Lightweight, superhydrophobic, lignin-based polyurethane foam composites for underwater pressure sensing

Abstract

Underwater flexible sensors are important for the exploration of and detection in underwater environments. In this paper, graphene and lignin-based polyurethane conductive foam (Gr-LPUF) composites were prepared by a one-step foaming process, the conductivity was improved by polymerizing a coating of polypyrrole (PPy) onto the porous foam surfaces, and then superhydrophobicity was achieved after dip-coating the porous material inside a poly(dimethylsiloxane) (PDMS) solution in order to prepare a superhydrophobic, high sensitive, stable, environmentally friendly, and flexible underwater sensor material. This superhydrophobic, conductive foam sensor (SCFS) has a rapid response time (100 ms), excellent pressure sensitivity, and excellent reproducibility and reliability for over 2000 cycles. This SCFS can be used not only as a wearable underwater sensor to detect human movement but also to accurately detect tiny water wave vibrations; such as falling water droplets, the movements of fish in the water, etc. This work will present an approach to manufacturing environmentally friendly, flexible underwater sensors for innovative, and widespread applications.