S. Guceri

Mechanical characterization of parts fabricated using fused deposition modeling

Layered manufacturing is an evolution of rapid prototyping (RP) techniques where the part is built in layers. While most of the previous applications focused on building “prototypes”, recent developments in this field enabled some of the prototyping methods to achieve an agile fabrication technology to produce the final product directly. A shift from prototyping to manufacturing of the final product necessitates broadening of the material choice, improvement of the surface quality, dimensional stability, and achieving the necessary mechanical properties to meet the performance criteria. The current study is part of an ongoing project to adapt fused deposition modeling to fabrication of ceramic and multi‐functional components. This paper presents a methodology of the mechanical characterization of products fabricated using fused deposition modeling.

Precision extruding deposition and characterization of cellular poly‐ε‐caprolactone tissue scaffolds

Successes in scaffold guided tissue engineering require scaffolds to have specific macroscopic geometries and internal architectures to provide the needed biological and biophysical functions. Freeform fabrication provides an effective process tool to manufacture many advanced scaffolds with designed properties. This paper reports our recent study on using a novel precision extruding deposition (PED) process technique to directly fabricate cellular poly‐e_rm;‐caprolactone (PCL) scaffolds. Scaffolds with a controlled pore size of 250 μm and designed structural orientations were fabricated.

Precision extruding deposition (PED) fabrication of polycaprolactone (PCL) scaffolds for bone tissue engineering

Bone tissue engineering is an emerging field providing viable substitutes for bone regeneration. Recent advances have allowed scientists and engineers to develop scaffolds for guided bone growth. However, success requires scaffolds to have specific macroscopic geometries and internal architectures conducive to biological and biophysical functions. Freeform fabrication provides an effective process tool to manufacture three-dimensional porous scaffolds with complex shapes and designed properties. A novel precision extruding deposition (PED) technique was developed to fabricate polycaprolactone (PCL) scaffolds. It was possible to manufacture scaffolds with a controlled pore size of 350 microm with designed structural orientations using this method. The scaffold morphology, internal micro-architecture and mechanical properties were evaluated using scanning electron microscopy (SEM), micro-computed tomography (micro-CT) and mechanical testing, respectively. An in vitro cell-scaffold interaction study was carried out using primary fetal bovine osteoblasts. Specifically, the cell proliferation and differentiation was evaluated by Alamar Blue assay for cell metabolic activity, alkaline phosphatase activity and osteoblast production of calcium. An in vivo study was performed on nude mice to determine the capability of osteoblast-seeded PCL to induce osteogenesis. Each scaffold was implanted subcutaneously in nude mice and, following sacrifice, was explanted at one of a series of time intervals. The explants were then evaluated histologically for possible areas of osseointegration. Microscopy and radiological examination showed multiple areas of osseous ingrowth suggesting that the osteoblast-seeded PCL scaffolds evoke osteogenesis in vivo. These studies demonstrated the viability of the PED process to fabricate PCL scaffolds having the necessary mechanical properties, structural integrity, and controlled pore size and interconnectivity desired for bone tissue engineering.

New developments in fused deposition modeling of ceramics

Purpose – To shift from rapid prototyping (RP) to agile fabrication by broadening the material selection, e.g. using ceramics, hence improving the properties (e.g. mechanical properties) of fused deposition modeling (FDM) products.Design/methodology/approach – This paper presents the development of a novel extrusion system, based on the FDM technology. The new set‐up, consisting of a mini‐extruder mounted on a high‐precision positioning system, is fed with bulk material in granulated form, instead that with the more common filament.Findings – Previous research showed that the applications of new materials with specific characteristics in a commercial FDM system are limited by the use of intermediate precursors, i.e. a filament. The new design described in this paper overcomes the problem thanks to the new feeding system.Research limitations/implications – The work presented in this paper is only the starting point for further development. The new system design was tested and encouraging improvements of th...

Accelerated differentiation of osteoblast cells on polycaprolactone scaffolds driven by a combined effect of protein coating and plasma modification

A combined effect of protein coating and plasma modification on the quality of the osteoblast-scaffold interaction was investigated. Three-dimensional polycaprolactone (PCL) scaffolds were manufactured by the precision extrusion deposition (PED) system. The structural, physical, chemical and biological cues were introduced to the surface through providing 3D structure, coating with adhesive protein fibronectin and modifying the surface with oxygen-based plasma. The changes in the surface properties of PCL after those modifications were examined by contact angle goniometry, surface energy calculation, surface chemistry analysis (XPS) and surface topography measurements (AFM). The effects of modification techniques on osteoblast short-term and long-term functions were examined by cell adhesion, proliferation assays and differentiation markers, namely alkaline phosphatase activity (ALP) and osteocalcin secretion. The results suggested that the physical and chemical cues introduced by plasma modification might be sufficient for improved cell adhesion, but for accelerated osteoblast differentiation the synergetic effects of structural, physical, chemical and biological cues should be introduced to the PCL surface.

Fabrication of three-dimensional scaffolds using precision extrusion deposition with an assisted cooling device

In the field of biofabrication, tissue engineering and regenerative medicine, there are many methodologies to fabricate a building block (scaffold) which is unique to the target tissue or organ that facilitates cell growth, attachment, proliferation and/or differentiation. Currently, there are many techniques that fabricate three-dimensional scaffolds; however, there are advantages, limitations and specific tissue focuses of each fabrication technique. The focus of this initiative is to utilize an existing technique and expand the library of biomaterials which can be utilized to fabricate three-dimensional scaffolds rather than focusing on a new fabrication technique. An expanded library of biomaterials will enable the precision extrusion deposition (PED) device to construct three-dimensional scaffolds with enhanced biological, chemical and mechanical cues that will benefit tissue generation. Computer-aided motion and extrusion drive the PED to precisely fabricate micro-scaled scaffolds with biologically inspired, porosity, interconnectivity and internal and external architectures. The high printing resolution, precision and controllability of the PED allow for closer mimicry of tissues and organs. The PED expands its library of biopolymers by introducing an assisting cooling (AC) device which increases the working extrusion temperature from 120 to 250 °C. This paper investigates the PED with the integrated ACs capabilities to fabricate three-dimensional scaffolds that support cell growth, attachment and proliferation. Studies carried out in this paper utilized a biopolymer whose melting point is established to be 200 °C. This polymer was selected to illustrate the newly developed devices ability to fabricate three-dimensional scaffolds from a new library of biopolymers. Three-dimensional scaffolds fabricated with the integrated AC device should illustrate structural integrity and ability to support cell attachment and proliferation.

Fabrication and plasma treatment of 3D polycaprolactane tissue scaffolds for enhanced cellular function

This paper reports a solid free-form fabrication (SFF) technology-based precision extrusion deposition (PED) process to manufacture three-dimensional (3D) polycaprolactane (PCL) scaffolds and their surface treatment with a plasma source for enhanced osteoblast cell adhesion and proliferation. The PED process allows us to manufacture tissue engineering scaffolds based on designed geometry with complete interconnectivity and controllable porosity. The as-fabricated PCL scaffolds have a pattern with a 0/90° strut configuration of 300 µm pore size and 250 µm strut width. In order to improve cellular activity on 3D PCL scaffolds, they were surface-treated with an oxygen-based plasma source. The surface hydrophilicity and total surface energy of PCL was increased with plasma treatment. Comparisons of different plasma treatment times, including 30 seconds, and 1, 2, 3, 5 and 7 minutes, were performed to identify the plasma treatment duration suggesting higher cellular adhesion and proliferation. The maximum value of total surface energy and its components (polar and dispersive) was observed in 3-min treated PCL scaffolds. In addition, the positive effect of plasma treatment was observed in stregth of cell adhesion, which was increased 55% on 3-min plasma-treated scaffolds compared to untreated and other plasma treatment duriations. Cell culture study over a 7-day period also showed that the cell number on 3-min treated scaffolds is 3-fold the number of cells on untreated scaffolds.

Solid Freeform Fabrication of Polycaprolactone∕Hydroxyapatite Tissue Scaffolds

Bone tissue engineering is an emerging field providing viable substitutes for bone regeneration. Freeform fabrication provides an effective process tool to manufacture scaffolds with complex shapes and designed properties. We developed a novel precision extruding deposition (PED) technique to fabricate composite polycaprolactone/hydroxyapatite (PCL/HA) scaffolds. 25% concentration by weight of HA was used to reinforce 3D scaffolds. Two groups of scaffolds having 60% and 70% porosities and with pore sizes of 450 μm and 750 μm respectively, were evaluated for their morphology and compressive properties using scanning electron microscopy and the mechanical testing. In vitro cell-scaffold interaction study was carried out using primary fetal bovine osteoblasts. The cell proliferation and differentiation were evaluated by Alamar Blue assay and alkaline phosphatase activity. Our results suggested that compressive modulus of PCL/HA scaffold was 84 MPa for 60% porous scaffolds and was 76 MPa for 70% porous scaffolds. The osteoblasts were able to migrate and proliferate for the cultured time over the scaffolds. Our study demonstrated the viability of the PED process to fabricate PCL scaffolds having necessary mechanical property, structural integrity, controlled pore size, and pore interconnectivity desired for bone tissue engineering.

Precision Extruding Deposition for Freeform Fabrication of PCL and PCL-HA Tissue Scaffolds

Computer-aided tissue engineering approach was used to develop a novel Precision Extrusion Deposition (PED) process to directly fabricate Polycaprolactone (PCL) and composite PCL/Hydroxyapatite (PCL-HA) tissue scaffolds. The process optimization was carried out to fabricate both PCL and PCL-HA (25% concentration by weight of HA) with a controlled pore size and internal pore structure of the 0°/90° pattern. Two groups of scaffolds having 60 and 70% porosity and with pore sizes of 450 and 750 microns, respectively, were evaluated for their morphology and compressive properties using Scanning Electron Microscopy (SEM) and mechanical testing. The surface modification with plasma was conducted on PCL scaffold to increase the cellular attachment and proliferation. Our results suggested that inclusion of HA significantly increased the compressive modulus from 59 to 84 MPa for 60% porous scaffolds and from 30 to 76 MPa for 70% porous scaffolds. In vitro cell–scaffolds interaction study was carried out using primary fetal bovine osteoblasts to assess the feasibility of scaffolds for bone tissue engineering application. In addition, the results in surface hydrophilicity and roughness show that plasma surface modification can increase the hydrophilicity while introducing the nano-scale surface roughness on PCL surface. The cell proliferation and differentiation were calculated by Alamar Blue assay and by determining alkaline phosphatase activity. The osteoblasts were able to migrate and proliferate over the cultured time for both PCL as well as PCL-HA scaffolds. Our study demonstrated the viability of the PED process to the fabricate PCL and PCL-HA composite scaffolds having necessary mechanical property, structural integrity, controlled pore size and pore interconnectivity desired for bone tissue engineering.

Precision Extruding Deposition of Polycaprolactone and Composite Polycaprolactone/Hydroxyapatite Scaffolds for Tissue Engineering

Precision Extruding Deposition (PED) process wasused to directly fabricate Polycaprolactone (PCL) and PCL/Hydroxyapatite (HA) composite tissue scaffolds. HA powder wasmelt blended with PCL, a biodegradable polymer. Scaffolds with controlled pore size porosity were fabricated. The scaffold morphology and the mechanical properties were evaluated using SEM and mechanical testing. In vivo biological studies were conducted to investigate the cellular responses of the PCLscaffolds. Results and characterizations demonstrate the viabilityof the PED process as well as the good mechanical property, structural integrity, controlled pore size, pore interconnectivity, and the biological compatibility of the fabricated scaffolds.