A documented timeline of the LETO 1 mechanical, electronics, and prototyping work recorded from October 2025 through June 2026.
The development archive began with reference research and early Fusion 360 work. The hand skeleton, palm geometry, and finger structure were refined before moving toward a printable first-generation design.
The first-generation hand moved from CAD into rapid prototyping. Printing the model created a physical baseline for checking proportions, clearances, joint movement, and the practical assembly of the mechanism.
Real-world flexion tests revealed knuckle hyperextension and excess fingertip extension. The discussion focused on adding a mechanical stop and revising tendon leverage so the fingers could close reliably without binding.
Initial electronics work documented an EMG signal-amplifier path and an updated ESP32 power supply. These schematics established the sensing and control foundation for later motor-driver and PCB integration.
The hand was reworked around a lighter linkage structure with routed tendons, revised finger geometry, and a more developed wrist interface. Successive renders show the mechanism becoming more compact and serviceable.
Motor dimensions and torque requirements were reviewed against the available wrist volume. The packaging plan returned to planetary gearboxes for higher torque and reliability, accepting a tighter battery-space constraint.
Physical testing led to a redesigned Tendon Control Module with PTFE inserts and improved cable retention. The archive then shows the mechanism integrated into a complete hand prototype with routed tendons and electronics wiring.
The EMG front end, power management, ESP32, and five motor-driver channels were consolidated into a circular board concept. The schematic and layout progressed toward a finalized fabrication-ready design.
The completed board design was prepared for fabrication, followed by a manual PCB review report. This marked the transition from circuit planning into hardware production and final pre-fabrication checks.
LETO 1 is presented as an engineering concept and is not a certified medical device or commercially available prosthesis.