Search results

The area of microfluidic systems has greatly enhanced the in vitro field of tissue engineering. Microfluidic systems such as microchannelled assays are now widely used for mimicking in vivo cell behaviour and studies into basic biological research. In certain cases engineered tissue cell design use 3D ordered geometrical configurations in vitro (such as microchannel assays) to reproduce native in vivo functions. The most common approach for manufacturing micro‐assays is now rapid prototyping (RP) technology. The choice of assay material is dependent on the proposed cell type and ultimately the tissue application. However, many RP technologies can be unsuitable for cell growth applications because of the construction methods and materials they employ. The purpose of this paper is to describe a comparison between two different RP 3D printing methods of fabrication and investigates the merits of each technology for direct cell culture applications using micro‐assays, while also examining the dispensing accuracy of both techniques.

Using a Thermojet and Spectrum Z510 printer pre‐designed micro‐assays incorporating different size microchannels are dispensed. The base materials of both methods are examined for cytotoxic effects while in solution with primary tendon fibroblasts (PFB) cells. After obtaining favorable results from the toxicology experiments, PFB cells are seeded onto the thermojet structures with a view to investigate cell adherence, encapsulation and how the channel width influences cell alignment.

This research concluded that the thermojet had a higher degree of accuracy when manufacturing structures that incorporate microchannels when compared with the Spectrum Z510. Both techniques show that the accuracy of the build decreases with reduction in channel width. The fact that the Spectrum Z510 structures have to be infiltrated with a hardening glue as a post‐processing technique (since the dispensed material is water‐based and hence soluble) causes a cytotoxic effect compared to the thermojet plastic which is not cytotoxic in solution with PFB cells. Seeding the PBF cells directly onto the thermoplastic structure caused problems due to the hydrophobic nature of the material and this necessitated the technique of soaking the structures in a collagen bath to penetrate the surface and reduce the interactions of hydrophobic species enhancing cell attachment and proliferation. Without this coating the thermojet structures induced strong hydrophobic interactions at the surfaces of the microchannels with the culture media resulting in non‐attachment and poor cell mortality.

This research paper describes a comparison between the base materials and methodology of two 3D printing techniques for applications in basic biological studies. This is achieved by analysing the dispensing accuracy of both technologies and the interaction between cells and surface at the interface.

Hydrogels with low viscosities tend to be difficult to use in constructing tissue engineering (TE) scaffolds used to replace or restore damaged tissue, due to the length of time it takes for final gelation to take place resulting in the scaffolds collapsing due to their mechanical instability. However, recent advances in rapid prototyping have allowed for a new technology called bioplotting to be developed, which aims to circumvent these inherent problems. This paper aims to present details of the process.

The paper demonstrates how by using the bioplotting technique complex 3D geometrical scaffolds with accurate feature sizes and good pore definition can be fabriated for use as biological matrices. PEG gels containing the cell‐adhesive RGD peptide sequence were patterned using this method to produce layers of directional microchannels which have a functionalised bioactive surface. Seeding these gels with C2C12 myoblasts showed that the cells responded to the topographical features and aligned themselves along the direction of the channels.

This process allows plotting of various materials into a media bath containing material of similar rheological properties which can be used to both support the structure as it is dispensed and also to initiate cross‐linking of the hydrogel. By controlling concentrations, viscosity and the temperature of both the plotting material and the plotting media, the speed of the hydrogel gelation can be enhanced whilst it is cross‐linking in the media bath. TE scaffolds have been produced using a variety of materials including poly(ethylene glycol) (PEG), gelatin, alginic acid and agarose at various concentrations and viscosities.

This paper describes one of the very few examples of accurate construction of 3D biological microporous matrices using hydrogel material fabricated by the bioplotting technique. This demonstrates that this technique can be used to produce 3D scaffolds which promote tissue regeneration.

Plantar force is the interface pressure existing between the foot plantar surface and the shoe sole during static or dynamic gait. Plantar force derived from gait and posture plays a critical role for rehabilitation, footwear design, clinical diagnostics and sports activities, and so on. This paper aims to review plantar force measurement technologies based on piezoelectric materials, which can make the reader understand preliminary works systematically and provide convenience for researchers to further study.

The review introduces working principle of piezoelectric sensor, structures and hardware design of plantar force measurement systems based on piezoelectric materials. The structures of sensors in plantar force measurement systems can be divided into four kinds, including monolayered sensor, multilayered sensor, tri-axial sensor and other sensor. The previous studies about plantar force measurement system based on piezoelectric technology are reviewed in detail, and their characteristics and performances are compared.

A good deal of measurement technologies have been studied by researchers to detect and analyze the plantar force. Among these measurement technologies, taking advantage of easy fabrication and high sensitivity, piezoelectric sensor is an ideal candidate sensing element. However, the number and arrangement of the sensors will influence the characteristics and performances of plantar force measurement systems. Therefore, it is necessary to further study plantar force measurement system for better performances.

So far, many plantar force measurement systems have been proposed, and several reviews already introduced plantar force measurement systems in the aspect of types of pressure sensors, experimental setups for foot pressure measurement analysis and the technologies used in plantar shear stress measurements. However, this paper reviews plantar force measurement systems based on piezoelectric materials. The structures of piezoelectric sensors in the measurement systems are discussed. Hardware design applied to measurement system is summarized. Moreover, the main point of further study is presented in this paper.

Bone tissue engineering is an emerging field providing viable substitutes for bone regeneration. Poly(ε‐caprolactone) (PCL) is a good candidate for scaffold fabrication due to its high mechanical strength and excellent resistance under moist conditions, but its hydrophobicity causes cell‐attached difficulties, thus limiting its clinical application. The paper aims to develop an air pressure‐aided deposition system for fabricating scaffolds made of synthesized PCL‐PEG‐PCL copolymers and to validate the biocompatibility and hydrophilicity improvement of fabricated scaffolds.

An air pressure‐aided deposition system that involves rapid prototyping technique has been developed to fabricate scaffolds for tissue engineering (TE) application. Poly(ethylene glycol) (PEG), a hydrophilic non‐ionic polymer, is adopted to reduce the hydrophobicity of PCL alone. The synthesis process of PCL‐PEG‐PCL copolymer is briefly introduced. Effect of viscosity in regard to scanning speed on the deposited strand is investigated. Scaffolds with different mean pore sizes are fabricated using the developed system. The fibroblast cells are seeded for culturing and biocompatibility of fabricated scaffolds are validated using methylthiazol tetrazolium assay.

The study finds that the air pressure‐aided deposition system is suitable for fabricating micro‐porous cellular scaffold, especially for thermal‐sensitive copolymers. In addition, the experimental results shows that at the molecular weight of 50,000, the molten form can be stably deposited through a heating nozzle at an air pressure of 0.3 MPa and no crack occurs after it solidifies. The scaffold with mean pore size of 339×396 μm is suitable for fibroblast binding and ingrowth. The synthesized copolymers are non‐toxic, biocompatible and can be used for biomedical application.

This study shows that weight ratio of PEG, 0.1, enhances the hydrophilicity of copolymer. Improvement regarding the weight ratio of PEG is necessary. Important challenges for further research are to optimize the fabrication parameter and pore interconnection for eliminating pore size error and enhancing cells proliferation, respectively.

An air pressure‐aided deposition system is successfully proposed to construct 3D tissue scaffolds. In addition, synthesized PCL‐PEG‐PCL copolymers are verified for biocompatibility and successfully fabricated into tissue scaffold with different mean pore sizes.

The purpose of this study is to characterize sintered hydroxyapatite (HA) samples produced by three-dimensional printing (3DP). This study is part of a project concerned with the fabrication of calcium phosphates implants by 3DP. However, before considering a more complex structure, like scaffolds or implants, a thorough knowledge of the role played by the sintering temperature on physical and mechanical the properties of porous HA is necessary.

The characteristics of sintered HA samples have been analyzed by means of x-ray diffraction, scanning electron microscope (SEM) and uniaxial compression tests. The 3DP parameters used to produce the HA samples were those who led to higher accuracy and mechanical stability.

Sintering temperature and powder morphology are critical factors influencing densification behavior, porosity, phase stability, mechanical strength and tangent modulus of the HA samples produced by 3DP. This study allowed us to conclude about the 3DP parameters to be used to produce porous HA specimens with the required integrity and dimensional accuracy, and the optimal post-processing sintering temperature which led to the best results in terms of porosity, microstructure, phase stability of HA and mechanical properties.

This paper provides a method to evaluate the manufacturability of calcium phosphate models produced by 3DP.

The purpose of this study is to evaluate how accurately a 3D printer could manufacture basic porous models. Geoscience research is evolving toward numerical prediction of porous rock properties, but laboratory tests are still considered a standard practice. 3D printing digital designs of porous models (proxies) is a way to bridge the gap between these two realms of inquiry.

Digital designs of simple porous models have been 3D-printed on an inkjet-style (polyjet) 3D printer. Porosity and pore-throat size distribution of proxies have been measured with helium porosimetry, mercury porosimetry and computed tomography (CT) image analysis. Laboratory results on proxies have been compared with properties calculated on digital designs and CT images.

Bulk volume of proxies was by 0.6-6.7 per cent lower than digital designs. 3D-printed porosity increased from 0.2 to 1.9 per cent compared to digital designs (0-1.3 per cent). 3D-printed pore throats were thinner than designed by 10-31 per cent.

Incomplete removal of support material from pores yielded inaccurate property measurements. The external envelope of proxies has been 3D-printed at higher accuracy than pores.

Characterization of these simple models improves understanding of how more complex rock models can be 3D-printed accurately and how both destructive (mercury porosimetry) and non-destructive (CT and helium porosimetry) methods can be used to characterize porous models.

Validation of 3D-printed porous models using a suite of destructive and non-destructive methods is novel.

The purpose of this study is therefore to detail an additive manufacturing process for printing TiD parts for implant applications. Titanium–diamond (TiD) is a new composite that provides biocompatible three-dimensional multimaterial structures. Thus, the authors report a powder-deposition and print optimization strategy to overcome the dual-functionality gap by printing bulk TiD parts. However, despite favorable customization outcomes, relatively few additive manufacturing (AM) feedstock powders offer the biocompatibility required for medical implant and device technologies.

AM offers a platform to fabricate customized patient-specific parts. Developing feedstock that can be 3D printed into specific 3D structures while providing a favorable interface with the human tissue remains a challenge. Using laser metal deposition, feedstock powder comprising diamond and titanium was co-printed into TiD parts for mechanical testing to determine optimal manufacturing parameters.

TiD parts were fabricated comprising 30% and 50% diamond. The composite powder had a Hausner ratio of 1.13 and 1.21 for 30% and 50% TiD, respectively. The flow analysis (Carney flow) for TiD 30% and 50% was 7.53 and 5.15 g/s. The authors report that the printing-specific conditions significantly affect the integrity of the printed part and thus provide the optimal manufacturing parameters for structural integrity as determined by micro-computed tomography, nanoindentation and biocompatibility of TiD parts. The hardness, ultimate tensile strength and yield strength for TiD are 4–6 GPa (depending on build position), 426 MPa and 375 MPa, respectively. Furthermore, the authors show that increasing diamond composition to 30% results in higher osteoblast viability and lower bacteria count than titanium.

In this study, the authors provide a clear strategy to manufacture TiD parts with high integrity, performance and biocompatibility, expanding the material feedstock library and paving the way to customized diamond implants. Diamond is showing strong potential as a biomedical material; however, upscale is limited by conventional techniques. By optimizing AM as the avenue to make complex shapes, the authors open up the possibility of patient-specific diamond implant solutions.