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**CANCELLED** Seminar 10/22/2014 - Dean DeLongchamp, NIST: Structure Measurements for Organic Photovoltaics and Manufacturing

Oct 22, 2014  ·  12:00 p.m. 1:00 p.m.  ·  Bowen Hall Auditorium

Abstract: Organic photovoltaics (OPV) is a promising candidate technology for the low-cost fabrication of modules to harvest solar energy.  Although OPV technology has significantly matured over the past few years, there remain significant challenges in addressing the gap between lab-scale devices and real manufacturing. Structure-property-performance relationships for OPV devices are still underdeveloped, and relationships based on one system are not necessarily transferrable to new, higher-performance systems. This talk will describe our efforts to develop measurements that support OPV manufacturing. Using a blade coating process as a prototype for slot-die coating, we have developed several techniques to observe the structure of OPV films in-situ as they dry. Our measurements include synchrotron-based X-ray scattering and a variety of optical methods. We use these techniques to identify the mechanisms by which formulation and processing choices influence the nanoscale structure of the films. Several OPV systems will be described including polymer/fullerene, small-molecule/fullerene, and polymer/polymer. Throughout solidification, we can follow the number of phases, their composition, and the extent of order within them. In-situ techniques provide far more information about the solidification process than can be obtained by measuring already-dried films, providing a valuable tool to guide the selection of formulation and processing parameters.

All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Seminar 11/3/2014 - Ana Claudia Arias, Univ. of California-Berkeley: Printed Flexible Electronics: Enabling New Integrated Systems

Nov 3, 2014  ·  12:00 p.m. 1:00 p.m.  ·  Bowen Hall Auditorium

This is a joint seminar with the Department of Electrical Engineering.

Abstract: The area of printed electronics has been focused on the use of new classes of semiconducting and conducting materials in two main applications, displays and photovoltaics. Both applications require materials long-term stability, long shelf life as well the need for patterning and deposition over large areas.  Over the past 10 years significant progress in the performance of printable materials has been reported including highly efficient solar cells, light emitting diodes and thin film transistors with mobilities as high as 10 cm2/Vs. The work is highly motivated by the potential for high through put, high volume, low cost manufacturing. While large area electronics continues to be a good application for printed flexible devices, wearable medical devices, which benefit from new form factors, represent a good shift in direction of research in the field.  Wearable medical sensors have the potential to play an essential role in the reduction of health care costs as they encourage healthy living by providing individuals feedback on personal vital signs and enable the facile implementation of both in-hospital and in-home professional health monitoring. In printed flexible electronics however, there are no standards for materials set, device models and fabrication methods. This lack of standards slows down design of new systems and the success of the technology as a whole. In this talk, I will review the state of the art of devices produced by printing and introduce a blade coating method that yields highly homogeneous flexible thin films that are applied to LEDS, photodiodes and TFTs.  The application of these devices as building blocks for flexible electronics systems will also be discussed.

Bio: Dr. Ana Claudia Arias is an Associate Professor at the Electrical Engineering and Computer Sciences Department at the University of California in Berkeley and a faculty director at the Berkeley Wireless Research Center (BWRC). Prior to joining the University of California she was the Manager of the Printed Electronic Devices Area and a Member of Research Staff at PARC, a Xerox Company, Palo Alto, CA. She went to PARC from Plastic Logic in Cambridge, UK where she led the semiconductor group. She did her PhD on semiconducting polymer blends for photovoltaic devices at the University of Cambridge, UK. Prior to that, she received her master and bachelor degrees in Physics from the Federal University of Paraná in Curitiba, Brazil. Her research focuses on devices based on solution processed materials and application development for flexible sensors and electronic systems. Ana Claudia is a member of the technical advisory board of Linde Nanomaterials, and the chair of ThinFilm Electronics Technical Advisory Council.

All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Seminar 11/5/2014 - Georg Steinhauser, Colorado State University: Radionuclide Analysis in Environmental Research after the Fukushima Nuclear Accident

Nov 5, 2014  ·  12:00 p.m. 1:00 p.m.  ·  Bowen Hall Auditorium

Abstract: The Fukushima nuclear accident will remain in public memory as one of the worst environmental disasters of the 21st century. In my presentation, I will focus on radionuclide monitoring after the accident and its challenges. Radionuclide monitoring is essential to understanding radioecological consequences and effects on food safety. In this context I will also discuss legal implications such as the regulatory limits of radionuclides in food.  Monitoring also is central to forensic work that may help understand the accident and its chronology. To date most of radionuclide monitoring has focused on volatile and ?-emitting radionuclides such as 137Cs, 131I, and 132Te. Relatively little work has been done on the monitoring of “difficult” radionuclides such as 90Sr or plutonium that are highly health relevant but much more laborious to measure compared with ?-emitters. We succeeded in obtaining unique sample material from inside the “exclusion zone” around the Fukushima power plant that was analyzed for 90Sr and plutonium. Our analyses revealed relatively high concentrations of 90Sr; however, these activity concentrations were exceeded by 137Cs by usually 3 to 4 orders of magnitude. In two spots within the exclusion zone we could also prove environmental presence of plutonium from Fukushima. Our studies show that, although the damaged Fukushima reactors emitted primarily volatile radionuclides, small but detectable amounts of less volatile radionuclides such as radiostrontium and plutonium have been emitted from the reactors, which was not expected for this accident scenario. The mechanisms of release of these radionuclides are not yet fully understood.

All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Seminar 11/12/2014 - Daeyeon Lee, University of Pennsylvania: Janus Particles as Solid Surfactants

Nov 12, 2014  ·  12:00 p.m. 1:00 p.m.  ·  Bowen Hall Auditorium

Abstract: Janus particles are asymmetric colloids with polar and apolar sides. Their amphiphilicity makes this new class of colloids exhibit behaviors that are similar to those of surfactant molecules.  The major goal of our work is to address the following intellectual questions: are Janus particles efficient “solid surfactants” for the stabilization of multiphasic fluid mixtures such as emulsions and foams? And how do their geometry and surface wettability influence their behaviors at fluid interfaces and, in turn, their properties as solid surfactants? In particular, we are inspired by how the chemical composition and shape of molecules influence the surfactant properties of molecular amphiphiles. In this talk, I will discuss our recent work on (1) understanding the effect of particle shape on the configuration and assembly of non-spherical Janus particles at fluid interfaces, (2) the thermodynamics of emulsion stabilization using Janus particles and (3) the emulsion stabilization and phase inversion emulsification using shape-changing/amphiphilicity-reversing Janus particles. I will first show that the configurations of nonspherical Janus particles such as ellipsoids and dumbbells at an oil-water interface strongly depends on the particle characteristics, such as their size, shape, aspect ratio, surface wettability, and the location of the Janus boundary. In the second part of my talk, I will discuss the thermodynamic aspect of emulsion formation using Janus particles.  Because the attachment energy of Janus particles to fluid-fluid interfaces is significantly larger than that of homogenous particles, it is possible to generate Pickering emulsions that are thermodynamically stable when Janus particles are used as emulsifiers. In the last part, I will discuss recently developed Janus particles that undergo significant changes in their shape and amphiphilicity in response to changes in the solution pH. We show that it is possible to stabilize different types of emulsions and also induce the phase inversion of emulsions using these stimuli-responsive Janus particles.

Bio: Daeyeon Lee is Associate Professor of Chemical and Biomolecular Engineering at the University of Pennsylvania. Daeyeon received his B.S. in Chemical Engineering from Seoul National University in 2001 and received his Ph.D. in Chemical Engineering/Program in Polymer Science and Technology at MIT in 2007 co-supervised by Robert E. Cohen and Michael F. Rubner.  After his Ph.D., Daeyeon was a postdoctoral fellow in the School of Engineering and Applied Sciences at Harvard University where he worked with David A. Weitz.  Daeyeon joined the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania in 2009.  Daeyeon has won numerous awards and recognitions including the 2010 Victor K. LaMer Award from ACS Colloid and Surface Chemistry Division, the NSF CAREER Award (2011), the 2011 Korean-American Scientists and Engineers Association Young Investigator Award, the 2012 KIChE President Young Investigator Award, the 2013 3M Nontenured Faculty Award, the 2013 AIChE NSEF Young Investigator Award and the 2014 Unilever Young Investigator Award for Outstanding Young Investigator in Colloid and Surfactant Science.
All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Seminar 11/19/2014 - Ertugrul Cubukcu, UPenn: Nano-Antennas Meet Mechanics and Graphene for Novel Opto-Electro-Mechanical Sensors and Devices

Nov 19, 2014  ·  12:00 p.m. 1:00 p.m.  ·  Bowen Hall Auditorium

Abstract and bio will be posted as we get closer to the event.
All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.

Seminar 12/10/2014 - Stephane Stebban, Laboratoire d' ’Optique Appliquée,– CNRS: Toward Compact and Ultrafast Soft X-Ray Lasers Sources

Dec 10, 2014  ·  12:00 p.m. 1:00 p.m.  ·  Bowen Hall Auditorium

Abstract: Emerging applications of coherent soft x-ray sources, notably in biology, require high energy and ultrashort pulse duration in the femtosecond-scale to probe the ultra-fast dynamics of matter in the nanometer scale. Alongside current efforts to provide high brilliance x-ray coherent sources with X-ray free electron lasers, significant potential lays in the realization of compact and relatively cheap ultra-intense x-ray coherent sources. Plasma-based soft x-ray lasers turn out to be good candidates since they can emit a large number of photon (up to 1015 per pulse) within a narrow linewidth and exhibit high-quality optical properties once seeded with high-harmonic sources. However, the duration of these sources has been limited so far to the picosecond range consequently restricting the field of possible applications.

In this presentation, we report on an original method able to generate intense femtosecond soft x-ray lasers pulse based on ultrafast ionization gain gating in a high-density plasma. By focusing a few 1018 laser driving pulse into a high-density optically pre-formed krypton plasma waveguide, we observed a strong amplified spontaneous emission at 32.8 nm. For electronic density as high as about 2x1020cm-3, the measurement of the gain life time provides evidence of generating about 100 fs soft soft x-ray lasers pulses containing a few µJ. Overcoming previous bottlenecks in terms of pulse duration and peak brightness, this scheme may be paving the way for prospective laboratory-scale ultra intense soft x-ray lasers beams.

Bio: Stéphane Sebban, is “”Directeur de Recherche” at the National Center for Scientific Research (CNRS-LOA- Palaiseau, France) since 1998. He is an experimental physicist who is experienced in the conception, development and characterization of femtosecond laser driven soft x-ray laser.

Stéphane Sebban obtained his PhD from the University of Paris XII in 1997 on the “optimization and applications on a neon-like soft-x-ray lasers”. He spent one year as a postdoc at the Institute of Laser Engineering (ILE) at Osaka in Japan before joining the CNRS in September 1998. He initiated and directed the development of soft x-ray laser techniques using femtosecond laser drivers at LOA, leading to the realization of a practical approach of high repetition rate seeded amplification geometry. From 2005 to 2011, Stéphane Sebban has been in charge of the “Femtosecond Laser for EUV to X-ray sources” (FLEX) group composed by 5 senior scientists, 1 engineer, 3 post-docs and 3 PhD students. The activities of his group has covered a large variety of laser-plasma sources including high order harmonic generation, X-ray lasers and hard X-ray radiation from relativistic electron beams. From 2011 he is also leading the Research Activity 2 of the ELI-Beamline facility in Prague (Czech Republic) in charge of the development and the implementation of laser-driven x-ray sources.

All seminars are held on Wednesdays from 12:00 noon-1:00 p.m. in the Bowen Hall Auditorium Room 222. A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.