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VO/VC Body Powered Hand

A body powered hand prosthesis capable of bi-directional grasping motions.

Employer: Shirley Ryan AbilityLab / RIC

Role: Research Engineer III

Traditionally, body powered hand prostheses suffered several design flaws.

  1. Terrible gear ratios, making the input to output forces exhausting for users

  2. Limited grapsing patterns (i.e. one fixed grasping pattern)

  3. A single direction of actuation. Imagine if you our hand was biased open and the only control authority you had was to close it, to a predetermined grasping pattern, with a fraction of the output force compared to the effort you exerted to generate the motion.

For the reasons listed above, body-powered hand prostheses where not popular and often abandoned for hooks despite the more anatomical cosmesis. Stemming from my work with the VO/VC hook and the RIC Arm, I combined many of the mechanical design innovations to create the first of its kind body-powered hand prosthesis.

Key Design Features:

  • Nearly 1:1 force ratio

  • Bi-directional control. Users had access to two modes of actuation, they could either use the actuation lever to close the hand or open the hand.

  • Multi-articulating fingers and positional thumb. This allowed for multiple grasping patterns and more functionality for users.

  • Independently locking fingers. This allowed users to move digits "out of the way". Prosthesis lack the proprioception of anatomical digits, users must use visual feedback to interact with their surroundings. It can be frustrating when the bulk of the device makes it difficult to obtain the appropriate visual feedback for fine motor tasks.

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