New designs for an old problem – Casey

This week showed some progress on the project overall. I’m continuing to do research on new models of prosthetics, but now the group has come up with two ideas that are definitely going to be tested. The first is based off of an article I spoke about last week written for the Journal of Rehabilitation Research and Development. This design uses a pulley to ensure that the first joint of the prosthetic finger rotates with minimal energy loss. The string that actuates the finger is pulled, which rotates the pulley in turn pulling the rest of the finger. Further development in this design could lead to a more efficient way of ensuring that the first joint of the finger bends when it needs to in relation to the last 2 joints. This is currently one of the bigger issues in the functional model we are working with.

The second design we thought of is a finger actuated by two strings of different lengths. These strings, however, would be pulled at the same time and attached to different areas of the finger and measured carefully to fine tune how the prosthetic’s grip closes. The inspiration for this new design wasn’t from research on prosthetics, but from research on how actual hands work.  I spent a few days reading through an anatomy textbook’s section on hands.  Here’s a diagram I found to help explain it.  You can also click here for another anatomy site I found that was helpful in learning how the hand functions.


The intricate combination of muscles and tendons allow humans to control which joints to bend when they need to in order to grasp an object. With more research hopefully we can determine the optimal position of the fingers when bent to grip an object, and design a prosthetic around that. For now the research will continue and the ideas will be put down into a growing list of prosthetics to prototype before we can decide on one or a few to develop further.

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