The body-powered prosthetic hand was a Ph.D. thesis project for a graduate student in the Grab Lab at Yale. It aims to be a passive, under-actuated, and anthropomorphic prosthetic powered by a traditional shoulder harness used by many upper body amputees. While most modern prosthetics are complex and expensive, this project hopes to bring a cheaper and more effective alternative. My part in the project was designing and manufacturing the fingers, grips, and palm for the hand.

I designed the prosthetic fingers based off the human hand and the robot finger technology used by the lab. The Grab Lab uses rubber joints that bend when a line is pulled rather than difficult-to-control motors. This first prototype was 3D printed to test the forms I made in CAD.

The Grab Lab manufactures robot hands through a process called Shape Deposition Manufacturing. In order to adapt this technique for a much more geometrically complex design, we experimented with new mold-making techniques. This prototype is the result of a multi-stage CNC milling and casting process.

Upon knowing how to eventually make the fingers, we continued with 3D printing for the sake of quick turn-around. This image shows the meshing of the internal mechanism with the external fingers and palm - a back-and-forth process of balancing form and function.

A view of the prosthetic hand in action, using a power grasp. By switching the side lever, the hand can shift between power (for large, robust objects) and precision (for small, delicate objects) grasps.

One fascinating part of this project was researching the perspective of prosthetic hand users. We worked with a hook user to better understand their needs and ensure that specific tasks easily accomplished with a hook (like holding a pencil or fork) can be done with our hand.