After a workshop accident where he smashed his hand, Ian Davis suffered a blood infection that ultimately led to amputations of four fingers on his left hand. To make matters worse, Davis learned that his insurance would have covered the cost of a prosthetic hand if he had lost his entire left hand - not just the four fingers because "fingers are not medically necessary."
Being a mechanical engineer, Davis decided to build himself a steampunk prosthetic hand - one that is better than a medical prosthetic hand, and at a fraction of the cost.
In this YouTube video, Davis managed to enable the splay function on his mechanical prosthetic hand.
Davis has also made specific prosthetic tools for his hand - in this clip below, he made a wearable Milwaukee impact driver prosthetic.