Liquid Crystal Elastomers as a Material for Neural Interfaces

Implantable microelectrode development aims to enable functional restoration in patients who suffer paralysis, strokes, limb loss, or neurodegenerative disease. However, the chronic reliability of such neural interfaces is compromised, in part, by the body’s own foreign body response (FBR), leading to localized astrogliosis and fibrotic encapsulation of the device. These factors can lead to accelerated mechanical/electrical device failure and/or neuronal dieback at the site of implantation. The use of polymer substrates for neural interfaces has gained traction due to advantages such as mechanical flexibility and compliancy, which have been shown to reduce FBR-induced encapsulation when compared to the current state-of-the-art substrates (i.e., silicon). Liquid Crystal Elastomers (LCEs), a subclass of liquid crystal polymers (LCPs), exhibit a low modulus and can be fabricated into shapes which exhibit a high degree of flexibility. Furthermore, this class of polymers can be molecularly aligned to enable programmable and reversible shape change when exposed to a stimulus such as heat, light, or specific solvent. This approach potentially enables the controlled deployment of small recording or stimulation sites to regions beyond that of the FBR induced encapsulation (50 – 100 µm). The overarching goal of this project is to demonstrate the feasibility of using LCE-based implantable electrode arrays in chronic cortical recording applications. First, we evaluate cytotoxicity, functional neurotoxicity, and manufacturability of LCE as a substrate material for novel neural interfaces in vitro. Second, we evaluate the electrochemical stability of LCE as an insulating substrate in vitro. Finally, we evaluate the electrochemical stability and recording capability of LCE as an insulating substrate and deployable device in vivo.