Additive Manufacturing, Modeling and Performance Evaluation of 3D Printed Fins for Surfboards

We demonstrate that Additive Manufacturing (3D printing) is a viable approach to rapidly prototype personalised fins for surfboards. Surfing is an iconic sport that is extremely popular in coastal regions around the world. We use computer aided design and 3D printing of a wide range of composite materials to print fins for surfboards, e.g. ABS, carbon fibre, fibre glass and amorphous thermoplastic poly(etherimide) resins. The mechanical characteristics of our 3D printed fins were found to be comparable to commercial fins. Computational fluid dynamics was employed to calculate longitudinal (drag) and tangential (turning) forces, which are important for surfboard maneuverability, stability and speed. A commercial tracking system was used to evaluate the performance of 3D printed fins under real-world conditions (i.e. surfing waves). These data showed that the surfing performance of surfboards with 3D printed fins is similar to that of surfboards with commercial fins

3D Printing of Transparent and Conductive Heterogeneous Hydrogel-Elastomer Systems

Hydrogel-based ionic devices represent an alternative approach to stretchable electronics through use of soft ionic conductors that are both highly stretchable and transparent. However, these devices require the integration of dissimilar materials, dielectric elastomers and hydrogels, into a single system; a process thus far achieved primarily via the combination of several different manufacturing techniques. We have developed a 3D extrusion printing technique capable of fabricating an entire ionic circuit that integrates a LiCl-doped poly(acrylamide) (PAAm) hydrogel with a poly(dimethylsiloxane) (PDMS) dielectric elastomer. By incorporating hygroscopic salts such as LiCl into the hydrogel, we are able to prepare an ionically conductive hydrogel with excellent water-retaining properties. For printing reliability, we have optimized the rheological properties of a high ionic-strength hydrogel precursor and the interfacial energy between PDMS and hydrogel. Printed ionic devices that consist of PAAm and PDMS exhibit outstanding mechanical and electrical stability when tested with up to 1000 cycles of uniaxial tension. Moreover, we successfully demonstrate functionality in terms of signal transmission and as a soft sensor by fabricating and characterizing an ionic cable and several strain gauges.Engineering and Applied Science

Age-Dependent Maturation of Toll-Like Receptor-Mediated Cytokine Responses in Gambian Infants

The global burden of neonatal and infant mortality due to infection is staggering, particularly in resource-poor settings. Early childhood vaccination is one of the major interventions that can reduce this burden, but there are specific limitations to inducing effective immunity in early life, including impaired neonatal leukocyte production of Th1-polarizing cytokines to many stimuli. Characterizing the ontogeny of Toll-like receptor (TLR)-mediated innate immune responses in infants may shed light on susceptibility to infection in this vulnerable age group, and provide insights into TLR agonists as candidate adjuvants for improved neonatal vaccines. As little is known about the leukocyte responses of infants in resource-poor settings, we characterized production of Th1-, Th2-, and anti-inflammatory- cytokines in response to agonists of TLRs 1-9 in whole blood from 120 Gambian infants ranging from newborns (cord blood) to 12 months of age. Most of the TLR agonists induced TNFα, IL-1β, IL-6, and IL-10 in cord blood. The greatest TNFα responses were observed for TLR4, -5, and -8 agonists, the highest being the thiazoloquinoline CLO75 (TLR7/8) that also uniquely induced cord blood IFNγ production. For most agonists, TLR-mediated TNFα and IFNγ responses increased from birth to 1 month of age. TLR8 agonists also induced the greatest production of the Th1-polarizing cytokines TNFα and IFNγ throughout the first year of life, although the relative responses to the single TLR8 agonist and the combined TLR7/8 agonist changed with age. In contrast, IL-1β, IL-6, and IL-10 responses to most agonists were robust at birth and remained stable through 12 months of age. These observations provide fresh insights into the ontogeny of innate immunity in African children, and may inform development of age-specific adjuvanted vaccine formulations important for global health

Development of conducting carbon inks for direct writing of soft strain gauges

Soft robotics is a rapidly emerging field, and the demand for intelligent, compliant actuators is on the rise. To this end, a strain gauge that can be 3D printed on a soft substrate is required, to match this ever-evolving field. Conductive carbon materials, such as carbon nanotubes (CNTs) have been previously presented as such a material. n this project, a vapour grown carbon nanofibre (VGCNF): gellan gum (GG) stable dispersion is projected through horn sonication, and is characterised through electrical, mechanical and rheological testing on a dry film, as well as a surface morphology

Conducting carbon nanofibre networks: dispersion optimisation, evaporative casting and direct writing

The optimisation of vapour-grown carbon nanofibres (VGCNFs) dispersed in the biopolymer gellan gum (GG) and its usage as an ink for the direct writing of conducting networks are reported. Sonication optimisation showed that dispersing 10 mg per mL VGCNFs required 3 mg per mL GG solution and 4 minutes of low energy probe sonication. Free-standing films prepared by evaporative casting were found to exhibit electrical conductivity values of up to 35 ± 2 S cm-1. It is demonstrated that sonolysis has a detrimental effect on electrical conductivity. The dispersions were easily modified to allow for direct writing of conducting networks on paper using a commercial fountain pen. The electrical characteristics of these direct written electrodes (on paper) improved with increasing number of layers. The written electrodes on paper were used to connect a battery to a light emitting diode to demonstrate that they can be used in simple devices

3D/4D Printing Hydrogel Composites: A Pathway to Functional Devices

The past few years have seen the introduction of a number of 3D and 4D printing techniques used to process tough hydrogel materials. The use of \u27color\u27 3D printing technology where multiple inks are used in the one print allows for the production of composite materials and structures that can further enhance the mechanical performance of the printed hydrogel. This article reviews a number of 3D and 4D printing techniques for fabricating functional hydrogel based devices