2.10 Contact angle measurement with water method

All contact angle measurements were undertaken with a CAM200 (KSV Instruments Ltd, Finland) integrated with KSV CAM Optical Contact Angle and Pendant Drop Surface Tension Software (ver. 4.01, KSV Instruments Ltd, Finland). Flat samples were compared against patterned samples for each material at the three selected concentrations. Five samples with a diameter of 11.8 mm each were measured for each concentration. This diameter was selected to minimise the potential occurrence of edge effects on the water droplets. For agarose, which is considerably hydrophilic, all results presented are for droplets with a volume of less than 40 μL. In contrast, for PDMS and gelatin, water droplets with a volume less than 60 μL were analysed. Prior to the contact angle measurements, all samples were dried with dry nitrogen gas to minimise any potential effects from surface moisture. In addition, experiments were conducted within an hour of peeling the material off the PDMS template. The surface energy of all the materials was determined using deionised water.

Results are presented as mean ± SEM. For statistical analysis, Student’s t-test or ANOVA was performed using GraphPad Prism 7 (GraphPad Software, USA). P values less than 0.05 were considered significant (*P<0.05, **P<0.01, ***P<0.001, and ****P<0.0001).