Thermally Drawn Optoelectronic and Optofluidic Polymer Fibres for Brain Applications

In the last two decades, optical techniques for modulating and monitoring neural activity have changed the landscape of neuroscience. This has created a research drive towards the development of soft, biocompatible optical fibres able to deliver and collect light in deep brain regions over long periods of time with minimal inflammation. Thanks to their low Young’s modulus and high versatility in terms of opto-mechanical properties, polymer-based fibres are an ideal platform to base this effort on. Furthermore, the interest in combining optical techniques with viral injections, pharmacology and electrophysiology while minimizing the number of surgeries has led to a strong interest in integrating different structures and functions in monolithic fibre-based devices. In this chapter, we will start by briefly introducing the most common functions that can be performed in the brain by elements integrated within polymer optical fibres. Afterwards, we will introduce the most commonly used polymers in neuroscience applications and describe all the steps required to fabricate optoelectronic and optofluidic fibres by thermal drawing process which is the most common technique for optical fibres fabrication. This will be followed by a discussion on the optimization of two parameters that are crucial for all multifunctional fibres targeted towards brain applications: the overall stiffness of the fibre, and the volume of tissue to which light can be delivered and from which light can be collected. Finally, we will introduce a recent application of the described technology to an emerging optical technique in the field of neuroscience: infrared neuromodulation.