Oral films (OFs) continue to attract attention as drug delivery systems, particularly for pedatric and geriatric needs. However, immiscibility between different polymers limits the full potential of OFs from being explored. One example is pullulan (PUL), a novel biopolymer which often has to be blended with other polymers to reduce cost and alter its mechanical properties. In this study, the state-of-the-art in fabrication techniques, three-dimensional (3D) printing was used to produce hybrid film structures of PUL and hydroxypropyl methylcellulose (HPMC), which were loaded with caffeine as a model drug. 3D printing was used to control the spatial deposition of films. HPMC was found to increase the mean mechanical properties of PUL films, where the tensile strength, elastic modulus and elongation break increased from 8.9 to 14.5 MPa, 1.17 to 1.56 GPa and from 1.48% to 1.77%, respectively. In addition, the spatial orientation of the hybrid films was also explored to determine which orientation could maximize the mechanical properties of the hybrid films. The results revealed that 3D printing could modify the mechanical properties of PUL whilst circumventing the issues associated with immiscibility.

Ti foams are advanced materials with great potential for biomedical applications as they can promote bone ingrowth, cell migration and attachment through providing interconnected porous channels that allow the penetration of the bone-forming cells and provide them with anchorage sites. However, Ti is a bio-inert material and thus only mechanical integration is achieved between the porous implant and the surrounding tissue, not the chemical integration which would be desirable. In this work particles of a biologically active material (Hydroxyapatite, HA) are blended with titanium powder, and used to produce Ti foams through the use of Metal Injection Moulding (MIM) in combination with a space holder. This produces titanium foams with incorporated HA, potentially inducing more favourable bone response to an implant from the surrounding tissue and improving the osseointegration of the Ti foams. To be able to do this, samples need to show sufficient mechanical and biocompatibility properties, and the foams produced were assessed for their mechanical behaviour and in vitro biological response. It was found that the incorporation of high levels of HA into the Ti foams induces brittleness in the structure and reduces the load bearing ability of the titanium foams as the chemical interaction between Ti and HA results in weak ceramic phases. However, adding small amounts of HA (about 2 vol%) was found to increase the yield strength of the Ti foams by 61% from 31.6 MPa to 50.9 MPa. Biological tests were also carried out in order to investigate the suitability of the foams for biomedical applications. It was found that Ti foams both with and without HA (at the 2 vol% addition level) support calcium and collagen production and have a good level of biocompatibility, with no significant difference observed between samples with and without the HA addition.

Fused deposition fabrication (FDF) three-dimensional printing is a potentially transformative technology for fabricating pharmaceuticals. The state-of-the-art technology is still in its infancy and requires a concerted effort to realize its potential. One aspect includes the processing parameters of FDF and the effect of formulation thereto, which, to date, have not been thoroughly investigated. To progress understanding, the effect of different molecular weight poly(ethylene glycol)s (PEG) on polycaprolactone (PCL) loaded with ciprofloxacin (CIP) was investigated. A rheometer was used, and adapted accordingly, to analyze three processing aspects pertaining to FDF: viscosity, solidification, and adhesion. The results revealed that both CIP and PEG affected all three processing parameters. The salient findings were that the ternary blend with 10% w/w PEG 8000 exhibited rheological and adhesive properties ideal for FDF, as it provided a desirably shear-thinning filament that solidified rapidly, and improved the adhesion strength, in comparison to both the PCL-CIP binary blend and other ternary blends. In contrast, the ternary blend with 15% w/w PEG 200 was unfavorable; despite having a greater plasticizing effect, whereby the viscosity was markedly reduced, the sample provided no benefit to the solidification behavior of PCL-CIP and, in addition, failed to display adhesive behavior, which is a necessity for a successful print in FDF. The original findings herein set the precedent that the effect of drug and PEG on FDF processing should be considered beyond solely modifying the viscosity.

In the case of Wall Climbing Robot (WCR) design, nature has always been one of the biggest inspirations. While WCR designs have been incorporating adhesion techniques inspired by organisms, including reptiles, insects, amphibians and marine invertebrates, most efforts have been focusing mainly on adhesion for dry surfaces. For WCRs to become widely applicable under all environments, given the vast areas of this planet described by high precipitation, the ability to scale vertical surfaces in wet conditions should be considered a design necessity. To this goal, this article focuses on the most commonly adopted adhesion mechanisms, while providing an overview on recent WCR technological advances through the prism of wet adhesion. An extensive outlook is also detailed, including promising research directions yet to be trialed in bio-inspirations and recent material developments, which could further bridge the gap between WCR design and wet adhesion towards all-environment climbing robots.

The successful fabrication of hydroxyapatite-bioactive glass scaffolds using honeycomb extrusion is presented herein. Hydroxyapatite was combined with either 10 wt% stoichiometric Bioglass^® (BG1), calcium-excess Bioglass^® (BG2) or canasite (CAN). For all composite materials, glass-induced partial phase transformation of the HA into the mechanically weaker β-tricalcium phosphate (TCP) occurred but XRD data demonstrated that BG2 exhibited a lower volume fraction of TCP than BG1. Consequently, the maximum compressive strength observed for BG1 and BG2 were 30.3 ± 3.9 and 56.7 ± 6.9 MPa, respectively, for specimens sintered at 1300 °C. CAN scaffolds, in contrast, collapsed when handled when sintered below 1300 °C, and thus failed. The microstructure illustrated a morphology similar to that of BG1 sintered at 1200 °C, and hence a comparable compressive strength (11.4 ± 3.1 MPa). The results highlight the great potential offered by honeycomb extrusion for fabricating high-strength porous scaffolds. The compressive strengths exceed that of commercial scaffolds, and biological tests revealed an increase in cell viability over seven days for all hybrid scaffolds. Thus it is expected that the incorporation of 10 wt% bioactive glass will provide the added advantage of enhanced bioactivity in concert with improved mechanical stability.

Ceramic honeycomb extrusion is a technique capable of attaining high strength, porous ceramics. However, challenges prevent the realisation of its potential. These include the design of an intricate honeycomb die and the formulation of an extrudable paste. The present study addresses the latter by using guar gum (GG) as a binder. GG was rationally selected because hydrogels thereof exhibit strong shear-thinning and high stiffness properties, which are required for extrusion. Rheological analyses demonstrated ceramic pastes with similar qualities were achieved, with hydroxyapatite (HA) used as the model ceramic. The shear stiffness modulus of HA pastes was determined as 8.4 MPa with a yield stress of 1.1 kPa. Moreover, this was achieved with GG as the sole additive, which further facilitates the overall fabrication process. The binder extraction notably occurred at relatively low temperatures when other high molecular weight polymers demand temperatures above 1000 °C; therefore the latter precludes the use of ceramics with low sintering onset. The process culminated in a porous HA scaffold with similar porosity to that of a commercial HA graft, but with higher compressive strength. Lastly, the study notes that the biological and water-soluble properties of GG can broaden its application into other ceramic fabrication processes.

In this study, we have developed hydroxyapatite (HA) scaffolds for synthetic bone graft from nano-sized HA particles using ceramic extrusion. We also demonstrate that these HA scaffolds show enhanced compressive strength (29.4 MPa), whilst possessing large pore sizes (> 600 µm) that are suitable for bone grafting. The extrusion process involved forming a ceramic paste by mixing the HA powder with a binder and distilled water. The ceramic paste was then fabricated using a ram extruder that was fitted with a honeycomb die to impart large, structured pores. Several green bodies were extruded and then subjected to the same drying and thermal debinding treatment. The samples underwent three different sintering temperatures and two varied dwell times, in order to determine the optimum sintering parameters. The scaffolds were then analysed for their chemical, physical, mechanical and biological properties to elucidate the effects of the sintering parameters on extruded HA scaffolds. The results revealed that the nano-sized particles exhibited a high sinterability, and XRD analysis showed phase purity until 1300 oC. At 1300 oC, trace amounts of phase impurities were detected, however, scaffolds sintered at this temperature exhibited the highest mean compressive strength. The findings demonstrated that traces of phase impurities were not detrimental to the scaffold’s compressive strength. In addition, scanning electron microscopy and density measurements revealed a highly densified solid phase was attained.

The field of biomaterials is an exuberant and enticing field, attracting interest across a number of scientific disciplines. Synthetic materials such as metals and ceramics have helped civilisation accomplish many feats, and this can also be said for the achievements in orthopaedic applications. Metals and ceramics have achieved success in non-load-bearing applications and attempts are made to translate the accomplishments into weight-bearing applications. For this, a material needs to be porous but with sufficient strength to withstand daily loading; however, both properties are mutually exclusive. The implant must also avoid causing adverse reactions and toxicity and, preferably, bond to the surrounding tissues. Metals such as stainless steels and chromium-cobalt alloys have been used due to their excellent mechanical properties that can withstand daily activities, but retrospective studies have alluded to the possibilities of significant adverse reaction when implanted within the human body, caused by the elution of metal ions. Lessons from metals have also demonstrated that materials with significantly higher mechanical properties will not necessarily enhance the longevity of the implant—such is the complexity of the human body. Ceramics, on the other hand, exhibit excellent biocompatibility, but their mechanical properties are a significant hindrance for load-bearing use. Thus, the chapter herein provides a select overview of contemporary research undertaken to address the aforementioned drawbacks for both metals and ceramics. Furthermore, the chapter includes a section of how metals and ceramics can be combined in a multi-material approach to bring together their respective properties to achieve a desirable characteristics.