thank you very much for your responses,
i took some time to answer to consider alternatives.
I did consider frigelli actuators, but given that I'll need more than 10 elements, it'll get pretty expensive.
cr0sh, thanks for your link,
it seems like the cheapest solution from all although it has to be done with a stepper motor instead of a regular DC for better accuracy.
do you know how the call these PVCs?
I have ordered 3 stepper motors and their driver, to begin some testing.
a different solution is a thing called bio-metal. its a spring or threat from an alloy that extends when heated, or when you pass electricity through it. (though it can not be used as a load bearing element, just like a mini muscle)
I'll probably check that too, its the simplest and probably the cheapest method (it doesn't need a driver, just plug and play), although I dont know how accurately one can control its deformations.
the site of the company is this :
its similar to shape memory alloys.