Plastic and viscoplastic contact mechanics modeling of biological disk-shaped nanoparticles: Human red blood cell

Interactions between materials and components, particularly at the nanoscale, involve contact phenomena that result in force transmission, deformation, and motion. A deeper investigation reveals that such contacts occur not only at the macroscopic level but also at the atomic scale. In this context, atomic force microscope emerges as a powerful tool, enabling precise analysis of these interactions with nanometric resolution. Contrary to the assumptions of classical contact mechanics theories, which often rely on the assumption of purely elastic behavior, this study adopts an innovative approach to explore plastic and viscoplastic behaviors in disk-shaped nanoparticles, especially in biological nanoparticles such as red blood cells. By developing advanced nonlinear models and considering a more realistic disk geometry as a representative of biological nanoparticles, a novel framework is proposed that allows for more accurate prediction of mechanical responses under time-dependent loading conditions. The key innovation of this work lies in integrating advanced theoretical modeling with experimental investigations using atomic force microscope to examine the biomechanical behavior of human red blood cells. Experimental data indicate that red blood cells exhibit a quasi-disk shape with a diameter of 9.19 ± 0.02 μm and an adhesion force of 110 ± 0.2 μN. The viscoplastic CVISC model provided more accurate estimates of indentation depth (520 nm) and contact area (13,500 nm²) compared to classical plastic models (350 nm depth, 9,000 nm² contact area). This research significantly advances the understanding of nanoscale contact mechanics in biological systems and offers valuable insights for biomedical applications.