Optoelectronic Tweezers Micro-Well System for Highly Efficient Single-Cell Trapping, Dynamic Sorting, and Retrieval

Optical sorting: past, present and future

Optical sorting combines optical tweezers with diverse techniques, including optical spectrum, artificial intelligence (AI) and immunoassay, to endow unprecedented capabilities in particle sorting. In comparison to other methods such as microfluidics, acoustics and electrophoresis, optical sorting offers appreciable advantages in nanoscale precision, high resolution, non-invasiveness, and is becoming increasingly indispensable in fields of biophysics, chemistry, and materials science. This review aims to offer a comprehensive overview of the history, development, and perspectives of various optical sorting techniques, categorised as passive and active sorting methods. To begin, we elucidate the fundamental physics and attributes of both conventional and exotic optical forces. We then explore sorting capabilities of active optical sorting, which fuses optical tweezers with a diversity of techniques, including Raman spectroscopy and machine learning. Afterwards, we reveal the essential roles played by deterministic light fields, configured with lens systems or metasurfaces, in the passive sorting of particles based on their varying sizes and shapes, sorting resolutions and speeds. We conclude with our vision of the most promising and futuristic directions, including AI-facilitated ultrafast and bio-morphology-selective sorting. It can be envisioned that optical sorting will inevitably become a revolutionary tool in scientific research and practical biomedical applications.

Microfluidic Chip for Cell Fusion and In Situ Separation of Fused Cells

Electrofusion is an effective method for fusing two cells into a hybrid cell, and this method is widely used in immunomedicine, gene recombination, and other related fields. Although cell pairing and electrofusion techniques have been accomplished with microfluidic devices, the purification and isolation of fused cells remains limited due to expensive instruments and complex operations. In this study, through the optimization of microstructures and electrodes combined with buffer substitution, the entire cell electrofusion process, including cell capture, pairing, electrofusion, and precise separation of the targeted fused cells, is achieved on a single chip. The proposed microfluidic cell electrofusion achieves an efficiency of 80.2 ± 7.5%, and targeted cell separation could be conveniently performed through the strategic activation of individual microelectrodes via negative dielectrophoresis, which ensures accurate release of the fused cells with an efficiency of up to 91.1 ± 5.1%. Furthermore, the survival rates of the cells after electrofusion and release are as high as 94.7 ± 0.6% and 91.7 ± 1.2%, respectively. These results demonstrate that the in situ cell electrofusion and separation process did not affect the cell activity. This chip offers integrated multifunctional manipulation of cells in situ, and can be applied to multiple fields in the future, thus laying the foundation for the field of precise single-cell analysis.