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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.

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  • $\begingroup$ I'd probably start with some sort of textured silicone rubber, but I don't have a lot of expertise in biomimetic materials. $\endgroup$
    – wwarriner
    Apr 28 '16 at 19:58
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    $\begingroup$ Sorbothane rubber is VERY tacky (no pun intended) and it bridges the gap between liquids and solids in terms of rheology. Since it is a urethane based rubber you might want to use a urethane adhesive to bond the Sorbothane to the "fingers" should you want to actually use Sorbothane. $\endgroup$
    – William Hird
    Apr 28 '16 at 20:42
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One very easy solution is to spray the required surfaces with latex based contact adhesive. This is fairly tacky when cured and the spray will also give a bit of texture.

Alternatively liquid latex is cheap and easily available and can be applied by dipping the fingertips and/or palm into it. Without fillers or vulcanisation it is not as durable as some other rubbers but it is convenient and easy to use for prototyping. Or you could use something like Plasti Dip

Another option is self amalgamating tape used for electrical insulation etc which is butyl rubber.

If the hand is human hand shaped you could also consider using gloves.

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A simple way to test out the effect would be to wrap or stretch some household rubber bands around the fingers/grippers to increase friction.

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Some leather variants give good grip, and are used for similar purpose on e.g. gloves. The 'grippiness' of the leather depends a lot on how exactly it has been finished and which side of the skin is outwards.

A local sewing supply store might be able to help you pick a suitable piece of leather.

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