Katarina Colic

Polymeric Biomaterials Based on Polylactide, Chitosan and Hydrogels in Medicine

Polymeric biomaterials represent large and very adaptable class of biomaterials, which makes them very suitable for diversity of biomedical applications. Polymers can be synthesized to have a variety of structures and suitable chemical, physical, biomimetic and surface properties. An overabundance of polymeric biomaterials with different compositions and physicochemical properties have already been developed and investigated; however, there are still many active studies about these materials. This chapter ensures a structural review of biodegradable polymers and discusses their physicochemical characteristics, structure property, applications and limitations in medicine. It is the authors’ intent to provide an insight over the available synthetic and natural polymer classes. Some types of polymer materials are less discussed than the other more relevant. A biocompatible, degradable polymer, polylactic acid is very popular so called green ‘eco-friendly’ material with a most promising development prospect. Besides biocompatibility and biodegradability, natural polymer, chitosan, possess outstanding properties. Hydrogels are super absorbent polymeric materials with one of the main role in health care. For these biopolymers, reviews are referenced to present guidance for further reading.

Experimental Dimensional Accuracy Analysis of Reformer Prototype Model Produced by FDM and SLA 3D Printing Technology

The subject of this paper is the evaluation of the dimensional accuracy of FDM and SLA 3D printing technologies in comparison with developed reformer polymer electrolyte membrane (PEM) fuel cell CAD model. 3D printing technologies allow a bottom-up approach to manufacturing, by depositing material in layers to final shape. Dimensional inaccuracy is still a problem in 3D printing technologies due to material shrinking and residual stress. Materials used in this research are PLA (Polylactic Acid) for FDM technology and the standard white resin material for SLA technology. Both materials are commonly used for 3D printing. PLA material is printed in three different height resolutions: 0.3 mm, 0.2 mm and 0.1 mm. White resin is printed in 0.1 mm height resolution. The aim of this paper is to show how layer height affects the dimensional accuracy of FDM models and to compare the dimensional accuracy of FDM and SLA printed reformer models with the same height resolution.

Application of Numerical Methods in Design and Analysis of Orthopedic Implant Integrity

In this paper a numerical analysis of hip implant model and hip implant model with a crack in a biomaterial is presented. Hip implants still exhibit problem of premature failure, promoting their integrity and life at the top of the list of problems to be solved in near future. Any damage due to wear or corrosion is ideal location for crack initiation and further fatigue growth. Therefore, this paper is focused on integrity of hip implants with an aim to improve their performance and reliability. Numerical models are based on the finite element method (FEM), including the extended FEM (X-FEM). FEM became a powerful and reliable numerical tool for analysis of structures subjected to different types of load in cases where solving of these problems was too complex for exclusively analytical methods. FEM is a method based on discretization of complex geometrical domains into much smaller and simpler ones, wherein field variables can be interpolated using shape functions. Numerical analysis was performed on three- dimensional models, to investigate mechanical behaviour of a hip implant at acting forces from 3.5 to 6.0 kN. Short theoretical background on the stress intensity factors computation is presented. Results presented in this paper indicate that acting forces can lead to implant failure due to stress field changes. For the simulation of crack propagation extended finite element method (XFEM) was used as one of the most advanced modelling techniques for this type of problem.

Short History of Biomaterials Used in Hip Arthroplasty and Their Modern Evolution

The hip joint is one of the largest joints in the body and is a major weight-bearing joint. The function of the hip is to withstand body weight during standing and walking; during single leg stance the hip joint must carry a load three times greater the body weight. However, Joint degeneration is the final phase of the joint cartilage destruction, leading to severe pain, loss of mobility, and sometimes even angular deformity of the limbs. The primary reasons for a large number of total hip replacements are osteoarthritis and osteoporosis of the femoral neck, which often leads to hip fractures. One of the most successful techniques to restore function of a degenerated joint is the total joint replacement. In this surgical procedure, diseased cartilage and parts of the bone are removed and replaced with an appropriate joint prosthesis. Several types of materials and techniques have been developed for this purpose: glass, polymer, metal alloy, ceramics, etc. Earliest prosthesis designs and biomaterials that have been developed to treat osteoarthritic hip degenerated joint surfaces were for the most part empirical and unsuccessful. Joint replacement heralded a revolution after the materials and replacement procedures developed by Sir John Charnley. A modern total hip prosthesis consists of a femoral and acetabular component, where the femoral head is made of cobalt-chrome alloy, alumina or zirconium, and the stem component is now usually made of Ti- or Co-Cr-based alloy. The search for improved designs and new hip implant biomaterials with better biocompatibility and more desirable mechanical properties is still underway.

3D Experimental optical analysis of titanium alloys for biomedical applications

In this paper is presented an example of experimental analysis of biomaterials based on optical measurement methodology. GOM optical system and Aramis software were used to perform 3D experimental optical analysis of titanium alloys for biomedical applications. The possibilities of using this method for analyzing materials for biomedical applications are discussed, and having in mind that the system used in this experimental analysis is utilized to solve problems in structural integrity analysis and determining properties of materials, it is concluded that this method is suitable for analysis of irregular object geometries made of various materials, as is often the case in biomedical applications. Considering that titanium alloys have high sensitivity to fatigue induced by notches, a sharp-notch tension test was performed. The goal of this in vitro study was to measure and analyze fracture behaviour of Ti6Al4V alloy specimens. The major strain field of the titanium alloy specimen for crack tip opening and fracture are presented. It is shown that the application of a modern 3D optical measuring method is useful in determining some of the key properties of metallic materials in biomedical applications.

High-temperature deformation behaviour of Ti3Al-11Nb intermetallic

Abstract A mechanism of high-temperature plasticity has been studied in terms of stress exponent and activation energy for deformation. A Ti3Al-based intermetallic was processed by hot-rolling in the two-phase field to accomplish a fine-grained microstructure. Compression stress – strain tests were conducted in the temperature interval ranging from 900 to 1 050 °C and strain rates between 6.9 · 10− 5 and 2.7 · 10− 2 s− 1. Results indicate that viscous-drag dislocation glide and grain boundary sliding are the main mechanisms of deformation. Activation energy for deformation suggests dependency on the solute content in the -phase.