Seminar, May 15: Sensors and RF Devices Using Eutectic Gallium Indium and Single Walled Carbon Nanotubes

This talk will discuss two classes of materials – carbon nanotubes and liquid metals - that are useful for flexible electronics, sensing, and RF devices. Conventional RF electronic circuits can be rendered flexible by using thin metal films like copper and gold on flexible substrates, which make the device flexible but not stretchable. Eutectic gallium indium (EGaIn) is a low viscosity, liquid at room temperature metal and possesses a thin oxide skin that provides mechanical stability to the fluid within the elastomeric channels. Here, we discuss its use to make flexible and stretchable antennas and RF devices with properties that are not possible using solid metals. The antennas can withstand mechanical deformation and return to their original state after removal of an applied stress. The ability of the fluid metal to flow during deformation of the elastomer ensures electrical continuity.   

Single walled carbon nanotubes (SWNTs) are also useful for flexible electronics.  Here, we discuss their use as a hypergolic fuel sensor. Semiconducting SWNTs have shown to dramatically increase or decrease their conductivity when exposed to gases like NO2 and NH3.  SWNT sensors have shown extremely fast response and a substantially higher sensitivity that that of the solid state sensors at room temperature.  Accurate and reliable detection of hypergolic fuels such as hydrazine and its derivatives is vital to missile defense, aviation, homeland security, and the chemical industry.  We studied the transport properties of surface modified networks of individual SWNTs grown on Si/SiO2 surfaces for their interaction with hypergolic fuel elements.  The results provided a model for sensing on the basis of electrochemical charge transfer from the redox couple on to the SWNTs.  In order to improve the selectivity of the device, an array of multiplexed module for the sensor study was developed.  

Dr. Desai received his BE in Electronics and Communication from Shivaji University, India (1999), a MS Physics (2004) and PhD. in Electrical and Computer Engineering (2009) from University of Louisville, KY under the guidance of Dr. Gamini Sumanasekera. He is currently a Post Doctoral Research Associate at North Carolina State University, in the lab of Dr. Michael Dickey. His research interests include nano material synthesis and characterization, nano and micro fabrication, thin film characterization, soft matter RF electronics and microfluidics.