# A Microfluidic Chip for Single-Cell Capture Based on Stagnation Point Flow and Boundary Effects

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## Abstract

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## 1. Introduction

## 2. Materials and Methods

#### 2.1. Microfluidic Channel Theory with Stagnation Point

#### 2.2. The Combination of the Boundary Effect, Stagnation Point Flow, and Resistance Channel

#### 2.3. Flow Chamber Simulation

#### 2.4. Design and Fabrication of Microfluidic Chip

#### 2.5. Cell Suspension Preparation

^{6}cells/mL. It is noteworthy that the majority of cells exhibited diameters ranging from 8 to 12 μm.

#### 2.6. Construction of Microfluidic Integrated System

## 3. Results

#### 3.1. Single-Cell Capture Experiments

#### 3.2. Stable Capture under Flow Disturbances

## 4. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) RS represents the curve boundary, while ST and TO denote the straight-line boundaries. (

**b**) The capture chamber system mechanism.

**Figure 2.**Flow velocity profile. (

**a**) Meshing diagram. (

**b**) View of capture port. (

**c**) Inlet flow rate of 60 μL/min. (

**d**) Inlet flow rate of 80 μL/min. (

**e**) Inlet flow rate of 120 μL/min.

**Figure 3.**Streamline comparison diagram. (

**a**) Three streamlines with circular capture ports. (

**b**) Three streamlines without circular capture ports.

**Figure 4.**(

**a**–

**c**) Simulation of streamlines with different diameters (${\mathsf{\varphi}}_{1}$ = 15 μm, ${\mathsf{\varphi}}_{2}$ = 20 μm, and ${\mathsf{\varphi}}_{3}$ = 25 μm). (

**d**–

**f**) Simulation of different inlet widths (${\mathrm{W}}_{1}$ = 12 μm, ${\mathrm{W}}_{2}$ = 16 μm, and ${\mathrm{W}}_{3}$ = 20 μm) for capturing microparticles of different diameters (${\mathsf{\varphi}}_{4}$ = 9 μm, ${\mathsf{\varphi}}_{5}$ = 14 μm, and ${\mathsf{\varphi}}_{6}$ = 18 μm). (

**g**–

**i**) Simulation of capture of microparticles of different diameters (${\mathsf{\varphi}}_{7}$ = 8 μm, ${\mathsf{\varphi}}_{8}$ = 10 μm, and ${\mathsf{\varphi}}_{9}$ = 12 μm) with same inlet width (${\mathrm{W}}_{1}$ = 12 μm).

**Figure 5.**(

**a**–

**c**) The design of the PDMS–glass-bonded microfluidic chip. The chip design is delineated as follows: A represents the capture chamber, while B represents the capture microfluidic channel system. The components are labeled as follows: 1—fluid injection inlets, 2—cell suspension inlet channel, 3—upper boundary curve, 4—lower boundary curve, 5—upper straight-line boundary, 6—lower straight-line boundary, 7—stagnation point capture port, 8—upper outlet channel, 9—resistance channel, 10—lower outlet channel, 11—cell suspension outlet channel, and 12—fluid outlet.

**Figure 6.**(

**a**) The experimental schematic diagram of the microfluidic system. (

**b**) The experimental platform construction diagram. The detailed description of the system is as follows: 13—fluid drive systems with cell suspension, 14—waste, 15—microfluidic chips, 16—imaging microscopes, 17—computer display systems.

Parameters | Values |
---|---|

n | 2.5 |

${\mathsf{\theta}}_{1}$ | 3/4π |

Cell diameter | 8~12 μm |

${\mathrm{W}}_{1}$ | 12 μm |

$\mathrm{The}\mathrm{diameter}\mathrm{of}\mathrm{the}\mathrm{capture}\mathrm{port}{\mathsf{\varphi}}_{1}$ | 15 μm |

Length L (x-direction) | 1 mm |

The width of the inlet W (y-direction) | 50 μm |

Height H (z-direction) | 60 μm |

$\mathrm{The}\mathrm{width}\mathrm{of}\mathrm{the}\mathrm{resistance}\mathrm{channel}{\mathrm{W}}_{\mathrm{r}}$ | 5 μm |

The rest of the channel widths | 50 μm |

Inlet flow rate | 60 μL/min, 80 μL/min, and 120 μL/min |

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© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Cheng, L.; Lv, X.; Zhou, W.; Li, H.; Yang, Q.; Chen, X.; Wu, Y.
A Microfluidic Chip for Single-Cell Capture Based on Stagnation Point Flow and Boundary Effects. *Micromachines* **2024**, *15*, 456.
https://doi.org/10.3390/mi15040456

**AMA Style**

Cheng L, Lv X, Zhou W, Li H, Yang Q, Chen X, Wu Y.
A Microfluidic Chip for Single-Cell Capture Based on Stagnation Point Flow and Boundary Effects. *Micromachines*. 2024; 15(4):456.
https://doi.org/10.3390/mi15040456

**Chicago/Turabian Style**

Cheng, Long, Xiao Lv, Wenchao Zhou, Huan Li, Qiushuang Yang, Xing Chen, and Yihui Wu.
2024. "A Microfluidic Chip for Single-Cell Capture Based on Stagnation Point Flow and Boundary Effects" *Micromachines* 15, no. 4: 456.
https://doi.org/10.3390/mi15040456