After the challenges encountered at the 2020 Cybathlon with the makeshift Touch Hand 4.0, it was decided to relook at the design of the hand itself from a fresh perspective for 2021, with the main objectives to lighten the structure as well as to make it more compact and functional.

With AEDG students Muhammed Lookmanjee and Wian van Aswegen assigned to the project, they looked at various concept possibilities early on where several design direction decisions were made. We were all fairly happy with the socket design, so that would be retained going forward and only tweaked if necessary. However, the hand itself was heavy, unwieldy, bulky and just needed cleaning up all round as it was a compromised design in the first place.

The decision was then made fairly early on that next iteration, Touch Hand 5.0 (TH5.0), would be a fully mechanical prosthetic hand in order to eliminate the very frustrating electronics issues experienced last time around. The TH5.0 is aimed at being simple, light, and manageable in size as well as cost effective and modular thus allowing the amputee pilot to do common simple day to day tasks comfortably and at an affordable price.




Touch Hand 5.0 would be string/cable driven. It would be controlled via extension of the shoulder blade that pulls on two individual Dyneema braided strings. One pulls on the thumb and the other pulls down a Whipple tree link setup that is connected to each individual finger...this allows for the fingers to take shape with equal pressure on any object being held. After which a spring or elastic band then return the fingers to its home position. The thumb is rotatable manually using a gear and lock setup to allow for different grips.

The reason for using the shoulder blade as the source of actuation is because it was noticed that the shoulder blade was the easiest place to harness movement without obstructing the hand’s movement.

The reason for not using the elbow is because most movements rely on the elbow. So having the elbow as a trigger to do daily tasks would be very inconvenient. Imagine having to grab and sip a cup of tea while having your elbow locked in one position...it is an unnatural action, and the focus on the design was to try and replicate day-to-day tasks in as functional method as possible.  

The prosthetic would be a modular design to allow easy changes and repairs for any part on the hand. It would also be designed with future upgrades and electronic adaptivity in mind.

Below are the grips that would be considered when designing the prosthetic.



Early Development

The early design concepts were as follows:


Overall Hand Structure

The overall hand superstructure would follow the following design concepts:


  • it would follow a general design used by most prosthetic designs researched online that allow individual finger movement using 1.5mm braided Dyneema rope (rated at 230kg break load).

popular wrist actuated prosthetic


  • the rope is run through the bottom of the fingers through its tunnels ‘within the finger links. 

  • the rope is then attached at the tip via a screw and can adjust tension within the rope by pulling the rope and tightening the screw. Like an old school bicycle cable brake system. 

  • the simple design allows to change the wire very quickly if it ever snaps or is somehow damaged. 

  • there is a finger cap to cover the screw at the fingertip and make it look more realistic.

  • springs return the fingers to an upright position when the hand is relaxed.

  • the links are screwed together so it can be disassembled easily if need be.

initial concept sketches


Palm Design

The internals of the palm would consist of the following set-up:

  • one cable runs all 4 fingers that are connected using links.

  • fingers 1 and 2 are linked together with a major link that connects to a further link for fingers 3 and 4.

  • the links in block A are moving in free space whereas the other links are fulcrumed on the hand itself

  • link X: Y allows for a mechanical advantage if needed.

  • the thumb is connected directly to the movement source.


initial palm concept


Motion Activation


The cabling system would work like a bicycle brake system where the cable is run under a rubber sleeve. 

Two straps are worn by the user such that, when he moves the shoulder blade up, the cable gets pulled under the sleeve which pulls the wires from the hand.

Motion Activation Concept



The hand was designed in proportion to an average sized male hand.

Keeping in mind modularity, the hand was then designed with inserts for all parts that could be damaged/replaced or upgraded at a later stage.

Also mindful of aesthetics, the hand would also be designed to look as life-like as possible with all 5 fingers and all 3 phalanxes per finger.


Distal Phalanx

The distal phalanx is also known as the tip of the finger.



Intermediate Phalanx

The intermediate phalanx joins the distal and proximal phalanx together. It sits between those two phalanxes.


Proximal Phalanx

The proximal phalanx joins the 2 phalanxes to the palm of the hand.




The palm is designed to allow addition and customization for the prosthetic. Thus, lots of room for inserts was added. The palm is very minimal to sigificantly reduce weight compatred to the TH4.0.


Palm Texturing Material

To assist in enhancing the grip, it was decided to affix a silicone textured pad to the palm of the hand. To facilitate this, the following geometric options were added:



To allow for better grip, the palm texture was turned into a lattice to allow silicone to properly bond within the lattice structure. 

(l) the textured lattice, and (r) the mold for the silicone insert



The photo below shows he routing of the cables through the fingers and into the socket...


Rotatable Thumbs

The Rotatable Thumb will consist of 5 parts, the center phalanx, a lock, a gear and 2 side guides.

The manually moved rotatable thumb allows for much more effective grips for the prosthetic hand.

It works by giving a tolerance between the center phalanx and the side guides to allow the phalanx to move about its axis.

The lock is spring loaded to grab onto the gear to lock its position when let off.

the central phalanx and the interconnecting components in which it rotates

an exploded view of the thumb assembly


Socket Adapter

The socket adapter is bolted using four screws to the side of the palm, it then clips onto the existing socket used in Touch Hand 4.0.

Many different types of inserts in the designs.

A hook insert was used to hold the elastic bands between the distal phalanx and the palm, this was to allow a return spring action on the finger to return the finger to home position when the hand was in a relaxed position.

Oval elastic inserts was used to guide the elastic band, so it stays neater within the fingers, and rail inserts on the palm guided the string from the links to the fingers. And the thumb rail insert guided the string to the thumb.

All designed inserts were press fit.


Mechanical Palm System

The mechanical advantage design was ditched as there was no need for it seeing as it was measured that the shoulder had enough movement to give the 40mm movement that was needed to fully retract the fingers.

The Whipple tree design allowed the fingers to grasp different shape objects with equal amounts of force at different contours.

The links were printed in 2 parts per link having a top and bottom. The string was then crimped around the supports. This design also meant that 1 input gave an output of 4.


That is the level of completion of the Touch Hand 5.0 at the moment...this design may be taken forward into the next team that is currently being set up for participation in the 2024 Cybathlon.