Deposition, morphology and functional properties of layers based on DLC:Si and DLC:N on polyurethane

Karol Kyzioł,Wiktor Niemiec,Daniel Kottfer,Piotr Jabłoński,Łukasz Kaczmarek,Aneta Łętocha,Janusz Prażuch

doi:10.1007/s00339-020-03939-y

Abstract

DLC:Si and DLC:N (diamond-like carbons doped with Si or N) functional layers in different configurations are deposited on polyurethane (PU) for bioengineering applications using CCP (capacitively coupled plasma) discharge generated in the PE CVD (plasma-enhanced chemical vapor deposition) system. Scanning electron microscopy (SEM) observations show that the obtained single and multilayers are continuous and well adherent to the substrates, but they differ in surface morphologies. DLC:Si layers form granular-like outer surfaces, while DLC:N ones a mosaic structure of plain areas. Topography analyses by atomic force microscopy (AFM) and optical profilometry reveal that Si-doped layers are characterized by significantly higher surface roughness (Ra ca. 5 nm) in comparison to N-doped layers (Ra ca. 0.3 nm) and also higher values of profile roughness parameter Rz (up to 32 μm vs. about 13 μm). Energy-dispersive X-ray spectroscopy (EDS) analysis indicates the homogenous chemical composition of the layers. DLC:N layers, are characterized by significantly higher polar component of surface free energy (up to ca. 5.0 mJ/m2). DLC:Si layers exhibit higher values of diiodomethane contact angle (up to ca. 90°) compared with DLC:N layers (up to ca. 55°). The attenuated total reflectance Fourier transform infrared spectroscopic measurements (ATR-FTIR) of the layers reveal that the addition of silicon to the DLC structure increases the content of terminal CHn bonds (n = 1, 2, 3) as well as beneficial Si–H and Si–CHn bonds, which significantly reduce the internal stresses in the layers. Both DLC:Si and DLC:N layers exhibit no cytotoxic effects using the human osteoblast-like cell line and human keratinocytes.

Highlights

IntroductionThe application of the plasma treatment or plasma chemical processes leads to generating high-energy species, such as radicals, ions or molecules, which (depending on the chemical composition) involves surface reactions, surface activation and modification
Polymers are an interesting group of engineering materials, which, due to their attractive properties, for example a quite good chemical resistance, low weight as well asThe application of the plasma treatment or plasma chemical processes leads to generating high-energy species, such as radicals, ions or molecules, which involves surface reactions, surface activation and modification
Our research shows that it is possible to control the surface roughness of the obtained structures in multilayer systems

Summary

Introduction

The application of the plasma treatment or plasma chemical processes leads to generating high-energy species, such as radicals, ions or molecules, which (depending on the chemical composition) involves surface reactions, surface activation and modification. DLC layers have wide-ranging properties, such as lowto-high hardness, smooth surface morphology, low friction coefficient, chemical inertness, wear resistance and biocompatibility. The physical and mechanical properties of the modified surface depend on the type of substrate, deposition method, the thickness of the layer as well as the precursors used, etc.[14]. Due to the high hardness of DLC layers, such coatings are commonly used in implantology, especially in hip joint implants [17, 18]

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