Dsa100 system

A ‘Drop Shape Analysis System’ Kruss DSA 100 system (Kruss, Hamburg, Germany) was used to measure the water contact angle. 40 µL of Hank’s solution was dropped over the sample surface on three randomly selected areas and the average contact angle was measured.

The hydrophilicity of ZnO NPs-PDA-SS/PVA, PDA-SS/PVA and SS/PVA were analyzed at 25 °C on a Krüss DSA100 system (Hamburg, Germany) via sessile drop contact angle. At five different positions, the process of water absorption was recorded by dispensing the water droplet on the surface of the sample.
The swelling of the composite films in phosphate buffer (PBS, pH 7.4) was measured by gravimetric method with a minor modification. The original films were weighed as W₁. Then, the swelling films were immersed into phosphate buffer at 37 °C, then taken out at separate time intervals and gently removed by filter paper. The mass of swollen composite films was marked as W₂. The swelling ratio (S) was calculated by the following equation:

The same operation was performed at least three times under the same condition. The swellability of the film was presented by average data.

The film’s wettability was assessed by the water contact angle which was measured on a Krüss DSA100 system (Hamburg, Germany) at 25 °C. To do this, 4 μL of water was dropped on the surface of the film. The complete process of water absorption at five different positions was recorded for each film. The water contact angle was calculated and averaged from five independent measurements.