From the first prototype to the current
Having developed our needs and wants, we began putting together building prototypes for our glove for RA. The overall design was to have strings attached to each finger that would be pulled in order to flex each finger and get the movement in the finger we believe would be beneficial to prevent buildup of fluid in the finger caused by RA.
In order to create the flexing motion we decided to use a servo motor attached to the wrist run by an arduino programmed to activate the servo to pull the strings attached to each finger at given intervals of time. Initially we went with a ski glove due to the stiffness it had, as while we had a mechanism to pull the fingers, we didn’t really have anything to extend the fingers back out. To help with this we cut pieces of milk jug and taped several pieces to the back of the fingers in order to provide extra stiffness to unflex the fingers once the servo quit pulling. In this prototype, thick fishing line, due to its strength and sturdiness , was attached to each finger and then all the lines were connected directly to the servo. However we quickly discovered that the lines would tangle up very quickly to the point where the fingers would not be flexed. Additionally we decided that the ski glove overall was just very hard to put on and too stiff to really effectively flex. So we decided to move on to another iteration.
For our second iteration, we decided to go with a cloth mitten as the main glove component to avoid the stiffness and hard use we found with the ski glove. We keep with the idea of tying line to each finger, however instead of using the thick fishing line, which often would deform after several uses, we used a type of thicker thread that did not deform but still provided solid strength. A component we added to this prototype was essentially adding an intermediate piece to the pulling mechanism. This piece was a washer where all of the finger strings were attached to it and then on the opposing side of it a single thread was tied to then be pulled by the servo. This effectively eliminated the thread from getting tangled by the servo that happened in the first prototype. A more flimsy plastic than the milk jug plastic was cut and was taped on the back of the mitten to provide the stiffness to allow the hand to flex back. We stayed with the servo and arduino pulling mechanism, however we moved the servo motor further up the forearm to allow more room for the thread to be pulled and allow more flexing of the fingers. A problem with this prototype was that because the thread was flimsy and the washer was not a good intermediate piece to keep the individual finger lines separate, the lines often got tangled up here. An additional problem we noticed was that the single line being pulled by the servo would often move out of straight line with the servo when the hand was relaxed where it often would then get caught on other parts of the prototype and not allow proper flexing of the fingers. Given these problems we moved on to our third iteration and current model.
For our third model, we found that the mitten was a good choice for glove as it allowed easy flexing of the fingers, it could be put on easy, and it was comfortable. We used the same plastic as the last iteration however we extended the plastic from just being on the fingers to going from the fingers all the way down to the wrist to cause more bending back of the hand to its original position after pulling. We also sewed the plastic inside the glove as it was more visually aesthetic. We replaced the intermediate washer piece with a smaller triangle piece which allowed all the finger strings to be attached at the base and the one string that would be pulled by the servo to be at the top point. This shape to be significantly more effective in preventing tangling and flexing the fingers. In order to prevent the string attached the servo from moving out of the correct position and getting attached to different areas of the prototype, we attached the end of a ziptie ( the part where the rest of the ziptie is feed into to lock it) to the servo and feed the thread through this before attaching it to the servo. This effectively kept the string in line (it was small enough where it easily passed through the ziptie piece and did not get stuck. The device was to easy to run repeatedly without any problems with the flexing mechanism occurring.
Overall this third model was not only more aesthetically pleasing but also significantly more effective than the first two models in providing the flexing function repeatedly.
BME Design 