Gripper Thumb Terminal Device

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The Gripper Thumb TD is an innovative terminal device designed for upper limb amputees that operates without a Bowden cable. This experimental device should be used under the clinical supervision of a Certified Prosthetist or Occupational Therapist, as it is still in its development phase and requires careful selection of printing materials to ensure optimal layer adhesion and durability. Evaluating this TD effectively can be achieved by partnering with a recipient who already has a prosthesis, thereby ensuring access to a prosthetist or occupational therapist. The modularity of the device allows users to easily switch between different devices, making it an ideal solution for various activities. Developed at the MAGIC ACT / e-NABLE Lab at Rochester Institute of Technology, the Gripper Thumb TD has evolved significantly over the past year, enabling users to perform many two-handed tasks with ease. The primary advantage of this terminal device lies in its ability to grasp and release objects using the unaffected hand, eliminating the need for a Bowden cable. By pressing an object against the frictional surface of the thumb tip, the user can force the thumb away from the fingers, allowing them to grip objects securely. This feature is particularly useful for tasks involving small or large objects. After grasping an object with the Gripper Thumb TD, users can manipulate other objects using their unaffected hand, such as applying toothpaste to a toothbrush or cutting food with a knife while holding the item steady with a fork. Another significant advantage of this device over traditional split hooks is its perceived attractiveness. The gripping mechanism relies on the force generated by a latex band, which should not be used by individuals with latex allergies. The device can be washed and sanitized using ordinary hand-washing procedures or even placed in a dishwasher when fabricated from materials that can withstand such processes. To attach the Gripper Thumb TD to the prosthesis, users must employ a standard bolt thread (1/2 - 20 in the US, M12 fine-thread elsewhere). The device can be easily exchanged with other terminal devices, and it can be removed or temporarily secured using a rubber band. The thumb pivots on a 6-32 (or M3) machine screw, while two similar screws hold the hex bolt in place. A flat washer is held in position by a rubber ring that provides both grasping force and frictional force, allowing users to rotate the device for optimal grip. Currently, testing has been conducted only with small size Gripper Thumb TDs, which are expected to be functional for users of all sizes. Medium and large size devices will be added to the STL files after they have been thoroughly tested. For printing, it is recommended to use an Ultimaker 2 printer with at least 0.05mm layers for nylon or 0.1 or 0.2mm layers for other materials. A brim should always be used, and at least 1.6mm shells and top and bottom layers are necessary for optimal results. Printing has been successful with SLS in nylon and FDM in various filaments, including ABS, PETG, Cheetah, and Armadillo.