(Dr. Andrei Federov, advisor)

"Fluid Mechanics and Ion Transport in Imaging of Biological Membranes Using AFM-Integrated Scanning Electrochemical Microscopy"

Abstract

An integrated atomic force (AFM) and scanning electrochemical (SECM) microscope is a new instrument that provides a unique opportunity to study cell communication processes in-situ with sufficient spatial and temporal resolutions. One of the main challenges in AFM-SECM experiments lies in data interpretation. Indeed, the state-of-art approaches for analysis of AFM experiments considerably simplify the physical/chemical processes taking place during imaging of biological cells (for example, the deformation of the cell membrane, the fluid motion, and the electric migration effects in the electrolyte are often neglected). In the SECM of flexible fluid-like biological membranes, deconvolution of topological and electrochemical information is always a challenge since the electric current is the feedback signal that depends on the electrode-to-sample separation distance and multi-ion transport effects.
This thesis will establish a theoretical foundation and computational tools to analyze the transport phenomena and cell biomechanics associated with AFM-SECM imaging of biological cells. In particular, it will address several issues that has never been analyzed before, including: (1) the effect of fluid mechanics of the inner and outer cellular fluids and the cell membrane deformation during an AFM tapping mode probing process will be quantified, (2) the effect of the charge double layer at the cell membrane surface on the AFM tip-membrane interactions will be assessed in a physiological system under conditions of local electrochemical equilibrium, (3) fundamentals of non-equilibrium ion transport across the flexible biological membrane will be investigated by modeling of SECM current response, and (4) the boundary integral solution methodology will be extended to simulation of a complex multiphysics problem, such as AFM-SECM imaging of biological specimens.