Update on Bionix I am finished with my basic hand structure i printed it irl and saw some errors and then fixed it in CAD next is to work on the thread routing channels!! keep following and checking out my github

Devlog: Final Engineering Push – Kinematics, Power Architecture, and Assembly Readiness

Date: June 19, 2026
Status: Design Locked / Fabrication Ready

The past several intensive engineering sessions have brought Bionix from a conceptual CAD model to a fully robust, physically viable electro-mechanical prototype. With the core palm and phalange geometry finalized, power distribution mapped out, and the bill of materials optimized, the project is officially ready for the physical fabrication and assembly phase.

⚙️ Mechanical Engineering & Kinematics

The primary mechanical challenge for a tendon-driven bionic hand is managing friction and preventing catastrophic mechanical failure during repeated flexion cycles. We entirely overhauled the internal routing and joint mechanisms to achieve competition-grade reliability.

• Frictionless Revolute Joints: We stripped out the threaded M2 screws from the phalange joints. The joints have been re-engineered to accept smooth 2.2mm solid brass dowel pins, providing a low-friction, high-strength pivot point that ensures fluid finger movement.
• Optimized Flexion Routing (The Active Grip): To eliminate the “bowstring” effect, we redesigned the entry tunnels on the palm. The four main finger tension lines now enter the palm cavity via perfectly aligned tunnels featuring a -10° downward draft angle. This forces the high-tensile braided line flush against the joint grooves, maximizing servo leverage. All sharp 90-degree channel exits were filleted into smooth “trumpet flares” to prevent the threads from shearing under load.
• Antagonistic Elastic Extension (Passive Return): For the fingers to snap back open instantaneously when the servos release, we implemented an external elastic extensor system. We modeled a Unified Wrist Anchor block at the base of the palm. 1mm shock cord anchors at the fingertips, routes seamlessly over the knuckles, and ties off securely at the base of the palm, providing the exact passive tension required for a lifelike, snappy release.
• Removable Maintenance Hatch: The palm features a custom-traced, screw-mounted top plate with a generous cutout for full thumb articulation. This protects the internal servo array while allowing rapid access for tension-line adjustments.

⚡ Electronics & Power Architecture

Running five high-torque micro servos simultaneously while reading delicate analog muscle signals requires isolating the high-current demands of the actuators from the logic board.

• Main Controller: The system is governed by a Raspberry Pi Pico (RP2040), chosen for its robust hardware PWM processing capabilities.
• Power Distribution: A 7.4V 2S Li-ion battery serves as the primary power source. This is routed through a high-efficiency 5V Buck Converter (rated for ≥3 Amps) directly to the servo power rails. The Pico is powered safely without having to sink the massive stall currents generated when the hand grips an object. A 1000uF decoupling capacitor bridges the 5V rail to smooth out transient voltage spikes.
• Biometric Input: We integrated the MyoWare 2.0 muscle sensor, passing raw electromyography (EMG) signals directly to the Pico’s ADC0 (GPIO26) pin.

devlog 5 or 4 i honestly dont remember lol: I am done with the Palm!!!! and I also assembled the fingers to check !!! yes lets goo!! Printing the index finger tomorrow

Devlog 4: I was already done with 2 fingers earlier, I made the 3rd one today and I used Ai to build the pinky and thumb finger as it was just copying the dimensions editing the sketch and fixing the hole problem

What I set out to build:
I wanted to complete the fingers in this session which I did achieve + I am done with palm’s basic layout and structure planning, In next session I will be improving and finalising the palm assembling all of it together for once to check it all fits then work on the forearm

Devlog 3 : Bionix

Ring finger design has been done and assembled in a sepearate folder I did not face any problems while making this design, Only pinky finger and thumb are left then I will start with palm and forearm respectively!

Devlog2 : Unbound bionix,

Update: last devlog I was finished with the index finger dimensions well I just printed index finger to confirm movement and it’s moving as expected, I also Made the middle finger design by editing sketch of index finger but fixing the hole sliding issue,

failures: I encountered multiple failures planning the design of index finger, but I did make it work and I am really happy for that,

what is left?
designing all fingers and thumb according to their dimensions and then designing the palm and forearm respectively and then moving on to the electronics part

session pic:
here is one session pic where I show the assembled middle finger design, for the middle finger the proximal phalange is 5 cm long, the distal phalange is 2 cm and the middle phalange is 3 cm!

Everyday tasks such as holding a bottle, typing on a keyboard, opening a door, or picking up a pen are actions most of us perform without thinking. For millions of people living with upper-limb loss, these simple activities can become significant challenges that affect independence, confidence, and quality of life.

While modern prosthetic technology has advanced considerably, many solutions remain prohibitively expensive, difficult to customize, or inaccessible to students, researchers, and people in developing regions. Devices that offer advanced functionality often cost thousands of dollars, creating a gap between innovation and accessibility.

Prosthetic Arm V1 is an attempt to bridge that gap.

The goal of this project is to design a lightweight, modular, and affordable prosthetic arm that can be manufactured using 3D printing and standard electronic components. Rather than focusing solely on appearance, the design prioritizes practical functionality, durability, and ease of maintenance.

Current Objectives
Design an anatomically inspired finger and joint mechanism.
Develop smooth and reliable tendon-driven motion.
Create a modular structure that allows individual parts to be replaced or upgraded.
Keep manufacturing costs as low as possible without sacrificing functionality.
Build a foundation for future versions with improved dexterity and sensor integration.
Progress

Today, I completed the initial CAD model for one of the fingers and started testing the joint geometry. The focus is on achieving a balance between strength, range of motion, and ease of assembly before moving on to full-hand integration.

This is only Version 1, and there is still a long way to go, but every iteration brings the project one step closer to creating an accessible prosthetic solution that anyone can build, improve, and use.

Next milestone: Complete the middle finger and begin integrating the tendon routing system.