Fluid-based switch, and method of making same

1. A switch, comprising:

first and second mated substrates defining therebetween a number of cavities;

a plurality of electrically conductive elements, extending to near at least a first of the cavities;

a switching fluid, held within a first of the cavities, that serves to electrically, but not physically, couple and decouple at least a pair of the electrically conductive elements, in response to forces that are applied to the switching fluid; and

a passivation layer covering at least a first of the electrically conductive elements, wherein the passivation layer i) separates the first of the electrically conductive elements from at least the first of the cavities, and ii) is a dielectric for a capacitor formed between the first of the electrically conductive elements and the switching fluid.

2. The switch of claim 1 , wherein the passivation layer comprises silicon dioxide.

3. The switch of claim 1 , wherein the passivation layer comprises silicon nitride.

4. The switch of claim 1 , wherein the passivation layer comprises silicon carbon.

5. The switch of claim 1 , wherein the passivation layer comprises polysilicon.

6. The switch of claim 1 , wherein the passivation layer covers a plurality of the electrically conductive elements and i) separates the plurality of electrically conductive elements from at least the first of the cavities, and ii) is a dielectric for capacitors formed between the electrically conductive elements and the switching fluid.

7. The switch of claim 6 , wherein the passivation layer is deposited between the electrically conductive elements.

8. The switch of claim 6 , wherein the passivation layer forms a uniform continuous surface over the electrically conductive elements.

9. The switch of claim 1 , wherein the passivation layer comprises multiple layers of different materials.

10. The switch of claim 1 , further comprising a plurality of surfaces to which the switching fluid wets within at least the first of the cavities.

11. The switch of claim 10 , wherein the surfaces to which the switching fluid wets comprise roughened portions of the passivation layer.

12. The switch of claim 10 , wherein the surfaces to which the switching fluid wets comprise layers of metal deposited on the passivation layer.

13. The switch of claim 10 , wherein the surfaces to which the switching fluid wets comprise layers of metal deposited on walls of at least the first of the cavities.

14. The switch of claim 10 , wherein the surfaces to which the switching fluid wets comprise at least one of: iridium, rhodium, platinum and chromium.

15. The switch of claim 1 , wherein the electrically conductive elements comprise conductive runners extending from near the first of the cavities to one or more exterior surfaces of the switch.

16. The switch of claim 15 , further comprising a plurality of bonding pads, formed at ends of the conductive runners that present on the exterior surface(s) of the switch.

17. The switch of claim 15 , wherein the conductive runners comprise layers of titanium, platinum and gold.

18. The switch of claim 1 , wherein the switching fluid comprises liquid metal.

19. The switch of claim 1 , further comprising an actuating fluid, held within one or more of the cavities, that serves to apply the forces to the switching fluid.

20. A method for forming a switch, comprising:

depositing a plurality of electrically conductive elements on a first substrate;

depositing a passivation layer on at least a first of the electrically conductive elements; and

mating the first substrate to a second substrate to seal a switching fluid in one or more cavities formed between the first and second substrates, the one or more cavities being sized to allow movement of the switching fluid between first and second states, and the passivation layer i) separating the first of the electrically conductive elements from the one or more cavities, and ii) serving as a dielectric for a capacitor formed between the first of the electrically conductive elements and the switching fluid.

21. The method of claim 20 , further comprising, prior to mating the first substrate to the second substrate, forming on the passivaton layer a plurality of surfaces to which the switching fluid wets.

22. The method of claim 21 , wherein the surfaces to which the switching fluid wets are formed by roughening portions of the passivation layer.

23. The method of claim 21 , wherein the surfaces to which the switching fluid wets are formed by depositing layers of metal on the passivation layer.

24. The method of claim 20 , wherein the passivation layer is deposited over a plurality of the electrically conductive elements and i) separates the plurality of electrically conductive elements from the one or more cavities, and ii) is a dielectric for capacitors formed between the electrically conductive elements and the switching fluid.

25. The method of claim 20 , wherein the passivation layer is deposited using a chemical vapor deposition process.

26. A switch, comprising:

first and second mated substrates defining therebetween a number of cavities;

a plurality of electrically conductive elements, extending to near at least a first of the cavities;

a switching fluid, held within at least the first of the cavities, that serves to electrically, but not physically, couple and decouple at least a pair of the electrically conductive elements, in response to forces that are applied to the switching fluid; and

means to cover at least a first of the electrically conductive elements, to i) separate the first of the electrically conductive elements from at least the first of the cavities, and ii) form a dielectric for a capacitor formed between the first of the electrically conductive elements and the switching fluid.