One-step direct laser writing of LIG/PDMS flexible piezoresistive sensors for underwater motion monitoring and communication

Abstract

About 71% of the Earth’s surface is covered by water. Increasingly frequent underwater exploration and operations have created an urgent demand for miniaturized, low-cost, and easily fabricated sensing devices. Laser-induced graphene (LIG) has attracted significant attention owing to its mask-free processing, high manufacturing efficiency, facile patternability, and highly tunable physicochemical properties. In this work, we present a patterned LIG/PDMS flexible sensor manufactured using a single-step direct laser writing (DLW) technique, comprehensively optimizing its processing parameters and evaluating its underwater sensing performance. Under optimal conditions (65% laser power and 70 mm/s scanning speed), the LIG network achieves an excellent 3D porous morphology and optimal electrical conductivity (100 S/cm). The subsequent in-situ PDMS encapsulation tightly preserves this porous structure while establishing a robust waterproof barrier. Consequently, the device delivers exceptional underwater piezoresistive performance, featuring a broad detection range (up to 3 MPa), reliable sensitivity (1-100KPa 21.1MPa−1), and outstanding cyclic stability (>5000 cycles). Furthermore, this work demonstrates the application of the device in real-time underwater human motion monitoring and simple signal transmission. These results provide a versatile solution with a simple fabrication process and scalable production potential for the development of long-term stable underwater flexible sensors.