A dome-shaped piezoelectric tactile sensor arrays fabricated by an air inflation technique

In this paper, we propose and demonstrate a dome-shaped piezoelectric tactile sensor fabricated by an inflation technique. The sensor module consists of a 4 × 4 dome-shaped cell, an Ag electrode layer, a polyimide film for electrode protection, a bump structure, and a PDMS diaphragm for supporting the sensor. The piezoelectric sensor can convert an applied contact force into an electrical signal by using the piezoelectric effect. A normal force applied to the sensor deforms the cell, and consequently generates an output voltage proportional to the cell deformation. Therefore, by using a dome-shaped structure instead of the conventional flat structure, the tactile sensor can obtain high sensitivity. To make the dome-shaped PVDF film, a simple fabrication process based on an inflation technique for controlling the trapped air has been developed. The dome-shaped PVDF film was successfully fabricated, and then used as a sensing structure for a tactile sensor. In order to compare the sensitivity of the sensor, a flat tactile sensor was fabricated with the same design as the proposed sensor. The achieved sensitivities of the sensor are 6.028 × 10^-3 V/mN, 7.89 × 10^-3 V/mN, and 8.83 × 10^-3 V/mN, for the flat sensor and for two dome-shaped sensors (with h = 0.5 mm and 1.0 mm), respectively. The sensitivity of the proposed device shows a maximum 46.4% greater than that of a conventional flat tactile sensor. Also, through measurements of frequency response and crosstalk, the proposed tactile sensor showed stable performance.