Fabrication of micro pneumatic valves with double-layer elastic poly(dimethylsiloxane) membranes in rigid poly(methyl methacrylate) microfluidic chips

This paper presents a novel method to fabricate a normally open micro pneumatic valve in rigid poly(methyl methacrylate) (PMMA) chips. The control and fluid substrates of the valve were prepared with PMMA sheets via hot embossing. After both control and fluid substrates were silanized with 3-aminopropyltriethoxysilane and treated with glow discharge plasma, each of them was irreversibly bonded to a plasma-treated PDMS membrane, forming a control half or a fluid half. Relying on the native adhesive force of the PDMS membrane, the control half and fluid half were then reversibly sealed to form a full microchip with the four-layer structure of PMMA-PDMA ⋅ ⋅ ⋅ PDMS-PMMA. The irreversible bonding between rigid PMMA substrate and elastic PDMS membrane in combination with the reversible sealing between the control half and fluid half not only eases the difficulties in chip bonding, but also allows the control half and fluid half to be replaced individually in routine analyses. The performance of the developed micro pneumatic valves was characterized, and potential applications of the valves in droplet generation and micro flow injection analysis were demonstrated.