Tunneling Percolation Mechanism of Conductivity for PEDOT:PSS in Hydrophilic PDMS Composite for the Fabrication of Highly Sensitive Strain Sensors. Issue 16 (7th July 2022) - Ali, Muhammad Zeshan
Abstract: Conducting polymer of poly(3, 4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has interesting properties of tunable electrical conductivity and facile processability. Stretchable electronic materials and devices have become the focus of research and industrial communities with increasing demand of the Internet of Things (IOT)‐based wearable gadgets. Stretchable applications based on PEDOT:PSS demand its blending with a durable polymer matrix such as polydimethylsiloxane (PDMS). In this research work, a homogeneous conductive ink comprising of hydrophilic PEDOT:PSS and hydrophobic PDMS is developed by using a bi‐functional (3‐glycidoxypropyl)trimethoxy silane (GPTMS) as coupling agent to form a cross‐link network through interphase interactions. Low percolation threshold of conductive ink is achieved at 0.236 wt% of solid PEDOT concentration. Power law of percolation behavior, from experimental results, reveals a nonuniversal critical component‐ t value of 3.04, signifying the occurrence of a tunneling‐percolation conductivity mechanism. Iterative curve fitting based on an analytical model gives a good simulated conductive behavior with relation to geometrical parameters of conducting particles such that optimal thickness of interphase is found to be 2.86 nm. The developed strain sensor is highly sensitive with gauge factor (GF) of 148 and stretchable up to 50% strain with fast response time of 130 millisecond and shows good dynamic stability with minimal hysteresis loss. The strain sensor successfully captures real‐time finger and wrist motions. Abstract : Miscibility of PEDOT:PSS and PDMS is reported. Tunneling percolation through an interphase layer around a conducting polymer and the good mixing are considered to achieve the lowest ever reported percolation threshold of 0.236 wt% of solid PEDOT which is verified through analytical model. The developed strain sensor shows very high sensitivity with maximum GF of 148, stretchability to 50% strain, fast response time of 130 ms and longer durability.