C. SEM studies
Fig. 4 shows the dynamics of the cell penetration process over time, recorded at 5  minutes to 5 hours using SEM imaging.   These images provide information,   although limited, of possible cell membrane deformation around the nanopillars or conform on the nanopillars.  The images clearly show the NIH 3T3 cell-nanopillar interface at different time points. Here, the nanopillars are 100-200 nm in tip diameter, 5-6 µm high at a density of 8x103 nanopillars/cm2. The sphere-shaped cells first settle onto the nanopillars (~5min), then gradually continue to adhere to the substrate which leads to cell spreading (30 min), followed by increase cell-pillar contact area (2 and 5 hours).