Fluid-based switches, such as liquid metal micro switches (LIMMS) have been made that use a liquid metal, such as mercury, as the switching element. The liquid metal may make, break, or latch electrical contacts. Alternately, a LIMMS may use an opaque liquid to open or block light paths. To change the state of the switch, a force is applied to the switching element. The force must be sufficient to overcome the surface tension of the liquid used as the switching element.
In one embodiment, a switch comprising first and second mated substrates is disclosed. The substrates define between them at least portions of a number of cavities. A plurality of electrodes is exposed within one or more of the cavities. One or more of the cavities holds a switching fluid that opens and closes at least a pair of electrodes in response to forces applied to the switching fluid by an actuating fluid held within one or more of the cavities. At least a portion of the switching fluid is coated with a surface tension modifier.
Illustrative embodiments of the invention are illustrated in the drawings in which:
The substrate 100 further includes a surface tension modifier 112 deposited in the switching fluid channel 104. By way of example, the surface tension modifier may be deposited into the switching fluid channel 104 using a syringe. Other methods may also be used to deposit the surface tension modifier into the switching fluid channel. Although
As will be described in more detail below, the surface tension modifier 112 may be used to coat at least a portion of the switching fluid used in a fluid based switch. The composition of the surface tension modifier may be selected so that it reduces the surface tension of the switching fluid. By way of example, a surface tension modifier may be selected that has an affinity for the switching fluid and some affinity for the actuating fluid used to apply a force to the switching fluid to cause the switch to change state. In one embodiment, the switching fluid comprises liquid metal, such as mercury or a gallium-bearing alloy and the surface tension modifier comprises an inert liquid with an affinity for metal, such as abietic acid dissolved in a suitable nonreactive low viscosity fluid, such as 3M Fluorinert. It should be appreciated that other surface tension modifiers may be used.
By reducing the surface tension of the switching fluid, the power requirements to cause the switch to change state may also be reduced. This may lead to benefits such as lower, more consistent drive power and decreased cooling requirements for the switch.
In one embodiment of the switch 300, the forces applied to the switching fluid 318 result from pressure changes in the actuating fluid 320. The pressure changes in the actuating fluid 320 impart pressure changes to the switching fluid 318, and thereby cause the switching fluid 318 to change form, move, part, etc. In
By way of example, pressure changes in the actuating fluid 320 may be achieved by means of heating the actuating fluid 320, or by means of piezoelectric pumping. The former is described in U.S. Pat. No. 6,323,447 of Kondoh et al. entitled “Electrical Contact Breaker Switch, Integrated Electrical Contact Breaker Switch, and Electrical Contact Switching Method”, which is hereby incorporated by reference for all that it discloses. The latter is described in U.S. patent application Ser. No. 10/137,691 of Marvin Glenn Wong filed May 2, 2002 and entitled “A Piezoelectrically Actuated Liquid Metal Switch”, which is also incorporated by reference for all that it discloses. Although the above referenced patent and patent application disclose the movement of a switching fluid by means of dual push/pull actuating fluid cavities, a single push/pull actuating fluid cavity might suffice if significant enough push/pull pressure changes could be imparted to a switching fluid from such a cavity. Additional details concerning the construction and operation of a switch such as that which is illustrated in
Switch 300 further includes surface tension modifier 322 coating switching fluid 318. Surface tension modifier 322 may coat the surface of the switching fluid where it is not sealed to electrodes 312, 314, 316. In alternate embodiments, surface tension modifier 322 may coat only a portion of switching fluid 318 where the switching fluid 318 will be making or breaking contact.
The composition of the surface tension modifier may be selected so that it reduces the surface tension of switching fluid 318. For example, the surface tension modifier may be a liquid that has an affinity for switching fluid 318 and some affinity for actuating fluid 320 (e.g., abietic acid dissolved in a suitable nonreactive low viscosity fluid, such as 3M Fluorinert). In one embodiment, using surface tension modifier 322 to reduce the surface tension of switching fluid 318 also reduces the power requirements to cause the switch to change state.
Switch 500 additionally includes surface tension modifier 530 coating at least a portion of switching fluid 518. Forces may be applied to the switching 518 and actuating 520 fluids in the same manner that they are applied to the switching and actuating fluids 318, 320 in FIG. 3. By using a surface tension modifier 530 to reduce the surface tension of switching fluid 518, the power requirements to cause the switch to change state may also be reduced.
Additional details concerning the construction and operation of a switch such as that which is illustrated in
An exemplary method for making a fluid-based switch is illustrated in FIG. 6. The method commences with forming 600 at least two substrates, so that the substrates mated together define between them portions of a number of cavities. Next, a surface tension modifier 605 is deposited on at least a portion of one of the substrates. A switching fluid is also deposited 610 on the other substrate. It should be appreciated that the surface tension modifier and the switching fluid may be deposited at any time and in any order before the substrates are mated together 615.
In one embodiment, the surface tension modifier may be deposited by using a small diameter syringe to dispense surface tension modifier on the substrate at a location that will be within a cavity holding the switching fluid. It should be appreciated that alternate means of depositing surface tension modifier are also contemplated. By way of example, surface tension modifier may be applied as a layer to the substrate at a location that will result in switching fluid being coated with surface tension modifier where a cavity holding switching fluid connects with one or more cavities holding actuating fluid. Alternately, surface tension modifier may be deposited directly on switching fluid before the substrates are mated together.
While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art.
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