Modular 3D Printed Prosthetic Hand (2015)

 From February 12th to March 11th 2015, I worked as a visiting prosthetics engineer for ROW3D, a non-profit organization based in Amman, Jordan. My mission was to design a prosthetic hand for a 12-year-old Syrian child who had lost two legs as well as three fingers and half of the thumb on his left hand, resulting from a barrel bomb.
 One of the challenges the team encountered was frequent printing failure with FFF 3D Printers, especially when working with flexible filaments. Since the fitting of the prosthetics and acquiring feedback from the patient are essential in prosthetic development, a couple days’ delay in delivery was a serious drawback within the tight schedule of the project. In addition, having a simplified BOM using single-source material is hugely important in limited resource settings such as the Zaatari Refugee Camp.
 Based on the finger design of the Flexi-Hand, I devised a modularized system where flexible filament is used to connect each part of the hand. This not only reduced the printing time and risk of failure while printing, it also improved the actual fitting experience of the patients. The distance between finger sockets and the glove is a crucial factor in the prosthetic hand staying tight while ensuring movement of the hand. Previous failures resulted from miscalculating the distance, costing an additional week just to readjust it and print the parts again. The new design made it possible to adjust the length during the fitting by pulling the cord longer or shorter and scorching it with a flame.  
 Although the actual improvement of the grip force was less than expected since the patient was fairly accustomed to handling objects with his remaining two fingers, there was substantial improvement in holding and catching of objects.
 The project was supported by ROW3D and DRB International.


Excerpt from France24 channel news report 

Silicon and plaster castings of patient's hand. 

The parts were printed with Filaflex flexible 3D printer filament and than connected together using the same material.

Prototype hand 

Ver.3(final). The cords are adjusted to optimal length during the fitting with the patient.

After coming back to Korea, I produced a demo mechatronic hand for the Royal Jordanian Medical Service(RMS) Prosthetics Center in Amman, based on a modified version of the Flexi-hand from a South Korean volunteer group 'FunMove'. Instead of using a myoelectric sensor which requires disposable electrodes, this version uses a FSR(force sensitive resistor) for better maintainability under demonstration uses. Sung-yeop Kim of CampusD helped with actual CAD work and fabrication.