Prosthetic Hand – Bear Lee's portfolio

Prosthetic Hand

Low-Cost Electronic Prosthetic Hand project
South Korea, Syria
a device / 2015~
variable size
EGM, Electrode, PLA, bolt, nut, silicon, wire and others

Mandro is committed to making electronic medical devices accessible to all. Founded in 2015, the company was inspired by a young man who lost both arms in a work accident. They developed a 3D-printed prosthetic hand, initially priced at $800 and now sold for around $1,200. With support from governments and international organizations, Mandro helps people in Korea and war-affected regions in the Middle East. Since 2015, I have assisted Mandro in completing their products and developing artificial skin for prosthetic hands, targeting production in 2019. Recently, Mandro partnered with Swisslims to expand into Africa, including Tanzania and Uganda, to provide affordable prosthetic solutions.

Mand.ro Prosthetic Hand Maker – Activity Report in Jordan Office 1 – 2018

Mand.ro Prosthetic Hand Maker – Activity Report in Jordan Office 1 – 2017

The development of the prosthetic hand has evolved 11 times.

The Composition of Mandro’s Prosthetic Hand

3D Printing for Mandro’s Prosthetic Hand

The overall appearance of the electronic prosthetic hand is printed on a 3D printer. This means you can make a prosthetic hand anytime, anywhere.

Assembly of Fingers and Installation of Motors

Sensor Circuit

A self-developed PCB sensor circuit detects weak muscle signals in the severed arm.

EMG Sensor

A self-developed dry electrode is used to stably receive the EMG signal.

Gloves of the Prosthetic Hand

Custom-made fabric gloves are used to provide anti-slip and functional enhancements.

EMG Sensor

A self-developed dry electrode is used to stably receive the EMG signal.

Electronic Charger

For charging and storage of electronic prosthetic hand, just place it as the world’s first stand of the electronic prosthetic hand, and the charge is completed in one hour.

Skin Work (Operation) of Electronic Prosthetic Hand

The Mandro’s electronic prosthetic hand has both scalability and limitations at the same time because it’s made from a PLA 3D printer. Although 3D printed and assembled on a 3D printer at any time and from anywhere, it is likely to be contaminated in an external environment and it is no friction when grabbing objects. For solving the frictional force, I use a rubber pelvis which is installed at the tip of the finger.I have worked to solve the two problems which were mentioned above, and additionally to create an artificial surface of a hand similar to a real one.

1. Electronic prosthetic hand coating

I filled up the empty space with coated non-foaming hard urethane material. Then, using the epoxy putty, a large space not to be caught by urethane was bridged.

2. Primer

I filled the fine section again with the primer, checked again, and identified the section that needs to be filled.

Change of the joint part

To address the issue of latex medical gloves pushing up or weakening the strength of the prosthetic hand during frequent use, a folded, staircase-like joint design was modeled.

Artificial Skin Test with silicone

For ease of testing, skin production of electronic prosthetic hand was tested with silicon.

1. Quantitative testing of various softener

I tested silicon with a softener. The thickness that can be reduced by hand was between 5.0mm to 1mm. I experimented with different amounts of softener. Adjusting the amount of softener was important because large quantities of softener weakened the strength of the material.

2. Optimized electronic prosthetic hand skin

The colour of each material was different, but the artificial skin made of red colour with the added 5% softener showed the appropriate flexibility. The strength of the rubber band on the fingers of the prosthetic hand is applied differently, in order, from the thumb to the small finger. According to the test result, the strength decided middle finger was the most appropriate. If the strength is too strong, the speed of spreading the hand is too fast and the force is too strong thus there has a problem when it is grabbed a particular object.

3. Artificial skin test of real skin and thickness

Current Stage of Development of Electronic Prosthetic Hand Skin

Mass production of the skin was delayed and replaced with cloth gloves as the form of the prosthetic hand continued to develop. In recent years, the form of prosthetic hand has become the first stage of completion and plans to produce skin 1 version in early 2019. In an interview with people who needed a prosthetic hand that I met through the first, I aimed to develop cheap and functional skin without problems because the physician demanded the functional function of the hand rather than the real thing. However, as the business of Mandro has expanded to foreign countries like Syria, I have found that there is a lot of demand for similar goods as the real thing. And technologically advanced, we are expecting customized skin and skin through 3D scanning. The result of the second test is awaiting the application. Those who use Mando’s prosthetic hand are very helpful to development.

Introduction on The Jordan Times

3D Printing for Mandro’s Prosthetic Hand

The overall appearance of the electronic prosthetic hand is printed on a 3D printer. This means you can make a prosthetic hand anytime, anywhere.

Introduction on Arirang TV
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