Study On Multi-functional Capillary Optical Fiber Tweezer

As an excellent micro-manipulation technique,optical tweezers have gradually become a powerful research tool in fields such as life sciences and interface physics since it was first proposed by Askin in the 1970s,after half a century of development.Among the various branches of optical tweezers research,fiber optic tweezers have unparalleled advantages in manipulation flexibility due to the unique compact structure of optical fibers.Like other types of optical tweezers,these mechanisms depend not only on direct momentum transfer between particles and incident light waves,but also on the combined action of optical forces and other external forces.In addition,as the application scenarios of fiber optic tweezers continue to expand,more and more manipulated objects are demanding higher manipulation functionality of fiber optic tweezers.Therefore,the study of functional fiber optic tweezers devices is increasingly favored by researchers.However,the research on functional fiber optic tweezers devices puts higher demands on the structure and even the working mechanism of fiber optic tweezers,especially the challenging task of integrating different optical manipulation methods into a single fiber optic tweezers.In response to this,this paper conducted research on functional composite capillary fiber optic tweezers devices,and proposed and demonstrated two new types of multi-functional capillary optical fiber tweezers,COFT and TCM-COFT.The specific work is as follows:The COFT,which stands for Capillary Optical Fiber Tweezer,is inspired by the integration of the structurally reconstructed functional device on a single optical fiber,a COFT prepared by cascading a single-mode fiber and a capillary fiber is designed based on the structurally reconstructed device.Compared to conventional optical fiber tweezers,COFT breaks the directional limitation of optical potential wells and expands the spatial range of optical potential wells,extending the optical manipulation range from the top of the fiber end to the surface near the fiber end.By using a coreless fiber formed by melting and fusion of SMF and COF,as well as a tapered air cavity,high-order modes are excited and a hollow beam is formed in the tubular cladding of the capillary fiber.The semi-ellipsoid fiber end designed for COFT is used to converge the hollow beam,achieving continuous multiple potential wells for capturing yeast cells and a transient field for transporting yeast cells on the fiber end surface.Experimental results show that COFT can capture multiple yeast cells simultaneously,and the maximum transport length and speed achievable are greater than 150μm and 10μm/s,respectively.Simulation results indicate that the continuous optical potential wells constructed by COFT have good well stiffness,with a range of 10-40 p N·μm^-1·W^-1.COFT greatly extends the manipulation region of optical potential wells and can guide and capture yeast cells distributed over the entire fiber end surface.In addition,COFT greatly enhances the optical capture performance of yeast cells,providing a new tool for the study of biological cells in the microscale realm,with potential applications in targeted drug delivery,cell dynamics analysis,and microfluidic chip driving,among other fields.The TCM-COFT,or Thermocapillary Migration-Capillary Optical Fiber Tweezer,is inspired by the fusion of multi-domain technologies,TCM-COFT was designed based on Light-induced thermal capillary migration to realize different manipulations on polystyrene microsphere chains and yeast cells.By constructing a tubular light field near the droplet gas-liquid interface using TCM-COFT,and using the temperature gradient induced by the outgoing light field near the gas-liquid interface,thermal capillary migration is induced near the droplet gas-liquid interface.The fluid drag induced by thermal capillary migration acts in conjunction with optical forces to manipulate micro-particles of different media.Experimental demonstrations have proven that TCM-COFT can capture a series of polystyrene particles in the far field and manipulate yeast cells in the near field.It is worth mentioning that the stable emission of tubular light field by TCM-COFT provides sufficient transverse optical gradient force,which can stably confine the manipulated micro-particles on the optical axis,providing a guarantee for subsequent manipulation of micro-particles along the optical axis.TCM-COFT combines optical forces with other external forces,expands the usage mode and practical performance of optical tweezers technology,and provides a new tool for the research of micro and nano-scale objects with optical tweezers technology.It is hoped that TCM-COFT can be applied in cutting-edge research fields such as the study of surface properties of colloidal particles such as O/W and W/O,the generation of simulated cell microreactors,and liquid-liquid phase separation.Overall,this work describes in detail the different working mechanisms of the two capillary optical fiber tweezers and verifies the multi-functional reusability through experimental simulation,providing a new successful case for the development of multi-functional integrated optical fiber tweezers.