Date of Award

Spring 5-25-2019

Document Type


Degree Name

Doctor of Philosophy (PhD)


Molecular Science and Nanotechnology

First Advisor

Leland W. Weiss


Hydrogen sulfide (H2S) is a colorless gas with a characteristic foul odor of a rotten egg. In the last two decades, H2S has been elevated from the toxic gas to a ubiquitous gas transmitter with numerous physiological functions. H2S is known to regulate numerous disease states including inflammation, cancer, cardiovascular, neurological, and gastrointestinal diseases. H2S detection is important for application that ranges from environmental to biomedical. This work reports fabrication, characterization, and development of H2S sensor integrated Lab-on-a-Chip (LOAC) device for point of care application.

The goal of this project is to detect all forms of H2S present in the plasma using a H2S sensor integrated LOAC device. The initial research examines the material test for LOAC device fabrication including a membrane test for H2S diffusion. Contact angles are measured on various potential substrates including different poly (dimethylsiloxaneethylene oxide polymeric) (PEO-b PDMS)/Polydimethylsiloxane (PDMS) mix. Various bonding techniques and their bonding strengths are reported. The LOAC device consists of three distinct layers with specific purposes, and a three-electrode setup. It operates with pH dependent liberation and trapping from samples introduced to the device. The first layer, the releasing layer, consists of a releasing chamber for the liberation of H2S. The second layer, a silicone membrane, is where gas diffuses from the sample layer to the third layer. The third layer, the trapping layer, is integrated with the electrode to determine the concentration of H2S.

The LOAC device uses an electrochemical detection method. Cyclic Voltammetry (CV) is used to investigate electrocatalytic oxidation of H2S. First, electrode performances are tested on the cell vial to establish suitability for subsequent LOAC incorporation. Common metal electrodes are compared with Boron Doped Ultra Nano Crystalline Diamond (BDUNCD) electrode, and Screen-printed electrodes (SPEs). The range of detection, detection limit, and sensitivity of the electrodes are characterized.

In conclusion, a proof of concept of an electrochemical sensing of H2S in a LOAC device is reported. Beta chips demonstrate that all form of sulfide transfer is possible. The first generation LOAC device transfer data indicated that 15% sulfide detected into the trapping chamber in a reproducible manner at 20 minutes. Furthermore, a 3D printed second generation LOAC device integrated with the disposable SPE is fabricated. The second generation LOAC device is portable, robust and can easily be fabricated. Transfer data indicated that 10% sulfide detected into the trapping chamber in a reproducible manner at 20 minutes. The H2S sensor integrated LOAC device shows a huge advantage over conventional techniques.