Supercapacitive Multimode Sensing with Tunable Graphene Sheet Film Electrodes

Abstract

Supercapacitive multimode sensing is gaining significant attention across diverse domains, particularly within burgeoning fields of intelligent wearables and human-computer interaction. Typically, these sensors are constructed using a matrix of conductive nanowires and soft materials such as polydimethylsiloxane (PDMS), which serve as electrodes in thin film supercapacitors (TFSs). To facilitate multimode sensing, ability to modulate response curves is crucial for practical application. In this study, we introduce porous conducting graphene sheet (GS) films with customizable thickness as TFS electrodes. We first develop a wafer-scale fabrication method using vacuum filtration, to yield GS films with adjustable sheet resistance that can approach the percolation threshold. The use of a hydrophilic cellulose acetate (CA) filter membrane facilitates spontaneuous and nondestructive detachment of the GS film from the membrane post-dehydration. The spontaneous separation mechanism is elucidated through time-dependent contact angle measurements on porous films. The GS film, once separated, can be seamlessly and consistently incorporated into TFS devices as electrodes. This integration allows for multimode sensing capability with simultaneous capacitive strain sensing and ionotropic temperature sensing. The tunable nature of these porous GS films by adjusting the electrode thickness, enables fine-tuning of the response curves for multimode sensing.