Vapor-induced porosity in graphene/PDMS: a scalable route to high-performance pressure sensors

In the present paradigm of flexible and wearable technologies, piezoresistive sensors hold immense promise as e-skin in sensing applications. Introducing porosity in these sensors elevates the performance multi-fold. However, fabrication of porous piezoresistive sensors is complicated, energy-intensive and cost-ineffective, negating their pertinent advantages. We present a new method of developing porous, thin films based piezoresistive sensors by utilizing the inherent vaporability of ethanol to introduce controlled porosity in graphene nanoplatelet (GNP)/ polydimethylsiloxane (PDMS) nanocomposites. The resulting vapor-channeled (VC) GNP/PDMS is formed without utilizing scaffolds, skeletons, high temperature etching or prolonged chemical processing. The fabrication process for porous nanocomposites is highly repeatable and controllable; the fabricated VC-GNP/PDMS thin films are reliable and show immense promise as flexible/wearable pressure sensors. The VC-GNP/PDMS achieves an achieve exceptional compressibility (up to 68.97% strain) without structural failure, yielding a flexible pressure sensor with an unprecedented linear response (R² = 0.99) across an ultra-wide dynamic range up to 2.5 MPa and a high sensitivity of 33.2% MPa^-1. The engineered porosity and micro-structure synergistically enable a tunable gauge factor, shifting from 0.66 (0-45% strain) to 1.72 (>45% strain). Critically, the sensor exhibits negligible hysteresis (1.08%), remarkable long-term stability over 5 weeks, and rapid response/relaxation (0.3/0.7 s), alongside robust insensitivity to temperature (25-60 °C) and humidity (5-100% RH). This unique fabrication strategy and the resulting high-performance pressure sensor, offering exceptional tunability in sensitivity and range, position it as a leading candidate for next-generation, cost-effective tactile biomechanical sensing.