Development of microneedle array electrodes for transcutaneous neural stimulation and recording applications
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Date
2019-09-17
Authors
Soltanzadeh, Ramin
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Abstract
Transcutaneous electrical nerve stimulation is one of the physical neuromodulation methods that stimulate a nerve and potentially its adjacent nerve fibers. To make this method more effective, it would be of value to design new electrodes that only target a specific nerve and prevent the co-stimulation of an adjacent nerve.
In this dissertation, different scenarios of tissue and blood capillary placements were analyzed through multiphysics simulation of a 3D model and the best microneedle array electrode was suggested as a new electrode for nerve stimulation. These studies showed that the design of the microneedle array plays a critical role in presenting a uniform electric field to a target nerve and the resulting performance benefits. Analysis showed that microneedle array electrodes can increase the distinguishability between a target nerve fiber and its adjacent nerve fibers up to 10% compared to conventional surface electrodes. Uniform electric field, effective thermal behaviour and consistent current density in different depths of tissue are the other advantages of using microneedle electrodes for stimulation. Different stimulation parameters were investigated and the analysis showed that the geometry of the microneedles on top of the electrodes, such as their tip-to-tip pitch, their numbers and shape can affect performance.
Microneedle arrays were fabricated and used for experimental verification of performance benefits. One study explored polymer microneedles molded from a polycarbonate master. They were coated with titanium and titanium-nitride to increase the mechanical strength, and molybdenum (which is a biocompatible metal) to increase the conductivity of the structure. In clinical study it was found that they enhanced the tissue-electrode interface parameters, such as decreasing the resistance and increasing the double-layer capacitance. In another study, low cost microneedle arrays were printed using 3D printing technology. In a clinical study comparing with the molded microneedles, it was found that the 3D printed ones had better high frequency performance (such as for EMG), and the molded microneedles performed better for low frequency signals (such as for EEG).
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Keywords
Microneedle Arrays, Transcutaneous Electrcial Nerve Stimulation, Biosignal Recording
Citation
Soltanzadeh, Ramin, et al. "Molybdenum coated SU-8 microneedle electrodes for transcutaneous electrical nerve stimulation." Biomedical microdevices 20.1 (2018): 1.