Derek Covill

Adaptive voids

Additive manufacturing processes have the potential to change the way we produce everyday objects. Design for additive manufacturing focuses on dealing with the characteristics and constraints of a given additive process. These constraints include both geometric and material constraints which have a major impact on the feasibility, quality and cost of the printed object. When designing for additive manufacturing, one of the desirable objectives is to reduce the amount of material while maximising the strength of the printed part. For this, the inclusion of cellular structures in the design has been an efficient way to address these constraints while supporting other application-specific requirements. These structures, which are commonly inspired by shapes found in nature, provide high strength while maintaining a low mass. In this paper we propose the adaptive voids algorithm, an automatic approach to generate, given a volume boundary, a parameterised adaptive infill primal and/or dual cellular structure for additive manufacturing. The produced output can potentially be applied in various applications, including design and engineering, architecture, clothing and protective equipment, furniture and biomedical applications.

Development of thermal models of footwear using finite element analysis.

Thermal comfort is increasingly becoming a crucial factor to be considered in footwear design. The climate inside a shoe is controlled by thermal and moisture conditions and is crucial to attain comfort. Research undertaken has shown that thermal conditions play a dominant role in shoe climate. Development of thermal models that are capable of predicting in-shoe temperature distributions is an effective way forward to undertake extensive parametric studies to assist optimized design. In this paper, two-dimensional and three-dimensional thermal models of in-shoe climate were developed using finite element analysis through commercial code Abaqus. The thermal material properties of the upper shoe, sole, and air were considered. Dry heat flux from the foot was calculated on the basis of typical blood flow in the arteries on the foot. Using the thermal models developed, in-shoe temperatures were predicted to cover various locations for controlled ambient temperatures of 15, 25, and 35 °C respectively. The predicted temperatures were compared with multipoint measured temperatures through microsensor technology. Reasonably good correlation was obtained, with averaged errors of 6, 2, and 1.5 per cent, based on the averaged in-shoe temperature for the above three ambient temperatures. The models can be further used to help design shoes with optimized thermal comfort.

Parametric 3D-fitted frames for packaging heritage artefacts

Packing fragile heritage artefacts is a challenge almost all heritage organisations have to deal with when faced with the task of transporting or storing the artefacts. The packaging solution requires fitting the artefact correctly in order to ensure the protection and safety of the item; but also to be easy and cost effective to produce. Different techniques have been traditionally used, such as double boxing, padding negative spaces and cushioning braces. However, the introduction of 3D technologies for documenting these artefacts enables innovative uses of this data for packaging purposes. Hence, this paper proposes the use of the generative modelling language in order to produce unique 3D-fitted containers for packaging heritage artefacts which fit tightly the artefact, and can be made to be reusable and more durable than traditional packaging solutions. We propose to adopt an octet lattice as a low density internal structure to the proposed container. By combining the parametric package design, 3D meshes acquisition and 3D printing techniques, we present a technology based solution to the traditional problem of protecting these valuable artefacts for transportation and/or storing purposes.

Electrochemical fecal pellet sensor for simultaneous real-time ex vivo detection of colonic serotonin signalling and motility

Various investigations have focused on understanding the relationship between mucosal serotonin (5-HT) and colonic motility, however contradictory studies have questioned the importance of this intestinal transmitter. Here we described the fabrication and use of a fecal pellet electrochemical sensor that can be used to simultaneously detect the release of luminal 5-HT and colonic motility. Fecal pellet sensor devices were fabricated using carbon nanotube composite electrodes that were housed in 3D printed components in order to generate a device that had shape and size that mimicked a natural fecal pellet. Devices were fabricated where varying regions of the pellet contained the electrode. Devices showed that they were stable and sensitive for ex vivo detection of 5-HT, and no differences in the fecal pellet velocity was observed when compared to natural fecal pellets. The onset of mucosal 5-HT was observed prior to the movement of the fecal pellet. The release of mucosal 5-HT occurred oral to the fecal pellet and was linked to the contraction of the bowel wall that drove pellet propulsion. Taken, together these findings provide new insights into the role of mucosal 5-HT and suggest that the transmitter acts as a key initiator of fecal pellet propulsion.

Take away body parts! an investigation into the use of 3D-printed anatomical models in undergraduate anatomy education

Understanding the three‐dimensional (3D) nature of the human form is imperative for effective medical practice and the emergence of 3D printing creates numerous opportunities to enhance aspects of medical and healthcare training. A recently deceased, un‐embalmed donor was scanned through high‐resolution computed tomography. The scan data underwent segmentation and post‐processing and a range of 3D‐printed anatomical models were produced. A four‐stage mixed‐methods study was conducted to evaluate the educational value of the models in a medical program. (1) A quantitative pre/post‐test to assess change in learner knowledge following 3D‐printed model usage in a small group tutorial; (2) student focus group (3) a qualitative student questionnaire regarding personal student model usage (4) teaching faculty evaluation. The use of 3D‐printed models in small‐group anatomy teaching session resulted in a significant increase in knowledge (P = 0.0001) when compared to didactic 2D‐image based teaching methods. Student focus groups yielded six key themes regarding the use of 3D‐printed anatomical models: model properties, teaching integration, resource integration, assessment, clinical imaging, and pathology and anatomical variation. Questionnaires detailed how students used the models in the home environment and integrated them with anatomical learning resources such as textbooks and anatomy lectures. In conclusion, 3D‐printed anatomical models can be successfully produced from the CT data set of a recently deceased donor. These models can be used in anatomy education as a teaching tool in their own right, as well as a method for augmenting the curriculum and complementing established learning modalities, such as dissection‐based teaching. Anat Sci Educ 11: 44–53.

Finite Element Analysis of the Heat Transfer in Footwear (P186)

This paper outlines the use of finite element analysis to describe the heat transfer in footwear. Experiments were conducted to determine the temperature distribution in footwear with a variety of environmental temperature and footwear properties considered. Finite element models describing the heat transfer between the foot, sock and shoe are presented with the conductivity, specific heat and density properties of each material presented taken from literature. Based on foot geometry obtained from plaster casts, these models predicted temperatures within footwear with conduction, convection and radiation taken into account. Results from the models were compared with experimental findings with generally good agreement; however the models were limited by a simplified heat input value based on whole body values which did not account for the counter current heat exchange and also by the absence of evaporation as a mode of heat transfer which was significant in hotter conditions. A sensitivity analysis on the heat transfer models showed that the major contributors to the in-shoe conditions under dry heat transfer were the ambient temperature and the initial temperatures of the foot, while the heat flux and sock conductivity also had a minor affect. Further studies are required to include the effects of evaporation and to include the counter current heat exchange as a control for heat input to the foot.

The effects of printing orientation on the electrochemical behaviour of 3D printed acrylonitrile butadiene styrene (ABS)/carbon black electrodes

Additive manufacturing also known as 3D printing is being utilised in electrochemistry to reproducibly develop complex geometries with conductive properties. In this study, we explored if the electrochemical behavior of 3D printed acrylonitrile butadiene styrene (ABS)/carbon black electrodes was influenced by printing direction. The electrodes were printed in both horizontal and vertical directions. The horizsontal direction resulted in a smooth surface (HPSS electrode) and a comparatively rougher surface (HPRS electrode) surface. Electrodes were characterized using cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. For various redox couples, the vertical printed (VP) electrode showed enhanced current response when compared the two electrode surfaces generated by horizontal print direction. No differences in the capacitive response was observed, indicating that the conductive surface area of all types of electrodes were identical. The VP electrode had reduced charge transfer resistance and uncompensated solution resistance when compared to the HPSS and HPRS electrodes. Overall, electrodes printed in a vertical direction provide enhanced electrochemical performance and our study indicates that print orientation is a key factor that can be used to enhance sensor performance.

3D Printed Molds Encompassing Carbon Composite Electrodes To Conduct Multisite Monitoring in the Entire Colon

The activity of the colon is regulated by chemical signaling, of which serotonin (5-HT) is a key transmitter. Monitoring of mucosal 5-HT overflow has been achieved to date using microelectrodes on a small segment of colonic tissue; however, little is known if such measurements are reflective with regards to 5-HT signaling from the entire colon. This study focused on developing an electrochemical array device that could be utilized to conduct multisite measurements of 5-HT overflow from the entire colon. A 3D printed mold was fabricated that could house 6 multiwall carbon nanotube composite electrodes and provide a fixed distance between the electrodes and the tissue along the entire length of the colon. The electrodes were assessed for sensitivity, stability, and crosstalk before conducting in vitro measurements using colons obtained from 6- and 24-month old mice. As composite electrodes can have a high degree of variability, normalization factors were required between electrodes for a given array. The device had the sensitivity and stability required for 5-HT measurements from intestinal tissue. Regio-specific changes in 5-HT overflow were observed with age, where increases in 5-HT overflow were observed in the distal colon due to an impairment/loss in the serotonin transporter (SERT). Our strategy can be utilized to develop arrays of varying sizes and geometries, which can offer practical solutions for large-scale tissue measurements.

Simplified 3-D FE model of thermal conditions inside a shoe

To design thermally comfortable shoes, the knowledge of thermal conditions inside the shoes and the variables affecting those conditions is necessary. A simplified 3-D thermal numerical model of a shoe has been developed. A new approach was adopted to construct the mesh. The model was developed to consider the dry heat transfer in the shoe and convective heat loss from the outer surface of the shoe. The foot was the source of the heat in the model. Model’s predictions were compared with the results obtained during the experiments. The predicted in-shoe temperatures correlated reasonably well with the measurements although they were higher than the measurements in some cases. Probable reasons behind some inconsistency between predictions and the measured temperatures have been discussed. The paper concludes that the model’s predictions can be improved by incorporating the effect of other variables.

Use of Static Stiffness Behaviour to Characterise Field Hockey Sticks (P185)

The aim of this paper was to quantify the static stiffness behaviour of a variety of field hockey sticks, and to move towards a standard for their characterisation. A range of stick designs were tested at two different sections of the stick for bending stiffness. An Instron 8500 tensile and compressive testing apparatus was used to load the sticks in a simple 3-point bending regime and the results were independent of testing geometry. The mean flexural rigidity (EI product) of the samples ranged from 430–1069 Nm2 towards the handle, and 310–636 Nm2 towards the head and these were directly comparable to those measured in other studies of field hockey sticks. Small but acceptable variations (standard deviation of 2%) were associated with the simplified compression adjustment factor, and these could be reduced further by minimising the compression at the point of load. The flexural rigidity for sticks of the same design were shown to vary considerably (up to 15% standard deviation from the mean).