Highly sensitive and flexible micro-patterned PPy/PDMS strain sensors with enhanced conductivity and stretchability for wearable electronics

Abstract

This study presents a pioneering approach to enhance the performance of flexible strain sensors based on polypyrrole (PPy) by incorporating micro-patterns onto polydimethylsiloxane (PDMS) substrates. Micro-patterned PPy films were generated through image-reversal photolithography and pattern lift-off followed by a straightforward chemical oxidative polymerization process to deposit the films. A method of surface treatment using the dopant sodium dodecylbenzenesulfonate (SDBS) was also used to enhance the conductivity of the degraded PPy films after the formation of patterns. We conducted a systematic exploration of various fabrication conditions, including unpatterned and three micro-patterned variants. Utilizing X-ray photoelectron spectroscopy analyses, we investigated the interplay between SDBS treatment, structural modifications, and strain sensor performance. Our results unveiled that micro-patterned sensors treated with SDBS and capped by PDMS layer showed remarkable performance attributes. The sensors fabricated by this method exhibited a gauge factor of 35 at 100 % strain, coupled with a very fast response time of similar to 2.8 ms under quasi-step function strain ranging from 0 to 1 % in 1.8 ms, demonstrating excellent durability across 500 stretching/release cycles. This study provides invaluable insights into enhancing the effectiveness of micro-patterned PPy/PDMS strain sensors, opening avenues for their widespread utilization in wearable electronics.