Helping Hands

Acknowledgements

Project Advisor: Dr. Susan Anderson

Technical Advisor: Prof. Jim Wong

Donations Made by: Craig Hospital

Video

Elevator Pitch

This is a universal cuff in order to improve the lives of people who are affected by spinal cord injuries. Specifically, this device is for patients who have C5 to C7 injuries, and who lose a lot of the function in their hands and fingers. This device is extremely low cost, able to be 3-D printed at home, and allows the user to access a level of independence that the current technology does not allow for. 

The device works by having the user press the top lever arm down into the ratchet system, which holds the cuff securely onto the hand. The user attaches their daily utensils to the clip portion of the design, and then is able to freely and easily swap between utensils at will. 

Design Approach

Design Solution

The original design goals for this project included universality, user friendliness, low cost, and durability. The team made these design considerations at high importance when creating prototypes and ultimately the final design. The Demand/Wish table below displays how the final design compares to what was originally asked by the client.

The ultimate and most important demand of this project was to increase the user’s independence. The final design allows the user to don and doff independently without the help of an assistant. The various sized end effectors work with a wide range of objects and tools used in their everyday life. The attachment mechanism provides tactile and auditory response back to the user while securing the tools to the cuff. Also, this device is manufactured by 3D printing; the user will only pay for material costs and access to a 3D printer, keeping the overall cost of the device significantly low compared to what is on the market now. The only category not passed was integrating the cuff onto a patient’s wheelchair. This was a wish discussed at the beginning of the project, but later dismissed as other criteria were more important.
The durability of the device was tested through experimental drop tests and FEA analysis. The FEA showed areas of high stress concentration around the hinge and pivot point. The testing confirmed this by breaking at the hinge when a force of 115 N was placed on the hinge. With this information, the team adjusted the design and improved areas of concern.

The final design is shown below in Figure 2. The top left image illustrates the cuff in the open position. The user would place their hand into the opening, and then tighten the ratchet down to the appropriate tightness. The top right shows the Cuff and the End Effector prior to being connected together. The user would then place their hand (with the Cuff already attached) onto the attachment, which would then snap into place resulting in the configuration shown in the bottom image.

Next Steps

In the future, the cleanability of the design could be improved. Currently, there are a lot of nooks and crannies that dirt and debris could become stuck in.  Also, the current material used, PLA, it is not dishwasher safe and must be hand washed. In the future, testing should be done to see if the material properties of nylon, which is dishwasher safe, have the same durability and 3D printing capabilities as the PLA. 

Some other work that still needs to be completed is choosing the correct padding for the cuff. The padding for the universal cuff is pertinent to the design. The padding assures universal hand size capability while creating comfort and security to the cuff. The team has come up with 3 viable options for padding, each with their own pros and cons. 2 of the designs use an inexpensive multipurpose foam padding cut into a 3x 3×1.5 inch block. The positive aspects of the foam padding are the malleability and comfort it provides for the user. However, the main negative is that the material can degrade and wear quickly.

Padding Options

The first design tries to compensate for the wear of the foam. This design utilizes a sewn cover that allows for removal and cleanability cover instead of damaging the foam. The fabric of the cover can incorporate waterproof or resistant properties to help elongate the life of the foam. The downside of this design is that the user would need help to sew the cover together and secure velcro onto the fabric. This design expects too much of the user to be able to effectively create this themselves.

The second design for the foam is to eliminate the sewing aspect of the design. The user would need help cutting an inch wide slit, approximately half an inch from the top, through the entire length of the block. This allows the foam to slide right over the top of the cuff. This is more accessible and easier to manufacture for the users, however the foam is more vulnerable to degradation and wear. The foam would need to be replaced more often than the foam with the cover.

The last design for the padding is a cut pool noodle. By cutting the bottom edge of the pool noodle and making it flat, the pool noodle fits correctly and is secured on the user’s hand. Also, the pool noodle is waterproof and easily cleaned. The downside to this design is that the pool noodle is more rigid and generates more tension on the top of the cuff and the hinge. This might cause the cuff to open unexpectedly because of this tension.

Meet the Team