Can superconducting circuits be immersed and still function efficiently?

[imported_Tick]

Could you, for instance, immerse a circuit board where all the exposed traces were superconductors, in say, water? Would be nice for ROV's. No need to seal them in water tight boxxes, just leave the thing open to the sea. Also nice for computers, no need for water blocks, just water cool the whole thing.

For this discussion, assume we are talking about room temperature superconductors.

 

[PowerEngineer]

Assuming that the superconductors have zero impedance (not just near-zero) at the temperature of the water, then I guess there would be effectively no current taking the parallel paths (to the circuit board runs) through the water. On the other hand, there will still be components on the board that have non-zero impedances and "open" transisters that would be shorted out by the water path, and the water still makes a low impedance path between runs that otherwise weren't connected. So, it seems to me that the answer is no.

 

[imported_Tick]

Originally posted by: PowerEngineer

Assuming that the superconductors have zero impedance (not just near-zero) at the temperature of the water, then I guess there would be effectively no current taking the parallel paths (to the circuit board runs) through the water. On the other hand, there will still be components on the board that have non-zero impedances and "open" transisters that would be shorted out by the water path, and the water still makes a low impedance path between runs that otherwise weren't connected. So, it seems to me that the answer is no.

What if the all surface mount components were properly sealed, just the traces were open to the water? Also assume anything that needs a heatsink has one. Further, isn't their always some leak current? How low would it need to be for this to work?

 

[PowerEngineer]

Even presuming you could waterproof the components, the bare (uninsulated) circuit board runs would be shorted to each other by the water. If your next step is to waterproof (i.e. add insualtion to) the runs, then you've just waterproofed the entire board (so why wait for room-temperature superconductors?)

You might be interested in oil-emmersed circuit boards (the advantage being that oil is essentially non-conducting at these voltages). See here.

 

[f95toli]

This must be one of the most hypothetical questions ever...

First or all, superconducting leads do NOT have zero impedance; they have zero RESISTANCE; as soon as you try to pass an AC current there will be some reactive impedance. Hence, it is possible to "short" a superconducting circuit with a normal conductor such as water and in fact this does cause some real problems when designing superconducting electronics (some substrates are slightly conductive).
(in type II superconductors there are also losses due to flux flow, but lets ignore those for now).

Secondly, there are no known room temperature superconductors so we can only speculate when it comes to what kind of chemical properties they would have. However, all known high-temperature superconductors are perovskites i.e. oxides and are very sensitive to water; if you expose to for e.g. YBCO to water it turns grey and stops being superconducting (I don't remember what kind of chemical reaction takes place). Fewc crystalline materials can withstand being immersed in water for long periods of time (salt water kills just about everything) so it is not very likely that keeping it immered in water would be a good idea.

Thirdly, if you have a room temperature superconductor and you only use it to transmitt DC or low frequency AC signals the losses are very small meaning there is virtually no heating, so there would be probebly be no need to cool it in the first place. The only reason why nitrogen is used to cool superconducting cables today is because the thermal insulation is less than perfect, i.e. the nitrogen is mainly used to "compensate" (cool) for the heat coming IN to the cable and prevent the cable to warm up, not to cool the cable itself.

 

[Eeezee]

I would assume the superconducting circuit would mostly work. Just use distilled water, it's not a good conductor.

 

[dkozloski]

FWIW, My boy put the TV flinker into his cup of Pepsi and it hasn't worked since. It's been rinsed and dried and it didn't help.

 

[bobsmith1492]

Originally posted by: dkozloski
FWIW, My boy put the TV flinker into his cup of Pepsi and it hasn't worked since. It's been rinsed and dried and it didn't help.

Man, you should see ours (assuming the "flinker" is the remote control...) My brother dropped a dumbell on it and cracked it in half. I popped it open and ran wires from via to via following the tracks that crossed the circuitboard at the crack but didn't solder them. It's worked perfectly ever since.