title: Numerical study of the hydrodynamic drag force in atomic force microscopy measurements undertaken in fluids.
abstract: When atomic force microscopy (AFM) is employed for in vivo study of immersed biological samples, the fluid medium presents additional complexities, not least of which is the hydrodynamic drag force due to viscous friction of the cantilever with the liquid. This force should be considered when interpreting experimental results and any calculated material properties. In this paper, a numerical model is presented to study the influence of the drag force on experimental data obtained from AFM measurements using computational fluid dynamics (CFD) simulation. The model provides quantification of the drag force in AFM measurements of soft specimens in fluids. The numerical predictions were compared with experimental data obtained using AFM with a V-shaped cantilever fitted with a pyramidal tip. Tip velocities ranging from 1.05 to 105 μm/s were employed in water, polyethylene glycol and glycerol with the platform approaching from a distance of 6000 nm. The model was also compared with an existing analytical model. Good agreement was observed between numerical results, experiments and analytical predictions. Accurate predictions were obtained without the need for extrapolation of experimental data. In addition, the model can be employed over the range of tip geometries and velocities typically utilized in AFM measurements.
authors: Centro de Nanociencias y Micro-Nanotecnología del IPN, Unidad Profesional Adolfo López Mateos, Calle Luis Enrique Erro s/n, Col. Zacatenco, C.P. 07738, México, D.F., Mexico; School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M60 1QD, UK. Electronic address: jmendezm@ipn.mx.
authors: J V
authors: JV
authors: Méndez-Méndez
authors: School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M60 1QD, UK.
authors: M T
authors: MT
authors: Alonso-Rasgado
authors: Manchester Institute of Biotechnology, School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester M1 7DN, UK.
authors: E Correia
authors: EC
authors: Faria
authors: School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia.
authors: E A
authors: EA
authors: Flores-Johnson
authors: Manchester Institute of Biotechnology, School of Chemical Engineering and Analytical Science, The University of Manchester, Manchester M1 7DN, UK.
authors: R D
authors: RD
authors: Snook
keywords: Atomic force microscopy (AFM); Computational fluid dynamics (CFD); Hydrodynamic drag force; Numerical simulation