Study On Fiber Optical Tweezers: Cell Capture Characteristics And Detection Methods

With advantages of non-contact, small size, easy operation and other characteristics, fiber optical tweezers can be used to capture, select, manipulate micro and nano particles, and has a wide range of applications in biology, medicine and related fields. In this paper, cell capture characteristics and cell detection methods of single fiber optical tweezers and dual fiber optical tweezers are studied.This paper presents a novel single-fiber optical tweezers based on a graded multimode fiber. The light field and the gradient force distribution near the tip of the probe are numerically calculated. The effects of cell shape parameters on capture are investigated. Compared with other types of fiber taper, the simulation results show that by optimizing the length of the multimode fiber taper, the gradient force may be four times higher than that of the single-mode optical fiber probe with the same shape. As is verified, a graded multi-mode fiber tip, produced by the experimental chemical etching, successfully captures the polystyrene beads and yeast cells stablely. The trapping force is also calculated. It is observed that when the probe moves to manipulate the optical fiber, making the particles in a horizontal or vertical direction slightly deviate from the equilibrium position, the trapping force pulls the particles quickly return to the equilibrium position. In that, the feasibility of such a single fiber optical tweezers and capture of particles is proved with good results. Due to its special structure, such a fiber optical tweezers, compared to single-mode fiber optical tweezers, has a longer capture distance and intensity. The requirements on the surface roughness are also not high.In terms of dual-fiber optical tweezers, the paper explores a method of combination of a fiber optic interferometer sensing and dual fiber optical tweezers. The method has advantages of low cost, high accuracy and ease of integration. Through analyzing the output spectrums of the fiber Fabry-Perot, the method can accurately achieve the cell diameter, refractive index, cell deformation, and some related parameters. It solves the problem that an ordinary microscope can not accurately observe and measure the particle size. The experimental optical system is built. The yeast cells and red blood cells are investiged to demonstrate feasibility of this approach. Because the Young’s modulus of cancer cells is larger compared to normal cells, the method provides a new way for the detection of cancer cells.