Control your 3D printed prosthesis using an open source app on your phone.

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Developed by Violet Forest and Vladimir Hermand.

Myoelectric Prosthestic hands rarely do a good job at imitating an actual hand. Sensors enable the users to open and close their prosthesis, but are not precise enough for discrete finger movements.
We wanted to enable users to create new grip patterns easily using their sound hand.
Once a new grip is created, the user simply needs to flex the muscles in their residual limb in order to open and close their prosthesis.

Mirru is a free and open source Android app with which one can control robotic prosthetic hands via optical hand tracking using tensorflow and mediapipe.
With our app, users can instantly mirror grips from their sound hand onto a bionic one, which can be 3D-printed and self-assembled at low cost.
With Mirru, we want to provide a cheap, intuitive and open end-to-end alternative to existing, costly, cumbersome and proprietary technology.

For our research and development, we used a modified version of Openbionics Brunel Hand. You can find the files to download and print your own on our github

We added a button on the back of the hand, and changed the electronics to an Arduino so that we could control it via bluetooth. 

The button can be used to open the hand, freeze and unfreeze the thumb, and record and load custom grips without having to use the app. 

In the future, we'd like to expand the capacities of the app and enable users to record " video patterns ". Wherein a user could record not just a simple grip, but a whole movement and have it loop on their prosthesis. It could prove very useful for playing musical instruments for example. 

We've tried reaching out to existing manufacturers of prosthetic hands so they could enable their devices to work with our app but never got and answer. Maybe with a bit of media traction it could be possible. 

Instructions for using the Android app with the Brunel Hand.

How to Pick up a cup

  • Hit the record, then hold the grip until the timer runs out You can choose 5s, 10s, 20s, infinite for timer
  • Only thumb, index, middle, ring fingers can be recorded
  • The thumb moves with an in and out motion. When picking up a cup, you want to first move the thumb in, then move the rest of the fingers.

How to Release an object

Hold the button the hand or use the app to release

How to freeze the thumb

For better control when recording a grip, you can freeze thumb. This is done in a two step process. First you record the position of the thumb that you need, let the timer run out, then click the button on the back of the hand to turn the freeze of the thumb. The LED should be illuminated when the thumb is frozen. Then you can record the rest of the fingers.

How to use the button on the back of the hand

Freeze Thumb / Unfreeze thumb (toggle) --> Quick Single click

Save current grip --> Quick Triple click

Load saved grip --> Quick Double click

Zip Archive - 2.08 MB - 05/28/2023 at 18:02


  • 1
    3D print and assemble a Prosthetic hand.

    Head over to our github and website, you will find all the instructions on how to 3D print, program and assemble your own Mirru-controlled Prosthesis. You can also design your own and use it with our app. 

  • 2
    Install the Mirru App on your phone

    Head over to the android store and download our app

  • 3
    Connect the app to your prosthesis

    Connect your app to the prosthesis using bluetooth.

View all 4 instructions

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