Theta lite

The effect of sorghum flour on the MCT/water interfacial tension was measured using a Theta Lite optical contact angle meter (Biolin Scientific, Stockholm, Sweden). The excess sorghum flour was added to ultra-pure water, ultrasonicated at room temperature for 10 min and then allowed to rest for 15 min. The obtained supernatant was loaded into the syringe. Then, a drop of supernatant solution was added to a cuvette containing MCT. The drop shape was recorded continuously and fitted with the Young–Laplace equation to calculate the interfacial tension. The solution with ultra-pure water instead of supernatant was also measured as control.

The surface wettability of PCL, E-VAL, and their blends was examined on well-dried 4 × 4 × 8 mm³ samples through static contact angle measurements at 10 s using a Theta Lite optical tensiometer (Attension, Biolin Scientific, Finland). The contact angle was measured using One Attension 1.0 type software on a droplet of water deposited on the surface of dry samples. Three measurements were performed for each sample, and the final value was taken from their average calculated from the arithmetic mean.

The average surface roughness (R_a) of each coating surface was measured using a 3D laser scanning confocal microscope (3D-LSCM, VK-X200, KEYENCE Co., Osaka, Japan) based on a minimum of three separate measurements obtained at different positions on the coating surface. The wettability of the coatings was determined by the static sessile drop method using DI water as the working fluid. Contact angle (CA) measurement is often used to estimate the wettability of solid surfaces in contact with a liquid. The surface static CAs of the coating surfaces were measured using a CA goniometer (Theta Lite, Biolin Scientific, Sweden) with a 4 μL droplet volume and a stabilization time of at least 5 s. For each coating, the CA was measured three times in order to determine the mean CA value and corresponding standard deviation.

The measurement of
the water contact angle was conducted using a Theta Lite (Biolin Scientific,
Espoo, Finland). The foam samples were cut into small pieces and placed
on glass slides. A droplet of deionized water, 4 μL in volume,
was placed on the foam surface through a microsyringe. One Attension
software (Nanoscience Instruments, Inc., Phoenix, AZ) was used to
determine the contact angle.

Static contact angles were measured on the Theta Lite fully automated optical tensiometer equipped with a Firewire digital camera and Attention from Biolin Scientific by drop-casting a sessile 4 μL water droplet onto the hydrophobic and Si substrates respectively. All contact angle measurements reported were repeated at least five times across each substrate and averaged.

Contact angles were measured using a Biolin Scientific Theta Lite optical tensiometer (TL, Finland) with Attension software (Biolin Scientific, v 2.1). Static contact angles were measured in air using DI water, toluene and hexane. The substrates used were glass slides coated with chitosan (12 g/L in 5% GAA), HEC and HEC + (12 g/L in DI water at pH = 6), air dried before each measurement. Sliding contact angles were measured in water using glass cuvettes. The bottoms of the glass cuvettes were coated with chitosan, HEC or HEC + by pipetting on it the polymer solutions (0.01 wt% chitosan solution in 5% GAA, or 0.1 wt% of either HEC or HEC + in DI) and subsequently rinsing it with DI after 1 min contact time. The cuvettes were then filled with DI and a droplet of the solvent (toluene, hexane or TCE) was contacted onto the polymer coated bottom of the cuvette with the aid of a glass Pasteur pipette.

The time-dependent water contact angles were measured with an optical tensiometer (Theta Lite, Biolin Scientific, Finland). 4 μL distilled water droplet was dripped on the DTPU films at 25 °C through a pipettor. And the images taken at different times were recorded. The results of three separate tests were averaged to assess the time-dependent water contact angles.