August 8, edit

I've also tried using other methods of suction. Using compressed air to create light suction, and just manually trying out a device that creates suction in one of the holes.

Some thoughts- the amount of suction necessary is pretty large. However, the higher pressure that you use, i think the more painful it becomes. In order to grasp the skin enough to avoid slipping, i think it might hurt.

I need a better way to test suction....

I built some initial prototypes to test out using suction to stretch the skin. I used the vaccuum in the lab to create the suction, and constructed two different end-effectors to attach to the skin, which can be seen below.

The first one I tried out only had two contact points. I thought the vaccuum would be strong enough to create suction through the straws and rotate/stretch the skin sufficiently.

observations

Then, I tried using a ring of contact points, since it seemed to work better with the polyurethane. You can see the skin being stretched on the back of my hand. This configuration worked pretty well. The vacuum was almost too strong, and really took ahold of the skin quickly and easily. It didn't seem to take much rotation to elicit strong feelings of skin being stretched, but the straws were also starting to cut into my skin because of the pressure and twisting motion. A softer coating might be useful.

Some quick notes- it SEEMS like using suction would require a binary input/output...slight rotations, using suction don't seem to be as noticeable as when applying slight rotations with the polyurethane but then, like I mentioned above, it doesn't seem to take a lot of rotation before the skin stretch starts to hurt...but that's also probably because I was using straws, and the edges are sharper than any of the previous techniques we used to stretch skin.

Can we combine the two methods? Provide a light amount of suction to reduce slipping, but in addition, have the softer, polyurethane adhesive properties?