Size-selective sorting of kaolinite micro/nanoflakes via microfluidic filtration for wound hemostasis†

Kaolinite, a natural micro/nano clay material, exhibits remarkable effect on wound hemostasis, yet its efficacy is critically limited by heterogeneous particle sizes. Therefore, sorting based on size differences is essential to improve its performance. However, kaolinite with a layer structure presents challenges in sorting compared to spherical or elliptical materials, and the size distribution ranges continuously from nanometers to micrometers, which poses significant challenges for precise sorting. Hence, we developed a dual-layer microfluidic filtration chip, to enable high-throughput sorting of kaolinite micro/nanoflakes (size from 1.582 to 0.377 μm). The dual-layer filter membrane structure with graded pore sizes enabled selective sorting of kaolinite particles within a specific size range, and the co-flow fluid arrangement was employed to alleviate membrane clogging. The hemostatic properties of kaolinite particles with different sizes were evaluated through in vivo and in vitro experiments, revealing the significant size-dependent effects of kaolinite on wound hemostasis. The mechanism of different sizes of kaolinite in the process of coagulation, especially the effect on platelet activation and coagulation factor activation, provided a theoretical basis for optimizing kaolinite-based hemostatic materials. This work established a scalable microfluidic strategy for precise sorting of sheet nanomaterials and improved the translational potential of kaolinite in emergency wound hemostasis.