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Abstract: This study enhances the bioactivity of polycaprolactone (PCL) scaffolds for tissue engineering by functionalizing them with oxidized hyaluronic acid glycine-peptide conjugates to improve endothelial cell adhesion and growth. Hyaluronic acid was conjugated with a glycine-peptide to create a bioactive interface on PCL (static water contact angle, SCA(H2O): 98°). The scaffolds were fabricated using a melt extrusion 3D printing technique. The HA-glycine peptide conjugates were oxidized and immobilized on aminolyzed PCL via Schiff-base chemistry, introducing hydrophilicity (SCA(H2O): 21°), multiple functional groups, and a negative zeta potential (-12.04 mV at pH 7.4). A quartz crystal microbalance confirmed chemical conjugation and quantified the mass (8.5-10.3 mg m-2) of oxidized HA-glycine on PCL. The functionalized scaffolds showed enhanced swelling, improved mechanical properties (2-fold increase in strength, from 26 to 51 MPa), and maintained integrity during degradation. In-vitro experiments demonstrated improved endothelial cell adhesion, proliferation and viability, suggesting the potential for vascularized tissue constructs.
Keywords: 3D printing, polycaprolactone, hyaluronic acid
Published in DKUM: 19.03.2025; Views: 0; Downloads: 0
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Abstract: Traditional prosthetic liners are often limited in customization due to constraints in manufacturing processes and materials. Typically made from non-compressible elastomers, these liners can cause discomfort through uneven contact pressures and inadequate adaptation to the complex shape of the residual limb. This study explores the development of bioinspired cellular metamaterial prosthetic liners, designed using additive manufacturing techniques to improve comfort by reducing contact pressure and redistributing deformation at the limb–prosthesis interface. The gyroid unit cell was selected due to its favorable isotropic properties, ease of manufacturing, and ability to distribute loads efficiently. Following the initial unit cell identification analysis, the results from the uniaxial compression test on the metamaterial cellular samples were used to develop a multilinear material model, approximating the response of the metamaterial structure. Finite Element Analysis (FEA) using a previously developed generic limb–liner–socket model was employed to simulate and compare the biomechanical behavior of these novel liners against conventional silicone liners, focusing on key parameters such as peak contact pressure and liner deformation during donning, heel strike, and the push-off phase of the gait cycle. The results showed that while silicone liners provide good overall contact pressure reduction, cellular liners offer superior customization and performance optimization. The soft cellular liner significantly reduced peak contact pressure during donning compared to silicone liners but exhibited higher deformation, making it more suitable for sedentary individuals. In contrast, medium and hard cellular liners outperformed silicone liners for active individuals by reducing both contact pressure and deformation during dynamic gait phases, thereby enhancing stability. Specifically, a medium-density liner (10% infill) balanced contact pressure reduction with low deformation, offering a balance of comfort and stability. The hard cellular liner, ideal for high-impact activities, provided superior shape retention and support with lower liner deformation and comparable contact pressures to silicone liners. The results show that customizable stiffness in cellular metamaterial liners enables personalized design to address individual needs, whether focusing on comfort, stability, or both. These findings suggest that 3D-printed metamaterial liners could be a promising alternative to traditional prosthetic materials, warranting further research and clinical validation
Keywords: bioinspired design, metamaterial model, cellular structure, additive manufacturing, lower-limb prosthetic, 3D printing, finite element method
Published in DKUM: 19.09.2024; Views: 0; Downloads: 315
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Abstract: This study investigated the thermomechanical behavior of 4D-printed polylactic acid (PLA), focusing on its response to varying temperatures and strain rates in a wide range below the glass transition temperature (Tg). The material was characterized using tension, compression, and dynamic mechanical thermal analysis (DMTA), confirming PLA’s strong dependency on strain rate and temperature. The glass transition temperature of 4D-printed PLA was determined to be 65 °C using a thermal analysis (DMTA). The elastic modulus changed from 1045.7 MPa in the glassy phase to 1.2 MPa in the rubber phase, showing the great shape memory potential of 4D-printed PLA. The filament tension tests revealed that the material’s yield stress strongly depended on the strain rate at room temperature, with values ranging from 56 MPa to 43 MPA as the strain rate decreased. Using a commercial FDM Ultimaker printer, cylindrical compression samples were 3D-printed and then characterized under thermo-mechanical conditions. Thermo-mechanical compression tests were conducted at strain rates ranging from 0.0001 s−1 to 0.1 s−1 and at temperatures below the glass transition temperature (Tg) at 25, 37, and 50 °C. The conducted experimental tests showed that the material had distinct yield stress, strain softening, and strain hardening at very large deformations. Clear strain rate dependence was observed, particularly at quasi-static rates, with the temperature and strain rate significantly influencing PLA’s mechanical properties, including yield stress. Yield stress values varied from 110 MPa at room temperature with a strain rate of 0.1 s−1 to 42 MPa at 50 °C with a strain rate of 0.0001 s−1. This study also included thermo-mechanical adiabatic tests, which revealed that higher strain rates of 0.01 s−1 and 0.1 s−1 led to self-heating due to non-dissipated generated heat. This internal heating caused additional softening at higher strain rates and lower stress values. Thermal imaging revealed temperature increases of 15 °C and 18 °C for strain rates of 0.01 s−1 and 0.1 s−1, respectively.
Keywords: smart materials, shape memory polymer, 3D printing, 4D printing, thermo-mechanical experiments
Published in DKUM: 29.05.2024; Views: 248; Downloads: 22
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Keywords: 3D printing, gelatin, collagen, hydroxyapatite, microstructure, compression
Published in DKUM: 09.04.2024; Views: 201; Downloads: 17
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Keywords: optical sensor layers preparation, spin coating, spray coating, inkjet printing, SFE, XPS, NH3, response, real-time response
Published in DKUM: 28.03.2024; Views: 198; Downloads: 13
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