Development of a micro force sensor for conduit guided wire and its application to micro master-slave systems

This paper describes fabrication of a micro force sensor for conduit guided wire which is often used to drive a catheter in medical treatment. The diaphragm type force sensor of 2 mm×2 mm×216 μm for the conduit with an outer diameter 320 μm, an inner diameter 150 μm and the wire with a diameter 100 μm is fabricated. Photolithography, wet and dry oxidation, B-diffusion, through hole etching by TMAH techniques are used. The relation between loaded force and output voltage is measured to be linear with a sensitivity of 10.2 mV/gf under a constant supplied voltage. A micro master-slave system driven by conduit guided wire is expected to be applied to delicate surgical operations, assembling precise and small parts, etc. This system consists of a micro sized slave robot and a master manipulator of which the size is adapted to a human finger. Displacement and torque of the master side are reduced and transferred to the slave robot by controlling the brake torque against the master torque by feeding back tension signals of the force sensor in the slave robot. The master can feel the tensions by the brake torque, though conduit guided wire has a nonlinear input-output characteristics due to friction force