Design optimization of bistable microdiaphragm valves

Microvalves incorporating a bistable diaphragm, which either closes or uncovers a valve opening, have to be energized only during the switching process. The differential pressure needed to switch the diaphragm may be much smaller than the pressure that is to be switched. In this report simple equations will be derived which allow the major features of these valves to be described and which can be used during design. Comparison of the calculations with the measurements shows good agreement, considering the approximations used. The tested microvalves allow pressures at the inlet to be switched that are twice the switching pressure generated by the microactuator. With suitable optimization of the design. a theoretical limit of the switching pressure is obtained, which is 75 times smaller than the inlet pressure. The equations presented here are not only important to microvalve design, but likewise to the description of the mechanical behaviour of diaphragms in general. For example, the diaphragm prestress and the Young's modulus of diaphragms exposed to compressive stress, and whose behaviour is also substantially determined by bending moments, can be determined from a simple measurement. (C) 1998 Elsevier Science S.A.