In Situ Quantification the Complex Poisson's Ratio of Single Cells Using a Magnetic-Drive Dynamic Atomic Force Microscopy Approach

In this letter, a dynamic atomic force microscopy approach using a magnetic bead probe (MBP) is presented for in situ quantification of the complex Poisson's ratio of single cells. The MBP is fabricated as a double-bead probe comprising a polystyrene bead and a magnetic bead superimposed thereon. The polystyrene bead is molded into a flat bottom to apply accurate global force to individual cells. The magnetic bead is magnetized at a certain angle to the longitudinal axis of the cantilever, which can simultaneously bend and twist the probe at off-resonant frequencies up to tens of kiloHertz. This allows for the dynamic measurement of viscoelastic properties of a single cell in the directions of shear and stretching, obtaining its complex Poisson's ratio. The performance of the proposed method was tested by measuring the complex Poisson's ratio of individual cells at different excitation frequencies and compression ratios. The experimental results show that the developed method has a wide range of applications for the field of cell mechanics.