Cool idea!

Concept/shape

• What specific activities or tasks do you envision users accomplishing with this cyborg thumb?
• Have you considered how easy it would be for users to put on and remove the cyborg thumb? Could the shape or attachment method be adjusted to make it more user-friendly?

Functionality 

• Could there be a locking mechanism to hold the thumb in place once it grips something, allowing the user to rest their leg without losing the grip?
• How comfortable is it to use over long periods? Would adding padding to the attachment point on the leg improve comfort?
• Have you thought about making the thumb detachable for easy storage or transport? 
• What materials are you considering for the thumb and strings if this was to be built in the future ? 
• Could there be a safety release mechanism if the spring or string pulls too hard to prevent potential injury?
• Over time, could this design be adapted to include electric motors or sensors? This would allow the thumb to operate autonomously without needing manual pulls, potentially controlled by subtle movements or pressure sensors.

Ideas for Prototyping

• For an initial prototype, try using lightweight, flexible materials like cardboard and soft foam to create a comfortable, functional version.
• Lights could provide feedback when the thumb is in use. For example, LED lights could turn on when the thumb grips something, signaling activation.
• A servo motor could enable more precise control over the thumb’s movement, making it more versatile. Here’s how to approach it:

1. Type of Servo:

   • Micro Servo: A small, lightweight servo is ideal for this project, as it would provide adequate torque without adding too much bulk or weight.

   • Continuous Rotation Servo: If you want the thumb to rotate freely in one direction, a continuous rotation servo is an option, but it may not be as effective for precise gripping.

2. Power and Control:

   • Battery Pack: A small battery pack can power the servo. A 5V power supply would work well with most micro servos.

   • Arduino or Microcontroller: To control the servo, you’ll need a microcontroller like an Arduino or a smaller alternative like an Adafruit Trinket. This will allow you to program movements and trigger actions.

These resources will be important for prototyping and inspiration

• https://sek.nuvustudio.com/posts/1013031-mechanisms
• https://sek.nuvustudio.com/projects/114402-07-low-fidelity-prototyping-wearable-cardboard-mock-ups/tabs/134119-example