Currently in the process of developing a 3d printed prosthetic hand and I am in need of advice on the type of rubber (or other material) we should use at the finger tips to give it more grip. The hand is capable of closing with a good amount of force, but it has a hard time holding heavier solid objects (like a glass cup, for instance) due to the lack of friction. I figure we only need small patches of some material at the contact points on each finger tip and potentially some in the palm, but I'd like to get insight from people who know more than I do.
We are considering using the inner tube of a bicycle and cutting it into small patches, but we are not sure if we would be better off with something thicker to allow the clutched objects to sort of sink in to the rubber more.