Fig. 2: Nanoscale characterization of the micropatterning of holey carbon EM grids using photomolecular adsorption.

a Schematic of an AFM cantilever scanning the surface of adsorbed gelatin surrounded by PLL-g-PEG. b A 2-step digital mask photopatterning method was used to create 5 µm squares with and without protein (upper panels). AFM probe scans clearly show squares with and without protein, which could be quantified with 0.5 nm resolution (lower panels). Representative images from triplicate measurements. c Custom ECM (Oregon green gelatin) 45 µm × 45 µm square pattern surrounded by PLL-g-PEG on the holey carbon film of a gold mesh grid imaged by the scanning electron microscope beam (at 2 kV) of the dual beam cryo-FIB instrument in cryo-SEM imaging mode. Representative image out of three repeats. The pattern is clearly visible as a depression, consistent with the atomic force microscopy results shown in b. d 2 nm thick slice of a representative tomogram of a patterned region. The fluorescence image of the ECM coating applied to the pattern was precisely overlaid on the cryo-ET image and the border between pattern and bio-passivated area was manually traced (white line). Scale bars 20 µm (c), 200 nm (d).