Comparison of two passive microvalve designs for microlamination architectures

Two passive, one-way microvalves have been created for use in microlamination architectures. The microlamination procedures involve the forming, alignment and bonding of thin metal laminae. A prerequisite to the creation of the flapper valve was the capability for selective bonding so as not to bond the flapper mechanism to the valve seat. A microprojection welding process was developed to meet this requirement. Projections as small as 125 µm in height were used to fabricate the microflapper valve. A microfloat valve, which consists of a small disk that floats up and down within a valve cylinder, was also fabricated. A capacitive dissociation process was developed to separate the small disk from within the valve body. Pressure drop tests were performed across each valve in order to evaluate the theoretical orifice size and the ratio of forward to backward flow over a wide range of mass flow rates. Forward flow was detected in all valves at pressures as small as 20 Pa. The results indicate that the best performing valve was the microfloat valve, with a theoretical orifice size of 629 µm and an average ratio of forward to backward flow of 12.76. Reasons given for these results include the ability for floats to reorient themselves to seal against surface asperities along the valve seat.