Fine Boffinry..
..gentlemen of N. Carolina. Have one on me.
Boffins have made a liquid metal device which can alter its shape through voltage alone, removing the need for clunky external pumps previously used to arrange such material. In a breakthrough which brings humanity much too close to the development of functioning T-1000s, boffins from North Carolina State University (NCSU) …
Technically a varactor isn't a switched circuit element - it's a reverse biased diode used as a variable capacitor, by altering the applied voltage. What it can't do is alter the optimum frequency of a physical aerial, so this discovery would enable control by voltage of all the necessary parameters for a receiver.
clever stuff, but probably not practical - yet.
Gallium, and liquid gallium alloys are a PITA to work with because they are damned difficult and risky to contain safely. For instance - except for Swissair (cos the Swiss make the stuff) gallium is banned from aircraft as any leaks would corrode through the aircraft floor and hull in record time.
You can really only package the stuff in glass - but then you have the obvious breakage risk. A lot of thought needs to be given to safe handling
I was interested by your comment and looked up Gallium on Wikipedia:
"samples of gallium metal are usually supplied in polyethylene packets within other containers"
So polythene, which can be made quite robust, can also be used as a container; also, I'd expect the amount present in a mobile phone or IoT device to be very small, probably less than a few grammes, so any leakage is likely to have minimal effect on an aircraft.
What they mean is a polythene protective layer inside something stronger.
The problems with gallium are
1) Its density - around 6g/cm3 meaning any container has to be strong
2) It expands on freezing - so giving the probability of shattering containers while in storage
3) How it reacts with other metals: to quote Wiki:
"Gallium attacks most other metals by diffusing into their metal lattice. Gallium, for example, diffuses into the grain boundaries of aluminium-zinc alloys or steel, making them very brittle."
It takes very little to do this - my understanding is that aircraft have been lost as a result of very small leaks.
Together they represent a fair headache to resolve, especially if placed in the hands of the public