Mechanical Engineering Graduate Seminar Series: Dr. Pratap Rao, WPI, "Printed Flexible and Stretchable Electronics and Sensors"

Abstract: This talk will describe recent work on printing of flexible and stretchable electronics and sensors, with applications including thin and flexible microcontroller circuits for aerospace monitoring, stretchable sensors and electronics laminated onto stretchable fabrics for wearable human-machine interfaces, highly stretchable sensors for surgical robotics and soft robotics, and soft skin-mounted electrodes for human health monitoring. The printed materials include conductive and insulating inks comprised of particle-loaded polymers or room-temperature liquid metal inks. The printing methodologies investigated include inkjet, screen, and nozzle extrusion printing. In each case, the printing method is understood and tuned to achieve desired printing characteristics, such as narrow line width and high electrical conductivity. Multilayer flexible circuits are achieved by alternately printing silver-particle conductive ink and insulating ink, and can be bent to 2mm radius for thousands of cycles. Multilayer stretchable circuits are achieved by repeatedly printing liquid metal conductive ink, placing components, and laminating elastomeric layers with laser-drilled via holes, and can be stretched to more than twice their original length (>200% strain) for hundreds of cycles with minimal change in electrical performance. Resistive and capacitive strain sensors with low drift are developed for measuring strains in the 10-100% range, which are out of the range of conventional strain gauges. Some emerging work in the area of printed robotic materials will also be previewed.

Bio: Pratap Rao is an Associate Professor in the Department of Mechanical and Materials Engineering at the Worcester Polytechnic Institute (WPI). He received his BS in 2007 from WPI and his PhD in 2013 from Stanford University. He has co-authored over 40 peer-reviewed journal papers that have appeared in Advanced Energy Materials, Nano Letters, Flexible and Printed Electronics, and other journals, and have collectively been cited over 4,000 times. His work on photo-catalytic materials for water treatment and clean hydrogen production has been funded by the U.S. National Science Foundation, the Massachusetts Clean Energy Center, and the U.S. Army DEVCOM Soldier Center. His work on printed flexible and stretchable electronics has been funded by the U.S. Department of Defense through the NextFlex Manufacturing USA Institute and the SEMI-FlexTech program; and by the Commonwealth of MA through the Massachusetts Manufacturing Innovation Initiative. At WPI, he is the recipient of the Harold L. Jurist ’61 and Heather E. Jurist Dean’s Associate Professorship and the James Nichols Heald Research Award.