Modeling the Debye dielectric response in the time domain for a liquid crystal-based biopotential optrode

Multielectrode arrays (MEAs) are widely used for recording biopotentials, with an ongoing research effort to improve their characteristics and performance. In this spirit, we are currently investigating a novel concept for a liquid crystal-based optical electrode (optrode) that has the potential to overcome some of the limitations of MEAs, including that of wiring complexity. In this paper we present a model to fully describe the electrical response of the proposed optrode to biopotentials, taking into account dielectric relaxation. Since the frequency dependence of the complex permittivity is difficult to specify in time-stepped finite element (FE) simulations, where the implementation of time-convolution is nontrivial, we adopt an alternative approach to dielectric relaxation via the polarization vector. This approach, which is based on the Debye model, is then implemented in a FE model of the optrode. We show that the dielectric response of the liquid crystal layer has an effect on the complex signal behavior of the sensed biopotentials that must be taken into account when modeling the optrode.