ABSTRACT
B. Pressure One o f the most commercially successful microsensor technologies is the pressure sensor. Silicon micromachined pressure sensors are available that measure pres sure ranges from around one to several thousand kPa, wi th resolutions as fine as one part in ten thousand. These sensors incorporate a silicon micromachined dia phragm that is subjected to fluid (i.e., l iquid or gas) pressure which causes dilation o f the diaphragm. The simplest o f these utilize piezoresistors mounted on the back o f the diaphragm to measure deformation, which is a function o f the pressure. Ex amples o f these devices are those by Fujii et al. [72] and Mal lon et al. [73]. A variation o f this configuration is the device by Ikeda et al. [74], which utilizes, instead o f a piezoresistor to measure strain, an electromagnetically driven and sensed resonant strain gage, as discussed in the previous section. Still another variation on the same theme is the capacitive measurement approach, which measures the capacitance between the diaphragm and an electrode that is r igidly mounted and parallel to the diaphragm. A n example o f this approach is by Nagata et al. [75]. A more complex approach to pressure measurement is that by Stemme and Stemme [76], which utilizes resonance o f the diaphragm to detect pressure. In this device, the diaphragm is capacitively excited and optically detected. The pres sure imposes a mechanical load on the diaphragm, which increases the stiffness and in turn the resonant frequency.
