Predicting sample heating induced by cantilevers illuminated by intense light beams

• Published in: Results in physics 2022-08, Vol.39, p.105718, Article 105718
• Main Authors: Tremoço, Frederico, Gómez-Varela, Ana I., Miranda, Adelaide, Lopez-Garcia, Martin, Silva, Ana G., De Beule, Pieter A.A.
• Format: Article
• Language: English
• Subjects: Atomic Force Microscopy (AFM); Finite Element Modelling (FEM); Finite-Difference Time Domain (FDTD); Fluorescence Microscopy; Hybrid AFM-Fluorescence Microscopy; Photothermal excitation
• ISSN: 2211-3797; 2211-3797
• DOI: 10.1016/j.rinp.2022.105718

•Temperature rises from material absorption of light beams is predicted using a Finite Element Model.•Temperature increases of cantilevers in liquids at 37 °C is determined for various illumination conditions.•Illuminating cantilevers with a confocal laser beam of 1 mW at 405 nM leads to temperature increases from 5 to 15 °C.•Temperature increase depends on cantilever type, focusing of confocal beam below the cantilever tip and thermal equilibrium distance. Hybrid microscopy based on Atomic Force Microscopy (AFM) and fluorescence microscopy represents a commonplace experimental approach to study cell biology processes in liquid media at physiological temperature. However, many types of experimental artifacts can arise depending on the fluorescence illumination and detection technique utilized. For example, fluorescence excitation light gets absorbed by AFM cantilevers inducing local heating provoking undesirable as well as uncontrollable cantilever deflections. Here we present a numerical modelling approach based on a Finite Element Model (FEM) to predict sample heating in liquid media quantitatively, depending on illumination wavelength, illumination pattern, and cantilever shape and composition. Modelling results indicate substantial local temperature increases in-line with temperature increases derived from experimental cantilever deflections induced by fluorescence excitation light. We predict temperature increases of ∼0.05 – 0.5 °C for wide-field illumination and ∼5 – 15 °C for confocal illumination within the boundary conditions established, which could, for example, induce local protein conformational changes. We conclude that sample heating is an important issue requiring consideration in experimental set-ups involving intense light illumination of AFM cantilevers, especially when conducting single molecule investigations.