Improving the consistency of external breast prostheses with voxel-based 3D printing

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Eighty percent of women after mastectomy wear an external breast prosthesis either permanently or during the period before breast reconstruction. External breast prostheses replace the removed breast and aim to recreate the original body shape. However, while each woman has a different chest wall and scar topology, most commonly used are standard commercial prostheses, which often fail to provide comfort and symmetry to the wearer.

Given the risks and costs associated with elective reconstruction surgery, women who decide to use external breast prostheses should be offered options that are as well developed as their surgical alternatives.

This project envisions an external breast prosthesis design method that allows the efficient manufacture of personalized forms. 3D scanning and 3D printing are suitable techniques to create solutions tailored to each person’s necessities. 3D scanning allows having a digital twin of the chest wall topology that helps create the geometry that perfectly matches an individual woman. 3D printing, on the other hand, eases the fabrication of patient-specific products. For this reason, this project considers 3D printing as a suitable technology for the production of personalized external breast prostheses.

Research has been conducted with breast care experts and women after mastectomy to explore the pain points associated with existing external breast prostheses, which helped identify several design opportunities. This project aims to achieve a specific main goal: To provide a realistic consistency of external breast prostheses to touch. Current solutions tend to be too stiff and hard, which makes them uncomfortable for the user.

Polyjet 3D printing offers the possibility to print with rigid, flexible, liquid, and gel-like materials. Furthermore, owing to the droplet-based working principle of this technology, it is currently possible to mix different materials with full control of the proportions and the design of the material distribution droplet by droplet. This allows achieving a mixture that works as a homogeneous material at a macroscopic scale and having tailored mechanical properties. This project approaches the challenge of external breast prosthesis redesign by exploring the possibilities and limitations of voxel-based Polyjet 3D printing; specifically, the different mixtures of liquid and gel-like materials encapsulated in an outer cover made with flexible material.

Extensive prototyping is performed throughout the project and compression tests are conducted to obtain quantitative data regarding the softness of prototypes and its similarity to a natural breast. Besides the objective information obtained from these tests, a user evaluation is conducted with ten participants to compare the objective data with human perception, which is ultimately more relevant for this topic due to the subjective nature of tactile experiences.