Polymer Optical Biosensor Based On Laser Direct Writing

As one of the key components of medical testing,biochips,and wearable devices,optical biosensors have been widely used in immune detection,online analysis,and even in vivo analysis due to their advantages of non-destructive operation,wide application targets,and fast response speed.Among the sensing mechanisms,optical waveguide devices possess label-free detection,high sensitivity,and easy integration,which have become a research hotspot in future biosensing research.In previous studies,the fabrication of optical waveguide devices relied on the existed semiconductor photolithography processing,which was unable to realize threedimensional structures and lack of flexibility and biocompatibility.Therefore,we developed the optical waveguide biosensors fabricated by two-photon polymerization laser direct writing technology.The prepared optical waveguide structures have micron-scale accuracy and can detect biological targets such as glucose and sodium chloride.The specific research content includes:Firstly,the design scheme of polymer optical waveguide sensors and their coupler with optical fiber was established.With the effective refractive index method,the guided mode's characteristic equation of the rectangular waveguide was established and the positive correlation between the effective refractive index and the clad refractive index was found,and the cross-sectional dimension of the optical waveguide should not be smaller than 4 ?m*6 ?m(height * width)to improve the sensing sensitivity and maintain the integrity of the optical mode field in the curved structure.In addition,hemispherical couplers have been developed for the stable coupling of optical waveguide structures with commercial optical fibers.Secondly,the laser direct writing scheme of polymer optical waveguide structure based on two-photon polymerization was established.The influence of scanning speed,exposure intensity,processing path,and other optimal parameters on the obtained structure was studied,and the optimal processing parameters were confirmed.A variety of optical waveguide structures with good morphology,controllable size,and good stability were obtained.The coupling efficiency of the hemispherical coupler was tested through the straight waveguide structure,and the ability to guide light was verified through the curved waveguide structure.Lastly,a kind of optical waveguide sensor based on the change of refractive index was developed.A refractive index sensor based on a tilted waveguide structure was fabricated to detect two common biological targets,glucose and sodium chloride,respectively.It not only verified the linear relationship between transmittance and target concentration,but also verified the influence of the cross-sectional area and deflection angle of the structure on the sensitivity of the sensor.Above all,this study has demonstrated that the laser direct writing technology of twophoton polymerization could be used in the construction of optical waveguide biosensors.Bending waveguides,MZI waveguides,tilted waveguides,and ring resonator waveguides have been achieved and present its properties to achieve rapid sensing and measurement of the refractive index of the solution.These results would promote the integration and functionalization of polymer optical waveguide sensing structures and promote the development of biosensors.