A dual-function flexible pressure/humidity sensitive sensor based on a polyaniline-coated melamine sponge

Abstract

Polyaniline (PANI) as a flexible matrix has been widely used in sensor applications, while the usage of pure PANI is hampered due to its insufficient electrical conductivity and limited surface area. Herein, a high-performance flexible humidity/pressure sensor has been developed based on a three-dimensional (3D) PANI-coated melamine sponge (MS) synthesized through protonic acid doping and dip coating methods, featuring breathable and environmentally benign properties. In this hybrid, the adhesion of PANI on the 3D MS matrix can enhance the active surface of PANI for superior pressure and humidity sensitivity, outperforming the single functionality and performance of a two-dimensional (2D) PANI film. Thus, this 3D MS@PANI sensor exhibits a superior sensitivity of 0.24 kPa⁻¹ within a pressure range of 5–14 kPa and maintains excellent cycling stability over 10 000 cycles with response and recovery times of 370 ms and 380 ms, respectively. As a humidity sensor, it shows high response sensitivities of 1.02 and 0.79 μA per %RH in dry air and N₂ environments, respectively, demonstrating good recognition ability and stability. Moreover, the as-prepared 3D MS@PANI sensor can be applied for real-time human motion monitoring. This PANI-based sensor, developed by transitioning from 2D flat films to 3D breathable sponges, provides a cost-effective and simple processing solution for the development of flexible electronic devices.