PAR Wuzhou SONG To my parents, to whom I owe what I am, to my sisters I could ever have had, to my teachers and friends, Many thanks! Acknowledge First of all, I would like to thank my thesis adviser Prof. Demetri Psaltis for giving me the opportunity to pursue research in his group. He can always motivate my research interest and strongly support my research activity. I also appreciate his valuable input in many aspects of science, life and human interaction. Absolutely my study in Switzerland

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... is my precious experience in all my life. Meanwhile, many thanks go to all my colleagues in our lab, particularly to Dr. Andreas Vasdekis who gave me much guidance at beginning on the optofluidic dye laser projects, eventually we have built a deep friendship through our numeric discussions and arguments. Our lab is a big harmonic group; we often exchanged our different opinions, helped each other and we have shared a fruitful time in the past 4 years. I am grateful to CMI staffs for their patient and assistance in teaching me and helping to solve many technical issues. I am also grateful to Dr. Catana Andre from the Technology Transfer Office (SRI EPFL) who gave me lots of substantial support to file the patent and make an elegant demo for it. He also helped us to build a close relationship with our industry partner in order to commercialize the patent. Thanks to Mr. Charles Dubout who is a PhD candidate in computer science. He helped me to develop software for the demo kit regarding the patent. I appreciate the help from Prof. Jürgen Brugger and Prof. Martinus Gijs who supported my application of SNSF fellowship. I am also grateful to many other professors and staff in EPFL who have taught me and helped me. In addition, I'd like to express my thanks to all of my friends; I will cherish all the happiness forever that we have shared in the past. Finally, my gratitude and love go to my family, for their deep love, silent care and consistent inspiration on me. Abstract The term of optofluidics defines an emergent research field that combines microfluidics and optics. In many lab-on-a-chip applications, these two technologies are used in combining the microfluidics for sample delivery and optics for sensing and controlling. Optofluidic represents the implementation of optics in microfluidic platform that produces an unprecedented level of integration. Moreover, optofluidic devices are easily and highly reconfigurable, which can be a significant advantage to the traditional solid optical components. As an elastomer, PDMS (polydimethylsiloxane) is one of the most popular materials in microfluidics. It exhibits excellent elasticity, bio-compatibility and optical transparence. Most microfluidic chips are made of PDMS using soft lithography. And multi-layer soft lithography has enabled large-scale integration of monolithic microfluidic valves and pumps on a single chip. Thus to develop the optofluidic elements within PDMS microfluidic chip is one of the most promising and desirable ways towards further integration of optofluidic and microfluidic functions together for more complex lab-on-a-chip applications. During my doctoral research, we worked on a batch of optofluidic devices that are based on PDMS material and soft lithography. They include the optofluidic dye lasers, optofluidic interferometer, optofluidic switch, and optofluidic differential spectroscopy. Such optofluidic elements provide a broad spectrum of toolbox with different optical functions that can be easily into many other PDMS microfluidic chips. They are compatible to the conventional PDMS microfluidic chip in terms of fabrication, operation and control. And they could provide important optical functions in lab-on-a-chip systems. For examples, the optofluidic dye laser can be integrated as a widely tunable coherent source for chip-scale fluorescence spectroscopy or cell flow cytometry. The optofluidic membrane interferometer can be easily integrated into conventional PDMS microfluidic chip for multi-site pressure and flow monitoring with high precision. Optofluidic switch can compose a reconfigurable optical circuit on single microfluidic chip. Optofluidic differential spectroscopy provides a simple and highly sensitive method for inline measuring of solution concentration. Among these devices, we have also developed and summarized a series of novel optofluidic turning methods that are controlled by pneumatic actuation. These simple turning methods also take the advantages of high precision and reliability. In addition to these elastomeric optofluidic devices, we are also working on several other optofluidic projects. In the last chapter of this thesis, we will give a partial preview of these works and also our perspective on the nano-optofluidics which represents a new trend of optofluidics.