Supercritical fluids transition between liquid and gas phases with slight changes in temperature so they have an ephemeral appearance.

Unfortunately supercritical fluids only exist at high pressure, making them inaccessible in everyday life.

So how to make them more available?

Bubbles can contain gas inside at very high pressure. The smaller the bubble, the higher the pressure that it can contain.

So my idea is to make very small bubbles that contain supercritical fluid. The bubbles would be made of glass, formed at a temperature when glass is liquid. The bubbles would be made in a high atmospheric pressure environment. A suitable gas is injected into the glass to form the microbubbles. The glass microbubbles cool and solidify and are removed from the high atmospheric environment.

The microbubbles diameter would be chosen to optimise the strength and visibility; I'm guessing somewhere between 10µm and 1mm in diameter.

The internal pressure of the microbubbles would be balanced against the tensile strength of the glass. This is similar to how tempered glass has internal and external pressures balanced to make it stronger than if there were no pressure difference.

The supercritical microbubbles could then be (carefully) embedded into a layer of clear resin (with the same refractive index as the glass).

The supercritical microbubbles layer would change appearance with temperature (analogous to liquid crystal thermochromic layers).

Could be used as a coating on windows, toys, cars, bathroom tiles, etc.

Another interesting use would be as tiny bubble chambers, which could be used to see subatomic particles flying through.
-- xaviergisz, Aug 12 2019

Laplace pressure https://en.wikipedi...ki/Laplace_pressure
pressure inside a bubble [xaviergisz, Aug 12 2019]

Supercritical fluid https://en.wikipedi...Supercritical_fluid
[xaviergisz, Aug 12 2019]

Supercritical CO2 in a Glass Tube https://www.youtube...watch?v=4Z-KbcLs-yo
[xaviergisz, Aug 12 2019]

hollow glass microspheres https://www.science...i/S0360319907003990
Apparently glass microballoons (GMBs) also known as hollow glass microspheres (HGMS) are known for storage of hydrogen at pressures up to 980 atmospheres! Storage of supercritical fluids at 70 atmospheres should be a cinch [xaviergisz, Sep 06 2019]

Only the bubble contents in the glass is changing state, right? The glass bead and the resin are going to have different expansion coefficients.
-- wjt, Aug 12 2019


I think I like this idea.
-- MaxwellBuchanan, Aug 12 2019


I also think [MaxwellBuchanan] likes this idea
-- hippo, Aug 12 2019


//Only the bubble contents in the glass is changing state, right? The glass bead and the resin are going to have different expansion coefficients.//

For a supercritical fluid the density of the gas phase and liquid phase are very similar. This is unlike a normal gas/liquid where the densities differ by orders of magnitude.
-- xaviergisz, Aug 12 2019


Please explain how one would see a sub-atomic particle flying through one of these.
-- pertinax, Sep 06 2019


// Please explain how one would see a sub-atomic particle flying through one of these.//

Admittedly speculative, but the idea is that a (polar) supercritical fluid that is *just* in a liquid state (metastable phase) will have visible ionization tracks as charged particles whizz through turning the liquid into gas (a la bubble chamber). The glass bubbles might need to be 1cm or larger to see this effect.
-- xaviergisz, Sep 06 2019



random, halfbakery