Fig. 5
From: Contamination-free non-contact wettability assessment system
Comparison between a conventional contact angle method and our air-jet based liquid squeezing method as realized in the non-contact wettability assessment system. Graph a shows the relationship between contact angle on the polystyrene surfaces treated with atmospheric-pressure nitrogen-plasma and this treatment time. Graphs b–d show the relationship between liquid squeezing diameter during air-jet application and contact angle. Dashed-line rectangles c, d in graph b indicate the region shown in graphs c, d, respectively. Graph e shows the relationship between liquid recovery time after ceasing the air-jet application and contact angle on the polystyrene surfaces. The blue- and yellow-background regions in graph e indicate recovering of liquid and the remaining squeezed area after ceasing the air-jet application, respectively, as shown in the paired photographs in graph e. The dashed vertical lines in graph e indicate the boundaries between the liquid recovery and the remaining squeezed area in the experiment and the values at the bottom end of each line are the contact angles at the boundaries. Dotted lines in graphs c–e are linear approximation lines for data points (R 2 the coefficient of determination is shown in each graph). Data points and error bars indicate mean values and standard deviations (n = 5), respectively. Graph f shows the relationship between the coefficient of variation (=standard deviation/mean value) and plasma treatment time for contact angle, liquid-squeezed diameter, and liquid recovery time