Scm pit

A diluted solution containing amyloid fibrils was dropped onto a freshly cleaved mica surface and then rinsed with distilled water or acidic solution three times, followed by nitrogen-based drying. AFM images of amyloid fibrils were obtained in the tapping mode of AFM using a diving board-shaped cantilever tip (TESP, Bruker). For KPFM imaging, the diluted solution was dropped onto a silicon substrate. KPFM imaging was performed using a conductive cantilever tip (SCM-PIT, Bruker). The details of KPFM imaging are reported in our previous works42 43 44 (link). The AFM and KPFM images of amyloid fibrils were analyzed using the Nanoscope Analysis software (Bruker).

The surface topography of the photopolymer after EHDL was examined by AFM in the tapping mode (Multimode, Veeco). To measure the surface topography and potential, we also configured the AFM in the SKPM mode. Antimony (n) doped Si tips (TESPA-V2, spring constant 42 N m^–1, resonance frequency of 320 kHz) and Pt/Ir coated tips (SCM-PIT, spring constant 2.8 N m^–1, resonance frequency of 75 kHz) were purchased from Bruker. The lift height and the amplitude set-point were set to be 100 nm and 0.28 V, respectively.

The PM samples were deposited on highly doped silicon under ambient conditions for the EFM measurements. The topographic images and EFM phase were measured on a scanning probe microscopic system (Bruker Dimension Icon, Santa Barbara, CA, USA) with a conductive tip in a two pass tapping mode (Figure 1). For each scan line, topographic information was obtained in the first pass, and then the tip was lifted to a given constant height of 20 nm above the sample surface and biased a DC voltage V_tip in the second pass. The cantilever was mechanically driven on resonance, and the phase shift of the cantilever oscillation was measured as a function of the tip position. Conducting Pr/Ir coated silicon tips (SCM-PIT, Bruker, Santa Barbara, CA, USA) with a resonance frequency of about 70 kHz were used; the spring constant of the probe was calibrated to be 4.2 N/m in the imaging.

The KPFM test is performed in lift mode along a line between two electrodes to obtain the surface potential data, as shown in Figure 2a. In the first scan, the height profile of the sample was recorded. In the second scan, the cantilever was lifted up to 90 nm, and scanned the surface potential by following the particular line which previously measured the height profile. The scanning rate was 0.1 Hz. In this frequency, it gives enough time to the feedback system to respond appropriately to the changes in height and surface potential so that a better resolution with the minimum noise level can be obtained [45 (link)]. Additionally, a sufficiently flat surface was required to improve lateral resolution. Platinum–iridium-coated conductive probes (SCM-PIT, Bruker) were used. Figure 2b shows the local topography of the test sample using an optical microscope. The environmental humidity is controlled to be about 1ppm to avoid the effect of the atmospheric water. All KPFM measurements were carried out in the glove box filled with N₂ at room temperature; the experimental setup is shown in Figure S3.