Gripper Thumb Terminal Device

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Developed by the MAGIC ACT / e-NABLE Lab at Rochester Institute of Technology, the Gripper Thumb TD has advanced significantly over the past year to effectively manage numerous two-handed tasks in a similar manner as the voluntary opening split hook that has been used successfully for more than 150 years. However, it is designed to function without a Bowden cable. Since the 3D printed device remains experimental, it should not be used without the clinical supervision of a Certified Prosthetist or Occupational Therapist. Special care must be taken in selecting the printing materials to ensure that there are no layer adhesion issues or other durability concerns. Perhaps the most effective way to evaluate this TD (and get through beta testing and design iteration) is to find a recipient who already has a prosthesis. This means they will likely already have a prosthetist or occupational therapist on board. If we have a winner here, the users and clinicians will see the value based on comparison to other devices they have used. The modularity of this device allows users to simply screw off their TD and screw on the Gripper Thumb TD. They can easily switch back and forth for different activities. The advantage over most other body-powered terminal devices is that the Gripper Thumb TD allows the user to grasp and release objects using the unaffected hand rather than a Bowden cable. Pressing an object against the frictional surface of the thumb tip can force the thumb to be pulled away from the fingers for an object to be gripped. Tasks with small objects (such as taking the nut off of a machine screw) or with large objects (such as opening and closing a jar, tube or bottle) can be undertaken this way. After placing an object in the grasp of the Gripper Thumb TD, the unaffected hand can then be used to manipulate other objects such as putting toothpaste onto a toothbrush or cutting food with a knife while holding the item steady with a fork held in the Gripper Thumb TD. Another advantage over traditional split hooks is that the Gripper Thumb TD is considered more attractive by some people. The gripping force comes from a latex band, so it should not be used by individuals with allergies to such materials. The Gripper Thumb TD can be washed using ordinary hand-washing and drying procedures. It can also be sanitized in a dishwasher when fabricated of materials that can withstand the process. The device is attached to the prosthesis using the bolt thread standard for the region (1/2 - 20 in the US, M12 fine-thread in most other places). It can be easily exchanged with other terminal devices, although a Bowden cable will not be used. The rubber band can also be used to remove or temporarily hold the TD out of the way. The thumb pivots on a 6-32 (or M3) machine screw and a pair of similar screws hold the hex bolt in place on the device. A flat washer is held in place on the bolt with the same type rubber ring that provides grasping force. Between the flat washer and the prosthesis, the ring also provides frictional force that allows the Gripper Thumb TD to be rotated for pronation or supination by the unaffected hand, but holds the TD steady in the chosen orientation. The elastic ring is easily connected to the palm and to the thumb by a pair of zip-ties without tools (although a vise and pliers might be useful for one-handed assembly). It can also be easily replaced by clipping the zip-ties. Individuals with latex allergies should not use this device. The Gripper Thumb TD was recently demonstrated at the Rochester Mini Maker Faire, and it can be seen in action at the end of this three-and-a-half-minute video: https://www.facebook.com/RochesterMiniMakerFaire/videos/1156348114403185/.