1. How do you guys feel about linear actuators for fingers? (high speed of course)
From what You've told us and from what I've seen in a video, solenoids
would do the job (you can get them in many places
). They are linear actuators that have two states only: fully extended and fully subtracted. Having one of them for each finger, with some soft material at the tip of each to prevent excessive force on the tested device, can do the trick.
2. I really like having the ability to move the fingers forward, backwards, side to side. What kinds of parts would I need for this. looks like the video uses some kind of small track.
Mechanism like that normally consists of threaded rod with a nut riding it and motor/servo/stepper motor spinning the rod, that way the nut acts as linear actuator (for extra low friction You can take a look at more expensive ball screws
). For what You want You'd need three of such actuators to get motion in X, Y and Z. Google DIY CNC
to get a better idea of what's what.
3. where the french toast can I get these parts? (I'm not too worried about price less than $5K would be good)
For me, good starting point when looking for parts is eBay and Google Shopping.
4. currently I have 2 actuators that each require their own control board and USB connection. If I start adding more parts how can I considerate multiple parts to one USB? (there has to be some kind of kick butt control board that has this ability)
If You fancy cheaper DIY route, going with microcontroller (which You have to program Yourself) with UART feature and an H-Bridge/Motor Driver for each actuator (note: not all actuators need external H-Bridges/Motor Drivers; some actuators might need more that one H-Bridge; it all depends on the type of actuator You choose;) You can make fairly good system. Microcontroller takes care of USB comms, calculations based on sensor feedback and positioning actuators. That way You only need one USB port. If You are willing to spend more money and do less soldering, Googling "USB motor controller"
is a good starting point.