Microcrack-Enhanced PEDOT:PSS Textile for Rapid-Response, Stable, and Breathable Wearable Sensors

The lightweight, wearable, comfortable, and high-performance sensors are crucial for future wearable electronics to facilitate the real-time monitoring of human health. In this paper, the textile-based flexible dry sensor is fabricated by coating waterborne polyurethane (WPU) enhanced poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) onto the commercial polyester fabric (PF). The WPU, containing both hard and soft segments, was synthesized by using the three-step acetaldehyde method. When the hard segment content was 30 wt %, it promoted better connectivity in the PEDOT regions, resulting in higher conductivity. Benefiting from the interaction among polymer chains of WPU and PEDOT:PSS, which enhances the orientation of PEDOT and phase separation of PEDOT with PSS, the PEDOT:PSS/WPU (PW) composite materials achieved conductivity as high as 3000 S cm^-1 after being treated with sulfuric acid (H₂SO₄). As a result, the PW-coated fabric (PWF) achieved the lowest resistance value of 71.69 Ω sq at room temperature. Notably, by prestretching of the stretchable PWF, the microcracks are induced on the PW coating, which optimize the internal structure and stress distribution and therefore endow the PWF with superior sensitivity and stability, enabling it to respond within 80 ms (at 400 Pa pressure) and maintain stability under multiple compression cycles (100 Pa) at frequencies between 0.05 and 0.5 Hz. Additionally, the prestretching process endows the PWF with a higher water vapor transmission rate (23.8 kg m^-2 d^-1) than the pristine fabrics, despite the reduced conductivity and mechanical integrity. The as-fabricated PWF shows great potential for wearable body motion and electrocardiogram monitoring.