## 1 Introduction
Several studies explored the potential of plasma-synthesized surfaces to control interactions of biological entities at the surface of biomedical materials. The design of plasma processes for biomaterial surfaces must be based on understanding the requirements of the bio-interface aimed in the application. In recent years PEO materials emerged as potential candidates for many biomedical applications, due to their non-specific and non-fouling biological properties toward a broad range of biomolecules and cells. In literature, it is shown that PEO-based materials can prevent the adsorption of proteins, the adhesion of platelets, and thrombus formation both in vitro and in vivo [12]. The antifouling properties of PEO are predominantly explained with the presence of high concentrations of hydrophilic ether oxygen moieties (CH\({}_{2}\)-CH\({}_{2}\)-O)\({}_{n}\)[13; 14]. These can bind four water molecules each in a water environment, so that the hydrated PEO surfaces do not look much different from the solution, from the energetic point of view. In this way, biomolecules and other biological entities do not \"see\" energetic advantages in the adhesion to the PEO surface, and remain in solution. Furthermore, the molecular weight of the PEO chains and surface density of CH\({}_{2}\)-CH\({}_{2}\)-O moieties (known as PEO-character), are also considered crucial to determine the non-fouling behavior of PEO-coated surfaces [15; 16; 17; 18]. Currently, conventional PEO polymers, approved by the Food and Drug Administration in the US, are used for fabricating blood-contacting devices and the manufacture of hydrogels for drug delivery [14; 19]. PE-CVD of PEO-like coatings could be used to tune cell adhesion on biomaterials by changing the PEO-character. Two strategies can be envisaged, at least: (1) deposition of organic coatings starting from a monomer with \"cell-repulsive\" moieties at optimized plasma parameters (i.e., input power, monomer flow rate, etc. ); (2) co-deposition of organic coatings from two monomers, one with \"cell-repulsive\" motifs, and the other showing \"cell-adhesive\" ones, at a controlled relative ratio in the feed (Figure 1). In the second route, a monomer for PEO-like deposition (i.e., a glyme) is fed with a monomer characterized by other functional groups, like carboxyl (COOH) or amine (NH\({}_{2}\)) groups, that are suitable for promoting non-specific cell adhesion [20]. The copolymerization of two monomers is a convenient and versatile method for adjusting the surface density of functional groups [21] and modulating the un-fouling character of the resulting surface. While several reviews on AP or LP processes have been published in recent years [22; 23], there is no detailed overview of differences, advantages, and disadvantages, in depositing PEO-like coatings using AP vs LP conditions, and this contribution is designed to address this gap. In the present study, the deposition of polyethylene oxide (PEO)-like functional coatings was carried out in LP on inorganic substrates of biomedical interest like titanium, and in AP plasmas on plastics (like polycarbonate, (PC)), as an example of the future application in biomaterials manufacturing (i.e., blood stents) or in microfluidic. The effects of three major operating parameters (deposition potential, input power, and gas feed composition) on the surface properties of PEO-like coatings were investigated. Different characterization techniques, such as contact angle (CA) measurement, FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and optical microscopy were used to examine the changes in the hydrophilicity, surface chemistry, and topography of the PEO-like coatings. Finally, the cell adhesion and repulsive properties of the PEO-like coatings were investigated by in vitro cell culture tests.