Sensor integration is a good fit with 3D-printed prosthetics

Engineers at Virginia Tech are integrating sensors into personalised 3D-printed prosthetics, an advance that could lead to more affordable electric prosthetics.

3D-printed prosthetics
The mould of Fraticelli’s hand that was scanned during the development of a personalised prosthetic (Photo by Logan Wallace/ Virginia Tech)

By integrating electronic sensors at the intersection between a prosthetic and the wearer’s tissue, the researchers can gather information related to prosthetic function and comfort, such as the pressure across the wearer’s tissue, that can help improve further iterations of the these types of prosthetics. The results are published in Plos One.

According to Virginia Tech, the integration of materials within form-fitting regions of 3D-printed prosthetics via a conformal 3D printing technique could create opportunities in matching the hardness of the wearer’s tissue and integrating sensors at different locations across the form-fitting interface.

Yuxin Tong, an industrial and systems engineering graduate student and first author of the study, said the ultimate goal is to create engineering practices and processes that can reach as many people as possible, starting with an effort to help develop a prosthetic for local teenager Josie Fraticelli.

To develop the prosthetics integrated with electronic sensors, the researchers started with a 3D scan of a mould of the Fraticelli’s limb. They used the 3D scanning data to guide the integration of sensors into the form-fitting cavity of the prosthetic using a conformal 3D printing technique.

“Personalising and modifying the properties and functionalities of wearable system interfaces using 3D scanning and 3D printing opens the door to the design and manufacture of new technologies for human assistance and health care as well as examining fundamental questions associated with the function and comfort of wearable systems,” said Blake Johnson, a Virginia Tech assistant professor in industrial and systems engineering.

Fraticelli was born with amniotic band syndrome, causing a lack of formation beyond the knuckles. Johnson used his related research expertise in additive biomanufacturing and a team of interdisciplinary undergraduate researchers to 3D print the bionic hand for Fraticelli that would become the basis of the research.

As they worked with Fraticelli, they continued tuning the prototype prosthetic by developing new additive manufacturing techniques that would allow for a better fit to Fraticelli’s palm, creating a more comfortable, form-fitting prosthetic device.

They found that contact between Fraticelli’s tissue and the prosthesis increased nearly fourfold compared to non-personalised devices. This increased contact area helped them pinpoint where to deploy sensing electrode arrays to test the pressure distribution, which helped them to further improve the design.

Sensing experiments were conducted using two personalised prosthetics with and without sensing electrode arrays. By running these experiments with Fraticelli, they found that the pressure distribution was different when she relaxed her hand compared to holding her hand in a flexed posture.

“The mismatch between the soft skin and the rigid interface is still a problem that will reduce the conformity,” said Tong. “The sensing electrode arrays may open another new area to improve the prosthetics design from the perspective of distributing a better balance of pressure.”