Date of Award

Summer 2025

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Sourav Banerjee

Abstract

The growing prevalence of cyanobacterial blooms and associated cyanotoxins, such as microcystin-LR (MC-LR), presents a significant threat to water quality and public health. Conventional detection methods, including ELISA and PCR, are often time-consuming, expensive, and require trained personnel, limiting their application in field settings. Hence, a miniaturized, quick testing sensor is proposed to circumvent the current sensing challenges for real time, in-situ diagnostics of MC-LR. The proposed high-frequency ultrasonic sensor employs surface acoustic waves (SAW). The sensor was designed using a multi-physics simulation tool to understand wave propagation in the piezoelectric substrate (lithium tantalate) and optimize the design of the electrodes to achieve resonance. Once the design was finalized, the sensors were fabricated to trigger and maintain shear-horizontal Love waves on lithium tantalate wafers. After fabrication, the sensors were functionalized with MC-LR antibodies following a specific, previously established protocol. To evaluate the functionality of the sensors, water samples were collected from stormwater and agricultural ponds in South Carolina. Each of these specimens were then assessed across six sensors with the designed electrodes. For each sample and each sensor, time-domain ultrasonic wave signals were collected at a resonance frequency of 12 MHz at 10-minute intervals after adding the samples. Signals were analyzed using a multi-fidelity feature extraction tool. Results demonstrated an MC-LR concentration-dependent frequency shift with a conservative limit of detection estimated at 5 μg/L. The sensor’s selectivity for MC-LR antigens over unrelated antigens was previously shown. Reproducibility was observed across all biosensors, though variability increased at higher concentrations, possibly due to environmental interference or progressive cyanobacteria lysis. This SAW biosensor shows promise as a rapid and portable tool for MC-LR detection. Future work will focus on sensor miniaturization, packaging refinement, and improved calibration across mid-range concentrations.

Rights

© 2025, Tally Bovender

Download

Share

COinS