High-sensitivity Optofluidic Refractive Index Sensor Based On A Seven-hole Teflon Cladding Fiber

With the continuous development of science and technology,interdisciplinary technologies continue to emerge,and disciplines such as life sciences and biotechnology are no exception.For disciplines such as life sciences,the detection of the content of biological chemicals is essential,which depends on analytical techniques and tools.With the advancement of research,the requirements for measurement technology and tools are constantly increasing.Optical sensors,as a kind of excellent sensor,have the advantages of high sensitivity and fast response speed,and thus are naturally favored by researchers in the field of biochemistry.Microfluidics is a new and emerging technology,and it is an interdisciplinary discipline involving chemistry,fluid physics,new materials,biology and biomedical engineering.Compared with traditional detection technology,microfluidic technology has significant advantages such as less sample usage,fast detection speed,and high functional integration.The cross-fusion of optics and the microfluidic technology has created the optofluidic technology,which combines the advantages of optical sensing and microfluidic technology.Microstructured optical fiber is a major advancement in the field of optical fibers,and has many features that traditional optical fibers do not have.The micro-holes in the fiber are the distinctive features of micro-structured optical fiber,which has a unique advantage in the field of optofluidic technology.The micro-holes can be used as fluid channels to ensure that the light and liquid are in full contact,which provides a new possibility for the development of novel optofluidic sensors.This paper proposes an optical microfluidic refractive index sensor based on seven-hole Teflon cladding fiber,which is suitable for the detection of water-based solutions.The polymer material Teflon is used as the material of the optical fiber cladding,combined with the structure of the seven-hole optical fiber,filled with liquid to form the seven-core optical fiber,and combined with the ordinary single-mode optical fiber to form a mode interferometer sensor.In this paper,the design idea of the sensor is introduced from the selection of fiber material,structure selection and working principle.The multiphysics finite-element method simulation software COMSOL was used to simulate the device.The transmission spectrum of the device and its microfluidic refractive index response were obtained.The influence of the geometric parameters of the seven-hole fiber on the sensitivity of the sensor was analyzed.Finally,the structure was optimized to have a very high sensitivity of24,577 nm/ RIU for liquid refractive index around 1.33.