Three-Dimensional Printing of a Flexible Capacitive Pressure Sensor Array in the Assembly Network of Carbon Fiber Electrodes and Interlayer of a Porous Polyurethane Dielectric

In this work, a facile three-dimensional (3D) printing of a one-piece flexible capacitive pressure sensor array is proposed with simple, economical, and scalable fabrication characteristics. The printed capacitive pressure sensor array is composed of continuous carbon fiber electrodes in the network and assembly of porous polyurethane dielectric. Also, the 3D printing way confers the fabrication with the advantage of time-saving by eliminating the assembly of electrodes and the dielectric layer. Salt microparticles were utilized as a kind of sacrificial material to embed micropores into the elastic dielectric layer of thermoplastic polyurethane, and a bundle of continuous carbon fibers extruded from the 3D printer nozzle was employed as the sensor electrodes. The formed one-point pressure sensor was constructed at the intersection by the cross-printing path of the upper and lower layers. The microporosity structure in the dielectric led to the sensor containing more compression amplitude, thus increasing the effective dielectric constant under pressure so that the sensor (5.15 N–1) with a 40% table salt content has a higher sensitivity than the unstructured sensor (0.32 N–1). Furthermore, the sensor exhibited a fast response/recovery time (60/80 ms), good stability (over 1000 cycles), and magnificent pressure resolution. Several one-point pressure sensors in the regular array were printed in one piece to be able to detect some distributed compression pressures. Thus, in the end, the sensor array was fixed to human joints such as fingers, knees, and elbows to collect limb motion signals and demonstrated potential application in the field of human motion detection.