Oca 15ec system

Water contact angles (WCA) were measured under static conditions by sessile drop method using an OCA 15EC system (DataPhysics Instruments GmbH, Filderstadt, Germany) coupled with a drop shape analysis software (SCA 20, DataPhysics Instruments GmbH, Filderstadt, Germany). A 1-μL drop was placed on the functionalized polymer surfaces, recording the images after 10 s. The WCA values are expressed as mean ± standard deviation (s.d.) of at least three measurements on the same sample in two independent experiments (i.e., at least six measurements for each result).

According to the result of HPLC analysis, 50% (v/v) acetonitrile solution, containing the biosurfactant, was evaporated and lyophilized to remove acetonitrile impurities. Then, the fine powder of biosurfactant was examined to determine the concentration, ensuring formation of micelles. Therefore, a series of biosurfactant dilutions in a concentration range of 0–250 mg L⁻¹ was analyzed in terms of ST.²⁶ A KRÜSS K6 Tensiometer (KRÜSS GmbH, Germany) equipped with a 1.9 cm De Noüy platinum ring was used at room temperature (25 °C). The CMC was determined graphically by plotting the relationship between ST and biosurfactant concentration. All the measurements were made in triplicate.
In order to verify the wetting ability of the viscosin solutions, contact angle measurements were carried out using the OCA 15EC system (DataPhysics, Filderstadt, Germany), and the drop shape was analyzed with SCA20 software (DataPhysics). For each measurement, a sample droplet of 0.2 μL was placed on a solid support. Silicone, polystyrene and glass surfaces were used as supports. All measurements were made at ambient temperature (25 °C) in a saturated vapor atmosphere to reduce droplet evaporation. The contact angle value is reported as the average of ten measurements.

The surface topography of the samples is observed using a field emission scanning electron microscope (FE-SEM, Quanta 450 FEG, FEI, USA) and an atomic force microscope (AFM, ICON, Bruker, Germany). The surface chemistry composition is characterized by X-ray photoelectron spectroscopy (XPS, ESCALAB 250XI, Thermo Fisher Scientific, USA). The line shape of Tougaard is chosen to analyze the XPS spectrums through the Avantage (Ver 5.976, Thermo Fisher Scientific, USA). The wettability of the surface is measured by an OCA15EC system (DataPhysics, Germany) under atmospheric conditions. The static water contact angles (WCA) are measured by the auto-pipette system with 5 μL of water deposited on the top sample surface at room temperature.