Universal Allen Key

Certain protein mixtures can change their mechanical characteristics with a change in applied voltage. If you could contain a mixture which when a voltage is applied it becomes rigid, (and the electrodes) in a tough flexible "bag" then when a voltage is applied it would become rigid. If this were attached to the end of a handle then the "bag" could be forced over the head of an Allen bolt (or possibly other fixings) at which point flexible "bag" would take on the internal geometry of the hexagonal hole on the head of the Allen bolt. Apply a certain voltage and it will become rigid (or very nearly) allowing you to undo this bolt, and bolts of other sizes and geometries. Then switch the voltage off and the mixture becomes fluid again.