Authors: T.H. Fan and A.G. Fedorov
Affilation: Georgia Institute of Technology, United States
Pages: 376 - 379
Keywords: AFM, electrohydrodynamics, biomembranes
In biological applications, AFM imaging needs to be performed in the natural (aqueous) living environment of the cell in order to observe molecular level interactions and biochemical processes in-situ in the electrolyte solution and to avoid the interference due to the capillary adhesion forces. Despite significant advances made in experimental application of AFM in cell imaging, the data interpretation and associated theoretical models are still in its infancy. This is perhaps owing to the overwhelming complexity of the physical/chemical phenomena taking place during an AFM imaging of flexible, electrochemically active biological samples, which includes intimately coupled fluid flow (inside and outside of the cell), dynamics of the cell membrane deformation, and electrodynamics of ionic interactions in the electrolyte and surface double layers. We investigate the electrodynamic effects upon the fluid motion and the surface forces in order to obtain an integrated electrohydrodynamic model of the AFM tip and biomembrane interactions. The model couples the fluid flow, the ion distribution, membrane surface charges, and dynamics of membrane deformation. Simulation results reveal the relative contributions to the force acting on the cell membrane during AFM probing that are due to induced fluid motion and Maxwell electric stresses. The proposed theoretical methodology provides unique insight and quantitative information that cannot be directly measured during the AFM experiment, which are essential for interpretation of the imaging data.