Research On The Application Of Optical Film In Optothermal Manipulation

Optical tweezers are a method of trapping or manipulating particles based on optical force.Due to their advantages of real-time manipulation,non-contact and no mechanical damage,optical tweezers have been widely used in the fields of microbial molecules,dispersion systems,and cell detection.However,with the rapid development of emerging field,conventional optical tweezers have limitations in long-range transportation and manipulation of target objects,and cannot manipulate many biological objects.Various types of novel tweezers have been developed to address this limitation of conventional optical tweezers,such as optothermal manipulation.In this paper,we discussed the optothermal effects of dielectric one-dimensional photonic crystals and gold thin film,as well as their applications in manipulating and assembling of micrometer-sized particles or biological cells.The main research works and conclusions are as following:1.Fabrication and characterization of one-dimensional photonic crystals.The dielectric multilayers are fabricated via plasma enhanced chemical vapor deposition,the thickness and refractive index of the multilayer layer were analyzed by a leak radiation microscope,which proved that the sample satisfied with the experimental requirements.2.Multifunctional optothermal manipulation of colloidal particles is realized using the optothermal effect of one-dimensional photonic crystal.The particles are guided along the direction of the propagating evanescent waves inside the illumination region,and the migration speed of particles is polarization and incidence angle dependent.Besides,it was found for the first time that the internal mode of one-dimensional photonic crystals would generate significant thermal convection.Under the combined action of optical force and thermal convection flow,large scale assembly and removal of particles can be achieved.This method does not require special structures to be fabricated,and have the advantages of low cost,reusable and strong practicability.3.It is proposed for the first time that the optothermal effect of one-dimensional photonic crystal can be applied to the optothermal manipulation of cells and particles,which expands the application field of one-dimensional photonic crystal.Firstly,we simulated the optothermal effect of focused waves by the finite element method,which including long-ranged flow-induced force,local thermophoresis force and short-ranged optical force.Based on the theoretical calculation,the focused Bloch surface waves are excited efficiently by ring-shaped laser beam with an azimuthal polarization.The interference field of excited Bloch surface waves forms a virtual optical probe at the center,we demonstrated controllable assembly of many yeast cells as well as E.coli cells.The optofluidic manipulation with the all-dielectric 1DPC platform opens a new way for long-range transportation,sorting,and self-assembly of biological cells,promoting potential applications in biomedical sciences,such as biofilm development,quorum sensing,and antimicrobial resistance.4.Due to the high efficiency of optothermal conversion of gold films,bubbles and Marangoni convection are induced on the surface using low-power focused laser.In addition,numerical simulations were performed to calculate the influencing factors of bubble assembly,which are consistent with the experimental observations and then further justify the feasibility of the proposed method.Proving that it a general selfassembly methodology,from medium particles,nanowires,algae to metal particles.This method has the characteristics of functional integration and strong practicability,which can be applied to micro-nano scale patterning.