I was searching for questions on this stack and I found this one asking why pneumatic/hydraulic artificial muscle robots aren't common, TLDR: the reason is that it is incredible hard to control them.
However, one thing that the asnwer didn't talked about was vacuum actuated artificial muscles.
My gut feeling says that they are as difficult as pneumatic ones, since they are simply the opposite, but even then I want to know.
With a vacuum you are limited to the pressure differential between zero and atmospheric (~100kPa or ~15PSI). With pneumatic you are limited to the pressure differential between atmospheric and whatever pressure you design your compressor and muscles to. A normal shop compressor easily exceeds 100PSI.
Also, with a compressor you can do things like store the compressed air at higher than the pressure you need and use a valve to regulate it which lets you use a smaller reservoir. You can't "store a more extreme vacuum" and then regulate the vacuum to be less. The only thing you can do is use a larger vacuum reservoir tank.
