[bluGill]

Does something like that exist? Can something like that exist? don't forget it needs to be food safe - including whatever it breaks down to, and whatever bacteria might grow on it - so long as the food itself is safe to eat.

Materials science has come a long way, but some problems still are not solved and it isn't always clear if the problem can be solved.

[BurningFrog]

Water ice fits the description, but it's hard to see how that would be practical.

[sph]

We need Ice 9: https://en.m.wikipedia.org/wiki/Ice-nine