Biocompatible waveguides

Researchers at Tufts University and the University of Illinois at Urbana-Champaign (UIUC) have demonstrated a new method for fabricating silk-based optical waveguides that are biocompatible and biodegradable.

The waveguides, which could be used in biomedical applications such as vivo glucose monitoring, can also be functionalised with active molecules.

The Tufts-UIUC team are said to have demonstrated light guiding through this new class of waveguides created by direct ink writing using Bombyx mori silk fibroin inks.

Direct ink writing is a simple, inexpensive technique that does not require harsh processing steps.

A computer-controlled three-axis translation stage precisely moves a syringe barrel that houses a viscous ink, which is extruded from a fine deposition nozzle under pressure.

The ink flows rapidly through the nozzle, and equally rapidly solidifies upon exiting to retain a filamentary shape while maintaining optical clarity to guide light.

‘In many biomedical applications, waveguides must interface directly with living cells and tissues, requiring the waveguide constituent to be biocompatible. Biodegradability is also desirable,’ said Tufts' Fiorenzo Omenetto, professor of biomedical engineering in the School of Engineering and professor of physics in the School of Arts and Sciences.

‘The use of a biocompatible, biodegradable polymer such as silk to guide light opens up new opportunities in biologically based modulation and sensing along with an opportunity to integrate light delivery within living tissue.’