Micro-/Nano-optical Fiber Microfluidic Sensors
Optical micro-/nanofiber (MNF) microfluidic sensors – the synergistic integration of MNF and microfluidics – provide a number of unique characteristics for enhancing the sensing performance and simplifying the design of microsystems. With diameter close to or below the wavelength of guided light and high index contrast between the MNF and the surrounding, an MNF shows a variety of interesting waveguiding properties, including widely tailorable optical confinement, evanescent fields, and waveguide dispersion. MNF sensor has been attracting increasing research interest due to its possibilities of realizing miniaturized fiber-optic sensors with small footprint, high sensitivity, fast response, high flexibility, and low optical power consumption. Note that most of the MNF sensors used MNFs suspended in air or mounted in a bulky volume flow chamber; thus, surface contamination and environmental factors are likely to affect the stability of these sensors. Microfluidics is the science and technology of systems that process or manipulate small amounts of fluids, using microchannels with dimensions of tens to hundreds of micrometers. The microfluidic chip can provide natural protection of the MNFs, small volume of samples, and new sensing mechanisms. The fusion of MNFs and microfluidics opens a door to the practical application of MNF sensors. This chapter describes the fundamentals of MNFs and microfluidics and reviews recent progress in MNF microfluidic sensors regarding their fabrication, waveguide properties, sensing structures, and sensing applications.