Philipp Drescher

Impact of Particle Size of Ceramic Granule Blends on Mechanical Strength and Porosity of 3D Printed Scaffolds

3D printing is a promising method for the fabrication of scaffolds in the field of bone tissue engineering. To date, the mechanical strength of 3D printed ceramic scaffolds is not sufficient for a variety of applications in the reconstructive surgery. Mechanical strength is directly in relation with the porosity of the 3D printed scaffolds. The porosity is directly influenced by particle size and particle-size distribution of the raw material. To investigate this impact, a hydroxyapatite granule blend with a wide particle size distribution was fractioned by sieving. The specific fractions and bimodal mixtures of the sieved granule blend were used to 3D print specimens. It has been shown that an optimized arrangement of fractions with large and small particles can provide 3D printed specimens with good mechanical strength due to a higher packing density. An increase of mechanical strength can possibly expand the application area of 3D printed hydroxyapatite scaffolds.

Cellular Ti6Al4V with carbon nanotube-like structures fabricated by selective electron beam melting

Purpose – The purpose of this paper is to fabricate cellular Ti6Al4V with carbon nanotube (CNT)-like structures by selective electron beam melting and study the resultant mechanical properties based on each respective geometry to provide fundamental information for optimizing molecular architectures and predicting the mechanical properties of cellular solids. Design/methodology/approach – Cellular Ti6Al4V with CNT-like zigzag and armchair structures are fabricated by selected electron beam melting. The microstructures and mechanical properties of these samples are evaluated utilizing scanning electron microscopy, synchrotron radiation X-ray and compressive tests. Findings – The mechanical properties of the cellular solids depend on the geometry of strut architectures. The armchair-structured Ti6Al4V samples exhibit Young’s modulus from 501.10 to 707.60 MPa and compressive strength from 8.73 to 13.45 MPa. The zigzag structured samples demonstrate Young’s modulus from 548.19 to 829.58 MPa and compressive st...

Investigation of powder removal of net–structured titanium parts made from electron beam melting

Selective electron beam melting (SEBM) is a relatively new additive manufacturing technology for metallic materials. Post–processing of parts produced by SEBM typically involves the removal of semi–sintered powder through the use of a powder blasting system. Current equipment has limited ability to enter net structures that have small pore sizes and/or require a large penetration depth. In this study, a basic evaluation of the removal of semisintered powder of several net–structured parts has been made. The aim of this study was to remove the residual powder with an established powder blast system and find relations between its penetration of depth and the pore dimensions of a part in order to predict the behaviour and feasibility of powder removal in future net–structured component designs. It was found that a linear dependency exists between the depth of penetration and pore dimensions.

An Investigation of Sintering Parameters on Titanium Powder for Electron Beam Melting Processing Optimization

Selective electron beam melting (SEBM) is a relatively new additive manufacturing technology for metallic materials. Specific to this technology is the sintering of the metal powder prior to the melting process. The sintering process has disadvantages for post-processing. The post-processing of parts produced by SEBM typically involves the removal of semi-sintered powder through the use of a powder blasting system. Furthermore, the sintering of large areas before melting decreases productivity. Current investigations are aimed at improving the sintering process in order to achieve better productivity, geometric accuracy, and resolution. In this study, the focus lies on the modification of the sintering process. In order to investigate and improve the sintering process, highly porous titanium test specimens with various scan speeds were built. The aim of this study was to decrease build time with comparable mechanical properties of the components and to remove the residual powder more easily after a build. By only sintering the area in which the melt pool for the components is created, an average productivity improvement of approx. 20% was achieved. Tensile tests were carried out, and the measured mechanical properties show comparatively or slightly improved values compared with the reference.

Effects of Build Orientation on Surface Morphology and Bone Cell Activity of Additively Manufactured Ti6Al4V Specimens

Additive manufacturing of lightweight or functional structures by selective laser beam (SLM) or electron beam melting (EBM) is widespread, especially in the field of medical applications. SLM and EBM processes were applied to prepare Ti6Al4V test specimens with different surface orientations (0°, 45° and 90°). Roughness measurements of the surfaces were conducted and cell behavior on these surfaces was analyzed. Hence, human osteoblasts were seeded on test specimens to determine cell viability (metabolic activity, live-dead staining) and gene expression of collagen type 1 (Col1A1), matrix metalloprotease (MMP) 1 and its natural inhibitor, TIMP1, after 3 and 7 days. The surface orientation of specimens during the manufacturing process significantly influenced the roughness. Surface roughness showed significant impact on cellular viability, whereas differences between the time points day 3 and 7 were not found. Collagen type 1 mRNA synthesis rates in human osteoblasts were enhanced with increasing roughness. Both manufacturing techniques further influenced the induction of bone formation process in the cell culture. Moreover, the relationship between osteoblastic collagen type 1 mRNA synthesis rates and specimen orientation during the building process could be characterized by functional formulas. These findings are useful in the designing of biomedical applications and medical devices.

IMPROVEMENT OF MECHANICAL PROPERTIES OF BONE TISSUE ENGINEERED SCAFFOLDS THROUGH SINTERING AND INFILTRATION WITH BIOPOLYMERS

Additive manufacturing is an innovative manufacturing technique that can build complex porous scaffolds. One promising additive manufacturing technology is 3D printing (3DP) which can be used to build individual scaffolds out of ceramics for bone tissue engineering. However, 3D printed ceramic scaffolds have rather bad mechanical properties and are therefore in focus for improvement. The aim of this study was to improve the mechanical properties of 3DP scaffolds through infiltration with biopolymers. The hypothesis is that through infiltrating the ceramic scaffold, micropores are filled with the polymer leading to a composite with higher compressive strength. As a ceramic, hydroxyapatite powder was used to generate porous scaffolds with a 3D printing machine. The 3D printed scaffolds were sintered and infiltrated with two different biopolymers. Mechanical tests show an improvement on compressive strength. Infiltrated scaffolds have the potential to be used for the treatment of bone defects in load bearing regions.

Comparison of Elisa Sensitivity Relating to Manual and Low-Pressure Loading of the Fluidic Test Device.

A novel point-of-care (POC) allergy diagnostic device was used to investigate the sensitivity of an enzyme linked immunosorbent assay (ELISA) in reference to a manual delivery of fluids via a syringe and an automatic delivery of fluids with the aid of a vacuum pump. The results were obtained with an optical reading device for quantitative analysis.