Researchers at École Polytechnique Fédérale de Lausanne in Switzerland have shown that an optical fiber as thin as a human hair can be used to create microscopic structures with laser-based 3D printing. The technique might one day be used with an endoscope to fabricate tiny biocompatible structures directly into tissue inside the body, enabling new ways to repair tissue damage.

By dipping the end of an optical fiber into a photopolymer – a liquid that solidifies, or cures, when illuminated with a specific color of light – the researchers were able to deliver and digitally focus laser light point-by-point into the liquid to build three-dimensional microstructures.

Their approach could be useful for studying how cells interact with various microstructures in animal models, which would help pave the way for endoscopic printing for human subjects. It could also serve as an add-on to today's commercially available 3D printers.

"By using one printer head with a low resolution for the bulk parts and our device as a secondary printer head for the fine details, multi-resolution additive manufacturing could be achieved," said research team leader Paul Delrot.

Laser-based microfabrication is not new, but current techniques require complex and expensive lasers to emit very short pulses as well as bulky optical systems to deliver the light. The researchers used their expertise in manipulating and shaping light through optical fibers to simplify the setup, using a low-power, continuous-wave laser. Light was emitted at 488-nanometer wavelength – visible-wavelength light that is potentially safe for cells – through an optical fiber small enough to fit in a syringe. It was then focused through an approach known as wavefront shaping in order to cure a small 3D point.

The team is currently working to develop biocompatible photopolymers and a compact delivery system. A faster scanning speed is also needed, but in certain cases this limitation could be overcome by using a commercial endoscope instead of the ultra-thin fiber. A technique to finalize and post-process the printed structure inside the body will also be required to create microstructures with biomedical functions.

"With further development our technique could enable endoscopic microfabrication tools that would be valuable during surgery," said Delrot. "These tools could be used to print micro- or nano-scale 3D structures that facilitate the adhesion and growth of cells to create engineered tissue that restores damaged tissues."