High-throughput sheathless focusing and sorting of flexible microalgae in spiral-coupled contraction-expansion channels.

Haematococcus pluvialis (H. pluvialis) is a critical natural source of astaxanthin, recognized for its potent antioxidant capacity, anti-inflammatory properties, and ability to suppress the proliferation of breast and skin cancer cells. The size difference between microalgae such as Chlorella vulgaris (C. vulgaris) and Haematococcus pluvialis (H. pluvialis), coupled with their high research value, makes size-based separation of microalgae essential for efficient extraction of valuable species and advancing directed algal evolution. In this study, we introduce an innovative method utilizing microfluidic devices that integrate spiral channels with contraction-expansion channels. We systematically examine how variables such as flow rate, cell concentration, cell size, and three distinct coupling configurations impact cell sorting. Our results highlight that each coupling configuration of the spiral and contraction-expansion channels exerts unique control over sorting performance, offering promising new approaches for optimizing microchannel design.