Experimental investigation on micro-fabrication of wearable dry-patching flexible substrate using transparent superhydrophobic polyimide

Abstract

Recently, flexible/stretchable devices have drawn much attention owing to their various applications and functions, which necessitates the development of flexible dry-patching platforms. Since wet-patching substrates display a short-term adhesive characteristic, we focused on developing a dry-patching platform that will not only be lightweight, transparent, and flexible, but will also maintain its patching performance for a long time without additional treatments. In this study, we investigated the fabrication of a dry-patching substrate using a polyimide superhydrophobic surface with self-cleaning and water-repellent properties. Polyimide substrates are widely used in microelectronics and micro-technology applications owing to their suitable properties (mechanical, thermal, optical, and chemical properties). To fabricate superhydrophobic surfaces, two key features are required: a material having a low surface energy and surface roughness, for this purpose, the polymer casting method used to fabricate cylindrical micropillar structures. Further, we determined the effect of pillar height and pitch on the surface contact angle. We achieved a contact angle of 179° with a minimum contact angle hysteresis of 10° and an imidized film transparency of 88%. Our approach will minimize the use of liquid gel in wearable devices, which causes unfavorable skin interaction, leading to limited application of wearable devices in daily life.