Microchannel heat transfer with liquid metals

1. An apparatus for controlling heat transfer between portions of a substrate comprising:

a substrate including at least part of a hydraulic circuit, the hydraulic circuit comprising a plurality of microconduits, the plurality of microconduits including a first microconduit and a second microconduit;

a liquid metal flowing through the hydraulic circuit; and

a magnetic field source configured to provide a magnetic field to selectively direct the flow of the liquid metal between the plurality of microconduits;

wherein the flow of the liquid metal through the hydraulic circuit transfers heat between a first portion of the substrate and the liquid metal; and

wherein the magnetic field is activated to initiate the flow of the liquid metal in a desired direction and is inactivated after the flow is initiated such that the flow of liquid metal continues in the desired direction through the hydraulic circuit via surface tension.

2. The apparatus of claim 1 , wherein the liquid metal electrically transports a signal.

3. The apparatus of claim 2 , wherein the first microconduit comprises a first signal receptor, and the second microconduit comprises a second signal receptor; and

wherein when the liquid metal is directed to the first microconduit, the signal is received by the first signal receptor, and when the liquid metal is directed to the second microconduit, the signal is received by the second signal receptor.

4. The apparatus of claim 1 further comprising magnetic particles dispersed within the liquid metal;

wherein the magnetic field applies a force to the magnetic particles.

5. The apparatus of claim 1 , wherein the magnetic field applies a magneto-hydrodynamic force to the liquid metal by interaction with a current within the liquid metal.

6. The apparatus of claim 5 , wherein the magnetohydrodynamic force is modulated by varying an electric current passing through the liquid metal.

7. The apparatus of claim 5 , wherein the magnetohydrodynamic force is a function of the magnetic field.

8. The apparatus of claim 1 , wherein the substrate comprises a second hydraulic circuit.

9. The apparatus of claim 8 , wherein the second hydraulic circuit is separate from the first hydraulic circuit.

10. The apparatus of claim 8 , wherein different types of liquid metal flow through each of the first and the second hydraulic circuits.

11. The apparatus of claim 1 , wherein the hydraulic circuit comprises a third microconduit, wherein the magnetic field selectively directs the flow of the liquid metal from the third microconduit between the first microconduit and the second microconduit.

12. The apparatus of claim 11 , wherein the first microconduit, the second microconduit, and the third microconduit are coupled at a junction.

13. The apparatus of claim 12 , wherein the third microconduit is located upstream of the junction and at least the first and second microconduits are located downstream of the junction;

wherein the magnetic field determines what fraction of the flow flows through each of the microconduits located downstream of the junction.

14. The apparatus of claim 12 , wherein the magnetic field is applied to at least one of the third microconduit and the junction.

15. The apparatus of claim 12 , wherein the first microconduit extends between the junction and a second portion of the substrate, and wherein the second microconduit extends between the junction and a third portion of the apparatus.

16. The apparatus of claim 15 , wherein the third portion of the apparatus is located external to the substrate.

17. The apparatus of claim 16 , wherein the third portion of the apparatus comprises a microcomponent supported by the substrate.

18. The apparatus of claim 1 , wherein the hydraulic circuit comprises:

a junction fluidly coupling each of the first microconduit and the second microconduit; and

a third microconduit fluidly coupled to the junction;

wherein the magnetic field provides switching forces between the first and second microconduits so as to selectively direct the flow of liquid metal between the plurality of microconduits; and

wherein after a flow of liquid metal is initiated along a desired direction, the magnetic field is deactivated and the flow of liquid metal continues along the desired direction due to a surface tension of the liquid metal.

19. The apparatus of claim 1 , wherein the hydraulic circuit leaves the substrate.

20. The apparatus of claim 19 , wherein the hydraulic circuit enters a microcomponent supported by the substrate.