Theses Doctoral

Microelectrode and MicroLED Arrays for Neural Applications

Kumar, Vikrant

Advancements in neural interfacing technologies, such as microelectrode arrays, have significantly contributed to understanding brain function and treating neurological disorders. Decoding the intricacies and functioning of neural circuits is key to further unlocking its potential. Two key approaches, electrical neural recording and optical imaging, have been the basis of stimulating and monitoring neural circuits. Despite the remarkable progress, several key issues such as reliable stimulation of neurons, closed-loop stimulation and monitoring, and undesired background fluorescence during widefield optical imaging remain challenging.

After giving a brief background on electrode and microLED arrays, the dissertation delves into the design, microfabrication, and characterization of microelectrode arrays for neural electrical stimulation, recordings, and microLED arrays as a light source for improving optical microscopy. We first discuss a dense conformal electrode array for high spatial resolution stimulation in electrosensory systems. The performance metrics of the integrated system are thoroughly examined through meticulous characterization and optimization processes. Special emphasis is placed on evaluating biocompatibility, electrical properties, and spatial resolution to ensure robust and reliable neural stimulation capability.

Next, we discuss a microelectrode device that combines simultaneous electrical recording and 2-photon imaging. We use an Indium Tin Oxide (ITO) material to fabricate a transparent electrode array with a design capable of single neuron recordings. The design, microfabrication, and electrooptical characterization are presented to demonstrate the device’s capability. A system integrating the array with a GRIN lens is also presented to record and image deeper into the brain tissue. Combining both the electrical and optical recordings of neuron ensembles and finding correlations can shed further light on the functioning of neural circuits.

To address the problem of unwanted background fluorescence during neural cell imaging, two microLED arrays as light sources are presented. With a microstripe array, we implement optical sectioning structured illumination microscopy (OS-SIM), and with the 2D microLED array, we implemented targeted illumination to reject background fluorescence and improve contrast. We examine the capability of the microLED as a light source with luminance-current-voltage, directivity, and transient measurements. Both implementations highlight the novel non-display application of microLED to address challenges in neural imaging. This research represents a significant contribution to the burgeoning field of neural engineering, offering novel methodologies and technologies that promise to revolutionize our approach to understanding brain functions.


This item is currently under embargo. It will be available starting 2025-05-29.

More About This Work

Academic Units
Electrical Engineering
Thesis Advisors
Kymissis, Ioannis
Ph.D., Columbia University
Published Here
July 3, 2024