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May 2019

Symposium EP13: Thermoelectrics—Materials, Methods and Devices

Hyejeong Lee, Gwangju Institute of Science and Technology

Enhanced Thermoelectric Performance of PEDOT:PSS Nanotubes via AAO Template-Assisted Growth

Written by Bharati Neelamraju

Hyejeong Lee works with Ji Young Jo on using variations of PEDOT:PSS for thermoelectric applications. Lee addressed how conducting polymers are a good choice for wearable thermoelectric devices like thermoelectric generators (TEG). She said PEDOT:PSS is one of the highest conductivity polymers but that it still suffers from low thermoelectric efficiencies compared to their inorganic counterparts. The researchers fabricated PEDOT:PSS nanotubes in a template for enhanced thermoelectric efficiencies. They saw an increase in electrical conductivity due to the stretching of PEDOT chains as well as the decrease in thermal conductivity through phonon scattering in these nanotubes made in their laboratory. They achieved better efficiencies by adding post processing treatments and adding a solvent to these thin films. Lee concluded her talk by explaining to the audience why heading toward low-dimensional nanotubes is an interesting path forward for these materials.


Materials Needs for Energy Sustainability by 2050—Incentivizing a Zero-Waste Future

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Moderator: Elizabeth A. Kócs, University of Illinois at Chicago

Panelists:

  • Gabrielle Gaustad, Alfred University
  • Lucas Mariacher, Phoenix Public Works Department
  • Karsten Schischke, Fraunhofer Institute for Reliability and Microintegration

Written by Aashutosh Mistry

Population growth intrinsically strains resources supporting human life. The glocal (global and local) nature of today’s communities, combined with population growth, causes sustainability issues. Two separate paradigms have been advocated to assist sustainability goals: Materials for Sustainable Development (e.g., photovoltaics) and more recently Sustainable Development of Materials—a broader approach that promotes materials based on both application as well as sustainability. Despite the recognition of sustainability, waste management has been historically underappreciated, with most of the efforts contained in a linear system that either incinerates the final product or disposes it to landfills.

A panel discussion was organized around sustainability and waste management on Tuesday evening. It was argued that zero waste is a lofty goal, and the end effects may not be apparent immediately. Zero waste is difficult to achieve through waste management, and attention should be focused on waste prevention. Ensuring zero waste is a tricky balance due to a variety of often negatively correlated factors such as the interconnected nature of a zero waste economy, technological as well as policy challenges, the participation of producer and consumer, and different local standards to name a few. Additional ambiguity arises from the fact that zero waste is not consistently defined. For example, San Francisco, California enforces participation in recycling, in contrast to Phoenix, Arizona where it is voluntary. Circular economy, where materials are designed to be reutilized at the end of product life, creates problems as well, especially when a material is banned, and it needs to be phased out from all the phases of the circular economy.

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The panelists agreed to a need for lucrative incentives to pursue recycling. Many times, rearranging the process sequence itself can be an effective incentive, for example, a large fraction of recycling cost is attributed to processing—sorting out different waste types, and it is economically more feasible to incentivize consumers to categorize trash than handling it at a recycling plant. This cost of sorting waste often decides whether recycling can be pursued and, in the presence of unacceptable overheads, incinerators or landfills are preferred.

Sustainability image

A unique aspect of this panel discussion was the interactive participation of the audience in the form of audience polling. It was argued that good policies go a long way in realizing the zero waste future. Good policies are to be built upon scientific rationale and statistical data, both of which require active participation from scientists and engineers.

This event was supported in part by NSF, MRS Focus on Sustainability, MRS Energy & Sustainability journal, and Symposium ES13.


Symposium SM01: Materials for Biological and Medical Applications

Sebastian Kollenda, University of Duisburg-Essen and Centre for Nanointegration Duisburg-Essen (CeNIDE)

A Biosensor on the Nanoscale—About the Fate of Functionalized Inorganic Nanoparticles in Living Cells

Written by Gargi Joshi

Due to the natural occurrence of calcium phosphate in bones and teeth, nanoparticles based on calcium phosphate are being considered as a biocompatible option for drug delivery applications to carry cargo molecules like DNA, RNA, and proteins. In his talk, Sebastian Kollenda presented his recent results on therapeutic applications based on these nanoparticles in treatment of inflammation and derived carcinogenesis, vaccination against retroviral infections, as well as viral clearance. Moreover, the main goal was to monitor intracellular pathways and ejection from the body for such therapeutic nanoparticles. The particles have aspherical morphology, and were monodispersed with a typical diameter of 50–150 nm. Time-resolved CLSM demonstrated successful endocytosis of the particles loaded with protein into the cell which was found to be highly dependent on the localized pH values. Thus, a smart tool was designed by using a pH-responsive biosensor to efficiently visualize the intracellular pathways.


Symposium EP13: Thermoelectrics—Materials, Methods and Devices

Xavier Crispin, Linkoping University

Electronic and Ionic Thermoelectric Effects with Conducting Polymers

Written by Bharati Neelamraju

Organic thermoelectric materials are gaining traction for use as the power source for flexible wearable devices. Xavier Crispin talks about two kinds of thermoelectric charge carriers: hole and ion. His research group looks at both the electronic and ionic thermoelectric properties of these materials. Crispin showed how the time evolution of the thermo voltage between a pure hole transport, a pure ion transport, and then a mixed transport conductor is different with the mixed having the highest voltages. Ionic thermoelectric energy storage systems can be used such that it charges during the day due to a variation in temperature while it discharges in the night providing electricity. Polymer electrolytes that conduct ions have high Seebeck coefficients which makes them an ideal candidate for use in supercapacitors. However, these ionic polymer electrolytes are easily affected by humidity. Crispin’s group did a series of experiments to understand this humidity-dependence.


Symposium CP04: Interfacial Science and Engineering—Mechanics, Thermodynamics, Kinetics and Chemistry

Henri-Louis Girard, Massachusetts Institute of Technology

Waterbowls – Reducing Impacting Droplet Interactions by Momentum Reduction

Written by Aashutosh Mistry

Interactions of liquid drops and solid surfaces have been a classical problem in transport phenomena and extensively studied in various contexts such as heat, momentum, and mass exchanges. Depending on the application, one would want to either enhance the effective transport, for example, faster condensation on a colder solid (going from film-wise to drop-wise condensation) or attenuate the intrinsic characteristics of the solid–liquid pair, for example, icing of impacting drops on aircraft wings is detrimental and in turn reduced heat transfer is desired. The former problem of enhanced transport has received considerably more attention than the latter.

Henri-Louis Girard’s research focuses on the problem of attenuating the aforementioned transport modes. From a simplistic understanding, one could argue that liquid-repelling (e.g., hydrophobic for water-repelling) surfaces should provide reduced transport interactions. However, upon a closer look, Girard found that even if the hydrophobic surfaces do not let drops stick to the surface, the impact, oscillations, and rebound transients provide a thorough contact between the sold and flattened drop shape during the oscillation stage. In other words, both time of contact, as well as area of contact, contribute to effective transport. For a hydrophobic surface, the time of contact is smaller, but the contact area is fairly high which jointly leads to not so small interactions. Building upon this interpretation, the research group hypothesized that if the surface has circular ridges, the contact area can be reduced. Further experiments with varying circular ridge dimensions revealed three interaction regimes: (i) when the radius of the ring is smaller than that of the drop, upon drop impact it spreads over the ring and the ring cannot divert the momentum during spreading; (ii) when the radius of the ring is fairly higher than that of the drop (greater than three times), the effectiveness reduces as it does not divert the drop contact early on; and (iii) in between these two regimes, there is an interesting regime where the usefulness of the circular ridges deteriorates with an increase in their radii. At present, the researchers are analyzing the implications of an offset impact of the drop with such ridges in terms of momentum diversion and consequent attenuated transport interactions.