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By building off of the lessons learned from the manufacturing of the previous prototypes, we were able to apply several design considerations into the final prototype. Carrying over the tolerance considerations of the laser cut acrylic, several in contact pieces were cut just oversized and then sanded to allow for a smooth and dynamic motion. Rather than using zip ties to attach the electric servo motor, we cut sandwiching acrylic pieces to link the motor to the crank slider. The use of shoulder bolts rather than standard threaded bolts kept the motion smooth and robust. Also, in order to lessen the effects of friction on the many links comprising the system, we used motor oil to grease the links and provide for a smooth operation. Finally, Velcro straps were added to the device to allow it to be attached to the inside of the user's hand. The links below contains a videos that demonstrates the device.
1Raspberry Pi Servo Guide: https://learn.adafruit.com/adafruits-raspberry-pi-lesson-8-using-a-servo-motor