Nanoliter-based microfluidic biosensor integrated with electrochemical sensor device

다국어 초록 (Multilingual Abstract)

This thesis presents the fabrication and characteristics of a nanoliter droplet-based biosensor chip integrated with a microfluidic system and multiple three-gold electrochemical sensors. This biosensor chip is capable of generating a nanoliter scale droplet and trapping this droplet in a designated microfluidic capture region (Ø600 µm). Combining this microfluidic system for generating and handling nanoliter droplets with small electrochemical sensor may realize a biosensor which can reduce the consumption of precious reagent substantially. Moreover, the microfluidic channel is also capable of on-chip reagent mixing thus further reducing cross contamination from reagent handling. In addition, multiple droplet capture regions equipped with electrochemical sensors enable analyzing multiple nanoliter droplet samples in one biosensor chip which simplifies the experimental process and reduces reagents amount or/and the detection time. The designed and fabricated microfluidic biosensor chip has multiple capture regions equipped with three-gold microelectrode electrochemical sensors and the testing results showed that it could precisely encapsulate 25 nL of nanoliter droplet reagent in each capture region. By further incorporating on-chip microvalve, fluid flow direction in the microfluidic chip can be easily controlled and manipulated. The fabricated microfluidic biosensor chip was applied into an enzyme activity assay using a nanoliter droplet in order to prove this chip can be used in real applications. Compared to other glucose oxidase (GOx) enzyme sensors, the proposed microfluidic biosensor chip required only a minimum of 25 nL of reagent. Even with this small volume of reagent, this proposed biosensor chip is capable of performing electrochemical test effectively and responding to various glucose concentrations with the lowest detectable glucose concentration of 3.125 mM. The result shows that this nanoliter droplet-based biosensor chip has a very promising potential to be improvised and applied as detection tools in various medical fields, particularly when only nanoliter volume of reagent is available or should be used for various reasons. The total dimension of the microfluidic biosensor chip is only 58 mm x 78 mm making it suitable for point-of-care design and consideration.

목차 (Table of Contents)

• ABSTRACT i
• LIST OF FIGURES vi
• LIST OF TABLES xv
• CHAPTER 1: INTRODUCTION 1
• 1.1 What is Microfluidics? 1
• 1.1.1 Continuous-Flow Microfluidics 2
• 1.1.2 Droplet-Based Microfluidics 3
• 1.2 Nanoliter-Droplet Microfluidics 4
• 1.3 Various Analytical Detection Techniques 6
• 1.4 Electrochemical Detection 9
• 1.5 Application in Enzyme Activity Study 11
• 1.6 Summary 12
• 1.7 Thesis Layout 12
• CHAPTER 2: MICROFLUIDIC CHANNEL 15
• 2.1 Introduction 15
• 2.2 Reagents and Materials 16
• 2.3 Instrumentation and Equipment 17
• 2.4 Fabrication of PDMS Microfluidic Channel 17
• 2.5 PDMS Microfluidic Flow Channel Components 20
• 2.5.1 Design of Droplet Formation 21
• 2.5.2 Design of Droplet Capture 22
• 2.6 Experimental of Droplet Generation 23
• 2.7 Result of Droplet Generation 24
• 2.7.1 Result of Droplet Formation 25
• 2.7.2 Result of Droplet Capture 28
• 2.8 Surfactant and Oil as Carrier Fluids 32
• 2.9 Surface Treatment and Surface Modification 34
• 2.10 Summary 36
• CHAPTER 3: MICROFLUIDIC MICROMIXER 37
• 3.1 Introduction 37
• 3.2 Reagents and Materials 39
• 3.3 Instrumentation and Equipment 40
• 3.4 PDMS Microfluidic Micromixer 40
• 3.4.1 Design of Microfluidic Micromixer 42
• 3.5 Experimental of Microfluidic Micromixer 43
• 3.6 Result of Microfluidic Micromixer 44
• 3.7 Summary 47
• CHAPTER 4: MICROVALVE 48
• 4.1 Introduction 48
• 4.2 Reagents and Materials 49
• 4.3 Instrumentation and Equipment 49
• 4.4 Fabrication of PDMS Microvalve 50
• 4.5 Fabrication of PDMS Microvalve-Microfluidic 53
• 4.6 PDMS Microvalve-Microfluidic 56
• 4.6.1 Design of Microvalve 58
• 4.7 Experimental of Fluidic Flow Control 60
• 4.8 Results of Fluidic Flow Control with Microvalve 60
• 4.9 Summary 64
• CHAPTER 5: MULTI THREE-GOLD MICROELECTRODE 65
• 5.1 Introduction 65
• 5.2 Reagents and Materials 65
• 5.3 Instrumentation and Equipment 66
• 5.4 Fabrication of Multi Three-Gold Microelectrode 66
• 5.5 Fabrication of Microfluidic Biosensor Chip 69
• 5.6 Multi Three-Gold Microelectrode Components 71
• 5.7 Microfluidic Biosensor Chip Components 73
• 5.7.1 Design of Electrochemical Detection 74
• 5.8 Experimental of Electrochemical Detection 75
• 5.9 Results of Electrochemical Detection 76
• 5.10 Summary 79
• CHAPTER 6: APPLICATION OF GLUCOSE OXIDASE ENZYME ACTIVITY STUDY 80
• 6.1 Introduction 80
• 6.2 Reagents and Materials 81
• 6.3 Instrumentation and Equipment 81
• 6.4 Fabrication and Preparation of GOx 81
• 6.5 GOx Enzyme Activity 82
• 6.6 Experimental of Enzyme Activity 84
• 6.7 Results of Multiple Droplet Capture and Multi Sensing 87
• 6.8 Results of Glucose Oxidase Enzyme Activity Study 94
• 6.8.1 Linear Sweep Voltammetry 94
• 6.8.2 Amperometry 96
• 6.9 Summary 96
• CHAPTER 7: CONCLUSIONS 98
• REFERENCES 101