The rapid pace of industrialization and urbanization has led to increasing concerns about air particulate pollution, which is now a major factor influencing quality of life and public health. Airborne particulate matter not only harms the respiratory system but also acts as a carrier for various pollutants. Long-term exposure to particulate pollution significantly raises the risk of respiratory diseases, cardiovascular issues, and even cancer. Furthermore, the effect of particles on human health is linked to their size, with smaller particles posing a greater risk. Therefore, we aim to design a T-type optical particle separation (TOPS) chip based on optical flow control technology to sort particles of different sizes. This research is crucial for advancing our understanding of the sources, transmission, and transformation mechanisms of atmospheric aerosol particles, as well as for developing effective prevention and control measures.

We investigate the behavior analysis and experimental validation of aerosol particles based on TOPS technology. First, in the sorting microchannel, the particle motion is simplified as a motion under a constant force field, considering both radiation and fluid drag forces. We derive a formula for the constant scattering force on spherical particles, which leads to the particle motion control equation. From this, the formula for the offset distance is obtained. A dimensionless parameter, S, is introduced, defined as the ratio of the offset distance to the characteristic width of the TOPS chip, which is used to describe particle behavior in TOPS and provides a theoretical basis for the chip’s preliminary design. Next, a physical model of TOPS is constructed using COMSOL software. The chip channel structure, medium, flow velocity, and boundary conditions are defined, and the transient solver is used to compute the movement trajectories and offset distances of particles of different sizes, which validates the effectiveness of the dimensionless parameter S in particle sorting. Finally, an experimental platform consisting of TOPS, an inlet module, a laser module, and an observation module is constructed. Experiments are conducted using polystyrene microspheres of various sizes under defined flow velocities and laser parameters. The experimental results are compared with COMSOL simulations to analyze the relative error in offset distances for particles of different sizes, which validates the effectiveness and practicality of the dimensionless parameter S and the TOPS system.

We address the limitations of the single-channel design in traditional cross-type optical particle separation (COPS) technology by proposing TOPS for the separation and collection of micron and submicron particles. The chip features an additional collection channel above the laser interaction zone, which enables the separation and collection of particles of varying sizes (Fig. 5). Moreover, this simple geometric design facilitates theoretical analysis and numerical simulation during the design and modeling process. It aids in predicting and optimizing fluid behavior and particle manipulation within the chip. Additionally, the chip can be integrated with various detection technologies, thus enabling an integrated approach for sample separation, processing, and detection. This integration enhances analytical efficiency and accuracy while reducing sample loss and cross-contamination. We also introduce the innovative dimensionless parameter S, which characterizes the movement of particles of different sizes within the microfluidic unit. Simulation results indicate that using the S value as a criterion accurately predicts the movement behavior of particles of various sizes within the TOPS system. Particles with an S value greater than 1 can be effectively separated, whereas those with an S value less than 1 cannot (Fig. 3). The calculation of the S value allows for the determination of particle trajectories, thereby providing a theoretical basis for the preliminary design of the separation chip. In experimental validation, particles of 2, 5, and 15 μm with different S values are introduced, and their position shifts under laser radiation force are observed (Fig. 9). The results show good agreement between the experimental displacement distances and the simulation results, with relative errors of 8.76%, 4.03%, and 8.83%, respectively (Fig. 10). These results fully validate the effectiveness of the S value in characterizing particle motion and the sorting process.

We introduce a T-type optical particle separation chip designed for particle separation and collection. A dimensionless parameter, S, is introduced to characterize the movement behavior of particulate matter in the channels of the microfluidic unit. The dimensionless parameter S for different particle sizes is calculated, and the movement trajectories of particulate matter in the chip are simulated using COMSOL software. The simulation results show that S governs the particle movement within TOPS: when S>1, particles enter the sorting channel; otherwise, they flow out through the main channel. An experimental platform is built to verify the effect of laser radiation force on the position shift of polystyrene microspheres. The experimental results indicate that the displacement distances for particles with diameters of 2, 5, and 15 μm are 10.5, 26.3, and 106.5 μm, respectively, with relative errors compared to the simulations of 8.76%, 4.03%, and 8.83%. These results validate the effectiveness of the dimensionless parameter S in particle sorting and preliminarily confirm the practicality of the TOPS system, providing crucial experimental and theoretical support for future research.