**Acknowledgements**

*Fiber Optics - From Fundamentals to Industrial Applications*

cues on the endocytosis and exocytosis process.

accessible through passive observation.

**5. Conclusions**

tacted with each other.

**4. Discussion**

the three cells reached the equilibrium with *γ* = 0.15, 0.1, and 0.12 (**Figure 7c3**). After that, RBCs started to resume their original shapes by turning off the laser at *t* = 9 s (**Figure 7c4–6**). Further, the normalized stress distribution on the RBC surfaces was also investigated, as indicated by the red arrows in **Figure 7e** and **f**. The stress was mainly distributed along the *x*-axis, and the stress direction was toward the outside of cells. Therefore, the RBCs were stretched and further became con-

From the above analysis, it can be seen that the multifunctional trap and manipulation can be conducted with the fiber probe-based optical tweezers. As we know, a precise control of cell behavior was essential in the research of the endocytosis and exocytosis process, especially for nanomedicine injection, intracellular signaling pathway, and pathogenic progress. After cells manipulated in a controlled manner, various microparticles or viruses can be brought into contact with the targeted cells at specific well-defined time points and positions. Meanwhile, the spatiotemporal effect can be quantitatively investigated of different extracellular

Then the potential application and advantages were discussed for fiber probebased tweezers on the endocytosis and exocytosis purpose. As for the nanomedicine injection, the cells can be located at a different distance to the medicine with the assistance of fiber probes, providing a great way to study the diffusion and transportation process. Further, the nanomedicine can be adjusted to approach various sites of the cell membrane. Then, the endocytosis efficiency on the interaction sites can be quantitatively investigated. Meanwhile, various nanomedicines can approach the targeted cell simultaneously with controlled sites, providing an insight into the study of selective phagocytosis progress. While for the intracellular signaling pathway, spatial manipulation will be beneficial to analyze the effect of contact distance on the cell interaction. As we know, the cell can interact with each other through the exchange of soluble signaling molecules or direct cell-cell contact, which can vary in both time and space continuously. Thus, it is of great importance in dynamically adjusting the cell-cell interaction distance and contact sequence, which can be conducted by using the fiber-probe tweezers. Further, the detailed pathway for the intracellular signaling can be individually investigated with the proposed technique. Besides, in the pathogenic progress, the specific infection site can be decided by using fiber probes to manipulate pathogenic bacterium and targeted cell simultaneously. Thus, the dependence of the contact site on the infection performance can be investigated, which opens up the possibility for analyzing pathogenic dynamics not

In this chapter, the fiber probe has been demonstrated to conduct the multifunctional manipulation of cell chains, including the sequential organization, precise regulation, and bidirectional transportation. Besides, the dynamic rotation and deformation of the human red blood cell were also realized using the fiber probes. With the advantage of ease integration, high flexibility, and noninvasive, the proposed technique can provide a great perspective in the investigation of the endocytosis and exocytosis purpose. The targeted cells and pathogenic bacterium can be dynamically manipulated simultaneously, which is anticipated to be useful in

**20**

This work was supported by the National Natural Science Foundation of China (No. 11774135, 11874183, and 61827822), the Tip-top Scientific and Technical Innovative Youth Talents of Guangdong Special Support Program (No. 2015TQ01X267), the Fundamental Research Funds for the Central Universities (No. 21618301), and the PhD Start-up Fund of Natural Science Foundation of Guangdong Province (No. 2018A030310501).
