Peak force quantitative nanomechanical mapping mode

AFM images of cellulose- and lignin modified surfaces as well as of different intermediate steps of the modification procedure were obtained using a Dimension Icon Scanning Probe Microscope (Nanoscope V, Bruker, Santa Barbara, CA, USA) equipped with a silicon tip on a silicon nitride cantilever (ScanAsyst-Air, Bruker) with a resonance frequency of 70 kHz and a nominal spring constant of 0.4 N m⁻¹. Spring constant and deflection sensitivity were calibrated prior imaging in the Bruker software. Topography and Peak Force Error images were obtained in Peak Force Quantitative Nanomechanical Mapping Mode (Peak Force QNM®, Bruker) with a scan speed in the range between 0.153 and 0.312 Hz collecting 256 or 512 pixels per line. Image processing as well as the evaluation of height profiles and surface roughness was performed using Gwyddion 2.56 (Nečas and Klapetek 2012 (link)). The raw data was treated with mean plane subtraction and row alignment before the surface roughness was evaluated from at least three image areas (5 × 5 µm).

The surface of both the control and AAF-treated fungal cells was measured using NanoScope V AFM (atomic force microscope) in the Peak-Force Quantitative Nanomechanical Mapping Mode (Bruker, Vecco Instruments Inc., Billerica, MA, USA) and NanoScope 8.15 software. The nominal spring constant of the RTESPA probe (Bruker, Billerica, MA, USA) (silicone tip on the nitride lever) was 40 N/m.