## 2 Materials and Methods
### Coatings  
The commercially available and patented ORMOCER(r) technology was used to apply a hydrophobic coating on the MicroPES membrane. Three different combinations of silanes were explored. The three different fluorosilanes investigated in this study have a different structure, different chain length, and different hydrophobizing properties. The monomers exhibit a bifunctional character and are able to form a stable combined inorganic-organic network. The synthesis procedure is presented in Figure 1.  
The process starts from an alcoholic solution of the R'Si(OR)\({}_{3}\) monomers, where R' is a functional non-reactive hydrophobic group or a polymerizable group, e.g., acryl or vinyl. R represents simple aliphatic groups, e.g., methyl or ethyl. By the addition of water and catalyst, both hydrolysis and polycondensation reactions can occur, resulting in the formation of Si-O-Si covalent bonds forming the inorganic network (Figure 2). The hydrolysis reaction results in the cleavage of a chemical bond by the addition of water. During the polycondensation reactions, two molecules combine to form a larger molecule by splitting a small molecule. Two of the OH groups formed after hydrolysis on the silica components can form H\({}_{2}\)O (polycondensation 1), or the unreacted OR group can react with an OH group to form ROH (polycondensation 2). After multiple polycondensation steps, an inorganic polymer network with a Si-O backbone is formed, resulting in a disperse solution, called the sol. In a second step, this sol is applied on the membrane surface using a bar coater, a roll-to-roll system, or spray coating. Finally, the coating is cured using a thermal or photochemicalcuring step using ultraviolet (UV) light, in which the polymerizable groups present in the solution will form the  
Figure 1: Coating procedure. Figure 2: Mechanism of the hydrolysis and polycondensation reactions. organic network. The nature of the chemicals used (acryl, vinyl, etc.) determines the organic network type. More details on the system can be found in the literature [34; 40]. Figure 3 shows the structure of the perfluorodecyl (PFD) silane. After the sol-gel processing this single component only forms the silica network in an alcoholic solution. No polymerizable group is present in this solution and hence, no organic network is formed in this system. The PFD system was only thermally dried at 80 \({}^{\circ}\)C for 30 min. i.e., thermal based evaporation of the solvents (water/alcohol), which led to a solid film. The second system is a four-component system where a mono-acrylic (Ak) component forms the reactive site for acrylic polymerization. The methyl (T) and dimethyl (D) silanes as well as the highly fluorinated silane (BTFO2N) are participating as hydrophobizing component in the organic network (Figure 4). A composition of Ak/T/D/BTFO2N of 20/44/34/2 wt. % was used. The third is a three component system including a vinyl silane (V), a 3-mercapopropyl silane (Mc) and a perfluoro-octyl silane (F13) with composition 49/49/2 wt. % V/Mc/F13 (Figure 5). The inorganic silica network is formed by the three components, while the organic network is formed by an addition reaction of the thiol-group to the vinyl group [41]. The hydrophobicity is provided by the perfluoro-octyl group. The UV-curing for the systems Ak/T/D/BTFO2N and V/Mc/F13 was performed using a mercury UV lamp, running with 1200 Watt power, a UV dose of 5000 mJ/m\({}^{2}\), and a UV curing duration 20 s. The UV-curing temperature is ca. 60-80 \({}^{\circ}\)C, which evolves from the UV-lamps. Table 1 shows the composition, the application method and the final network of the different coatings applied in this study. Coatings 1, 2, and 4 were applied using a roll-to-roll system, coatings 3 and 5 were applied using a bar coater system. Coatings 6 and 7 use the same components as for coating 5, but are applied using spray coating (6 as single side coating, 7 as double side coating).