A Three-Axis Flexible Tactile Sensing Array Based on Novel Capacitance Mechanism

In this work, we present the development of a capacitive normal and shear sensing array realized by using MEMS fabrication techniques and flexible printed circuit board (FPCB) technologies. The sensing array, which consists of two micromachined polydimethlysiloxane (PDMS) structures and a flexible FPCB, will be used as the artificial skin for robot applications. The shear sensing element, which comprises four capacitive sensing elements arranged in a 2?2-array form, can decompose the contact force into normal and shear components. Each capacitive sensing element has two sensing electrodes and a common floating electrode. The sensing electrodes as well as the metal interconnect for signal scanning are implemented on the FPCB, while the floating electrode is patterned on one of the PDMS structures. This special design can effectively reduce the complexity of device structure and thus makes the device highly manufacturable. In order to accurate detect shear force, the bump and the pillar structures of each shear sensing element are implemented. An 8?8 shear-stress sensing array been realized. Each sensing element can detect normal and shear stresses applied on its top surface. The average measured sensitivity for the normal stress (i.e., the z-direction) is 1.1%/mN, and average measured sensitivities are 1.72%/mN, 1.65%/mN in the x and y-directions, respectively. Measurement of a single sensor shows that the full-scale range of detectable force is about 100 mN. The corresponding scanning circuit are also designed and implemented.