Fig. 4: Effect of flow-time on the grafted layer.

a Schematic top view of the microfluidic channel showing the inlets and outlet ports. The dashed lines indicate the location (i.e. the center of zone 2) where the AFM images were acquired. Panel a also includes the AFM images of the grafted layers obtained with flow times ranging from 1 to 60 min at a fixed flow rate of 50 µL min⁻¹. Scale bars in a: 2 µm. b Graph obtained from the analysis of the AFM images acquired at zone 2. The thickness of the grafted layer increases with the flow time. c shows how the number (black) and diameter (red) of corrals vary with respect to the flow time. Error bars represent the standard deviation of at least three different measurements. d–g AFM image (in d) indicating the sections used to generate the three topographic profiles presented in e, f, and g. The results presented in d–g was obtained from the experiment performed with a flow rate of 50 µL min⁻¹ for 120 min. Scale bar in d: 500 nm. Note that time dependent experiments were separately performed for each time point and the grafted layers on HOPG substrates prepared with different experimental times were independently characterized.