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Lancaster University 3D-printing integrates electronics into living tissues

22 Mar 2023

Multiphoton fabrication method could produce printable bioelectronics or interfaces.

A project at the UK's Lancaster University has developed a 3D printing method that allows flexible electronics made from conducting polymers to be incorporated into a biocompatible manufactured object.

Published in Advanced Materials Technologies, the work could offer a route to laser-printed materials able to be used for implants in surgical procedures, or allow new techniques for repair of such medical devices.

"This approach potentially transforms the manufacture of complex 3D electronics for technical and medical applications, including structures for communication, displays and sensors," commented Lancaster's John Hardy.

"One day technologies like this could be used to fix broken implanted electronics through a process similar to laser dental or eye surgery. Once fully mature, such technology could transform a currently major operation into a much simpler, faster, safer and cheaper procedure."

Incorporating electronic circuitry into 3D-printed objects made via additive manufacturing (AM) became an active topic of research as the variety of conducting polymers available increased, but manufacturing biocompatible components in similar fashion has remained challenging.

Multiphoton fabrication methods are a promising solution, potentially allowing highly complex structures to be produced to exacting dimensional accuracy at useful depths within tissues. The Lancaster project applied this principle to the printing of conducting polypyrrole (PPY)-based structures within insulating elastomers such as polydimethylsiloxane (PDMS) and shape memory polymers.

Having developed suitable formulations, the team investigated whether it was possible to directly 3D-print structures of these conducting polymers onto or into living tissues, a breakthrough not previously reported, according to the project.

Tailor-made bioelectronic implants

In a two-stage study, the researchers first used a Nanoscribe 3D printer operating at 780 nanometers to 3D-print an electrical circuit directly within a PDMS matrix, and demonstrated that the conducting polymer could be used as a neural interface by attaching it to a slice of in vitro mouse brain. The circuit successfully stimulated neuronal responses in the tissue.

For an in vivo trial, the project then 3D-printed similar conducting structures directly into C. elegans nematode worms, as a first demonstration that the full processing sequence - ink formulation, laser exposure and printing - was compatible with living organisms. This required consideration of potential toxicity and of key laser parameters, so that the lowest possible laser power needed for polymerization was employed.

Functioning photoresist structures were successfully printed in live C. elegans, although the team noted that printing accuracy and precision are affected by the complex moving environment of the worm. Techniques such as adaptive optics are likely be needed with more complex organisms, although the current trial still "represents a technological leap from examples of printing non-conductive structures in vivo" noted the team.

This kind of 3D printed electronics may allow fundamental studies of living systems, or manufacture of bioelectronic devices capable of continuous monitoring and modulation of neural activity. The nature of 3D-printing means the electrode arrays could potentially be tailored specifically to match particular patients and their needs, according to the project.

"Although improvement in infrared laser technology, smart ink formulation and delivery will be critical to translating such approaches to the clinic, it paves the way for very exciting biomedical innovations," said Lancaster's Alexandre Benedetto.

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