INV-1243
The typical structure for a MEMS microvalve includes an orifice and a moveable plate that can be actuated to press against the orifice. When the plate does not press against the orifice, fluid can flow through the orifice and therefore through the valve. When the plate is pressed against the orifice, fluid flow through the valve is restricted. Although the flow is restricted, this type of microvalve does not fully seal, and some flow continues through the orifice. This does not provide adequate sealing for long periods of time.
Some sealable valves in prior art use surface tension, however, they are usually permanently sealable and hence not reusable.
Northeastern University inventors have developed a leak-free, sealable microvalve that can be repeatedly opened and sealed. Such a microvalve can be used in various vacuum applications, or to seal in the contents of a closed space and to prevent entry into that space by molecules or atoms from outside. Such a microvalve may then be used to open the previously closed space for example to modify the contents of the space. The space may be repeatedly sealed and opened in this manner. This device is different from existing microvalves in that it is substantially leak-free in the closed state and has a relatively high flow rate in the open state, and the seal can be reversibly opened and closed (i.e. the seal is not permanent).
This device relies on the surface tension of a molten seal material to establish a leak-free seal. The sealable port is located in the center of a first island structure supported on a thermally-insulating membrane in a frame. The through via is surrounded by a low aspect ratio ring of meltable sealing material. Opposite this island is a second island that does not contain a through via. This island is supported on thermally insulating tethers that include piezoelectric actuators that can move the second island closer to or further away from the first island. To seal the valve and prevent flow through the via, the sealing material is heated until it melts, for example by passing a current through a resistive heater on the back of the first island. To reopen the valve, the heater is used to melt the seal material again. The actuators are actuated in order to separate the two islands. When the islands are separated, flow passes freely through the through via.