## 2 Materials and Methods
### Methods  
The Corona plasma device (3 DT, MULTIDYNE 1000, Germantown, WI, USA) consisted of a treating head that contained two hook-shaped wire electrodes. The plasma was generated under high voltage at an electrode of 2 \(\times\) 12 kV and a frequency of 50 Hz at atmospheric pressure conditions, using ambient air as a carrier gas. The distance between the electrode and flattened catheter was 2 \(\pm\) 0.1 cm.  
The parameters of an air low pressure radiofrequency plasma discharge were: The plasma frequency was 13.56 MHz; the power was 18 W; the pressure was 2 Torr; the times of irradiation varied at 10, 20, and 30 s; and the volume of the discharge chamber was 840 cm\({}^{3}\). Dried compressed air used for the radiofrequency plasma treatment of catheters was supplied by Oxygen & Argon Works, Ltd. (Caesarea, Israel), moisture was less than 10 ppm, and the concentration of oxygen was 20-22%.  
The diffuse coplanar surface barrier discharge was created by the DBD plasma unit RPS 40, supplied by Roplass (Brno, Czech Republic), the maximal power was 40 W, and frequency \(\sim\)20 KHz. The distance between the electrode and flattened catheter was 0.5 mm. The time span of the plasma treatment varied within 15-60 s.  
Apparent contact angles were established using the Rame-Hart goniometer (Model 500). A typical picture of a water droplet placed on a pristine PVC catheter is shown in Figure 1. A total of 8 measurements were taken to calculate mean apparent contact anglesat ambient conditions. The apparent contact angles were taken on both sides of a droplet and the results were averaged.  
Contact angle hysteresis was established with the tilted plane method. A 5 \(\mu\)L water droplet was placed on the PVC sample mounted on the glass slide. The slide was tilted until the drop began to move. The front and rear contact angles at which the droplet started to slip are regarded as the advancing \(\theta_{adv}\) and receding \(\theta_{rec}\) contact angles, correspondingly, as depicted in Figure 2.  
The difference \(\Delta\theta\ =\ \theta_{adv}-\theta_{rec}\) is called the contact angle hysteresis [35; 36; 37; 38; 39]. In spite of the fact that the \"tilted plane experiment\" was criticized as a method for the accurate establishment of the contact angle hysteresis, it is still broadly used for its estimation [39; 40]. In parallel, the contact angle hysteresis was measured with a needle-syringe method.  
The 5 \(\mu\)L water droplet placed on the flattened catheter was inflated with a syringe as shown in Figure 3A. When the contact (triple line) was pinned and the contact angle was increased till a certain threshold value beyond which the triple line moved. This threshold contact angle \(\theta_{adv}\) was regarded as the advancing contact angle [35; 36; 37; 38; 39]. When a droplet was deflated as depicted in Figure 3B, its volume decreased to a certain limiting value; in parallel the contact angle decreases till a threshold value \(\theta_{rec}\), interpreted as the receding contact angle [35; 36; 37; 38; 39].  
Figure 1: Wettability of pristine Polyvinylchloride (PVC) catheter is illustrated. The apparent contact angle is close to \(\frac{\pi}{2}\).  
Figure 2: Water droplet placed on the tilted PVC surface is shown. The advancing \(\theta_{adv}\) and receding \(\theta_{rec}\) contacting angles are depicted.  
The chemical composition of the pristine and cold plasma-treated PVC catheters was studied with SEM/EDS (scanning electron microscopy/energy dispersive spectrometry) carried out with SEM (MAIA3 TESCAN).