Development of capillary-driven microfludic biosensors for food safety and quality assurance

• Main Author: He, Fei
• Language: ENG
• Published: ScholarWorks@UMass Amherst 2014
• Subjects: Food Science
• Online Access: https://scholarworks.umass.edu/dissertations/AAI3615418

Rapid detection technologies with high sensitivity and selectivity for pathogenic bacteria are critical in food safety and quality assurance. Traditional laboratory benchtop techniques (i.e. culture and colony counting) are time consuming and require complex sample handling. Microfluidics-based Lab-on-a-Chip (LOC) systems offer a detection alternative where all detection steps are on one portable miniaturized device. The miniaturization of rapid foodborne pathogen detection at a low cost is especially ideal for resource-limited settings or for field-use. The goal of this study was to develop a disposable miniaturized microfluidic device for on-site pathogen detection. Capillary-driven microfluidics have been introduced in this study. Compared to traditional microfluidics which rely on external devices for operation, our capillary-driven biosensors are self-priming microfluidics in which fluid flowing is actuated by surface wetting. Polymer substrates are used instead of standard silicon-or glass- based materials, due to the ease of microfabrication and their low cost for disposable applications. Two fabrication methods for polymeric microfluidic chips were developed. A plastic replication technique by hot embossing was developed in order to produce plastic prototypes from a master made from copper and photoresist (SU-8). The second rapid prototyping method included laser ablation and adhesives-bonding was developed. Electronic components have been developed using inkjet-printing techniques, due to their low cost and ease of design. The inkjet-printed silver and gold electrodes have been used in enzyme-based electrochemical biosensors in this study. The On-chip Electrowetting (EW) Valve concept was incorporated, for the sequential delivery of reagents to the reaction site in a miniaturized capillary-driven microfluidic biosensor. The valve could be actuated at a low voltage (4.5 V) and was realized on various substrates. Bacteriophage-based detection is used for pathogenic bacteria, due to the fact that phages can be extremely host-specific and phage-based detection allows the differentiation between live and dead bacteria. Immunomagnetic separation (IMS) was used for sample pre-incubation and rapid separation. As a result, different capillary-driven microfluidic platforms have been developed for various applications, such as chemiluminescence detection for nucleic acid target, colorimetric immunoassay as well as electrochemical detection of T7 bacteriophage.