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

Abstract

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.

Hybrid Architectures of Heterogeneous Carbon Nanotube Composite Microstructures Enable Multiaxial Strain Perception with High Sensitivity and Ultrabroad Sensing Range

“…Additionally, the pressure sensitivity and detection range could be simply modulated by adjusting the areal distribution of the micropyramids. Micropillars were also utilized to enhance the sensing performance of e‐skins . Micropillar‐based e‐skins showed higher sensitivity over pressure and shear compared to planar e‐skins.…”

Flexible Shear and Normal Force Sensor Using only One Layer of Polyvinylidene Fluoride Film

“…We demonstrated how to make piezoelectric force sensors in a very simple fabrication process that can detect not only the normal but also the shear forces. Previous studies have been able to detect three-axis forces, but electrode patterning is essential, which involves complex processes such as lithography and sputtering [21,25,26]. In our method, this work makes it possible to detect biaxial forces simply by embedding a commercial piezoelectric film into the PDMS.…”

“…In contrast, the piezoelectric ones have the characteristic advantage of being self-powered, i.e., they generate electrical signals under external mechanical inputs [22,23]. With this benefit, several studies have been performed with piezoelectric force sensors that can measure shear forces [20,21,[24][25][26]. Specifically, therein, some researchers have assembled polydimethylsiloxane (PDMS) bump structures on flat or micropillar-type polyvinylidene fluoride (PVDF) and have used electrodes of specific shapes for effective sensing, resulting in the detection of shear and normal forces.…”

Multidirectional Cylindrical Piezoelectric Force Sensor: Design and Experimental Validation

“…For example, many studies have been conducted to improve the performance of the sensor by applying various shapes, such as pyramids [ 31 ], domes, pillars [ 32 ], and springs [ 33 ], to resistive materials. However, the most common design concept of piezoelectric force sensors includes assembling a bump structure from a flat- or micro-pillar-shaped piezoelectric structure or to use electrodes of specific shapes [ 29 , 34 , 35 ]. In other words, the structure of the piezoelectric force sensor is quite limited.…”

“…The sensor has four inner column electrodes and four outer row electrodes. Previous multidirectional force sensors using the piezoelectric effect have a limitation in that the number of electrodes must be greatly increased to increase the resolution, and its wiring becomes more difficult [ 29 , 34 , 35 ]. However, our sensor can achieve a relatively high resolution with a small number of electrodes.…”