasing food supply, reducing air pollutant emissions, and for harnessing renewable energy.

“It’s a field we cannot live without today and also, of course, tomorrow,” he said, before delving into the goal and the promise of his pioneering work on atomic-scale transmission electron microscopy under working reaction conditions to deepen the understanding of catalysis and advance catalyst research.

Helveg first highlighted how recent advances in electron microscopy have been able to address challenges in catalyst research. With tremendous advances in electron microscopy over the past 10 years, scientists can now observe materials at the atomic scale. Helveg and his colleagues, for example, published an article in 2014 showing how they were able to resolve the sites of single cobalt atoms in a Co‐Mo‐S catalyst that is used in desulfurization processes at oil refineries by analyzing the material at the single‐atom level. “There has been a debate for decades where Co atoms lie,” he said. “This really shows the power of electron microscopy.”

His work has been devoted to harnessing this power for insights into nanostructured catalysts. Researchers have in recent years focused on developing nanocatalysts given their abundant sites for catalysis, and to increase the activity of those sites by sculpturing and composing them. The challenge is that nanostructures are very sensitive to changes in their surroundings, he said. Chemical reactions can alter their surface, morphology, phase, and make them clump together or break apart. Understanding what happens to catalysts at the nanoscale under industrial chemical reaction conditions is critical to improve catalysis, and has driven his research at Haldor Topsoe A/S, Helveg said.

InnCharTalk2_800x533

“Introducing reaction conditions into a microscope is really like mixing fat and water,” he said. Microscopes are high-vacuum machines that work at room temperature, while chemical plants work at high pressures and temperatures. Nonetheless, he and others have developed technologies such as aperture gas cells that have allowed performing reaction conditions from an industrial plant in a microscope. These tools have yielded key insight into several phenomena in catalysts, such as generation of active sites, restructuring, and compositional changes. Helveg offered a more detailed look on two case studies that illustrate the practical application of these techniques.

In one, they used high-resolution TEM to study vanadium oxide supported on titanium dioxide, which is a catalyst for removing nitrogen oxide emissions. They found that the vanadium oxide (001) facets oscillate between a clean edge and a smeared edge as the researchers switched between oxidizing and reducing conditions. Using this information on the catalyst system, Helveg is now working with researchers at Aarhus University and Innovation Fund of Denmark to create a better NOx reduction catalyst.

Another case study involves the use of a specialized window cell that the Haldor Topsoe A/S team developed with researchers at TU Delft and ThermoFisher Scientific. The cell is a tiny gas flow channel made with two 1-µm-thick silicon nitride membranes separated by 5-µm-tall pillars. Windows that are just 15-nm wide act like a nanoreactor, allowing atomic-resolution imaging of sub-nanoliter volumes of catalyst at ambient pressures of up to 14 bar and elevated temperatures of 660°C.

This device helped the research group elucidate previously unseen phenomenon during the oxidation of carbon monoxide by platinum. Many catalytic reactions oscillate, and it has been known for decades that this is because of dynamic changes to the catalyst surface. But no one had observed these changes in nanoparticle catalysts. Using their nanoreactor, Helveg and his colleagues saw that the nanocrystals undergo reversible refacetting, going back and forth between a rounded shape to a more pointed shape as the reaction oscillates.

To sum up, Helveg stressed how advances in electron microscopy have allowed the study of nanoparticle dynamics under meaningful catalytic conditions, and how he and his colleagues have linked their observations to functional analysis. Going forward, he appeals to those in the electron microscopy field to look into two critical issues: improving the understanding of the right electron dose for a chemically relevant signal, and understanding the mass-temperature distribution inside commercial reactor devices. “The future certainly looks very bright from where we are,” he concluded.

The Innovation in Materials Characterization Award honors an outstanding advance in materials characterization that notably increases knowledge of the structure, composition, in situ behavior under outside stimulus, electronic behavior, or other characterization feature, of materials. It is not limited to the method of characterization or the class of materials observed.

Helveg’s award citation is “for pioneering atomic-scale transmission electron microscopy under reactive gas environments, leading to groundbreaking insights in catalysis, crystal growth and corrosion.”

The Innovation in Materials Characterization Award has been endowed by Dr. Gwo-Ching Wang and Dr. Toh-Ming Lu.


Symposium ES01: Organic Materials in Electrochemical Energy Storage

Erin Ratcliff, University of Arizona

Organic Semiconductor Photoelectrochemical Flow Cells—Integrating Photoelectrochemical Solar Energy Conversion with Redox Battery Energy Storage

Written by Bharati Neelamraju

Having limited sunlight during the day poses as a major barrier for organic photovoltaic (OPV) based research and hence energy storage directly connected to energy generation has been a major area of research. Developing new organic electrode systems to store this energy in a controlled chemical reaction which can be analogous to photosynthesis is one approach to solve this issue. Understanding various events that occur in an organic photovoltaic at time scales ranging from femto to milliseconds has led to the OPV growth that exists today. Erin Ratcliff’s group looks at the electrochemistry events that occur in the milli second timescale region to better understand the charge transfer kinetics at the electrode. They used techniques like electrochemical impedance spectroscopy (EIS) and cyclic voltammetry combined with the Marcus-Gerischer relationship to predict the rate of electron transfer. They further showed that the overlap of density of state (DOS) of the electrode and the redox probe govern this electron transfer event. The researchers demonstrated that selective electron transfer can be achieved by manipulating this DOS by changing the microstructure of the polymer using different processing conditions. Ratcliff’s current work involves creating deliberate heterogeneity in a polymer system to understand its consequences to electron transfer events. She concluded her talk reminding the community that while looking at the different time-scale of events is important, researchers also need to keep the electrochemical behavior across different length scales in mind.


Symposium SM04: Translational Materials in Medicine—Prosthetics, Sensors and Smart Scaffolds

Julian Jones, Imperial College London

3D Printable Bouncing Hybrids for Cartilage Regeneration

Written by Chiung-Wei Huang

Cartilage rupture is a common knee injury, usually due to strong twisting of the knee joint. Surgery requires devices that can stably sit on the injured surface of the articular cartilage, helping to regenerate and repair the cartilage tissues. Julian Jones showed an animation video illustrating the healing process followed by several key developments advanced by his research team. The device they designed is a three-dimensional (3D) printable scaffold device that mimics the articular cartilage-like matrix. The advantage of the 3D printing technique is to offer bespoke scaffold capability. The material, in the meantime, needs to be printer-applicable. Jones introduced the new biomaterial, a silica-polymer mixture, as the ink to produce the scaffold device. The synthesis method renders the mixed material with strong linkage while flexible, opening routes to a new class of biomaterials.


Seek your Way with Magnetic Electronics

PhD student Gilbert Santiago Canon Bermudez from Helmholtz-Zentrum Dresden presented his research work on magnetosensitive skins, titled "Magnetosensitive Skins with Multi-Range Detection Capabilities for Interactive Electronics" as a part of Symposium EP04: Soft and Stretchable Electronics - From Fundamentals to Applications, on Day 4 of the 2019 MRS Spring Conference. 

Bermudez started by talking about why magentic fields are such an attractive source to control and create interactive electronics. They are present all around us, they're easily scanned, and they are vectors and thus can be used to create different kinds of motion. He detailed the fabrication of magnetoresistive skins which are multilayers deposited on thin plastic substrates that can can resist strong bending and folding and still show reliable performance - thereby creating skin-like patches that can be applied to your finer, arm, or the palm of your hand. These can then act as on-skin angle detectors and even be used to control various electronic devices by simulating actions such as turning a dial, moving the volume rocker up or down, or even as a virtual keyboard. He also talked about the development of geomagnetosensitive skins that can detect and work with the earth's magnetic field (in the microTesla range) to create flexible skins that can act as a compass. His demonstration video showed him in the woods as the skin pointed out the magnetic north to him. Moreover, the capability of these skins to perform even in the microTesla range extends their capabilities to act as flexible point-of-care diagnostic devices, possibly eliminating the need for rigid and bulky magnetic-field based devices for healthcare monitoring. To read more about Bermudez's research in this field, you can click here.  


Best Poster Award Winners – Wednesday



Poster_Wednesday_800x588

 



Jinghan Wang, Key Laboratory for Special Functional Materials of the Ministry of Education

QN08.08.13

Fabrication of Porphyrin Assemblies and Biological Applications

 

Pan Xia, University of California, Riverside

EP02.05.06

Controlling the Surface Chemistry of Quantum Confined Silicon Nanoparticles for NIR to Visible Upconversion

 

Michael Wang, University of Michigan

ES04.05.03

Mixed Electronic and Ionic Conduction Properties of Reduced Lithium Lanthanum Titanate

 

Ashley Gaulding, National Renewable Energy Laboratory

ES15.10.11|ES15.09.05

Spotlight Talk—Conductivity Tuning via Doping with Electron Donating and Withdrawing Molecules in Perovskite CsPbI3 Nanocrystal Films