Scientists Develop a New Class of Materials For Optical Biointerfaces

A team of researchers from the College of Engineering, Carnegie Mellon University has invented an optical platform that will likely become the new standard in optical biointerfaces. They have made the first-ever biocompatible and fully flexible integrated photonics platform.

The team led by Maysam Chamanzar has labelled this new field of optical technology “Parylene photonics,“. They recently published their research in the Nature Microsystems and Nanoengineering journal.

The Problem
We have an ever-growing demand for miniaturized and flexible optical tools. These tools are helpful for on-demand imaging and manipulation of biological events in the body.

Integrated photonic technology has mainly evolved around developing devices for optical communications. Silicon photonics was a turning point in miniaturizing the tools.

The problem with silicon is that it is a dangerously rigid material for interacting with soft tissue in biomedical applications. This increases the risk for patients to undergo tissue damage and scarring.
The aim of this research was to solve this flexibility issue in optical tools.

Maysam Chamanzar, an assistant professor at CMU, observed this pressing need for an optical platform built with both optical capability and flexibility.

To create this new photonic material class, Chamanzar’s lab designed ultracompact optical waveguides by fabricating silicone (PDMS), an organic polymer with a low refractive index, around a core of Parylene C, a polymer with a much higher refractive index.

The contrast in the refractive index allows the waveguide to pipe light effectively, while the materials themselves remain extremely flexible. The result is a platform that is flexible, can operate over a broad spectrum of light, and is very thin.

“We were using Parylene C as a biocompatible insulation coating for electrical implantable devices, when I noticed that this polymer is optically transparent. I became curious about its optical properties and did some basic measurements,” said Chamanzar. “I found that Parylene C has exceptional optical properties. This was the onset of thinking about Parylene photonics as a new research direction.”

Chamanzar’s design was created with neural stimulation in mind. This allowed for targeted stimulation and monitoring of specific neurons within the brain. Crucial to this is the creation of 45-degree embedded micromirrors.

ECE alumna Maya Lassiter (MS, ’19), who was involved in the project, said, “Optical packaging is an interesting problem to solve because the best solutions need to be practical. We were able to package our Parylene photonic waveguides with discrete light sources using accessible packaging methods, to realize a compact device.”

Journal Reference:
Jay W. Reddy, Maya Lassiter, Maysamreza Chamanzar. Parylene photonics: a flexible, broadband optical waveguide platform with integrated micromirrors for biointerfaces. Microsystems & Nanoengineering, 2020; 6 (1) DOI: 10.1038/s41378-020-00186-2

Press Release: College of Engineering, Carnegie Mellon University