Development and application of rough viscoelastic contact models in the first phase of 3D manipulation for biological micro-/nanoparticles by AFM

Bio-particles are usually considered as an elastic material, while it has been proven that these particles such as viruses and cells behave more like viscoelastic materials because of the liquid cytoplasm in cells and also the protein capsid around viruses; thus, this property is not ignorable because it leads to a non-precise prediction in simulations. On the other hand, the surface of these particles is usually considered smooth, while the topography shows asperities on them. In this paper, the viscoelastic contact model along with the asperities’ distribution of the bio-particles is considered near reality. Simulation results reveal that the prediction of the viscoelastic contact models is more precise and closer to the experimental data than the elastic state. Using experimental results and applying their effect, asperities’ radii are obtained and comparison shows that the rough viscoelastic theory is more accurate and closer to the experimental data in comparison with viscoelastic models without asperity. The simulation of the first phase of the manipulation, applying three states of the elastic, the viscoelastic, and the rough viscoelastic in addition to a comparison with similar modes, shows that in the particle’s sliding on the substrate, tip sliding on the particle, and the particle rolling modes, the critical force has the highest magnitudes in the rough viscoelastic, the elastic, and the viscoelastic, respectively. However, results for the critical time are different, i.e., the highest critical times are related to the elastic, the viscoelastic, and the rough viscoelastic states, respectively.