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Abstract:
Biodegradable 3D-printed polycaprolactone scaffolds for bone tissue engineering applications have been extensively studied as they can provide an attractive porous architecture mimicking natural bone, with tunable physical and mechanical properties enhancing positive cellular response. The main drawbacks of polycaprolactone-based scaffolds, limiting their applications in tissue engineering are: their hydrophobic nature, low bioactivity and poor mechanical properties compared to native bone tissue. To overcome these issues, the surface of scaffolds is usually modified and covered with a ceramic layer. However, a detailed description of the adhesion forces of ceramic particles to the polymer surface of the scaffolds is still lacking. Our present work is focused on obtaining PCL-based composite scaffolds to strengthen the architecture of the final product. In this manuscript, we report qualitative and quantitative evaluation of low temperature plasma modification followed by detailed studies of the adhesion forces between chemically attached ceramic layer and the surface of polycaprolactone-nanohydroxyapatite composite 3D-printed scaffolds. The results suggest modification-dependent alteration of the internal structure and morphology, as well as mechanical and physical scaffold properties recorded with atomic force microscopy. Moreover, changes in the material surface were followed by enhanced adhesion forces binding the ceramic layer to polymer-based scaffolds.

Keywords:
surface modification, low temperature plasma, atomic force microscopy, bone tissue engineering

Abstract:
Composite scaffolds of bioactive glass (SiO2-CaO) and bioresorbable polyesters: poly-L-lactic acid (PLLA) and polycaprolactone (PCL) were produced by polymer coating of porous foams. Their structure and mechanical properties were investigated in micro and nanoscale, by the means of scanning electron microscopy, PeakForce Quantitative Nanomechanical Property Mapping (PF-QNM) atomic force microscopy, micro-computed tomography and contact angle measurements. This is one of the first studies in which the nanomechanical properties (elastic modulus, adhesion) were measured and mapped simultaneously with topography imaging (PF-QNM AFM) for bioactive glass and bioactive glass – polymer coated scaffolds. Our findings show that polymer coated scaffolds had higher average roughness and lower stiffness in comparison to pure bioactive glass scaffolds. Such coating-dependent scaffold properties may promote different cells-scaffold interaction.

Keywords:
bone tissue engineering, composite scaffold, bioactive glass, mmechanical properties

Abstract:
The aim of the contribution is to formulate an engineering theory describing the dynamic behaviour of periodically waved shell-like elements, called wavy plates. On the basis of the proposed theory, the effect of coupling between free macro- and micro-vibrations of a wavy plate is investigated. It is also shown that the homogenized model of wavy plates (obtained by scaling down the wavelength parameters) cannot be applied in the analysis of dynamic problems.

Abstract:
In this contribution an averaged refined model of a rigid heat conductor with micro-periodic structure is formulated. The proposed model describes the effect of a microstructure length dimension on the time-dependent heat transfer processes. It is shown that this effect plays a crucial role in the analysis of nonstationary problems and hence the known effective modulus theories of heat conduction (where the microstructure is scaled down), have the range of applicability restricted to steady-state problems.

Abstract:
The effect of interlaminar bonding imperfections on behaviour of shells, investigated in [1], is elaborated here for a special case of laminated plates. The problem is stated for linear elastic materials, within the small displacement gradient theory. The obtained results are ilustrated by an example.

Abstract:
In this contribution the effect of interlaminar initial imperfections on a composite shell behavior is investigated. The constitutive equations for shells with initial interlaminar bonding imperfections are obtained.