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Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Biomedical Engineering

Supervisor

Yang, Jun

Abstract

In the recent years, point-of-care (POC) devices are continuously being demanded in the healthcare field due to the advantages of low-cost, easy-to-use, rapid and on-site detection. Among all kinds of POC devices, electrochemical biosensors are superior candidates because of the miniaturization simplicity, fast analysis and high selectivity nature to the sensing analytes. Traditional fabrication method of electrochemical biosensors by drop-casting process suffers from uneven thickness of functionalization layer and low reproducibility. Nowadays, inkjet printing has been a promising technique for biosensor fabrication. The merits, such as precise position, micro-dispensing, minimum contamination, less waste and potentiality for mass production as valuable features of inkjet printing, have attracted significant attention by researchers. However, there are still some issues that need to be addressed to promote inkjet printing technique for the POC applications. The most important problems include: 1. deficient investigation towards the effect of inkjet printing on the sensing element of biosensor, which is critical for the improvement of the sensor performance; 2. inadequate printing strategy for multi-functional layers printing, which is essential for the development of a stable and sensitive biosensor ; 3. lack of demonstration for the construction of inkjet-printed biosensor system towards point-of-care testing, which will be significant for the development of POC devices.

To bridge these gaps, I firstly studied the influence of mechanical stress on the biological materials of enzymes based on the pressure wave propagation mechanism. Then, based on the first enzyme printing study, a reagentless enzyme-based biosensor was fabricated through a novel multi-layer printing strategy. In the end, to demonstrate the inkjet-printed biosensor for point-of-care analyte detection, a smartphone-supported biosensor system was constructed, consisting of a smartphone, an Android APP, a portable potentiostat and a functionalized scree-printed electrode (SPE) via inkjet printing.

In general, the investigation of inkjet printing technique towards fabrication of POC devices opens a door for further research and development of an increasing variety of inkjet-printed POC devices. Through the work presented in this dissertation, I thoroughly investigated the effect of printing on enzymes, and substantially build upon the multi-layer printing strategy and biosensor system for inkjet-printed POC devices. The work in this research paves a way toward creating high performance, low-cost, easy-to-use and rapid POC diagnostic devices.

Summary for Lay Audience

Inkjet printing has not only been widely used in our daily life, but also been applied or demonstrated for point-of-care applications. Although some studies have been done for inkjet-printed biosensors, including the development of printing biomaterials, the optimizations of printing formula and the symbolizations of the sensor configuration, etc., issues still exist. For example, the effect of inkjet printing on the biological materials from the aspect of printing mechanism, printing strategies for multi-functional layers printing or complex sensor structure, and realization of inkjet-printed point-of-care applications are still needed to be addressed.

This thesis investigates the influence of printing parameters on the biological materials of enzymes. The results revealed that it is possible to modulate the enzyme activity through settings of printing parameters. Then, the thesis presents an inkjet-printed reagentless biosensor based on the printing strategy of multi-functional layers for analyte detection. Uniform deposition and enhanced electrochemical performance were achieved by the proposed multi-layer inkjet printing method compared to traditional drop-casting method. A linear response which covers the physiological range of serum phosphate was obtained. The proposed simple, affordable, labor-free and reagentless printing strategy can be easily applied to measure other analytes of interest by simply modulating the components of the ink. Additionally, a smartphone-supported inkjet-printed biosensor system was developed for point-of-care analyte detection. The biosensor system is extremely user-friendly that untrained individuals can easily operate. This developed prototype of biosensor system demonstrates a reliable and reproducible biosensor fabrication route for the reference of other POC applications.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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