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Title:Capacitive droplet sensing system for a microdialysis neural probe
Author(s):Licudine, Alyssa
Contributor(s):Vlasov, Yurii
Neural probe
Interdigitated electrodes
Capacitive sensing
Relaxation oscillator
Abstract:This thesis presents the construction and design choices behind an on-chip capacitive droplet-counting and content-sensing system that will enhance temporal and spatial resolution of neurochemical sensing of a silicon microdialysis neural probe. The parameters of a coplanar interdigitated capacitor system were optimized to the microfluidic channel design of the probe through theoretical analysis, simulations via finite element analysis, and testing of the fabricated designs. The performance of these designs was assessed by the differential capacitance measured between water and oil droplets; a larger differential allows for more accurate distinction between the two liquids as they pass through the sensor. The use of a relaxation oscillator circuit as a method of measurement for sufficient resolution of sub-picofarad differentials, along with techniques for de-embedding shunt and stray capacitance contributions, are explored. The resulting droplet counting system achieves 0.01 pF resolution within one second and enables facile, on-line, on-chip droplet detection, consequently improving temporal, spatial, and chemical resolution when analyzing the samples with various options for sensing modalities, including capacitance, electrochemistry, and mass spectrometry.
Issue Date:2020-12
Date Available in IDEALS:2021-01-04

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