## Results
### LP Plasma Deposition of Differently Cell-Repulsive Coatings
Through different \(\phi\)He-TEGDME aerosol/\(\phi\)He-carrier ratios, therefore, different PEO-characters for PEOA and PEOB were obtained. The C1s best fittings of PEOA and PEOB coatings deposited at different frequencies and applied voltage values are reported in Figure 2:2  
Figure 2:3 Best fitting of C1s spectra acquired on PEOA (**a**,**b**,**d**,**f**) and PEOB (**c**,**f**) coatings deposited at 16 kHz (**a**,**d**) and 26 kHz (**b**,**c**,**e**,**f**) by changing the applied voltage from 6.5 kV\({}_{\rm P-P}\) (**a**–**c**) to 8.5 kV\({}_{\rm P-P}\) (**d**–**f**). The \(\phi\)He-TEGDME aerosol is fixed to 3.15 slm. Figure 2:4 Evolution of WCA values and thickness of the vertical gradient film after the three-step AP PE-CVD deposition process carried out using an applied voltage of 8.5 kV\({}_{\rm P-P}\), and frequency of both 26 and 16 kHz. The topmost layer deposited in step 3 corresponds to the PEOA film (step 3: 4.85 slm He-carrier, 3.15 slm He-TEGDMEaerosol, 8.5 kV\({}_{\rm P-P}\), 300 s; see Table 1). As observed earlier (Figure 8), the PEO-character of the PEO-like layer can be modulated by changing the relative flow of TEGDME aerosol in the discharge with respect to the He carrier gas [28]. This is observed in Figure 11 and is also shown for the uppermost PEO-like coatings deposited at the end of the three steps approach [28]. When deposited with \(\phi\)He-carrier of 4.85 slm the coating exhibits a good monomer structure retention, with 70% of PEO-character (II component of Figure 11a,b,d,e) whatever other experimental conditions used. Instead, a higher \(\phi\)He-carrier (6.85 slm) led to deposit PEO-like film with about 50% of PEO-character (Figure 11c,f). The effect of \(\phi\)He-TEGDME aerosol/\(\phi\)He-carrier ratio influenced the chemistry of the coating much more than the electrical parameters like excitation frequency and applied voltages, in the ranges investigated. Slight differences are reported, in fact, for coatings deposited at two different peak-to-peak voltages (6.5 and 8.5 kV\({}_{\text{p-p}}\)) or frequency values (16 and 26 kHz) by keeping the other experimental parameters constant. This corresponds also to very slight wettability (WCA) differences in the coatings, that have WCA of about 50\({}^{\circ}\) whatever the plasma condition used (Table S2). The deposition rate of these coatings is around 30 nm\(\cdot\)min\({}^{-1}\) (Table S2). AR-XPS analyses for PEOA samples indicated a progressive increase in the O/C ratio with the decrease in the sampling depth (Figure 12). The topmost layer shows a chemical composition and a C1s spectrum (Figure 12) very similar to PEO-like coating deposited in the single-step process reported in Figure 2:5  
In vitro, biological experiments were carried out on PEOA and PEOB coatings deposited on PC as reported in Figures 13 and 14. These cell adhesion tests allow us to assess both the stability in complex water media (i.e., cell culture medium) and the biological responses to the coated PC with the three steps strategy. The cell repulsive films deposited in LP PE-CVD (PEO_LP, 0.5 sccm DEGDME, 5 sccm Ar, 53 Pa, 5 W, 60 min) with a PEO-character of 70% have been used as a reference. Figure 2:6 O/C ratio for PEOA (Step3: 4.85 slm \(\phi\)He-carrier, 3.15 slm \(\phi\)He-TEGDME aerosol, 8.5 kV\({}_{\text{p-p}}\), 27 kHz, 300 s) measured in angle-resolved (AR) mode and C1s best-fitted spectra from the lowest (TOA 28\({}^{\circ}\)) to the highest sampling depth (TOA 78\({}^{\circ}\)). The II C1s contribution attributed to the PEO-character changes from 69% (TOA 28\({}^{\circ}\)) to 55% (TOA 78\({}^{\circ}\)) at deeper sampling depth. As shown in Figure 13, cell culture data indicate that when the mildest AP PE-CVD conditions are used (i.e., lowest f and Va), the detachment of the coating from the underlying substrate is observed (Figure 13c). This effect can be, most likely, due to insufficient cross-linking of the PE-like primer coating (step 1 of the process).