Tunable three-dimensional elasto-inertial focusing of particles and cells in the ultrastretchable microchannel

Microfluidic cytometry is an emerging technology for single-cell analysis and offers rich biochemical information about cells. Three-dimensional focusing of cells is a key function for microfluidic cytometry. However, the existing microfluidic chips have fixed geometries and are designed for specific cells, limiting the applicability of microfluidic cytometry. In this work, we develop the ultrastretchable microchannel for size-tunable three-dimensional elasto-inertial focusing of particles and cells. This channel can be modulated by stretching the chip, enabling the focusing of particles and cells with a wide range in sizes. The focusing performance of this ultrastretchable channel is characterized experimentally at different particle sizes, flow rates, polyethylene oxide concentrations, and stretch ratios, showing the great capability in three-dimensional focusing of particles. Finally, the applicability of our ultrastretchable microchannel to biological cells is verified by three-dimensional focusing of yeast cells and fibroblast cells (3T3 cells). The ultrastretchable microchannel is easy for mass production and can be integrated with optical sensing modules for downstream single-cell imaging and analysis.