I know the title is quite a mouthful, but let me explain (also, I couldn't find anything on the subject, maybe because I'm using the wrong words).
I saw some time ago a video about a variable suspension system that used a variable viscosity fluid that changes its viscosity based on a electromagnetic field applied to it (it is just a fluid with ferromagnetic particles on it [I think]).
(The link redirects to the video in the exact moment its working mechanism is explained).
To me it seems quite an interesting system that could allow for solenoid/active valves with no moving parts that can instantaneously and progressively change the flow of its fluids by changing its viscosity until nothing can flow.
But I couldn't find any papers on the subject, this makes me wonder if such system would even work...
Of course, I don't think it would be able to withstand the absurd pressures on industrial hydraulic systems, but smaller (maybe hobbyist) things.