When I saw the title, I thought they'd figured out a way to make use of something other than helium, but I guess I was wrong. I was thinking maybe they built se

When I saw the title, I thought they'd figured out a way to make use of something other than helium, but I guess I was wrong. I was thinking maybe they built self-resizing vacuum chambers in order to reduce the weight/volume ratio. Like, there would be two membranes, and between them, supports that can extend or shorten to change the volume of the vacuum-space, and affect the overall density that way. Does anyone know if this has been done, or if it's at all feasible?