Micro-electromechanical valve shutter assembly
View Patent ↗A micro-electromechanical shutter assembly includes an elongate actuator that is anchored at one end to the wafer substrate to be in electrical contact with the drive circuitry layers. A closure member is mounted on an opposite end of the elongate actuator. The actuator is configured to receive an electrical signal from the drive circuitry layer to displace the closure member between a closed position in which the closure member covers the fluid supply opening and ink is inhibited from flowing through the fluid supply channel and an open position. The elongate actuator is shaped so that, in a rest condition, the actuator encloses an arc. The actuator includes a heating portion that is capable of being heated on receipt of the electrical signal to expand. The heating portion is configured so that, when the portion is heated, the resultant expansion of the portion causes the actuator to straighten at least partially and a subsequent cooling of the portion causes the actuator to return to its rest condition thereby displacing the closure between the closed and open positions.
1. A micro-electromechanical shutter assembly for controlling a fluid flow through a fluid supply channel defined by a wafer substrate and drive circuitry layers positioned on a first surface of the wafer substrate, the fluid supply channel terminating at a fluid supply opening, the shutter assembly comprising;
an elongate actuator anchored, at one end, to the first surface of the wafer substrate so as to be in electrical contact with at least one of the drive circuitry layers; and
a closure member fixedly mounted on an opposite end of the elongate actuator so as to be movable between a closed position, in which the closure member covers the fluid supply opening and prevents ink from flowing through the fluid supply channel, and an open position, in which the fluid supply opening is opened to allow the ink to flow through the fluid supply channel, wherein
at least a portion of the actuator is arranged such that, upon receiving an electrical signal from the drive circuitry layer, it heats up and, thereby, changes its shape so as to displace the closure member from closed to open position.
2. A micro-electromechanical shutter assembly as claimed in claim 1 , the portion having an arcuate shape and being arranged such that, in the absence of electric current, the closure is in its closed position, wherein the arcuate portion is also arranged to:
straighten, at least partially so as to open the closure when an electric current is passed through the circuitry layer and the portion is heated; and
return to its initial shape and brings the closure back in closed position during the subsequent cooling after the current has been stopped.
3. A micro-electromechanical shutter assembly as claimed in claim 2 , in which each actuator includes a body portion that is of a resiliently flexible material having a coefficient of thermal expansion which is such that the material can expand to perform work when heated, the heating portion being positioned in the body portion and defining a heating circuit of a suitable metal.
4. A micro-electromechanical shutter assembly as claimed in claim 3 , in which the heating circuit includes a heater and a return trace, the heater being positioned proximate an inside edge of the body portion and the return trace being positioned outwardly of the heater, so that an inside region of the body portion is heated to a relatively greater extent with the result that the inside region expands to a greater extent than a remainder of the body portion.
5. A micro-electromechanical shutter assembly as claimed in claim 4 , in which a serpentine length of said suitable material defines the heater.
6. A micro-electromechanical shutter assembly as claimed in claim 4 , in which the body portion is of polytetrafluoroethylene and the heating circuit is of copper.
7. A valve assembly as claimed in claim 2 , in which each actuator defines a coil that partially uncoils when the heating portion expands.