~Final Product

 Our final design consisted of four linear sliders (Figure 1), a four bar mechanism (Figure 2), and finger attachments (Figure 3), all driven by a motor (Figure 4). The mechanism linkages were all laser cut and connected by 5mm shafts and bearings. The plate connecting to the bases of the fingers was also laser cut, and attached to a bar of the four bar mechanism with super glue. The plate had a foam padding underneath for comfort, and attached to the large third of the fingers with velcro straps (Figure 5). The fingertip attachments were 3D printed, and they were also secured to the fingertips with velcro straps. The sliders were attached to elastic bands to provide assistance to the user while extending their fingers (Figure 6). The linear sliders were offset vertically to account for curvature in the hand. Overall, our machine was able to perform its function, however it was not ideal. The linkages were not the perfect size to achieve our desired 0-90 motion, and this caused the mechanism to not operate smoothly. If we were to further improve this hand exercise machine, we would make interchangeable plates to fit different hand sizes, and make the vertical offset of the sliders adjustable. We would use a stronger motor to allow the user to operate the machine passively, as the current one is not strong enough to do so. We would also need to improve how the fingertip attaches to the slider, as our current method tends to slip off after a few revolutions.

Figure 1: Sliders and figure attachments

Figure 2: Four bar mechanism

Figure 3: Finger Attachment

Figure 4: Motor and Arduino

Figure 5: Hand plate

Figure 6: Final product