RESUMO
We propose an optical electrode 'optrode' sensor array for biopotential measurements. The transduction mechanism is based on deformed helix ferroelectric liquid crystals which realign, altering the optrode's light reflectance properties, relative to applied potential fields of biological cells and tissue. A computational model of extracellular potential recording by the optrode including the electro-optical transduction mechanism is presented, using a combination of time-domain and frequency-domain finite element analysis. Simulations indicate that the device has appropriate temporal response to faithfully transduce neuronal spikes, and spatial resolution to capture impulse propagation along a single neuron. These simulations contribute to the development of multi-channel optrode arrays for spatio-temporal mapping of electric events in excitable biological tissue.
RESUMO
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.