fig4

Figure 4. Evaluation of the pressure mapping resolution of PCN-128 films. (A) Image processing for film color uniformity assessment; (B) Algorithm for calculating film eigenvalues. Optimization of solvent (C), crystal loading (D), and substrate modification (E) based on film eigenvalues; (F) Comparison of film eigenvalues of PCN-128 film before and after substrate modification under compression. Calculation algorithm for the color difference (ΔE_ab) of PCN-128 film before (G) and after (H) substrate modification. (a₀, b₀) and (a_p, b_p) represent the average characteristic values of the PCN-128 film before and after compression; (I) ΔE_ab of PCN-128 film before and after substrate modification; (J) Color change of PCN-128 films versus pressure; (K) Schematic diagram of sandpaper indentation test. Different grits (320-, 600-, 800-, 1000-, and 3000-grit sandpaper) of sandpaper (L) and corresponding ΔE_ab images (M) of PCN-128 film (scale bar: 500 μm), and the illustration in the figure is a close-up. Error bars indicate standard deviation (sample size n = 5). DMF: Dimethylformamide; THF: tetrahydrofuran; ΔE_ab: the color difference of PCN-128 film before and after compression.