Authors: A. Tuantranont, T. Lomas and V.M. Bright
Affilation: National Electronics and Computer Technology Center (NECTEC), Thailand
Pages: 351 - 354
Keywords: MEMS, Piezoresistive, tactile sensor, MUMPs
This paper discusses the design, fabrication and testing of a 5x5 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 an anisotropic etching of 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 dimension of 200 micron x 200 micron with 250 micron center-to-center spacing. The entire sensor area is 1.25 mm x 1.25 mm. The micromachined piezoresistive tactile sensor array has been successfully fabricated by the commercial available surface micromachining foundry (MUMPs) with bulk-etching post-processing technique. The bulk etching of silicon substrate through cut through substrate mask is successfully done with a complete undercut of a central contacting plate and create a suspended structures. The response of the sensor structure to pure normal stress loading was experimentally evaluated. Linear sensitivity of the sensors with normal force load was approximately 0.02 mV/micro-Newton as tested with pre-known weight microneedle. The individual sensor element shows the linear response to normal force with good repeatability.