Emerging trends in the development of flexible optrode arrays for electrophysiology

Abstract

Optical-electrode (optrode) arrays use light to modulate excitable biological tissues and/or transduce bioelectrical signals into the optical domain. Light offers several advantages over electrical wiring, including the ability to encode multiple data channels within a single beam. This approach is at the forefront of innovation aimed at increasing spatial resolution and channel count in multichannel electrophysiology systems. This review presents an overview of devices and material systems that utilize light for electrophysiology recording and stimulation. The work focuses on the current and emerging methods and their applications, and provides a detailed discussion of the design and fabrication of flexible arrayed devices. Optrode arrays feature components non-existent in conventional multi-electrode arrays, such as waveguides, optical circuitry, light-emitting diodes, and optoelectronic and light-sensitive functional materials, packaged in planar, penetrating, or endoscopic forms. Often these are combined with dielectric and conductive structures and, less frequently, with multi-functional sensors. While creating flexible optrode arrays is feasible and necessary to minimize tissue–device mechanical mismatch, key factors must be considered for regulatory approval and clinical use. These include the biocompatibility of optical and photonic components. Additionally, material selection should match the operating wavelength of the specific electrophysiology application, minimizing light scattering and optical losses under physiologically induced stresses and strains. Flexible and soft variants of traditionally rigid photonic circuitry for passive optical multiplexing should be developed to advance the field. We evaluate fabrication techniques against these requirements. We foresee a future whereby established telecommunications techniques are engineered into flexible optrode arrays to enable unprecedented large-scale high-resolution electrophysiology systems.

An Integrated Neural Optrode with Modification of Polymer-Carbon Composite Films for Suppression of the Photoelectric Artifacts

“…Optogenetics-based neuromodulation tools are key to the study of neuroscience, which can regulate specific neurons expressing photosensitive proteins through light stimulation and record neuronal responses electrophysiologically with high spatiotemporal resolution. Since the concept of optogenetics was proposed, many researchers have introduced optogenetic tools with different structures for neuroscience research over the past few decades. − The traditional light source coupling optrode, that is, the laser or high-power light-emitting diode (LED) is coupled with the optical fiber as the light source, and the metal wires are used as the recording electrode, or alternatively, an external light source is coupled with the waveguide on a silicon-based substrate. − While this kind of optrode has little damage to the animal brain area, and it relies on an external light source, which will limit the range of animal activity. With the development of semiconductor materials and their processes, integrated LED optrodes have emerged, combining light sources and recording electrodes through semiconductor processes. − In 2015, Wu et al first proposed the concept of fabrication of an integrated four-shank silicon-based probe on a commercial wafer, with each probe containing 12 μLEDs and 32 recording microelectrodes .…”