Piezocapacitive Flexible E-Skin Pressure Sensors Having Magnetically Grown Microstructures

Flexible pressure sensors are highly desirable in artificial intelligence, health monitoring, and soft robotics. Microstructuring of dielectrics is the common strategy employed to improve the performance of capacitive type pressure sensors. Herein, a novel, low-cost, large-area compatible, and mold-free technique is reported in which magnetically grown microneedles are self-assembled from a film of curable magnetorheological fluid (CMRF) under the influence of a vertical curing magnetic field (B-curing). After optimizing the microneedles' fabrication parameters, i.e., magnetic particles' (MPs') concentration and B-curing intensity, piezocapacitive sensors capable of wide range pressure sensing (0-145 kPa) with ultrafast response time (50 ms), high cyclic stability (>9000 cycles), as well as very low detection limit (1.9 Pa) are obtained. Sensor properties are found dependent on microneedles' fabrication parameters that are controllable, produce variable-sized microneedles, and allow to govern sensing properties according to desired applications. Finally, the sensor is employed in holding a bottle with different weights, human breath, and motion monitoring, which demonstrate its great potential for the applications of human-machine interaction, human health monitoring, and intelligent soft robotics.