Document Type



Doctor of Philosophy (PhD)


Electrical and Computer Engineering

First Advisor's Name

Nezih Pala, Ph.D.

First Advisor's Committee Title

Commitee chair

Second Advisor's Name

Shekhar Bhansali, Ph.D.

Second Advisor's Committee Title

committee member

Third Advisor's Name

Jean Andrian, Ph.D.

Third Advisor's Committee Title

Committee member

Fourth Advisor's Name

Chunlei Wang, Ph.D.

Fourth Advisor's Committee Title

Committee member


ZnO, sonochemistry, biosensor, sweat analysis, flexible platform

Date of Defense



The aim of this research is to develop highly sensitive, flexible, wearable enzymatic and immuno-sensor arrays for continuous and selective sensing of ethanol, lactate, and glucose in human sweat. Human sweat has clinical importance and has been recommended as an early pointer for many health conditions and diseases. Thus, for many health applications, point-of-care non-invasive monitoring of different biomarkers in sweat is ultimately important. The major challenges of the sweat analysis biosensors include selectivity, sensitivity, flexibility, sweat collection, and storage for analysis. In this research, sonochemical synthesis of two-dimensional (2D) Zinc Oxide Nanoflakes (ZnO NFs) and wearable sweat analysis biosensors based on them have been studied. ZnO-NFs with a high surface-to-volume ratio help improve the sensitivity. In electrochemical biosensors, selectivity is attained typically by using antibodies or enzymes. However, binding such biomolecules require a linker layer which introduces an additional resistive path for the electrons and hence adversely affects the sensitivity. With their high isoelectric point, ZnO-NFs do not require a linker layer and can deliver better sensitivity while providing selectivity. Moreover, the well-oriented growth of ZnO nanostructures (NSs) can be achieved through the sonochemical method on arbitrary substrates, including polyethylene terephthalate (PET). These ZnO NSs/Au/PET-based biosensors are biocompatible and flexible. We prepared the flexible sensors that form conformal contact with the skin and minimizes the sweat volume to perform proper sweat analysis for continuous monitoring of the targeted biomarkers.

The research demonstrated highly sensitive, selective lactate, alcohol, and glucose sensors based on sonochemically synthesized ZnO-NFs. Biosensing capabilities of the fabricated sensors were characterized by cyclic voltammetry and electrochemical impedance spectroscopy measurements. The measured sensitivities were found to be significantly higher compared to the conventional sensors based on other electrode materials that require a binding agent. The repeatability measurements showed low relative standard deviation while the shelf-life studies demonstrated that the performance of the proposed sensors was significantly stable over a one-month period.

This platform would allow for non-invasive, continuous monitoring to ensure health and quality of life of patients; early detection of anomalies, developing and monitoring customized treatments, among many other potential health applications, thus saving countless lives.





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