**3.2 Optofluidic organization and transport of the cell chain**

Except for the precise regulation, the organized cell chain can also be dynamically transported with an optofluidic strategy, by implanting a large-tapered-angle fiber probe (LTAP) into the microfluidic technique. As shown in **Figure 4a**, when an *E. coli* cell was delivered toward the LTAP tip by the flow, it will suffer from the opposite optical scattering force. The cell kept slowing down until it was trapped stably. Then, *E. colis* were trapped one after another, and a cell chain was organized along the optical axis of LTAP (i.e., *x*-axis). Further, the distance between the probe tip and cell chain (*D*) can be dynamically adjusted so that the cell chain can be under bidirectional transportation.

Then, the experiment was conducted to demonstrate the bidirectional transportation of the cell chain (**Figure 4b**). The flow velocity was fixed at *V* = 10 μm/s, while the laser power (*P*) was set to be 75 mW. At *t* = 0 s, a chain consisted of eight cells was organized in front of LTAP at *D* = 27 μm. After *P* decreased from 75 to 60, 45, 30, and 15 mW, the chain was transported toward LTAP with *D* varied from 27 to 22, 17, 10, and 0 μm (**Figure 4b2–6**), respectively. Further, the cell chain can be pushed away from the probe tip by increasing the laser power. As shown in **Figure 4c**, with *P* increased from 15 to 30, 45, 60, 75, and 90 mW (**Figure 4b2–6**), the cell chain was continuously pushed away from the LTAP tip with *D* varied from 0 to 10.3, 16.5, 21.4, 26.6 and 32.9 μm, respectively.

In addition, spherical eukaryotes (e.g., yeast cells) can also be organized and transported with the proposed optofluidic technique (**Figure 5a**). The flow velocity and laser power were set to be *V* = 20 μm/s and *P* = 40 mW, respectively. First, four yeast cells were trapped and then arranged into a cell chain at *t* = 0 s. Then the cell chain was transported toward the LTAP tip with *V* increased to be 32 μm/s. Meanwhile, *D* was decreased from 23 to 18 μm (**Figure 5a3**). By varying *V* to 17 and 13 μm/s, the cell chain was further transported with *D* changed to 25 and 27.5 μm, respectively. Further, the optofluidic transportation of human red blood cells (RBCs) was also conducted to investigate the potential application in the blood diagnose. The flow velocity was fixed at 10 μm/s along the −*x* direction. Notably, an LTAP tip with a more flat facet was fabricated to ensure the manipulation stability for the larger RBCs (**Figure 5b**). After the laser beam was injected into LTAP (*P* = 40 mW), two RBCs were transported along the −*x* direction by the flow and then trapped by the LTAP (**Figure 5b1**). At *t* = 4, 8, and 12 s, the cell number of the RBC chain was increased from 2 to 3, 4, and 5, respectively. After organizing cell chain, it can be transported by adjusting the laser power. As shown in **Figure 5c**, a cell chain was organized in front of the probe tip. With *P* increased from 30 to 55 mW, *D* was also varied from 8.2 to 21.2 and 35.2 μm, as shown in **Figure 5c2** and **c3**, respectively. After that, the chain

**17**

**Figure 5.**

**Figure 4.**

*increasing the laser power [39].*

*(a) Schematic of optofluidic organization and transport of cell chain. (b) The cell chain was transported toward the LTAP tip by decreasing the laser power. (c) The cell chain was pushed away from LTAP tip by* 

*(a) Optofluidic transport of yeast cell chain under various flow velocities. (b) Optofluidic organization of RBC* 

*chain consisted of five red blood cells. (c) Optofluidic transport of the RBC chain [39].*

*Optical Fiber Probe-Based Manipulation of Cells DOI: http://dx.doi.org/10.5772/intechopen.81423*

*Optical Fiber Probe-Based Manipulation of Cells DOI: http://dx.doi.org/10.5772/intechopen.81423*

*Fiber Optics - From Fundamentals to Industrial Applications*

stably trapped and shifted with FP 2.

under bidirectional transportation.

0 to 10.3, 16.5, 21.4, 26.6 and 32.9 μm, respectively.

*θ* = 0°. **Figure 3b** shows the torques exerted on *E. colis* after turning off the laser in FP 2. The torques were positive and negative in the region I (80° < *θ* < 130°) and II (130° < *θ* < 180°), respectively. At *θ* = 130°, the torque exerted on *E. coli* 3 was zero so that *E. coli* 3 will be stably trapped and oriented along the axial direction of FP 1. Moreover, during the shift process of FP 2, the optical force and torque exerted on *E. coli* 3 were calculated as shown in **Figure 3c**. During the shift process, the optical force was negative while the torque remained to be zero, indicating *E. coli* 3 will be

Further, the numerical simulations show that the method can be used for the regulation of cell chains consisted of cells with different sizes and shapes (e.g., spherical). After the FPs incorporated into lap-on-chip platforms, the presented regulation method is expected to enable a new opportunity for the investigation of

Except for the precise regulation, the organized cell chain can also be dynamically transported with an optofluidic strategy, by implanting a large-tapered-angle fiber probe (LTAP) into the microfluidic technique. As shown in **Figure 4a**, when an *E. coli* cell was delivered toward the LTAP tip by the flow, it will suffer from the opposite optical scattering force. The cell kept slowing down until it was trapped stably. Then, *E. colis* were trapped one after another, and a cell chain was organized along the optical axis of LTAP (i.e., *x*-axis). Further, the distance between the probe tip and cell chain (*D*) can be dynamically adjusted so that the cell chain can be

Then, the experiment was conducted to demonstrate the bidirectional transportation of the cell chain (**Figure 4b**). The flow velocity was fixed at *V* = 10 μm/s, while the laser power (*P*) was set to be 75 mW. At *t* = 0 s, a chain consisted of eight cells was organized in front of LTAP at *D* = 27 μm. After *P* decreased from 75 to 60, 45, 30, and 15 mW, the chain was transported toward LTAP with *D* varied from 27 to 22, 17, 10, and 0 μm (**Figure 4b2–6**), respectively. Further, the cell chain can be pushed away from the probe tip by increasing the laser power. As shown in **Figure 4c**, with *P* increased from 15 to 30, 45, 60, 75, and 90 mW (**Figure 4b2–6**), the cell chain was continuously pushed away from the LTAP tip with *D* varied from

In addition, spherical eukaryotes (e.g., yeast cells) can also be organized and transported with the proposed optofluidic technique (**Figure 5a**). The flow velocity and laser power were set to be *V* = 20 μm/s and *P* = 40 mW, respectively. First, four yeast cells were trapped and then arranged into a cell chain at *t* = 0 s. Then the cell chain was transported toward the LTAP tip with *V* increased to be 32 μm/s. Meanwhile, *D* was decreased from 23 to 18 μm (**Figure 5a3**). By varying *V* to 17 and 13 μm/s, the cell chain was further transported with *D* changed to 25 and 27.5 μm, respectively. Further, the optofluidic transportation of human red blood cells (RBCs) was also conducted to investigate the potential application in the blood diagnose. The flow velocity was fixed at 10 μm/s along the −*x* direction. Notably, an LTAP tip with a more flat facet was fabricated to ensure the manipulation stability for the larger RBCs (**Figure 5b**). After the laser beam was injected into LTAP (*P* = 40 mW), two RBCs were transported along the −*x* direction by the flow and then trapped by the LTAP (**Figure 5b1**). At *t* = 4, 8, and 12 s, the cell number of the RBC chain was increased from 2 to 3, 4, and 5, respectively. After organizing cell chain, it can be transported by adjusting the laser power. As shown in **Figure 5c**, a cell chain was organized in front of the probe tip. With *P* increased from 30 to 55 mW, *D* was also varied from 8.2 to 21.2 and 35.2 μm, as shown in **Figure 5c2** and **c3**, respectively. After that, the chain

cell growth, intercellular singling pathway, and pathogenic processes.

**3.2 Optofluidic organization and transport of the cell chain**

**16**

#### **Figure 4.**

*(a) Schematic of optofluidic organization and transport of cell chain. (b) The cell chain was transported toward the LTAP tip by decreasing the laser power. (c) The cell chain was pushed away from LTAP tip by increasing the laser power [39].*

#### **Figure 5.**

*(a) Optofluidic transport of yeast cell chain under various flow velocities. (b) Optofluidic organization of RBC chain consisted of five red blood cells. (c) Optofluidic transport of the RBC chain [39].*

kept stationary with *D* remained at 35.2 μm (**Figure 5c4**). Besides, the distance can also be changed by adjusting the flow velocity, which was similar to the case of yeast cell chain. These results demonstrated that various cell chains can be dynamically transported by adjusting the laser power or flow velocity.
