Study of Wearables with Embedded Electronics through Experiments and Simulations

Wearables with flexible electronics are being increasingly used to monitor human metrics for health and fitness purposes. In the course of their application, these devices may be stretched, bent, and twisted frequently and repetitively under a variety of conditions. In this ongoing project, a variety of potential mechanical loads are being studied and compared to simulated models to improve the understanding the failure modes of these devices. Several existing products are being studied at Georgia Tech using applied mechanical loads as well as environmental conditions to understand resulting effects on device performance and reliability. In this paper, we examine one of these devices, a smart fitness sock that uses textile pressure sensors connected via a conductive yarn to a communication anklet. In this work, the sock is subjected to various mechanical stretching loads while the electrical resistance of its conductive yarn is monitored. The applied stretching conditions are analogous to the conditions experienced by the sock yarns during the process of putting it on as well as while being worn over a number of hours. Strain contours from stretching experiments are determined through digital image correlation (DIC) and are compared with the results from finite-element simulations. The sock is also subjected to several other conditions including exposure to a sweat-like solution as well as multiple laundry wash cycles, and the effects of such exposure are examined. Based on the work, a better understanding of sock reliability and performance is obtained and can be applied to other emerging wearables.