Development of various designs of low-power, MEMS valves for fluidic applications

Automated, controlled fluid delivery is an important operation in micro-total analysis systems (μTAS). Actuated micro-valves have been proposed to separate a pressurized fluid from the channel to be filled. This scheme greatly reduced the energy required to move the fluid. The design, micro-fabrication and performance of arrays of single-use valve, which constitute an integral part of this actuation mechanism, is presented. The addressable constituent of the valve is a thin metallic ohmic resistor, whose design dictates the actuation voltage. The resistor is patterned on a silicon nitride membrane that constitutes the flow barrier, which stands on a silicon wafer. Rapid heating via an electric pulse induces thermal stresses in the membrane/resistor, which in turn breaks the membrane opening the valves. The chosen processing steps allow for wafer-level device fabrication using standard MEMS processing tools. Different size membranes with various thicknesses (1, 2 and 3 μm) are tested. Valves that withstand a pressure differential of up to 5 bar (3 mm × 3 mm, 3 μm-thick silicon nitride membranes) were chosen for the study. Investigated valves were activated with a potentials ranging between 14 and 140 V and required activation energies from tens to hundreds of milliJoules.