Flexible three-axial tactile sensors with microstructure-enhanced piezoelectric effect and specially-arranged piezoelectric arrays

Flexible tactile sensors with high sensitivity, good flexibility and the capability of measuring multidirectional forces are urgently required in modern robot technology and flexible electronic applications. Here, we present a flexible three-axial tactile sensor using piezoelectricity enhanced P(VDF-TrFE) micropillars. For achieving three-axis force measurement, the vertical aligned P(VDF-TrFE) micropillars are sandwiched between four square bottom electrodes and a common top electrode to form four symmetrically arranged piezoelectric sensing units. An elastomeric PDMS bump is fixed on the common top electrode surface to effectively transfer the contact force to the four sensing units. Taking advantage of the high sensitivity and good flexibility of the imprinted P(VDF-TrFE) micropillars, the resultant four distributed piezoelectric units are highly sensitive to the strain and can generate related signals corresponding to the compressive and tensile stress, from which the direction and the amplitude of the applied force can be deduced. The structural design, manufacturing technique, the three-axial force measuring principle, and sensing performance characterization of the proposed tactile sensor are presented in this paper. The sensitivities for X-, Y-, and Z-axis force components are calibrated as 0.3738 V N-1, 0.4146 V N-1, and 0.3443 V N-1 in experimental study. Furthermore, the proposed tactile sensor array is successfully integrated with a magnetic bar consist of NdFeB/PDMS composites to construct a magnetic actuator with sensing ability. These results give the flexible three-axial tactile sensor high potential for use in advanced robots, wearable electronics and a variety of human-machine interface implementations.