Contactless calibration of microchanneled AFM cantilevers for fluidic force microscopy

Titelangaben

Sittl, Sebastian ; Helfricht, Nicolas ; Papastavrou, Georg:
Contactless calibration of microchanneled AFM cantilevers for fluidic force microscopy.
In: VIEW : Illuminating Wellness. Bd. 5 (2024) Heft 1 . - 20230063.
ISSN 2688-268X
DOI: https://doi.org/10.1002/VIW.20230063

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Abstract

Atomic force microscopy (AFM) is an analytical technique that is increasingly utilized to determine interaction forces on the colloidal and cellular level. Fluidic force microscopy, also called FluidFM, became a vital tool for biomedical applications. FluidFM combines AFM and nanofluidics by means of a microchanneled cantilever that bears an aperture instead of a tip at its end. Thereby, single colloids or cells can be aspirated and immobilized to the cantilever, for example, to determine adhesion forces. To allow for quantitative measurements, the so-called (inverse) optical lever sensitivity (OLS and InvOLS, respectively) must be determined, which is typically done in a separate set of measurements on a hard, non-deformable substrate. Here, we present a different approach that is entirely based on hydrodynamic principles and does make use of the internal microfluidic channel of a FluidFM-cantilever and an external pressure control. Thereby, a contact-free calibration of the (inverse) optical lever sensitivity (InvOLS) becomes possible in under a minute. A quantitative model based on the thrust equation, which is well-known in avionics, and finite element simulations, is provided to describe the deflection of the cantilever as a function of the externally applied pressure. A comparison between the classical and the here-presented hydrodynamic method demonstrates equal accuracy.