ated stand atop micro vacuum cavities that are constructed by a specially designed, vacuum sealant process. Thus pressure changes cause a deflection of the diaphragm, the magnitudes of which are detected by using built-in piece resistive elements that are positioned on the surface of the diaphragms. Both square and circular-shaped sensors with nominal diameters in the range of 100 microns have been fabricated and tested. Optimized designs that include position orientation and length of the piece resistive elements have been analyzed. The attendant fabrication process is completely compatible with integrated circuit processing techniques in use today. Consequently, using stable technology, today, microelectronic structures can be fully integrated with micro sensors to create micro scale mechatronics systems. Prototype pressure sensors which have been designed for 100 psi full operational scale, have a measured sensitivity of 0.15 mV/V/psi and a maximum linearity error in the range of +/- 0.1% full scale span.
In another application (Damgaard, 1997), a micro scale biosensor for continuous measurement of methane partial pressure is based upon use of the counter diffusion principle. Here methane oxidizing bacteria is placed in the micro sensor and utilizes oxygen from an internal oxygen reservoir, which is generated when the methane from the exterior diffuses through the tip membrane. The transducer represents an internal oxygen sensor with its tip positioned between the oxygen reservoir and the tip of the sensor membrane. The external partial pressure of methane determines the rate of bacterial oxygen consumption within the sensor cavity. By designing the geometry of the sensor, devices can be implemented which can exhibit a linear response in the full range of zero to one atmosphere of partial methane pressure. Alternatively, the devices can demonstrate a linear response at lower gas concentrations.
Today, the technology...