System identification of biological cells by atomic force microscopy

Biological cells are living organisms which are not only complex, but also considered as life's building blocks. The mechanical properties of biological cells play an essential role in disease diagnostics and treatment. This paper presents a system identification technique for atomic force microscopy characterisation of biological cells. A lumped spring-damper system model combined with the cantilever dynamics, tip geometry and sample force is developed to describe the cantilever-cell interaction. Based on this, a parameter estimator is developed to identify cell mechanical properties in real time. Further, the proposed technique is also integrated with nonlinear finite element modelling to simulate and analysis the cantilever-cell mechanical interaction. Simulation and experimental results demonstrate that the cell mechanical properties identified by the proposed technique matches the measured from atomic force microscopy experimental data. The proposed technique can also be used for online mechanical identification of other micro/nano elastic materials.