Study on fabrication methods for designable crack patterns on flexible substrate

Abstract

Generation and propagation of cracks are problems that we have faced as long as there have been man-made structures. Conventionally, the existence of cracks represents mechanical failure of materials. However, cracks can modify the electrical property of materials in a significant manner. As a result, crack-based sensing devices are highly sensitive due to the novel physical property of cracks. Comparing to sensors use random cracks reported by most of previous works, sensors with guided cracks can provide higher sensitivity and better device controllability. Therefore, we studied two approaches to guide crack generation simply using photoresist and photolithography technology to generate concentrated stresses on flexible substrates. The first approach is about guiding cracks using concentrated stresses at patterned notches, however, a uniformity issue was observed. Then, a revised approach using highly localized stresses at patterned sharp corners was proposed and studied. Comparing to previous research, our method is capable of fabricating much more diverse crack patterns in a relatively large scale with good fabrication reliability and reproducibility.