Micromachined piezoresistive tactile sensor array fabricated by bulk-etched MUMPs process

This paper discusses the design, fabrication and testing of a 5×5 micromachined tactile sensor array for the detection of an extremely small force (micrometer-Newton range). Central contacting pads that are trampoline-shape suspended structures and sensor beams are formed using anisotropic etching of the silicon substrate of a MUMPs process chip. A piezoresistive layer of polysilicon embedded in sensor beams is used to detect the displacement of the suspended contacting pad. Each square tactile has dimensions of 200 μm × 200 μm with 250 μm center-to-center spacing. The entire sensor area is 1.25 mm × 1.25 mm. The device was characterized under various normal force loads using weight microneedles. Individual sensor elements show linear response to normal force with good repeatability.