Tactile sensor using piezoelectric resonator

A new type of tactile sensor probe head which detects compliance of live tissue has been developed. The sensor consists of Colpitts circuit including a 1.5 mm x 1.5 mm piezoelectric resonator on a mounter sized 2.4 mm in diameter. This size is small enough to be inserted into human body. We have experimentally found that the oscillating frequency change versus the contact force is related with the object compliance. Especially, the maximum gradient of the oscillating frequency versus contact force curve is the most noticeable to identify the difference of the compliance. It is possible to measure accurate compliance without setting the contact force constant.