One Page Summary

Motivation:

 Currently, the prosthesis are, and have always been, the opportunity that is offered to those people who have suffered the loss of a member or have been born with some pathology in them, to return to resume their normal activities. Its applications go back to ancient Egypt, where cosmetic prosthetics were made so that the deceased would go to the other life with their complete bodies. 

However, the prosthesis that allow more complex activities, date from the 19th century. In the last decades, the prosthesis industry has seen a big leap in terms of capability and characteristics that they possess, thus allowing to perform almost any activity using customized prosthesis for different tasks.

With the advance of low-cost technologies for manufacturing and controlling, expansion will tend to move towards the manufacture of low-cost prosthesis. This is important in case of children, who must receive a large number of prosthesis to follow the growth of their bodies or in the case of people who cannot acquire one due to its cost. Our case is aimed to children with disabilities, who have been born with some pathology in their hand, investing in the design and development of prosthesis through 3D printing and cooperating with associations such as the case of Social Changes Innovation.

Objetives:

The main objective of this project is to design a prosthetic hand with a low cost/useful life for children born with pathologies in any of their hands. On the other hand, we have specific goals such as:

• Produce the prosthesis adapting the design to Disney or Marvel characters.

• Design fingers that allow flexing by at least two points.

• Design and optimize the adequate materials as well as its surface finishing.

• Evaluate the production costs and influences. 

Prosthesis proposal by 3DZings:

After carrying out a biomechanical study and knowing in advance the advantages and the disadvantages of the aforementioned materials, we decided that our prosthesis should be manufactured in semi-rigid PLA. With this softer material, we get the most realistic finishing, as well as printing in a high range of colours. 

The hand, mainly has two movements directed by two joints. The radiocarpal joint (union of the radius with the bones of the first row of the carpus) and the midcarpal joint, composed of two rows or phalanges. In our design, we did not take into account the second phalanx or row that corresponds to the midcarpal joint, but it has been given a curvature thus allowing us to imitate this movement. Regarding the foundation of the movement, we use elastic cable located inside the fingers to provide passive extension, and non-elastic cable, inside the palm to provide flexion. 

On the other hand, we have designed a lace, which assembled to the palm through axes also made in 3D printing, imitates the movement of the radiocarpal joint. This lace has tensors on the outer surface, where the non-elastic cables are situated. The inner surface of the lace contains Velcro that allows the child to adjust his arm.   

Advantages over other prosthesis in the market:

• Made in semirigid PLA, allowing children to play with other teammates without causing damages. 

• Marvel or Disney character designs, causing less complex for the affected, feeling more confident and with greater social integration with the rest of the children. In addition, each prosthesis carries the mask of the associated character. 

• Appropriate dimensions. This is the most important advantage, since the prosthesis that are on the market, are designed with large dimensions (Figure 1) and are very showy for children. The prosthesis designed by 3DZings, adapts to the size of each child's hand.