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Novel Capacitive Sensors for Chemical and Physical Monitoring in Microfluidic Devices

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Novel Capacitive Sensors for Chemical and Physical Monitoring in Microfluidic Devices Novel Capacitive Sensors for Chemical and Physical Monitoring in Microfluidic Devices A dissertation presented to the faculty of the Russ College of Engineering and Technology of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Parthiban Rajan May 2019 © 2019 Parthiban Rajan. All Rights Reserved. 2 This dissertation titled Novel Capacitive Sensors for Chemical and Physical Monitoring in Microfluidic Devices by PARTHIBAN RAJAN has been approved for the School of Electrical Engineering and Computer Science and the Russ College of Engineering and Technology by Savas Kaya Professor of Electrical Engineering and Computer Science Dennis Irwin Dean, Russ College of Engineering and Technology 3 Abstract RAJAN, PARTHIBAN, Ph.D., May 2019, Electrical Engineering Novel Capacitive Sensors for Chemical and Physical Monitoring in Microfluidic Devices Director of Dissertation: Savas Kaya Lab-on-a-Chip (LoC) devices integrate the elements of advanced electronics and microfluidic technology to create robust, cost-effective, state-of-the-art chemical, environmental and biomedical analysis platforms to be used for wearable health monitors, analytical monitoring and portable point-of-care diagnostics solutions. Demand in these applications are expected to grow exponentially in next decade and efficient, low-cost capable microfluidics platforms can define the success of this on-going revolution along with the printed electronics (PE) that enhance the capability, affordability and scalability of LoC systems. Key to design of such compact and low-cost LoC systems is the variety, size and capabilities of novel nanosensors. Accordingly, this dissertation aims at fusing the PE and microfluidic technology in creating application- specific novel LOC devices. In particular, the vast prospects of capacitive sensing technology have been comprehensively explored. By altering the printed capacitive design elements, microfluidic design and flow properties, a number of novel nanosensors categorized into capacitance based physical and chemical capacitive sensors have been developed. In this dissertation, the concept of capacitive sensing, with a distinct focus on planar printed interdigitated capacitors (IDC) integrated into microfluidic devices, has been investigated. Initial focus has been on process development for efficient activation of printing surfaces for IDC fabrication and microfluidic integration. Force-spectroscopy via an atomic-force microscopy was used to guide this development work, which has not been explored previously. Together with accompanying software development and 3D printed molds, an efficient platform for sensor enriched microfluidic devices is developed. It is shown that low-cost and scalable capacitors that can be printed on flexible media and glass can be adapted to detect multiple physical and chemical parameters. Starting from an analytical approximation of printed IDC and fully utilizing the dielectric loading effect, novel sensors were designed and developed for a variety of sensing 4 modalities including proximity and motion, temperature, humidity, electro-kinetic flow, ionic concentrations (proton and divalent metal ions such as Zn, Cu, Ni) in unique microfluidic designs. Based on these distinct sensing approaches, novel device arrangements that include cross-shaped IDCs on flexible paper surfaces, or nanogap capacitors with ~10nm electrode gaps have been adapted as effective and suitable sensing elements in future applications. Thus, this research work provides both principle and practical basis for development of highly capable and flexible capacitive sensing platforms in an upcoming era where effective use of computational resources and CMOS compatibility may become the key enabler for environmental, chemical and biomedical monitoring systems. 5 Dedication To Dad, Mom and Bavya. 6 Acknowledgments I would like to thank Dr. Savas Kaya, my mentor, for always backing me up on my journey through this PhD. His suggestions, motivation, training and guidance in both academic and personal life, for the past 8 years has been one of the primary reasons this work has developed into what it is now. I would like to thank Dr. Wojciech Jadwisienczak for being another important part of this PhD journey. Dr.J has been one of the best professors I have worked with. He has been a solid support and inspiration. I would like to thank Dr. Craig Nunemaker, who has been a strong support in making this collaborative work possible. He has always explained patiently about the biological part of this study, constantly motivated me and pushed me towards achieving goals in this research. I would like to thank my committee members, Dr. Avinash Karanth, Dr. Monica Burdick and Dr. David Tees for their support, time and feedback. I am grateful to them for being a part of my PhD committee. This PhD would not have been possible without the love and support from my family. My dad, my hero, Dr. Rajan, my mom Dr. Amaravathy Rajan and sister Dr. Bavya Rajan. I am out of words to express my love and gratitude to them. Next, I would love to thank my brother Shankar Narayanan. The one person who has seen me grow and been with me, supporting me, holding me and pushing me to success my entire life. I would like to thank him for all his guidance and advice in helping me develop all the software tools in this work by training me on the software development part (Thama, thank you da). I would like to thank Akanksha Rohit, for coming into my life, for travelling with me through this journey and being there for me every minute of the day. She has been one of the reasons which helped me stay focused and strong at all stages of my PhD. I would like to thank my brothers Thoshy Felix, Aby Abraham, Jayakrishnan Muraleedharan Nair and Sai Goutham Koya. Thank you for just being there and supporting me every single time and through all sorts of phases in life, all these years. You guys are the best. Next, I would like to thank Jason Wright, my friend, my roommate and one of the most inspiring person I have ever met in life. Thank you, buddy. For all the late-night research talks and support you have given me all these years. I would like to thank Patrick Hanlon, Tianyi Cai, Nicholas Whitticar and Akanksha Rohit for all their help and contributions in this research. Their help definitely made me more productive in achieving results on time. 7 Table of Contents Page Abstract ............................................................................................................................... 3 Dedication ........................................................................................................................... 5 Acknowledgments............................................................................................................... 6 List of Tables .................................................................................................................... 11 List of Figures ................................................................................................................... 12 List of Abbreviations ........................................................................................................ 20 Chapter 1: Introduction ..................................................................................................... 21 1.1 Sensor Integrated Microfluidics – Lab-on-a-Chip .................................................. 21 1.2 Motivation ............................................................................................................... 23 1.3 Sensor Fusion Era.................................................................................................... 24 1.4 Research Goals & Accomplishments ...................................................................... 25 1.4.1 Research Goals ................................................................................................. 25 1.4.2 Accomplishments ............................................................................................. 26 1.5 Dissertation Characteristics & Organization ........................................................... 27 Chapter 2: Background ..................................................................................................... 29 2.1 Nanoscience and Surface Study .............................................................................. 29 2.1.1 Activated Surfaces ............................................................................................ 31 2.2 Lab-on-a-chip (LoC) – Microfluidic Devices ......................................................... 33 2.2.1 Evolution of Microfluidic Devices ................................................................... 34 2.2.2 Types of Microfluidic Devices ......................................................................... 36 2.2.2.1 Traditional Microfluidic Devices .............................................................. 37 2.2.2.2 Paper Microfluidics ................................................................................... 38 2.2.3 Fluid Mechanics in a Microfluidic Channel ..................................................... 40 2.3 Printed Electronics .................................................................................................. 42 2.3.1 Types of Printing .............................................................................................. 43 2.4 Bio & Chemical Sensors ........................................................................................
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