FLEX A MUSCLE AND THE HAND OBEYS — YOU CAN 3D PRINT THIS BIONIC HAND
A 3D-printed prosthetic hand that reads muscle signals and mirrors your grip — research-grade bionic you can build from common parts.
by Patrick Slade and the Bretl Lab
Open-hardwareHealth
Built withArduino3D printing
- difficulty
- ●●●●●
- time
- several weekends
- license
- Unlicense
- repo
- repo ACTIVE27 stars
●●●●● · several weekends · Unlicense · 27 stars · repo ACTIVE
WHAT YOU’LL NEED
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COMPAREE VERDICT
Tact is a myoelectric prosthetic hand from Patrick Slade and the Bretl Research Lab at UIUC, published with a 2015 paper. The idea is that EMG sensors on the forearm read muscle contractions and drive the fingers, and the authors put a complete myoelectric system at under 250 dollars. What the repository actually contains is the mechanical hand: eleven STL files and an assembly PDF with a priced parts list (about 100 dollars: five Escap 16 coreless gear motors, an SG90 servo for the thumb, screws, steel cable and ABS) and step-by-step assembly. There is no firmware, EMG code or forearm socket, so the sensing and control side comes from the paper or from your own work. The mechanical build is approachable; getting stable EMG readings and mapping them to grips is the hard part, especially if you have never worked with biopotential signals. It is released under the Unlicense, so you can use it freely, but it is a 2018-era research artefact with no active support. If you want to understand how a low-cost myoelectric hand is put together, it is a rare open starting point.
IN THE REPO
GOOD TO KNOW
- —STL files for the hand (fingers, palm, thumb, motor housings and spools) are in the repository; there is no forearm socket.
- —No firmware is published — the repository holds the printable hand and an assembly PDF; EMG processing and motor control are left to you (the paper describes the approach).
- —An assembly PDF walks through the mechanical build step by step; the research paper (linked in the README) describes the design and testing.
- —The assembly PDF has a priced parts list for the mechanical hand (about 100 dollars: five Escap 16 coreless gear motors, an SG90 servo for the thumb, screws, steel cable, ABS).
- —Released under the Unlicense — effectively public domain, so you can use, modify and sell it with no conditions.
- —This is a 2015 research prototype (repository last updated in 2018); the author later co-founded PSYONIC, a commercial prosthetics company.
Parts to buy
11 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
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Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the assembly PDF in the repository and the research paper linked from the README (Start with Tact/TactAssembly.pdf (parts list and assembly steps) and the 2015 paper linked in the README.)
- 2.Order the mechanical parts from the assembly PDF's parts list, and choose your own EMG sensors, microcontroller, motor drivers and battery(The PDF lists five Escap 16 coreless gear motors, an SG90 servo, M2 hardware, steel cable and rubber bands; Escap motors are older parts, so you may need to find equivalents.)
- 3.Print the hand parts from the Tact folder as listed in the assembly PDF(The PDF uses ABS at 10 percent infill and 0.2 mm resolution, and lists how many of each part to print (for example four Finger1 and five Finger2).)
- 4.Assemble the hand and test the finger motors and thumb servo with a simple driver sketch before adding EMG sensing.(Get the mechanical side working first — the EMG layer adds complexity.)
- 5.Add EMG sensing and control with your own microcontroller code — none is published in the repository(Electrode placement and skin prep are critical; the linked 2015 paper describes the authors' approach.)
KNOWN ISSUES
- The parts list in the assembly PDF covers only the mechanical hand (about 100 dollars). The EMG sensors, microcontroller, motor drivers and battery for the myoelectric side are not specified, so you choose them yourself.
- EMG sensors are finicky — dry skin, poor electrode contact, or nearby electrical noise will give you garbage signals. Budget time to learn proper placement and skin prep.
- There is no control code in the repository: you write your own EMG processing and grip control, using the paper for the approach, and tune it to your own muscle signals.
- The repository was last updated in 2018 and contains only the mechanical design — expect to source modern equivalents for the 2015-era motors and write your own control code.
- There is no socket or forearm attachment in the files, so fitting the hand to a person or a test rig is your own design work.
- The team moved on to a commercial closed product (PSYONIC) — do not expect support or active development on this repository.
Can I use this if I am not an amputee?
Yes — the EMG sensors work on any forearm muscles. Many builders use it as a research platform or demonstration without a prosthetic application. You will still need to train the classifier with your own muscle signals.
What EMG sensor board should I buy?
The repository does not specify one. Common hobby EMG boards such as MyoWare are a reasonable starting point; check the linked paper for the authors' setup.
How many grips can it do?
The paper describes the grips the authors tested; the repository contains only the mechanical design, so grip patterns depend on the control code you write.
Is there tactile feedback like the name suggests?
Not in the published files. The repository contains only the printable hand and its assembly guide; any sensing or feedback is up to your own electronics.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
The repository gives you the hand and the assembly PDF, but no EMG code. If you built it, how would you turn muscle signals into grips — and where on your forearm would you place the electrodes?
Patrick Slade and the Bretl Lab
Patrick Slade developed Tact through the Bretl Research Lab at the University of Illinois and published it in the 2015 paper "Tact: Design and performance of an open-source, affordable, myoelectric prosthetic hand". The goal was a complete myoelectric hand for under 250 dollars, and the design is released into the public domain under the Unlicense.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM2mo agoedited
Practical notes from our verification: the repository was last updated in 2018 and contains only the mechanical design — eleven STL files and an assembly PDF with the parts list and the build steps for the fingers, motors and thumb. There is no firmware or EMG code in the repo, so the signal-processing side has to come from the research paper linked in the README or from your own work. The README puts a complete myoelectric system at under 250 dollars, and it is released under the Unlicense, so you can use it freely. The biggest time sink will not be printing or assembly, it is getting stable EMG readings and mapping them to grips. If you have never worked with biopotential sensors before, start with a simple EMG breakout board and a basic sketch to understand signal conditioning before you tackle the full hand. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.