Compressible CNT Ink-Wrapped Thermoplastic Polyurethane Sponge for Piezoresistive Sensing and Solar Steam Generation

The rapid development of wearable flexible electronic devices has brought the demand for supporting functional devices and energy storage devices. Filling conductive materials into elastomeric polymer or rubber films have been proven to be suitable sensing materials to fabricate flexible piezoresistive sensors (PRSs), but they are still confronted with low sensitivity and poor stability. Herein, a porous thermoplastic polyurethane (TPU) sponge is constructed by a simple sacrificial sugar-template strategy. An aqueous printable carbon nanotube (CNT) ink is prepared by a physical ball milling process to improve the conductivity of the TPU sponge. After coating a thin CNT ink layer, a highly compressible and conductive p-TPU@CNT sponge with a 3D porous structure is fabricated. It exhibits a large compressibility (up to 80% compression strain), good structural stability (over 6000 cycles), high piezoresistive sensitivity (7.85 kPa^–1), and fast response time (54 ms), which can be directly used as a flexible PRS device to monitor and collect joint movements and physiological signals and can be assembled into a compressible supercapacitor with stable electrochemical performance. Furthermore, the hydrophilic p-TPU@CNT sponge with good mechanical and photothermal conversion properties can also be used for solar steam generation with a high efficiency of 92% under 1 sun irradiation.