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

The\nrapid development of wearable flexible electronic devices has\nbrought the demand for supporting functional devices and energy storage\ndevices. Filling conductive materials into elastomeric polymer or\nrubber films have been proven to be suitable sensing materials to\nfabricate flexible piezoresistive sensors (PRSs), but they are still\nconfronted with low sensitivity and poor stability. Herein, a porous\nthermoplastic polyurethane (TPU) sponge is constructed by a simple\nsacrificial sugar-template strategy. An aqueous printable carbon nanotube\n(CNT) ink is prepared by a physical ball milling process to improve\nthe conductivity of the TPU sponge. After coating a thin CNT ink layer,\na highly compressible and conductive p-TPU@CNT sponge with a 3D porous\nstructure is fabricated. It exhibits a large compressibility (up to\n80% compression strain), good structural stability (over 6000 cycles),\nhigh piezoresistive sensitivity (7.85 kPa<sup>–1</sup>), and\nfast response time (54 ms), which can be directly used as a flexible\nPRS device to monitor and collect joint movements and physiological\nsignals and can be assembled into a compressible supercapacitor with\nstable electrochemical performance. Furthermore, the hydrophilic p-TPU@CNT\nsponge with good mechanical and photothermal conversion properties\ncan also be used for solar steam generation with a high efficiency\nof 92% under 1 sun irradiation.