Electrically-activated, normally-closed diaphragm valves

Single-use, thermally actuated paraffin valves for microfluidic applications

“…Most of the conventional active microvalves couple a flexible diaphragm to an electromechanical actuator operating based on thermo-pneumatic [1,2], bimetallic [3,4], shapememory [5], electrostatic [6], piezoelectric [7], or electromagnetic principle [8]. For example, the thermo-pneumatic microvalve developed by Zdeblick et al made use of resistive heating that caused boiling of a trapped liquid and resulted in a high pressure [1].…”

“…The pressure pushed a thin silicon (Si) membrane that modulated the "current" of fluid in the regulated channel. Jerman [3] demonstrated a normally closed thermal bimorph actuation scheme for a microvalve for gas flow control using an aluminium layer fabricated on a Si membrane. Shoji, et al [7] demonstrated the use of a separately fabricated stacked piezoelectric actuator as a means of closing a Si micromachined valve.…”

Microvalves for Natural-Gas Analysis With Poly Ether Ether Ketone Membranes

“…While early works on microvalves focused mainly on liquid handling, most microvalves developed for gas applications use active actuation principles, such as electromagnetic [5], [6], electrostatic [7]- [9], piezoelectric [10]- [13], or thermal [14], [15] actuation. The membranes are mostly made of metal or silicon.…”

Fundamentals of Microfluidics Devices

“…A bimetallic strip-driven microvalve with an 8 mm thick silicon membrane and a 5 mm thick aluminum layer that provides fully proportional control of flows has been demonstrated. 54 Another actuation mechanism that depends on transfer of thermal energy uses shape memory alloys that allow for compact designs and can generate large forces. Valves using these alloys can also be built using thin films of the alloys on membranes.…”