Spring 2018 Thesis Defense Schedule

Thesis Defense Schedule


Spring 2018

Wednesday, May 30

Devon Griggs

Chair: Dr. Pierre D. Mourad
Candidate: Master of Science in Electrical Engineering

3:30 P.M.; DISC 464
Different Brain States are Differentially Responsive to Ultrasonic Stimulation

It is well known that direct, non-invasive, spatially specific ultrasonic stimulation of the brain can activate neural responses, however it is less studied how the brain’s state itself affects the responses. This thesis explores the differential responses to different brain states in mice, particularly the anesthetized brain state as induced by isoflurane and the sedated, awake-like brain state as induced by medetomidine. The electrocorticographic (ECoG) technique was utilized to record responses in the visual cortex (V1), the somatosensory cortex, and the auditory cortex when a flash of light was cast on the retina of the eye and when a burst of pulsed ultrasound was focused on V1. It was found that the responses due to these two stimulation techniques of the same brain state were largely similar. For example, under isoflurane, each stimulation generated slow waves; under medetomidine, they did not. This preliminary result serves to confirm the effects of different brain states regardless of stimulation technique. Differences were discovered, too. For example, it was also found that direct visual stimulation generated stronger neural responses than did ultrasonic stimulation for both brain states. All results presented here are preliminary due to the small sample size but will guide future studies. Taken together, these preliminary results pave the way to further investigation of the similarities and differences of direct ultrasonic stimulation of the cortex and indirect neural stimulation of the cortex via light cast on the retina of the eye, as well as other sensory input such as sound and pinching, when applied to mice experiencing various brain states.

Friday, June 1

Paul Gregory Marsh

Chair: Dr. Hung Cao
Candidate: Master of Science in Electrical Engineering

10:30 A.M.; DISC 464
Flexible pH Sensors for Water Quality and Biomedical Research

Due to mounting global water scarcity and source contamination concerns, significant water monitoring efforts are required, though current data suggests significant gaps in monitoring coverage and a lack of cost effective and versatile sensing devices. A complete device is proposed and demonstrated herein which monitors a water quality indicator of high importance, solution pH. As it happens, this device is also suitable for biomedical applications with minor modifications, so it was designed and tested with both in mind. The device combines the high pH sensitivity and stability of iridium oxide (IrOx) with the efficiency of electrodeposition and conformability and biocompatibility of polyimide substrates; additionally, the device was designed to communicate wirelessly and make use of both Bluetooth-Low-Energy (BLE) transmission and frequency-based load modulation (FM) transmission with inductive power coupling.

The probes were fabricated by traditional lithography and a cyclic voltammetry method using an oxalate-containing solution; evaluation is performed by voltammogram investigation, scanning electron microscopy (SEM), profilometry, electron dispersive x-ray spectroscopy (EDS/EDX), x-ray photoelectron spectroscopy (XPS), and optical and laser microscopy. Reference electrodes were fabricated by application of silver chloride (AgCl) ink. Gold (Au), copper (Cu), and silver (Ag) substrates were evaluated, Cu being discarded as a viable substrate.

Probe performance was characterized in terms of pH sensitivity, sensitivity with respect to surface area, linearity, responPse time, lower limit of detection, cationic selectivity, and response to mechanical stress. Some attempts were made to programmatically and electrically reduce noise and programmatically characterize experimental results via Matlab.

Applicability is demonstrated by both a review of previous packaging work and current wireless schemes. Wireless schemes based around amplitude modulation (AM), frequency modulation (FM), and Bluetooth are demonstrated. FM communication with inductive power coupling is deemed to be the most appropriate for the widest variety of applications.

Finally, future work is discussed in terms of a completed patch design, possible surface material modifications, packaging improvements, and monitoring vehicle concepts.

Back to top

Questions: Please email eegrad@uw.edu

Thesis Candidates
Devon Griggs
Paul Gregory Marsh