10-09 :: September 2010

nanotimes Companies

W.S. Tan, R.E. Cohen, M.F. Rubner, S.A. Sukhish- vili from Massachusetts Institute of Technology, USA, presented with “Self Assembled Block-copo- lymer Nanocomposite Multilayer Thin Films for Reversible Temperature Triggered Responses” in session “Polymer Nanotech: Copolymer surfaces: Applications ”, an investigation of a block copolymer solution.

Thermo-mechanically responsive surfaces in aqueous environments are sought after for a variety of bio- logical and micro-fluidic applications. Electrostatic self assembly of an A-B-A triblock co-polymer with a suitable polyanion was used to create smart surface coatings with up to 500% fully reversible, tempera- ture dependent swelling from all aqueous processing. The dry thickness of the films can be easily con- trolled between 50nm-1um. Poly(2-(dimethylamino) ethyl methacrylate)-b-polypropylene oxide-b- poly(2- (dimethylamino)ethyl methacrylate) (PDMAEMA- PPO-PDMAEMA) was used as a dual pH and temperature responsive component and to create hydrophobic nano-domains within an electrostatical- ly bound matrix. Incorporation of stimuli responsive block copolymers into electrostatically assembled thin films requires special attention to be paid to the molecular configuration of the stimuli responsive block. Their work investigates the block copolymer solution configuration and correlates how different aggregation states affect the temperature response of thin films assembled from these polymers. De- tailed studies have uncovered key factors necessary to achieve high fidelity large extent yet fully reversi- ble temperature induced volume transitions of multi- layer thin films. The temperature dependent swelling of such thin films is applied to control membrane permeability. Further, such coatings can also be used

http://web.mit.edu/dmse/rubner/index.htm

M. Reimark from TranSiC, USA, spoke about “Efficient Power Transistors in Silicon Carbide for PV applications”.

Silicon carbide (SiC) semiconductor devices for high power are becoming more mature and are now com- mercially available. Schottky diodes have been on the market since a few years. SiC power transistors in the form of bipolar junction transistors (BJTs), JFETs and MOSFETs are this year reaching the commercial market. The interest is rapidly growing for SiC power devices in demanding power and high temperature applications. The BJT has market leading low con- duction losses, fast switching capability and very predictably operate, in normally-off mode, in a very wide load/temperature range. They are the natural choice as a successor for the commonly used silicon IGBT of today. Reimark‘s presentation showed how losses can be greatly reduced and temperature range increased while system mass and volume are significantly reduced by the use of SiC BJT devices. Current state of the art in active switching device performance with special emphasis on BJTs was reviewed in perspective of demanding applica- tions. The performance of the SiC BJT will be com- pares to Silicon bipolar and unipolar devices over a wide temperature interval. http://www.transic.com/index.php/news/78

to be continued ...

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for cell sheet engineering as well as selective small molecule binding and release.