Development of Sensors for the Improvement of Precision Livestock Farming of Ruminants

Knoepfel, Abbey

Development of Sensors for the Improvement of Precision Livestock Farming of Ruminants

Restricted

Author:: Knoepfel, Abbey
Graduate Program:: Materials Science and Engineering
Degree:: Doctor of Philosophy
Document Type:: Dissertation
Date of Defense:: July 24, 2024
Committee Members:: John Mauro, Program Head/Chair
Shashank Priya, Special Member
Nutifafa Yao Doumon, Major Field Member
Bed Poudel, Chair & Dissertation Advisor
Bo Cheng, Outside Unit & Field Member
James Adair, Major Field Member
Keywords:: Zinc oxide
Biosensor
Gas Sensors
Electrochemical system
Metal oxide semiconductors
Abstract:: Zinc oxide (ZnO) has been widely researched for sensing applications due to its ease of fabrication, unique morphologies and tunable properties. Herein, ZnO-based sensors have been studied for applications ranging from ultraviolet light detectors to greenhouse gas and aqueous volatile fatty acid sensors. The development of ZnO-based wearable ultraviolet light (UV) monitor has been demonstrated. Thin films of a tetrapod ZnO (T-ZnO), ZnO nanoparticles (ZnO-NP), and microparticles (ZnO-MP) were prepared as UV sensors. The sensitivity was studied by exposing the films to UV wavelengths of 365 nm, 302 nm, and 254 nm and measuring the resulting resistance change. T-ZnO films had a stable response upon exposure to both 365 nm and 302 nm light and exhibited the highest sensitivity compared to the ZnO-NP and ZnO-MP films. This was attributed to the porous interconnected network forming a higher number of chemical reaction sites which led to an improved response signal. Methane gas sensors based on ZnO nanorod (ZnO-NR) and T-ZnO morphologies were compared as chemiresistive sensors at lower operating temperatures. The effects of noble metal nanoparticle decoration and thermal or ultraviolet light excitation on sensor performance were also investigated. The catalytic effects of a uniformly dispersed palladium nanoparticle (PdNP) coating were compared with localized palladium and palladium-silver dots (Pddots and Pd-Agdots) deposited onto the surface of the ZnO films. It was determined that there is an upper loading limit for the Pd nanoparticles, above which the sensor response decreases significantly. The T-ZnO films exhibited the highest response to methane at elevated temperatures compared to ZnO-NR films. The Pd¬dots/T-ZnO film had the fastest response and recovery times at both elevated temperatures and under UV excitation, compared to the uniformly dispersed Pd nanoparticles. 3D-printed tetrapod ZnO films were fabricated via a direct ink writing method and the carbon dioxide sensing performance of pristine and surface-decorated films was investigated. The ZnO films were functionalized with carbon nanotubes (CNT) and gold nanoparticles (AuNPs) to evaluate the effects on CO2 sensing. Additionally, the effect of thermal and ultraviolet excitation were studied on the sensor performance. The best response was from the 3D-printed T-ZnO film at ~75 ℃, compared to the Au/T-ZnO and CNT/T-ZnO films. At ambient temperature, the resistance change due to UV excitation dominated over the resistance change upon exposure to CO2. A composite tetrapod ZnO/molecularly imprinted polymer-based sensor for detection of the volatile fatty acid, acetate, is reported. Polypyrrole was selected as it is a biocompatible in low concentrations, conductive polymer that provides a stable surface for the electrochemical reaction to occur. The sensing performance of the composite sensor was compared to molecularly imprinted polymer, nonimprinted polymer, tetrapod ZnO/nonimprinted polymer, and tetrapod ZnO films on a screen-printed carbon electrode utilizing electrochemical measurements. The selectivity was verified with testing in increasing concentrations of propionate, another VFA present in the rumen.

Tools