A new 3D-printable hearing aid made of materials inspired by the bones of the ears has been developed, marking the evolution of a new generation of hearing aids.
Conductive hearing loss (CHL) is a condition related to dysfunction or trauma of the middle ear. It affects more than 5% of the global population and over 15% of the elderly. Supported by the Marie Skłodowska-Curie Actions program, the COLLHEAR project developed a new 3D-printable hearing implant to replace the small bones of the middle ear, known as ossicles. "
I wanted to rethink the design of the prosthesis," explains lead researcher Mario Milazzo. He focused on defining new geometric shapes, in collagen, optimized for performance and to meet the requirements of 3D manufacturing technologies. "
Current manufacturing technologies for middle ear implants have not considered 3D printing as a viable option, which I believe, can lead to the best prosthetic solutions in terms of shape and functionality," he says.
Next-Generation Hearing Aids
Milazzo, who is based at the Sant'Anna School of Advanced Studies, printed prototypes at the Massachusetts Institute of Technology (MIT) and at Tufts University in the United States of America, where part of the project was conducted. The 3D printing process presented numerous challenges. "The devices are tiny, and printing to the order of a few millimeters can be difficult. Selecting the right manufacturing parameters is complex," Milazzo notes. The prostheses are made of type 1 collagen and hydroxyapatite, a natural mineral form of calcium. "These are the native components of bones," Milazzo explains. Printing these materials was also problematic: "
Finely tuning the density and viscosity of the composite to make 3D printing reliable was a challenge," he adds. However, he succeeded in proceeding and continued to test the prostheses in human temporal bones. "
Due to administrative and ethical issues, the prostheses have not yet been placed in real patients, although this is the ultimate goal."
Performance
The results are encouraging. Acousto-mechanical evaluation showed performances comparable to commercial prostheses. "
But our device has the advantage of being made from a more biocompatible material," Milazzo explains. This should make the implants less prone to rejection. To find out if that was the case, Milazzo placed the printed implants in a bioreactor, a piece of equipment capable of reproducing specific physicochemical conditions that mimic the final target environment in which the prosthesis will be used. "I took advantage of a bioreactor previously designed by some of my Italian collaborators, but I customized it for my specific application," adds Milazzo. Tests revealed the construction's capacity to host epithelial and mesenchymal cells on the surfaces of the prosthesis, a promising result opening an exciting future for in vivo studies. The activities related to modeling, manufacturing, and acousto-mechanical evaluation took place in America, involving MIT, Tufts University, and Massachusetts Eye & Ear, an affiliate of Harvard University. The biological evaluation took place in Italy between the Sant'Anna School of Advanced Studies and the University of Pisa.
Next Steps
Milazzo is now actively discussing with project partners and head and neck domain clinicians new funding opportunities to further contribute to the field of micro-prostheses. "
The Marie Curie fellowship indeed gave me the chance to broaden my research horizons in terms of knowledge and skills, and to meet and work with the best scientists worldwide who have deeply contributed to my personal and scientific growth."
For more information see:
COLLHEAR Project