title: Torque-actuated valves for microfluidics.
abstract: This paper describes torque-actuated valves for controlling the flow of fluids in microfluidic channels. The valves consist of small machine screws (> or =500 microm) embedded in a layer of polyurethane cast above microfluidic channels fabricated in poly(dimethylsiloxane) (PDMS). The polyurethane is cured photochemically with the screws in place; on curing, it bonds to the surrounding layer of PDMS and forms a stiff layer that retains an impression of the threads of the screws. The valves were separated from the ceiling of microfluidic channels by a layer of PDMS and were integrated into channels using a simple procedure compatible with soft lithography and rapid prototyping. Turning the screws actuated the valves by collapsing the PDMS layer between the valve and channel, controlling the flow of fluids in the underlying channels. These valves have the useful characteristic that they do not require power to retain their setting (on/off). They also allow settings between "on" and "off" and can be integrated into portable, disposable microfluidic devices for carrying out sandwich immunoassays.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Weibel
authors.forename: Maarten
authors.initials: M
authors.lastname: Kruithof
authors.forename: Scott
authors.initials: S
authors.lastname: Potenta
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Sia
authors.forename: Andrew
authors.initials: A
authors.lastname: Lee
authors.forename: George M
authors.initials: GM
authors.lastname: Whitesides
mesh_terms: D007118:Immunoassay; D007070:Immunoglobulin A / Q000032:analysis / Q000276:immunology; D007074:Immunoglobulin G / Q000032:analysis / Q000276:immunology; D044085:Microfluidics / Q000295:instrumentation* / Q000379:methods*; D019415:Torque
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G