Fiber Optofluidic Manipulation And Sensing Based On Optical Force And Photothermal Effects

Optofluidics is a hot field in the world,which integrates photonic technology and microfluidics.It has a wide application prospect in new photonic devices,biological sensing and health diagnosis,environmental monitoring,etc.The physical mechanism based on the interaction between photon and microfluid?power,heat,light and sound,etc.?is the basic scientific problems of optofluidics.Optofluidics can achieve manipulation,sensing,display and many other applications based on the photo physical effects like optical force,photothermal effect,etc.The optical force can achieve non-contact capture and precise control of micro-/nano-meter sized objects.The photothermal effect can serve for accurately detecting a variety of physical and chemical properties of the surrounding environment or a single object.The research of photo physical effect in existing microfluidics mainly uses lens to couple the light into microfluidic system,with the disadvantages of large volume and poor integration.Moreover,traditional optical manipulation and optical tweezers technology generally use lens with large numerical aperture,which is difficult to operate and has a small adjustable range.Optical fiber has the characteristics of low transmission loss,good flexibility and small size.The optical microfluidic technology based on optical fiber structure has the advantages including small size,high integration,handy operation and precise performance.Therefore,the fiber optofluidics is a platform for the study of the photo physical effects in the microfluidic flow.In sensing applications,the traditional optical fiber sensing technology mainly adopts the solid state of special optical fiber structures,which is difficult to manufacture and has poor reconfiguration.This paper proposed the optical fiber manipulation and sensing technology based on optical force and photothermal effects,with the advantages of simple structure and fabraction process,low cost and easy reconfiguration.This paper uses the photo physical effects as the point of penetration,and achieves manipulation,sensing,and microbubble array with fiber tip based on optical force and photothermal effect.Based on the optical force,this technology achieves optical manipulation with the help of the fluidity of microfluidic system.The manipulated object can be contiously adjusted along the light transmission direction in a wide range.The flow rate sensing in a large dynamic measurement range can also be achieved using the the manipulated object as a movable sensing element.Based on the photothermal effect,this technology achieves sensing for temperature,flow rate,and concentration by using the reconfigurable microbubble probe structure on the optical fiber tip.A controllable microbubble array is also demonstrated.The main research contents of this paper are as follows:?1?Establishing the theoretical model of optical fiber optic effect,and simulating the optical field distributions of flat end of single-mode fiber,multimode graded index fiber,tapered and graded index multimode fiber.We analyzed the characteristics of optical force based on the three fiber structures,and found the influence factors on light field distribution.It is convenient for the experimental study and parameter optimization of fiber manipulation and sensing technology..?2?Proposing two controllable fiber optical manipulations based on optical force with Fabry-Perot cavity and stress.The controllable optical manipulation with Fabry-Perot cavity uses a graded index fiber taper to focous the light.It can adjust the manipulation length by caivity length,or the balance of optical force and flow rate.The maximum manipulation length is up to 177mm.The controllable optical manipulation with stress can adjust the manipulation length by stretching the fiber,or adjusting the balance of optical force and flow rate.It can focus the light with self-focusing effect of graded index fiber,and achieve the maximum manipulation length of 1314.1mm.?3?Proposing fiber optofluidic flow rate sensing with the help of optical manipulation based on optical force.Comparing with graded index multimode fiber,the single mode optical fiber further reduces the cost of the device and the difficulty of operation,easy to mass production.Besides,the the stability and range of sensing has been improved.The dual-mode detection method further improves the flow rate sensing performance,and realizes the flow sensing with a detection limit of 10 nL/min and a range of 10 nL/min to 100 000 nL/min.?4?Proposing the fiber optofluidic sensing with the reconfigurable microbubble structure,and the controllable microbubble array based on the photothermal effect.The fiber optofluidic sensing uses the optical absorption materials on the fiber tip to improve the photothermal effects,and form a reconfigurable microbubble on the fiber tip.The temperature,flow rate,and concentration of microfluidics were detected by monitoring the growth rate of microbubble.With the carbon nanotube film,the sucrose sensing of 0.5 wt%-50.0 wt%,and the hydrogen peroxide sensing of 10^-5 M-1 M has been achieved.The maximum sensitivities are up to 5.1?m/%and 93.84?m/?M,separately.Further,the controllable optical fiber microbubble array technology is proposed.This method can produce and arrange microbubble array with low laser power.This paper proposed and demonstrated the fiber optofluidic manipulation and sensing based on optical force and photothermal effects.It provides a new research idea for the study of the interaction of photon and microfluid,and also provides a basic support for the biochemical application based on optical microfluidic technology.