Yes, you can do that but you still need a cheap valve with a size ideally smaller than one dowel pin 'cell' at standard braille densities. AFAIK this does not exist commercially, if it does it would be cost prohibitive, and therefore would need to be designed in some unknown manner focused on low fabrication cost. Since most valves operate based upon electromagnetism (solenoid-driven) you also have an electrical control problem. All in all, not an attractive solution path.
then you can use whatever large, cheap, widely spaced, easy to access, easy to maintain, valves you can find. The trade would be size, noise, and power, but the gain would be easy to build, mass produced parts, easy to repair, large and solid and relatively reliable.
Most valves are actuated by solenoids which use a lot of power. An array of them is not only physically huge but will exceed USB power availability at a count of one or two valves and you need many per braille block. Worse, you generally need to actuate huge numbers of them simultaneously. This approach is therefore difficult to consider for a real world deployment.
The top comment on this thread by gostsamo is "As someone blind, my two pens [pence?] are that noise, power consumption, and fragility are things that could be compromised to a large degree."
How many do you consider 'huge numbers'? There's another comment saying a Braille cell is 8 dots, and if you average changing half of the dots each time to change state, you could barely get into double digits to keep ahead of the fingers.
> "This approach is therefore difficult to consider for a real world deployment."
It only had 10 seconds of thought; I just skim read the article which was all about mechanical actuation and the difficulty of making so many small and precise and reliable actuators cheaply enough, and wondered about options that didn't require that part. Air, electric current (e.g. the vibration felt in a pot on an induction hob vibrating some loose rods without having to actually lift them), or a one-finger glove where there is only a few actuators and they change as the finger slides over a table, or no actuators - a design like the way a CRT screen has a scanning electron beam activating each pixel, although I have no ideas how a design like that could activate Braille dots.
