Idea: pneumatic-hydraulic tube gripper tool

[theosanderson]

Writing this down while I remember - I'll likely give it a go sometime but posting it here in case anyone else has the same inclination.

Background

Unlike some other robots, OpenTrons does not support exchanging tools (mid-run). This means some creativity is need to come up with a way of gripping items. I previously made a passive tool that could be collected like a pipette tip and then allowed eppendorf tubes to be picked up:

https://www.youtube.com/watch?v=Jm4h6dKwD3c&feature=youtu.be https://www.thingiverse.com/thing:2622398

But this relies on their conical shape and does not grip them in the most logical place (nearer the top). It also wouldn't work for 2 ml eppendorfs.

Idea

In order to make an active gripper that closes around a target one needs a way to control whether it is open or closed. Previously I thought this would need require messy electronics - but now I wonder if one can do it using the pipette aspirate/dispense function. For example, if you attached a 1ml syringe to the end of a pipette tip, then its plunger would move up and down as the pipette aspirated and dispensed air.

The idea here would be to convert that movement into the opening and closing of a gripper with a simple 3D printed mechanism.

If one did this with just air there would be a lot of slop as the air could compress when the pipette dispensed, rather than closing the gripper. To minimise that we could fill as much of the system as possible with liquid (while avoiding any getting into the pipette), which I think would allow more than enough force. [Edit actually with the right design I think you could just use air, and I'm not sure it's feasible for liquid to help without it potentially reaching the pipette]

If anyone has tried anything similar let me know!

[kristinellis]

This is awesome Theo!!!

[theosanderson]

Pivoted to https://twitter.com/theosanderson/status/1151515787317993472 - but the gripper could still be useful in some circs too.