Imperial College London

DrConnorMyant

Faculty of EngineeringDyson School of Design Engineering

Senior Lecturer
 
 
 
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Contact

 

connor.myant Website

 
 
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Location

 

M224Royal College of ScienceSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

60 results found

Vladescu S-C, Agurto MG, Myant C, Boehm MW, Baier SK, Yakubov GE, Carpenter G, Reddyhoff Tet al., 2023, Protein-induced delubrication: How plant-based and dairy proteins affect mouthfeel, FOOD HYDROCOLLOIDS, Vol: 134, ISSN: 0268-005X

Journal article

Barrak FN, Li S, Mohammed AA, Myant C, Jones JRet al., 2022, Anti-inflammatory properties of S53P4 bioactive glass implant material., Journal of Dentistry, Vol: 127, ISSN: 0300-5712

OBJECTIVES: To assess whether the dissolution products of S53P4 bioactive glass (BG) affect cellular response of macrophages and clinically relevant peri-implant cell populations to dental implant particles in vitro. Cells chosen were human gingival fibroblasts (HGFs), osteoblasts and bone marrow derived stromal cells (HBMSCs). METHODS: Melt-derived S53P4 bioactive glass were prepared. HGFs, Saos-2 human osteoblastic cell line, HBMSCs and macrophages, derived from THP-1 human monocytic cell line, were cultured in the presence of particles from commercially pure titanium (Ti-CP4), grade 5 titanium alloy (Ti-6Al-4V), titanium-zirconium alloy (Ti-15Zr) or zirconia (Zr) (with respective diameters of 34.1 ± 3.8, 33.3 ± 4.4, 97.8 ± 8.2 and 71.3 ± 6.1 µm) with or without S53P4 dissolution products (conditioned media contained 327.30 ± 2.01 ppm Ca, 51.34 ± 0.41 ppm P and 61.48 ± 1.17 ppm Si, pH 8.01 ± 0.21). Inflammatory and macrophage polarisation markers including TNF-ɑ, IL-1, IL-6 and CD206 were quantified using enzyme-linked immunosorbent assay (ELISA). RESULTS: The presence of Ti-6Al-4V implant particles significantly induced the expression of pro-inflammatory markers in all tested cell types. S53P4 BG dissolution products regressed the particle induced up-regulation of pro-inflammatory markers and, appeared to suppress M1 macrophage polarisation. CONCLUSIONS: Implant particles, Ti-6Al-4V in particular, resulted in significant inflammatory responses from cells. S53P4 BG may possess anti-inflammatory properties and potentially mediate macrophage polarisation behaviour. CLINICAL SIGNIFICANCE: The findings highlight that the use and benefits of BG is a promising field of study. Authors believe more collective efforts are required to fully understand the reliability, efficiency and exact mechanisms of action of BG in the search for new generation of treatme

Journal article

Burge TA, Jeffers JRT, Myant CW, 2022, Performance and Sensitivity Analysis of an Automated X-Ray Based Total Knee Replacement Mass-Customization Pipeline, JOURNAL OF MEDICAL DEVICES-TRANSACTIONS OF THE ASME, Vol: 16, ISSN: 1932-6181

Journal article

Burge T, Jones G, Jordan C, Jeffers J, Myant Cet al., 2022, A computational tool for automatic selection of total knee replacementimplant size using x-ray images, Frontiers in Bioengineering and Biotechnology, Vol: 10, Pages: 1-11, ISSN: 2296-4185

Purpose: The aim of this study was to outline a fully automatic tool capable of reliably predicting the most suitable total kneereplacement implant sizes for patients, using bi-planar X-ray images. By eliminating the need for manual templating or guidingsoftware tools via the adoption of convolutional neural networks, time and resource requirements for pre-operative assessmentand surgery could be reduced, the risk of human error minimized, and patients could see improved outcomes.Methods: The tool utilizes a machine learning-based 2D – 3D pipeline to generate accurate predictions of subjects’ distal femur andproximal tibia bones from X-ray images. It then virtually fits different implant models and sizes to the 3D predictions, calculatesthe implant to bone root-mean-squared error and maximum over/under hang for each, and advises the best option for thepatient. The tool was tested on 78, predominantly White subjects (45 female/33 male), using generic femur component and tibiaplate designs scaled to sizes obtained for five commercially available products. The predictions were then compared to the groundtruth best options, determined using subjects’ MRI data.Results: The tool achieved average femur component size prediction accuracies across the five implant models of 77.95% in termsof global fit (root-mean-squared error), and 71.79% for minimizing over/underhang. These increased to 99.74% and 99.49% with ±1size permitted. For tibia plates, the average prediction accuracies were 80.51% and 72.82% respectively. These increased to99.74% and 98.98% for ±1 size. Better prediction accuracies were obtained for implant models with fewer size options, howeversuch models more frequently resulted in a poor fit.Conclusion: A fully automatic tool was developed and found to enable higher prediction accuracies than generally reported formanual templating techniques, as well as similar computational methods.

Journal article

Hong F, Tendera L, Myant C, Boyle Det al., 2022, Vacuum-Formed 3D Printed Electronics: Fabrication of Thin, Rigid and Free-Form Interactive Surfaces, SN Computer Science, Vol: 3, ISSN: 2662-995X

Vacuum-forming is a common manufacturing technique for constructing thin plastic shell products by pressing heated plastic sheets onto a mold using atmospheric pressure. Vacuum-forming is ubiquitous in packaging and casing products in the industry, spanning fast moving consumer goods to connected devices. Integrating advanced functionality, which may include sensing, computation and communication, within thin structures is desirable for various next-generation interactive devices. Hybrid additive manufacturing techniques like thermoforming are becoming popular for prototyping freeform surfaces owing to their design flexibility, speed and cost-effectiveness. This paper presents a new hybrid method for constructing thin, rigid and free-form interconnected surfaces via fused deposition modelling (FDM) 3D printing and vacuum-forming that builds on recent advances in thermoforming circuits. 3D printing the sheet material allows for the embedding of conductive traces within thin layers of the substrate, which can be vacuum-formed but remain conductive and insulated. This is an unexplored fabrication technique within the context of designing and manufacturing connected things. In addition to explaining the method, this paper characterizes the behavior of vacuum-formed 3D printed sheets, analyses the electrical performance of printed traces after vacuum-forming, and showcases a range of sample artefacts constructed using the technique. In addition, the paper describes a new design interface for designing conformal interconnects that allows designers to draw conductive patterns in 3D and export pre-distorted sheet models ready to be printed.

Journal article

Zhou Y, Myant C, Stewart R, 2022, Multifunctional and stretchable graphene/textile composite sensor for human motion monitoring, Journal of Applied Polymer Science, Vol: 139, ISSN: 0021-8995

Sensors based on electronic textiles (e-textiles) have become increasingly prominent in the field of biomechanical monitoring technology due to multiple properties such as being lightweight, flexible, and comfortable, with increasing potential in incorporating into long-term monitoring devices. Previous research has been conducted into textile strain sensors based on graphene for human motion monitoring, however most graphene e-textile strain sensors exhibit poor sensitivity and stretchability. To our knowledge, no previous research has looked at knitted graphene-based fabrics in regards to the fabric composition of the substrate. In this paper, we propose a graphene/fabric composite sensor using a cost-effective dip coating method of an acrylic/Spandex knit fabric, and further explores its mechanical, electrical, and sensing properties. The developed graphene/textile composite sensor has a wide sensing range (up to 344%) and exhibits a good sensitivity with a high gauge factor of up to 16. As a wearable sensor, our sensing fabric can detect both large and subtle human motions and is able to distinguish between various ranges of joint movements, demonstrating its ability to function as a human motion monitoring system. Our sensor further exhibits the ability to be used as a supercapacitor or capacitive pressure sensor.

Journal article

Burge T, Jeffers J, Myant C, 2022, A computational design of experiments based method for evaluation of off-the-shelf total knee replacement implants, Computer Methods in Biomechanics and Biomedical Engineering, ISSN: 1025-5842

A methodology to explore the design space of off-the-shelf total knee replacement implant designs is outlined. Generic femur component and tibia plate designs were scaled to thousands of sizes and virtually fitted to 244 test subjects. Various implant designs and sizing requirements between genders and ethnicities were evaluated. 5 sizes optimised via the methodology produced a good global fit for most subjects. However, clinically significant over/underhang was present in 19% of subjects for tibia plates and 25% for femur components, reducing to 11/20% with 8 sizes. The analysis highlighted subtly better fit performance was obtained using sizes with unequal spacing.

Journal article

Hong F, Hodges S, Myant C, Boyle DEet al., 2022, Open5x: Accessible 5-axis 3D printing and conformal slicing, Conference on Human Factors in Computing Systems - Proceedings

The common layer-by-layer deposition of regular, 3-axis 3D printing simplifies both the fabrication process and the 3D printer's mechanical design. However, the resulting 3D printed objects have some unfavourable characteristics including visible layers, uneven structural strength and support material. To overcome these, researchers have employed robotic arms and multi-axis CNCs to deposit materials in conformal layers. Conformal deposition improves the quality of the 3D printed parts through support-less printing and curved layer deposition. However, such multi-axis 3D printing is inaccessible to many individuals due to high costs and technical complexities. Furthermore, the limited GUI support for conformal slicers creates an additional barrier for users. To open multi-axis 3D printing up to more makers and researchers, we present a cheap and accessible way to upgrade a regular 3D printer to 5 axes. We have also developed a GUI-based conformal slicer, integrated within a popular CAD package. Together, these deliver an accessible workflow for designing, simulating and creating conformally-printed 3D models.

Journal article

Zhou Y, Zhang C, Myant C, Stewart Ret al., 2022, Knitted Graphene Supercapacitor and Pressure-Sensing Fabric, E-Textiles 2021, Publisher: MDPI

Conference paper

Bahshwan M, Gee M, Nunn J, Myant CW, Reddyhoff Tet al., 2022, In situ observation of anisotropic tribological contact evolution in 316L steel formed by selective laser melting, Wear, Vol: 490-491, Pages: 1-12, ISSN: 0043-1648

A consensus on the tribological performance of components by additive-versus conventional manufacturing has not been achieved; mainly because the tribological test set-ups thus far were not suited for investigating the underlying microstructure's influence on the tribological properties. As a result, utilization of additive manufacturing techniques, such as selective laser melting (SLM), for tribological applications remains questionable. Here, we investigate the anisotropic tribological response of SLM 316L stainless steel via in situ SEM reciprocating micro-scratch testing to highlight the microstructure's role. As-built 316L SLM specimens were compared against annealed wire-drawn 316L. We found that: (i) microgeometric conformity was the main driver for achieving steady-state friction, (ii) the anisotropic friction of the additively manufactured components is limited to the break-in and is caused by the lack of conformity, (iii) the cohesive bonds, whose strength is proportional to frictional forces, are stronger in the additively manufactured specimens likely due to the dislocation-dense, cellular structures, (iv) low Taylor-factor grains with large dimension stimulate microcutting in the form of long, thin sheets with serrated edges. These findings uncover some microstructurally driven tribological complexities when comparing additive to conventional manufacturing.

Journal article

Burge TA, Jeffers JRT, Myant CW, 2022, Development of an automated mass-customization pipeline for knee replacement surgery using biplanar X-Rays, Journal of Mechanical Design, Vol: 144, Pages: 1-11, ISSN: 1050-0472

For standard “off-the-shelf” knee replacement procedures, surgeons use X-ray images to aid implant selection from a limited number of models and sizes. This can lead to complications and the need for implant revision due to poor implant fit. Customized solutions have been shown to improve results but require increased preoperative assessment (Computed Tomography or Magnetic Resonance Imaging), longer lead times, and higher costs which have prevented widespread adoption. To attain the benefits of custom implants, whilst avoiding the limitations of currently available solutions, a fully automated mass-customization pipeline, capable of developing customized implant designs for fabrication via additive manufacturing from calibrated X-rays, is proposed. The proof-of-concept pipeline uses convolutional neural networks to extract information from biplanar X-ray images, point depth, and statistical shape models to reconstruct the anatomy, and application programming interface scripts to generate various customized implant designs. The pipeline was trained using data from the Korea Institute of Science and Technology Information. Thirty subjects were used to test the accuracy of the anatomical reconstruction, ten from this data set, and a further 20 independent subjects obtained from the Osteoarthritis Initiative. An average root-mean-squared error of 1.00 mm was found for the femur test cases and 1.07 mm for the tibia. Three-dimensional (3D) distance maps of the output components demonstrated these results corresponded to well-fitting components, verifying automatic customization of knee replacement implants is feasible from 2D medical imaging.

Journal article

Butt H, Nissim L, Gao L, Myant C, de Boer G, Hewson Ret al., 2021, Transient mixed lubrication model of the human knee implant, Biosurface and Biotribology, Vol: 7, Pages: 206-218

The human knee implant is computationally modelled in the mixed lubrication regime to investigate the tribological performance of the implant. This model includes the complex geometry of the implant components, unlike elliptical contact models that approximate this geometry. Film thickness and pressure results are presented for an ISO gait cycle to determine the lubrication regime present within the implant during its operation. It was found that it was possible for the lubrication regime to span between elastohydrodynamic, mixed and boundary lubrication depending on the operating conditions of the implant. It was observed that the tribological conditions present in one condyle were not necessarily representative of the other. Multiple points of contact were found within the same condyle, which cannot be computed by the elliptical contact solvers. This model can be used to balance forces in all directions, instead of only the normal loads, as often done in elliptical contact models. This work is an initial step towards understanding the role of the complex geometry in the tribological characteristics of the human knee implant when operating in physiological conditions.

Journal article

Nissim L, Butt H, Gao L, Myant C, Hewson Ret al., 2021, Role of protein concentration on transient film thickness in synovial fluid lubricated joints, Biotribology, Vol: 28, Pages: 1-14, ISSN: 2352-5738

A computational model of protein aggregation lubrication has been developed for predicting transient behaviour in lubricated prosthetics. The model uses an advection-diffusion equation to simulate protein transport in order to map concentration changes throughout the contact and inlet zones of an elasto-hydrodynamic contact. Concentration increases lead to exponential increase in fluid viscosity giving rise to lubricating film thicknesses an order of magnitude larger than would be expected using conventional elasto-hydrodynamic theory. The model parameters have been calibrated such that good agreement in transient film thickness is achieved with observed experimental results.KeywordsProtein aggregation lubrication; Elasto-hydrodynamic lubrication; Prostheses

Journal article

Kalossaka LM, Mohammed AA, Sena G, Barter L, Myant Cet al., 2021, 3D printing nanocomposite hydrogels with lattice vascular networks using stereolithography, JOURNAL OF MATERIALS RESEARCH, Vol: 36, Pages: 4249-4261, ISSN: 0884-2914

Journal article

Li S, Tan Y, Willis S, Bahshwan M, Folkes J, Kalossaka L, Waheed M, Myant Cet al., 2021, Toward mass customization through additive manufacturing: an automated design pipeline for respiratory protective equipment validated against 205 faces, International Journal of Bioprinting, Vol: 7, ISSN: 2424-7723

Respiratory protective equipment (RPE) is traditionally designed through anthropometric sizing to enable mass production. However, this can lead to long-standing problems of low-compliance, severe skin trauma, and higher fit test failure rates among certain demographic groups, particularly females and non-white ethnic groups. Additive manufacturing could be a viable solution to produce custom-fitted RPE, but the manual design process is time-consuming, cost-prohibitive and unscalable for mass customization. This paper proposes an automated design pipeline which generates the computer-aided design models of custom-fit RPE from unprocessed three-dimensional (3D) facial scans. The pipeline successfully processed 197 of 205 facial scans with <2 min/scan. The average and maximum geometric error of the mask were 0.62 mm and 2.03 mm, respectively. No statistically significant differences in mask fit were found between male and female, Asian and White, White and Others, Healthy and Overweight, Overweight and Obese, Middle age, and Senior groups.

Journal article

Kalossaka LM, Sena G, Barter LMC, Myant Cet al., 2021, Review: 3D printing hydrogels for the fabrication of soilless cultivation substrates, Applied Materials Today, Vol: 24, Pages: 1-16, ISSN: 2352-9407

The use of hydrogels in academic research is fast evolving, and becoming more relevant to real life applications across varying fields. Additive Manufacturing (AM) has paved the way towards manufacturing hydrogel substrates with tailored properties which allow for new functionalities and applications. In this review, we introduce the idea of fabricating hydrogels as bioreceptive structures to be used as soilless cultivation substrates. AM is suggested as the fabrication process to achieve structures with features similar to soil. To evaluate this, we first review hydrogel fabrication processes, highlighting their key differences in terms of resolution, printing speed and build volume. Thus, we illustrate the examples from the literature where hydrogels were 3D printed with microorganisms such as algae. Finally, the challenges and future perspectives of printing soilless cultivation substrates are explored.

Journal article

Li S, Waheed U, Bahshwan M, Wang LZ, Kalossaka LM, Choi J, Kundrak F, Lattas A, Ploumpis S, Zafeiriou S, Myant CWet al., 2021, A scalable mass customisation design process for 3D-printed respirator mask to combat COVID-19, Rapid Prototyping Journal, Vol: 27, Pages: 1302-1317, ISSN: 1355-2546

PurposeA three-dimensional (3D) printed custom-fit respirator mask has been proposed as a promising solution to alleviate mask-related injuries and supply shortages during COVID-19. However, creating a custom-fit computer-aided design (CAD) model for each mask is currently a manual process and thereby not scalable for a pandemic crisis. This paper aims to develop a novel design process to reduce overall design cost and time, thus enabling the mass customisation of 3D printed respirator masks.Design/methodology/approachFour data acquisition methods were used to collect 3D facial data from five volunteers. Geometric accuracy, equipment cost and acquisition time of each method were evaluated to identify the most suitable acquisition method for a pandemic crisis. Subsequently, a novel three-step design process was developed and scripted to generate respirator mask CAD models for each volunteer. Computational time was evaluated and geometric accuracy of the masks was evaluated via one-sided Hausdorff distance.FindingsRespirator masks were successfully generated from all meshes, taking <2 min/mask for meshes of 50,000∼100,000 vertices and <4 min for meshes of ∼500,000 vertices. The average geometric accuracy of the mask ranged from 0.3 mm to 1.35 mm, depending on the acquisition method. The average geometric accuracy of mesh obtained from different acquisition methods ranged from 0.56 mm to 1.35 mm. A smartphone with a depth sensor was found to be the most appropriate acquisition method.Originality/valueA novel and scalable mass customisation design process was presented, which can automatically generate CAD models of custom-fit respirator masks in a few minutes from a raw 3D facial mesh. Four acquisition methods, including the use of a statistical shape model, a smartphone with a depth sensor, a light stage and a structured light scanner were compared; one method was recommended for use in a pandemic crisis consider

Journal article

Xu Y, Cartwright B, Advincula L, Myant C, Stokes JRet al., 2021, Generalised scaling law for soft contact tribology: Influence of load and asymmetric surface deformation, TRIBOLOGY INTERNATIONAL, Vol: 163, ISSN: 0301-679X

Journal article

Whitehouse S, Myant C, Cann PM, Stephens Aet al., 2021, Fluorescent imaging of razor cartridge/skin lubrication, SURFACE TOPOGRAPHY-METROLOGY AND PROPERTIES, Vol: 9, ISSN: 2051-672X

Journal article

Hong F, Myant C, Boyle D, 2021, Thermoformed Circuit Boards: Fabrication of highly conductive freeform 3D printed circuit boards with heat bending, CHI Conference on Human Factors in Computing Systems, Pages: 1-10

Fabricating 3D printed electronics using desktop printers has become moreaccessible with recent developments in conductive thermoplastic filaments.Because of their high resistance and difficulties in printing traces invertical directions, most applications are restricted to capacitive sensing. Inthis paper, we introduce Thermoformed Circuit Board (TCB), a novel approachthat employs the thermoformability of the 3D printed plastics to constructvarious double-sided, rigid and highly conductive freeform circuit boards thatcan withstand high current applications through copper electroplating. Toillustrate the capability of the TCB, we showcase a range of examples withvarious shapes, electrical characteristics and interaction mechanisms. We alsodemonstrate a new design tool extension to an existing CAD environment thatallows users to parametrically draw the substrate and conductive trace, andexport 3D printable files. TCB is an inexpensive and highly accessiblefabrication technique intended to broaden HCI researcher participation.

Conference paper

Vlădescu S-C, Bozorgi S, Hu S, Baier SK, Myant C, Carpenter G, Reddyhoff Tet al., 2021, Effects of beverage carbonation on lubrication mechanisms and mouthfeel, Journal of Colloid and Interface Science, Vol: 586, Pages: 142-151, ISSN: 0021-9797

The perception of carbonation is an important factor in beverage consumption which must be understood in order to develop healthier products. Herein, we study the effects of carbonated water on oral lubrication mechanisms involved in beverage mouthfeel and hence taste perception. Friction was measured in a compliant PDMS-glass contact simulating the tongue-palate interface (under representative speeds and loads), while fluorescence microscopy was used to visualise both the flow of liquid and oral mucosal pellicle coverage.When carbonated water is entrained into the contact, CO2 cavities form at the inlet, which limit flow and thus reduce the hydrodynamic pressure. Under mixed lubrication conditions, when the fluid film thickness is comparable to the surface roughness, this pressure reduction results in significant increases in friction (>300% greater than under non-carbonated water conditions). Carbonated water is also shown to be more effective than non-carbonated water at debonding the highly lubricious, oral mucosal pellicle, which again results in a significant increase in friction. Both these transient mechanisms of starvation and salivary pellicle removal will modulate the flow of tastants to taste buds and are suggested to be important in the experience of taste and refreshment. For example this may be one reason why flat colas taste sweeter.

Journal article

Bin M, Cheung PYK, Crisostomi E, Ferraro P, Lhachemi H, Murray-Smith R, Myant C, Parisini T, Shorten R, Stein S, Stone Let al., 2021, Post-lockdown abatement of COVID-19 by fast periodic switching, PLoS Computational Biology, Vol: 17, Pages: 1-34, ISSN: 1553-734X

COVID-19 abatement strategies have risks and uncertainties which could lead to repeating waves of infection. We show—as proof of concept grounded on rigorous mathematical evidence—that periodic, high-frequency alternation of into, and out-of, lockdown effectively mitigates second-wave effects, while allowing continued, albeit reduced, economic activity. Periodicity confers (i) predictability, which is essential for economic sustainability, and (ii) robustness, since lockdown periods are not activated by uncertain measurements over short time scales. In turn—while not eliminating the virus—this fast switching policy is sustainable over time, and it mitigates the infection until a vaccine or treatment becomes available, while alleviating the social costs associated with long lockdowns. Typically, the policy might be in the form of 1-day of work followed by 6-days of lockdown every week (or perhaps 2 days working, 5 days off) and it can be modified at a slow-rate based on measurements filtered over longer time scales. Our results highlight the potential efficacy of high frequency switching interventions in post lockdown mitigation. All code is available on Github at https://github.com/V4p1d/FPSP_Covid19. A software tool has also been developed so that interested parties can explore the proof-of-concept system.

Journal article

Hong F, Myant C, Boyle DE, 2021, Thermoformed Circuit Boards: Fabrication of highly conductive freeform 3D printed circuit boards with heat bending., Publisher: ACM, Pages: 669:1-669:1

Conference paper

Bahshwan M, Myant CW, Reddyhoff T, Pham MSet al., 2020, The role of microstructure on wear mechanisms and anisotropy of additively manufactured 316L stainless steel in dry sliding, Materials and Design, Vol: 196, ISSN: 0264-1275

Wear control, which relies on understanding the mechanisms of wear, is crucial in preserving the life of mechanical components and reducing costs. Additive manufacturing (AM) techniques can produce parts with tailored microstructure, however, little has been done to understand how this impacts the mechanisms of wear. Here we study the impact of initial grain arrangement and crystal orientation on the wear mechanisms of austenitic stainless steel (SS) in dry sliding contact. Specifically, the anisotropic sliding wear behavior of as-built, AM-ed 316L SS is compared against annealed, wire-drawn counterparts. We describe, in-detail, how the sliding wear mechanisms of delamination, abrasion, oxidation, and plastic deformation are attributed to the initial surface microstructure under different loading conditions using a number of techniques. This new understanding sheds light on how different AM-induced microstructures affect wear, thereby allowing for better utilization of this technology to develop components with enhanced wear properties.

Journal article

Waheed U, Myant CW, Dobson SN, 2020, Boolean AND/OR mechanical logic using multi-plane mechanical metamaterials, EXTREME MECHANICS LETTERS, Vol: 40, ISSN: 2352-4316

Journal article

Li S, Ploumpis S, Zafeiriou S, Myant Cet al., 2020, Design automation for mass customisation via additive manufacture: A case study on continuous positive airway pressure mask

Additive Manufacturing (AM) has been identified as a key enabler for Mass Customization (MC) due to its negligible tooling cost associated with producing one-off items. This is especially valuable for the medical industry where the ability to create patient-specific products can greatly improve performance and comfort. However, the use of AM so far has only been limited to previously custom-made devices due to the prohibitive design costs associated with a knowledge-intensive and highly manual design process. The research community has often overlooked this area and as yet no study has shown a completely automated process that can reduce or even eliminate this design cost for existing mass-produced ergonomic products (e.g. respirators). This study investigates the methodology of developing a completely automated design pipeline through a case study on Continuous Positive Airway Pressure (CPAP) mask. Through a parametric design approach, a fully automated pipeline was constructed based on a large-scale statistical shape model "learnt"from 9,663 high-resolution facial scans. The pipeline accepts a single "in-the-wild"facial image as the only data input and produces a CAD model of CPAP mask in under a minute. The significant reduction in design time, ease of data acquisition and the complete removal of a manual CAD modelling process can make AM more accessible for CPAP masks manufacturers. The same workflow can potentially be employed to construct automation pipelines for other types of wearables, therefore encouraging the adoption of AM for MC of a wider selection of products.

Conference paper

Waheed U, Myant C, 2020, Passive mechanical metamaterial sensor and actuator

In recent years, and with the continual development of additive manufacturing technologies, mechanical metamaterials have been explored for their programmable nature. This has opened a new design space into devices using functional materials. In this paper, a novel mechanical metamaterial device is designed, combining anisotropic 3D unit cells to slender beams. By controlling the separation distance between the fixed ends of a slender beam, the mechanism can be tuned to transition between monostable and bistable states. This behaves as a sensor and actuator, allowing mechanical signals to pass only when the correct actuation pattern is received. The device is shown to be inherently passive as it returns to a monostable state after actuation. Two different designs have successfully demonstrated this repeatable behaviour. A multi-material PolyJet printed mechanism joining unit cells to a Von Mises Truss, and an SLA printed compliant mechanism coupling unit cells to thin slender beams. A novel approach in performing AND/OR mechanical logic has also been successfully demonstrated by manipulating the mechanical metamaterial when in a bias state. The proposed devices have application in soft robotic systems, the aerospace industry and in the nuclear sector, where there is a need for passive safety systems that are not reliant on electronic systems, and respond to environmental stimuli. The printed mechanisms highlight the potential for mechanical metamaterials to be used as tunable sensors and actuators for future engineering applications.

Conference paper

Shin S, Alyasiri, D'Auria M, Otter W, Myant C, Stokes, Tian Z, Ridler NM, Lucyszyn Set al., 2019, Polymer-based 3-D printed Ku-band steerable phased-array antenna subsystem, IEEE Access, Vol: 7, Pages: 106662-106673, ISSN: 2169-3536

This paper introduces the first fully 3-D printed tunable microwave subsystem, consisting of 26 circuit elements. Here, a polymer-based 3-D printed Ku-band 4-element steerable phased-array antenna with fully integrated beam forming network is demonstrated. Polyjet was adopted for fabricating the main body of the subsystem, as it is capable of producing a geometrically complex structure with high resolution over a large volume. Low-cost fused deposition modeling was chosen to manufacture the dielectric inserts and brackets for the phase shifters. The measured radiation pattern revealed that the phased-array antenna subsystem has total beam steering angles of 54° and 52° at 15 GHz and 17 GHz, respectively. Excellent input return loss behavior was observed across the optimum operational frequency range of 15 to 17 GHz; with a worst-case measured return loss of 12.9 dB. This work clearly shows the potential of using 3-D printing technologies for manufacturing fully integrated subsystems with complex geometric features.

Journal article

Carpenter G, Bozorgi S, Vladescu S, Forte A, Myant C, Potineni R, Reddyhoff T, Baier Set al., 2019, A study of saliva lubrication using a compliant oral mimic, Food Hydrocolloids, Vol: 92, Pages: 10-18, ISSN: 0268-005X

Due to ethical issues and the difficulty in obtaining biological tissues, it is important to find synthetic elastomers that can be used as replacement test media for research purposes. An important example of this is friction testing to understand the mechanisms behind mouthfeel attributes during food consumption (e.g. syrupy, body and clean finish), which requires an oral mimic. In order to assess the suitability of possible materials to mimic oral surfaces, a sliding contact is produced by loading and sliding a hemispherical silica pin against either a polydimethyl siloxane (PDMS), agarose, or porcine tongue sample. Friction is measured and elastohydrodynamic film thickness is calculated based on the elastic modulus of the samples, which is measured using an indentation method. Tests were performed with both saliva and pure water as the lubricating fluid and results compared to unlubricated conditions.PDMS mimics the tongue well in terms of protein adhesion, with both samples showing significant reductions in friction when lubricated with saliva versus water, whereas agarose showed no difference between saliva and water lubricated conditions. This is attributed to PDMS's OSi(CH3)2- group which provides excellent adhesion for the saliva protein molecules, in contrast with the hydrated agarose surface. The measured modulus of the PDMS (2.2 MPa) is however significantly greater than that of tongue (3.5 kPa) and agarose (66–174 kPa). This affects both the surface (boundary) friction, at low sliding speeds, and the entrained elastohydrodynamic film thickness, at high speeds.Utilising the transparent PDMS sample, we also use fluorescence microscopy to monitor the build-up and flow of dyed-tagged saliva proteins within the contact during sliding. Results confirm the lubricous boundary film forming nature of saliva proteins by showing a strong correlation between friction and average protein intensity signals (cross correlation coefficient = 0.87). This demonstrates

Journal article

Shin S, Alyasiri D, D’Auria M, Otter W, Myant C, Stokes D, Tian Z, Ridler N, Lucyszyn Set al., 2019, Fully 3-D printed tunable microwave subsystem, International Microwave Workshop Series on Advanced Materials and Processes (IMWS-AMP), Publisher: IEEE

Conference paper

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