The goal of this project is to design and manufacture a mechanical prosthetic finger to fit inside a realistic silicone covering. The final prototype should be an individualized finger prosthesis that is affordable, aesthetically and mechanically functional. Ideally it will restore flexion and extension movement of an amputated residual finger, while still being able to fit inside a realistic silicone sleeve. The client desires that the prototype be 3D-printable.

Project Status

  • Updated SolidWorks of the MTS Stage Adapter.
  • Began a protocol for MTS testing
  • Ordered Liquid Latex for Qualitative testing
  • Finished MTS Stage Adapter.
  • Updated SolidWorks for the MTS test.
  • Changed to test with “Tough” Resin.

Next Steps:

  • Finalize MTS protocols.
  • Perform testing


  • Fatigue/Lifetime testing (with Rubber Band)
  • Force to detach from residuum cap
  • Qualitative testing

402 – 18 – Tong – Finger Prosthesis – Executive Summary

In the world of hand prosthetics, patients have to consider several factors when deciding on their device, including the amount of functionality that is restored, level of discretion that the device can provide, and cost. Often times, it is difficult or impossible to find a device which satisfies all of these requirements, so one or more must be forgone for the others. Current products, such as M-Fingers by Partial Hand Solutions or The PIPDriver from Naked Prosthetics, primarily focus on functionality and cost.

These solutions allow mobility of prosthetic fingers but at the cost of a mechanical, unrealistic appearance, and bulky attachments. Our client, Gregory Gion of Medical Arts Prosthetics, focuses on discretion and cost, offering a molded silicone sleeve with incredibly life-like models of extremities, with details down to the smallest freckle and wrinkle. Unfortunately, his prosthetics are entirely made of molded silicone, so they are without any means of actuation, and therefore provide little in the way of returned functionality to the patient. The goal of this design project is to create a device which will allow our client to incorporate functionality while maintaining an affordable price and discretion. Our team has worked to create a functional prototype frame for a new prosthetic to be incorporated with life-like silicone models. The design consists of 3D printable pieces replicating bones and joints of the patients finger, which would fit into the corresponding silicone sleeve.

The device would be attached to a PMMA cap the patient would slide onto the residuum of their finger. In addition, a pair of lateral ‘bridges’ located on the underside of the finger allow the patient to flex their prosthetic using the nearest finger. A system of elastic bands keep the finger extended when not being actively flexed. This design is unique because it incorporates a simple method of actuation, which improves patient functionality with minimal detriment to the aesthetic purpose of the device, and features a simple 3D printable frame, which would allow our client to easily customize the external appearance of the device to the patients needs at relatively little cost and production time.

There were three primary concerns the team had when testing the design. First, the device could survive the normal forces experienced by a finger; second, the elastic bands could survive for an acceptable lifetime; and third, the device was comfortable to use. For the first criteria, the team ran a Charpy impact test to assess that the device would not break from the PMMA cap at or below 25N of force, the average force a finger is able to exert. A breakage at or below 25N of force would raise the conclusion that our finger will detach from the PMMA cap before breakage.

For the lifetime, the team ran a fatigue test which involved actuating the finger repeatedly over 1000 cycles, to assess for signs of wear which previously occurred at 600 cycles. For the final criterion, one of the team members wore a modified version of the prototype for a day, and gave qualitative feedback. Our design would provide a low cost and discrete alternative to functional finger prosthetics. Our prototype costs ~$4 plus the cost of the silicone sleeve when the skeleton is printed on a Form 2 Resin 3D printer; compare this to the average cost of ~$5000 for assembling a finger prosthetic. The coupling of realistic appearance and functionality would help to provide easier rehabilitation for psychological trauma and hand impairment. Additionally, the lifespan of the finger prosthesis would be lengthened from the protective silicone sleeve. The silicone sleeve would provide protection from water, dust, and snagging of the mechanical or actuating components which can be an issue for other functional finger prosthetics.

Preliminary Presentation


Poster BME 402 Prosthetic Finger

Final Manuscript-Finger Prosthetic

Contact Information

Team Members

Advisor and Client