Effect of capillary bridges on the interfacial adhesion of wearable electronics to epidermis

Wearable electronics integrated with flexible biosensors provides robust, noninvasive and long-lived interfaces to monitor the electrophysiological and electrochemical signals of the human body. Sweat from the body forms capillary bridges at the weak adhesion interface, furthermore, capillary bridges exhibit different shapes on the circular and thin rectangular sensors. Capillary bridge and fracture models are developed to study the behavior of sweat between wearable electronics and epidermis. The sensor sizes of wearable electronics have significant effects on the opening behaviors of the interface cracks due to the growth of sweat capillary bridges. Dissimilar mechanical properties between the epidermis and the substrates clearly affect the opening behaviors of the penny-shaped and slender cracks. This study provides a useful framework to investigate the underlying mechanisms of the detachment of the wearable electronics due to sweat from the body, which is very valuable for the design of wearable electronics mounted on the epidermis for healthcare applications.