Femtosecond-Laser-Assisted Fishbone-Inspired Patterning of Selective Liquid Metal Dewetted Electrodes for Flexible Electronics

Abstract

Femtosecond-laser-induced selective fishbone-inspired and trapezoidal structures provide low surface energies for liquid metal (LM) and LM-phobic surfaces. This laser-based technique is suitable for processing heat-vulnerable flexible substrates and minimizing changes in their physical properties, which can be analyzed by Fourier-transform infrared spectroscopy. In this study, we developed a femtosecond-laser-assisted fishbone-inspired patterning process for a selective LM wettable surface on a flexible substrate. Because the ribs of the fishbone-inspired structure were developed between laser-ablated lines, the entire LM-phobic pattern was covered without processing the entire surface area. In the fishbone-inspired pattern, the region directly exposed to the femtosecond laser served as the "spines", while the burrs, which were a byproduct of laser processing, acted as the "ribs". A minimum line width of ∼40 μm was realized using this structural mechanism. The patterned LM-phobic surface exhibited low surface energy with a 156°contact angle for the LM material. The patterned LM on a flexible poly(dimethylsiloxane) substrate maintained a stable electrical connection with minimal deviations, even under bending, twisting, and stretching conditions. These processes and structures can be used to fabricate flexible, stretchable, and wearable electronic devices.