Efficient Single-Cell Mechanical Measurement by Integrating a Cell Arraying Microfluidic Device with Magnetic Tweezer

Cell stiffness is an essential label-free biomarker used to diagnose and sort cells at the single-cell level. Here, we integrated magnetic tweezers on an efficient cell arraying microfluidic device to evaluate the mechanical properties of single cells. Two motion modes under pulsed electromagnetic fields have been proposed for magnetic beads. They were magnetically actuated to approach the measuring cells at a distance in rotation mode and move experimentally with the maximal velocity of 23 μm s-1 under a rotating magnetic field of 45 Hz and 45 mT. In contrast, the magnetic beads were driven at close range in translation mode to approach and apply extrusion pressure on the target cells under a locally constant magnetic field gradient. The simulation results of the fluid field caused by the moving bead revealed the difference distribution in velocity and pressure under two motion modes, proving the rationality of the motion mode setting. Experimentally, Hela cells and C2C12 cells arrayed in the microfluidic device were physically squeezed by magnetic tweezers, and cell stiffness was measured. Compared to the measurement results with AFM, the proposed method used to measure Young's modulus of the cells was thought to be dependable. We envision the proposed on-chip platform integrated with the magnetic tweezer could show a potential application for the efficient and flexible measurement of biomechanical properties in the future.