SUBJECT: Ph.D. Proposal Presentation
BY: Justin Chow
TIME: Thursday, December 6, 2018, 2:00 p.m.
PLACE: MARC Building, 201
TITLE: Failure Mechanism and Damage Evolution in Flexible Electronics under Axial and Twist Strains
COMMITTEE: Dr. Suresh Sitaraman, Chair (ME)
Dr. Antonia Antoniou (ME)
Dr. Karl Jacob (ME/MSE)
Dr. Madhavan Swaminathan (ECE)
Dr. Jeff Meth (DowDuPont Electronics and Imaging)


Electronic devices have found use in a variety of flexible form factors such as structural health monitors, wearable human health monitoring devices, and body suits. These form factors expose the electronic components (printed traces, passives, active devices, etc.) to a wide range of mechanical strains that are not typically seen in traditional rigid electronic systems. This is because the utility of the flexible wearable electronic systems depends on their ability to stretch, bend, and twist. With such stretching, bending, and twisting, the electrical conductance and thus, the overall performance of the flexible wearable electronics will change, and a clear understanding of the relationship between applied loading and the evolution of damage as well as the change in electrical properties is lacking. In this work, printed silver conductors on various flexible substrates such as polyimide, polyethylene terephthalate (PET), and thermoplastic urethane (TPU) are subjected to both monotonic and cyclic stretching while the in-situ DC resistance is monitored. A mechanism-based failure mode is developed based on in-situ and post-situ imaging. Additionally, an innovative test apparatus is designed and fabricated to apply controlled twists to printed samples for both monotonic and fatigue testing and different failure mechanisms are explored for this loading mode. Finally, combinations of simultaneous stretch and twist are applied to conductors to understand resistance change and damage evolution. In addition to DC measurements, selected high-frequency measurements will also be explored to understand the behavior of conductors intended for high-frequency applications.