Monolithic LIG-VIA embedded in colorless polyimide for durable interlayer channels

Abstract

Protecting electronic circuits is essential for devices that directly interface with harsh external environments, as exposure to chemical contaminants and physical stimuli can lead to adverse effects, including corrosion, degradation, and disconnection. To address this challenge, we present an embedded monolithic vertical interconnect access (VIA) structure composed of conductive laser-induced graphene (LIG), fabricated through successive laser pyrolysis of a colorless polyimide (CPI) film in an out-of-plane orientation. This approach enables seamless integration between external functional units and internal conductive pathways, effectively isolating circuits from hazardous environments to ensure more robust and reliable operation. To evaluate its effectiveness, we tested two LIG network configurations—with and without the LIG-VIA (LIG-V)—under corrosive chemical conditions using 35 % H₂O₂ solution. The results confirmed that the LIG-V structure imparts chemoresistive properties while retaining conductivity after 1000 cycles at 0.79 % bending strain under repetitive bending. Furthermore, we demonstrated that the final structure functions as either a standalone bidirectional input/output device or as an auxiliary component to enhance other functional elements, such as a thermochromic display. By integrating the LIG-V structure into a transparent CPI substrate, this work presents promising potential for applications in wearable monitoring devices and on-demand feedback stimulation systems, unlocking new possibilities for functional electronics in dynamic and demanding environments.