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Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim Part 9

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Tham khảo tài liệu 'microsensors, mems and smart devices - gardner varadhan and awadelkarim part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | APPLICATIONS 223 Table 7.2 Technical specification of microvalves Valve part Value Valve chamber size mm Valve chamber material Fluid chamber size mm Actuator chamber size mm Inlet opening diameter pm Membrane diameter mm Membrane thickness pm Membrane material Membrane deflection pm Maximum flow rates and inlet pressure Lifetime load cycles 5x5x1 PMMA Diameter 3 height 0.125 Diameter 3 height 0.125 100 3 25 Polyimide 120 max. 0.49 m s at 740 hPa 285 million Figure 7.67 Characteristics of a microvalve fabricated by the AMANDA process a actuation pressure and b volumetric flow rate data on these microvalve samples are listed in Table 7.2 and the measured characteristics of the micro valve are presented in Figure 7.67. Applications include integral components of pneumatic and hydraulic systems systems for chemical analyses of liquids and gases dosage systems for medical applications and so on. AMANDA has also been used to fabricate transducers. For polymer membranes the low Young s modulus results in large deflections and strains at comparatively low pressure loads. Therefore polymer pressure transducers are suitable for measuring small differential pressures. A schematic view of a pressure transducer is shown in Figure 7.68 Martin et al. 1998 the outer dimensions of this transducer are 5.5 X 4.3 X 1.2 mm3. The thin polyimide diaphragm supports strain gauges made of gold covered by a 30 pm-thick polyimide disk. This disk bends by the pressure dropped across the diaphragm and the generated strain is measured with a Wheatstone bridge. A volume flow transducer based on pressure difference measurement is shown in Figure 7.69 Martin et al. 1998 . The pressure drop along a capillary is measured and the flow rate is then calculated. These transducers can be easily integrated into the polymer micropump and microvalves developed by the AMANDA process to form a fully integrated microfluidic system. 224 MICROSTEREOLITHOGRAPHY FOR MEMS a Strain gauge Crowning -effect Adhesive .