Multifunctional flexible carbon black/polydimethylsiloxane piezoresistive sensor with ultrahigh linear range, excellent durability and oil/water separation capability

The achievement of favorable pressure sensor integrated with large linear working range, high sensitivity and excellent response durability is still a great challenge for flexible and wearable piezoresistive materials. In this paper, a facile and scalable strategy is proposed to fabricate a porous foam sensor based on carbon black/polydimethylsiloxane (CB/PDMS). CB particles were decorated onto the surface of the cell walls and some particles were embedded into PDMS matrix after the ultrasonication treatment. The density and porosity of the foam are 0.13 g/cm3 and 76.1%, respectively. A very high linear working range (up to 91%), an excellent response stability, a fast response time (45 ms), and a superior durability (>15000 cycles) are achieved synchronously. Here, the large linear sensing range is mainly related to the nice CB conductive network on the cross-linked PDMS foam and the high modulus and elasticity of the composite material, which ensure the homogeneous deformation of the foam under compression. It is worth noting that the response behavior of CB/PDMS foam is maintained well even in water owing to its excellent hydrophobic property (water contact angle up to 149°), indicating that this material can be used as a waterproof piezoresistive sensor. Our CB/PDMS foam is then assembled as a wearable sensor, and it exhibits nice capability of monitoring human body motions, such as the bending of fingers and elbow, walking, jumping and squatting, etc. The porous foam sensor also has a good oil/water separation ability, showing a multifunctional characteristic.