Seena Ph.D Thesis_Final Version_29Oct2011

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Transcript of Seena Ph.D Thesis_Final Version_29Oct2011

Polymer Nanomechanical Cantilever Sensors with Novel Electrical Transduction Schemes for Bio/chemical Sensing Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy by Seena.V (Roll Number: 06407601) Supervisors: Prof. V. Ramgopal Rao Prof. Soumyo Mukherji Department of Electrical Engineering INDIAN INSTITUTE OF TECHNOLOGY, BOMBAY 2011 ii Dedicated to My Parents, In-Laws, Husband Dr. Pradeep Kumar, Son Jagdeep and Brother Sanith A humble offering at the lotus feet of my AMMA, Sadguru Sri Mata Amritanandamayi Devi iv Declaration I declare that this written submission represents my ideas in my own words and where others ideas or words have been included, I have adequately cited and referenced the original sources. I also declare that I have adhered to all principles of academic honesty and integrity and have not misrepresented or fabricated or falsified any idea/data/fact/source in my submission. I understand that any violation of the above will be cause for disciplinary action by the institute and can evoke penal action from the sources which have thus not been properly cited or from whom proper permission has not been taken when needed. _________________________________ Seena.V Roll No. 06407601 Date: ________________ \ v Indian Institute of Technology Bombay, India Certificate of Course Work This is to certify that Seena.V was admitted to the candidacy of the Ph.D. degree in the Department of Electrical Engineering after successfully completing all the courses required for the Ph.D. degree program. The details of the coursework done are given below. S. No. Course No. Course Name Credits 1 EE 661 Physical Electronics 6 2 EE 669 VLSI Technology 6 3 EE 671 VLSI Design 6 4 EES 801 Seminar 4 5 HS 699 Communication and Presentation Skills 4 6 EE 672 Physics of Transistors 6 7 EE 620 Microelectronics Lab 6 8 BM 658 Biomedical Microsystems 6 9 EE 724 Nanoelectronics 6 10 MM 669 Mechanical Behaviour of Thin Films 6 11 EE 661 Electronic System Design 6 IIT Bombay Dy. Registrar (Academic) Date: vi Acknowledgments I am highly indebted to my guide Prof. V. Ramgopal Rao, for his constant and valuable guidance at every stage of my work. It was through him that I got inducted to the field of microelectronics. His positive approach in solving problems, and the faith and confidence he has shown on me, motivated me in pursuing my Ph.D. I am grateful to my co-guide Prof. Soumyo Mukherji for his support and timely suggestions in the course of my research work. He has been a constant source of encouragement throughout my Ph.D. I am extremely thankful to him for the guidance he gave me in writing thesis. I owe my sincere gratitude to Prof. Prita Pant for all the guidance and support she gave me in characterizing the mechanical behavior of films and devices. I also owe my sincere thanks Prof. Prakash.R.Apte for boosting my interest in systematically analyzing and solving problems and for the valuable suggestions he gave me during the final stages of my work. My sincere acknowledgement to Prof. Rudra Pratap, Department of Mechanical Engineering, Indian Institute of Science, and Bangalore, India for the LDV characterization experiments on polymer cantilevers and microaccelerometers performed at IISC under his guidance. I express my sincere thanks to my Research progress Committee members Prof. D.Bahadur and Prof. Anilkumar for their acceptance to be in my panel and having spent their valuable time in reviewing my annual progress reports and for providing valuable inputs. I take this opportunity to acknowledge the partial funding received from the Department of Information Technology, Government of India, through the Centre of Excellence in Nanoelectronics. I sincerely thank Tata Consultancy Services, India for the fellowship for my doctoral studies at IIT Bombay. I sincerely acknowledge Prof. Dinesh. K. Sharma for his support through TCS fellowship scheme. I hereby thank the staff and students of Centre for Excellence in Nanoelectronics for their constant and efficient services. I thank Prof. Pinto for his support in terms of guidance vii for staff and students of CEN in maintaining the fabrication facility. I wish to acknowledge the Nanoindenter facility and Central SPM facility of IIT Bombay. I acknowledge to the project support received from Department of Science and Technology, Govt. of India for developing the explosive sensors using microcantilevers. The project helped in bringing focus to my research in developing low cost polymer microcantilevers for explosive sensing. I thank Dr Pramod Soni from TBRL India for providing the calibrated TNT vapour generator for the explosive vapour experiments. I would also like to thank my colleagues Prajakta, Prasenjit, Anukool, Avil, Ravishankar, Nidhi, Akash, Ramesh, Rohit, Harshil, Bijesh and Nikhil for all kinds of co-operation, support and discussions during experimental work. I appreciate Prajakta for her contributions to microaccelerometer developments. My special thanks to Ramesh for all his help for pentacene depositions using his optimized parameters. I thank Karuna for all her support during nanoindentation experiments. I take this opportunity to thank my friends, Naveen, Rajashree and Harshil for proof reading my thesis. I owe my sincere thanks to Naveen who has been very sincere in helping me by discussing the results. My special thanks to Shweta Deora who has been a wonderful friend right from beginning of my Ph.D. I would like to thank Ms. Tanvi Shelatkar, Ms. Arti, Mr. Santosh, Ms. Madhu, Ms. Vaishali and others in EE Dept., IRCC and administrative staff of IIT Bombay for their timely help in various official matters. I am indebted to my in-laws, who came to support me and my husband during really hard times of our Ph.D. I am ever indebted to my parents, who have always been my source of motivation for studies throughout my life. I render my appreciation to my mother and mother in-law who did their best at different times to support me by taking care of my son. My heartfelt appreciation is extended to my husband, Dr. Pradeep Kumar, who motivated me to join for Ph.D. and constantly supported me in stressful times during my research work. With his experiences in doing Ph.D. at IIT Bombay, he could guide me in many aspects throughout my Ph.D. My son, Master Jagdeep, has been a perennial source of enthusiasm and cheer at all times through his constant inquiries and innocent playful tricks. Seena.V viii Abstract Bio/chemical sensing applications in the areas such as environmental monitoring, healthcare, biomedical technology, clinical analysis and food processing demand fast, hand-held, easy to use, inexpensive and highly sensitive methods for detection of very low levels of chemical or biological substances. The demand for miniaturized high throughput sensors supported by advancements in micro electro mechanical systems (MEMS) and nanotechnology had led to the development of simple, versatile and promising class of sensors known as nanomechanical cantilever based bio/chemical sensors. The nanomechanical cantilever based bio/chemical sensors translate molecular interactions into nanomechanical motions that can be measured by different external (optical) and integrated transduction (electrical) techniques. Self-sensing microcantilevers with integrated electrical transduction mechanism overcome the practical limitation with optical microcantilevers pertaining to the field deployment of sensors. The conventional microcantilever sensors are mostly silicon-based with their design and performances limited by their high stiffness structures. Polymers such as SU-8, on the other hand have a much lower Youngs modulus compared to silicon based materials which can be exploited for achieving improvement in sensitivity. The cost of fabrication of polymer devices are known to be much lower compared to conventional silicon microfabrication processes. This research work focuses on the development of ultra-sensitive and cost effective polymer nanomechanical cantilever sensors with novel integrated electrical transduction schemes for bio/chemical sensing applications. The first part of this research work aimed at the development of an optimized and highly sensitive SU-8 nanomechanical cantilever bio/chemical sensor with embedded polymer nanocomposite of SU-8 and Carbon Black (CB) as the piezoresistive layer. The optimization targeted improving its electrical, mechanical and transduction characteristics. An optimum concentration of CB in SU-8 in the range of 89 vol. % was arrived at by performing systematic mechanical and electrical characterizations of the SU-8/CB nanocomposite. Mechanical characterization of SU-8/CB nanocomposite thin