3D printing can potentially transform traditional electronics manufacturing by allowing for the accurate direct digital manufacture of complex electronic structures with a much smaller process footprint. However, there are challenges which restrict the use of 3D printing for electronic manufacturing. One significant challenge is the characterization of the electromagnetic properties of the 3D printed materials such as their resultant dielectric permittivity. This work reports on the investigation of existing mixture models to establish their suitability for predicting the dielectric permittivity of 3D printed binary materials for the test frequency range of 1 GHz to 10 GHz. The identified models included volume fraction mixture models which considered the material volume concentration of the binary material and shape factor mixture models which consider the geometry and distribution of the mixture constituents. The fused filament fabrication 3D printing process was used for this work. 3D printed samples were produced with varying percentage volume compositions and varying infill patterns. The dielectric permittivity of the samples was investigated using the two-layer stripline measurement method and the measured data compared to the mixture model estimates. The shape factor mixture models were found to not be in good agreement with the measured values of dielectric permittivity. This result was attributed to the relatively small size of the discontinuities within the 3D printed substrate being insufficient to present anisotropy relative to the wavelength of the applied test signals. The volume fraction models were found to be in close agreement for samples with select infill patterns.

Noninvasive monitoring methods can potentially improve the quality of patient care for noncommunicable diseases such as diabetes and chronic kidney disease. However, many communities most affected by noncommunicable diseases are low- and middle-income. 3D printed electronics can potentially offer a simple and low-cost solution for the manufacture of noninvasive measurement sensors. In this work the impact of the infill patterns of a 3D printing manufacturing method for a flexible double u-slot patch antenna is investigated. A rigid version of the patch using a traditional glass-epoxy circuit board has been previously considered for noninvasive measurement. This work considers a flexible 3D printed substrate for the patch. The patch performance is examined using the measured S11 reflection coefficient for each antenna. The measured data suggests that the changes in the infill patterns result in a shift and variation in the number of resonant frequencies and the magnitude of the response.

Printed circuit assemblies (PCAs) are an integral part of most modern electronic devices. With the significant supply chain issues affecting the electronics industry there has been renewed interest in new ways to reshore and revitalise the electronics manufacturing sectors. A PCA is composed of a substrate, interconnections, passive and/ or active components which when combined allow an electronic device to function. These constituents are made of a variety of materials including conductive, insulating and semiconductor. In considering the application of 3D printing (3DP) to the manufacture of PCAs a necessary criterion would be the need for multi-material 3D printing (MM3DP). The aim of this review is to report on the recent progress in the application of MM3DP technologies for the manufacture of PCAs. Emphasis is placed on the realisation of fully automated, standalone MM3DP systems. The review identifies the dominant MM3DP technologies utilised in the industry as well as the limi-tations of the currently available technologies. Finally, the review proposes five characteristics of the ideal MM3DP system for manufacturing PCAs and discusses the important opportunities for future research in each of the areas.

3D printing technologies (3DP) leverage the benefits of additive manufacturing across many areas including electronics, food, medicine and optics. These technologies allow varying materials to be precision deposited, forming structures ranging from simple to complex composites such as organs and satellites. One important application for 3DP is printed electronics which is expected to exceed USD10 billion in market value by 2030. However, while considerable work has been reported in areas including inter alia: mechanical, thermal and multiple aspects, there has been less emphasis on the critical electromagnetic (EM) domain. In the EM domain, related work for 3DP encompasses interrelated EM studies of materials, processes and built structures and examines material characteristics including permittivity, permeability, electrical conductivity, which are foundational to 3D printed electronics design and fabrication. This paper presents a comprehensive report of 3DP technologies as applied to EM research & development (R&D) and end applications in order to inspire exploratory work in related areas by providing sufficient breadth for newcomers and depth for experts. The paper contributions include: summarization of the major R&D and applications areas for 3DP, thereby quantifying the prevalence of EM related work; examination of mainstream 3DP technologies applied to EM related R&D and end applications based on their materials, technology highlights and known issues; examination of relevant research which incorporates traditional printing, proprietary methods and composite 3DP methods; and classification of 3DP built EM structures as reported by research teams. Finally, the key challenges and opportunities for future research are identified and discussed.

The resultant relative permittivity of 3D printed polylactide (PLA) substrates with varying percentage volumes of PLA are measured using a two microstrip line method. The resultant relative permittivity of the PLA substrates is also predicted using five existing heterogenous mixture models. The measured and predicted values of relative permittivity are compared to identify the degree of fit of the mixture models to the measured values. The measured relative permittivity was found to increase as the percentage volume of PLA was increased. The measured values also increased with increasing signal frequency. The mixture models showed varying degrees of fit with two models, Rayleigh (RAY) and Refractive Index (RI), showing the best fit out of the five models. None of the models considered the frequency dependence of the relative permittivity. The results allow for the identification of opportunities for future work related to frequency dependent mixture models and detailed testing of 3D printed substrates.

Wireless wearable applications which allow for remote biomedical data gathering, analysis and visualisation present a significant opportunity to improve patient care [10] . However, the design and manufacture of wearable systems does present a challenge as relates to their flexibility [11] and ensuring their safe operation [12] - [13] . In this work our goal was to examine the behaviour of a traditional Planar Inverted-F Antenna (PIFA) structure across the frequency band of 700MHz - 4GHz. The specific scenario was a wireless wearables application where nylon was used as a flexible substrate and the antenna was placed directly against the underlying tissue. The RF characteristics were considered for the structure under the action of applied forces which produced multiplanar deformations that correspond to the natural modalities of the antenna and underlying tissue. A shift in the characteristics of the antenna structure was noted due to the change in substrate and effects of the underlying tissue, which was not unexpected [13] . However our specific interest was in understanding how the physical changes to the antenna geometry and surrounding tissue resulted in changes to the RF behaviour. It was observed that the electric field energy varied based on the zone of application of the applied force to the antenna surface. Furthermore, there was greater concentration of the electric field energy into the underlying tissue at higher frequencies.

Non-communicable diseases (NCDs) have globally become a prevalent problem, accounting for more than 60% of the mortality worldwide. NCDs impose socioeconomic consequences to low-income countries as 80% of NCD deaths occur in such countries [1, 2]. The World Health Organization has necessitated that cost-effective preventive measures, which have an immediate impact on the burden at population level, are required in low to middle-income countries [3]. Non-invasive technology offers a low cost and less painful alternative for effective management of NCDs [4]. This technology, in the form of wearable sensors, confers advantages in the healthcare management of NCDs due to the ability to continuously monitor the patient's health. This introduces a paradigm shift in diagnostics as practitioners can better and progressively diagnose a patient. In chronic kidney disease, an NCD, blood creatinine levels increase due to impaired filtration and distal tubule secretion of creatinine. However, creatinine clearance measurement is both cumbersome and error-prone. Indirect estimation of the estimated glomerular filtration rate (eGFR), the typical measure of renal function, from the serum creatinine concentration [5], has resulted in imprecise estimation of creatinine excretion and hence impairs chronic kidney disease management [6, 7]. This motivates the need to develop a sensor for non-invasive and continuous monitoring of blood creatinine concentrations as a preventive measure to mitigating the occurrence of end stage renal failure to a patient. Microwave non-invasive planar sensor based on a circular complementary split ring resonator (CSRR) has been found to be sensitive for the permittivity measurement of a specimen kept in contact with the sensor at resonant frequency [8]. A 3D model of this sensor was recreated in the COMSOL Multiphysics® software using the RF Module. The human skin was incorporated into the geometry, with the relevant material properties, as the specimen in contact with a circular CSRR. The material properties, relative permittivity, relative permeability and conductivity were set to the values in the frequency range (1-10 GHz) for wave excitation at the lumped port on a microstrip copper line below the plane of the CSRR. This frequency range is representative of the acceptable range for medical applications [9] and provides the penetration depth into the skin tissue for detecting blood permittivity changes. Changes in blood analyte concentrations within the skin provide a platform for detecting changes in the dielectric properties of blood due to the effect of an applied electric field [10]. The COMSOL® software is used to simulate changes in dielectric properties of blood via a parametric study of blood permittivity for a relative permittivity range of 1 to 100. The preliminary results (Figures 1 and 2) have showed a shift in the resonant frequency and depth change due to changes in the relative permittivity of the skin in contact with the sensor. These results implicate the potential of using microwave sensors for management of NCDs as the resonant frequency shift can be taken as a measure of the blood analyte concentrations, such as creatinine, due to relative permittivity changes. Reference [1] B. Nojilana et al., Persistent burden from non-communicable diseases in South Africa needs strong action. South African Medical Journal, 106(5), pp.436-437, 2016. [2] D.K. Sanghera, Emerging Epidemic of Non-Communicable Diseases (NCDs) in South Asia: Opportunities for Prevention. J Diabetes Metab,7(647), p.2, 2016. [3] A. Alwan, Global status report on noncommunicable diseases 2010. World Health Organization, 2011. [4] A. J. Bandodkar and J. Wang, Non-invasive wearable electrochemical sensors: a review. Trends in biotechnology, 32(7), pp.363-371, 2014. [5] A.S. Levey, et al., Using standardized serum creatinine values in the modification of diet in renal disease study equation for estimating glomerular filtration rate. Annals of internal medicine, 145(4), pp.247-254, 2006. [6] S. S. Waikar et al., Creatinine as the gold standard for kidney injury biomarker studies?. Nephrology Dialysis Transplantation, 24(11), pp.3263-3265, 2009. [7] A.S. Levey et al., Serum creatinine and renal function. Annual review of medicine, 39(1), pp.465-490, 1998. [8] M. A. H. Ansari et al., Design and Application of the CSRR-Based Planar Sensor for Noninvasive Measurement of Complex Permittivity. Sensors Journal, IEEE, 15(12), pp.71817189, 2015. [9] IEC.60601-2-6..1984.. Medical Electrical Equipment. Part 2: Particular Requirements for the Safety of Microwave Therapy Equipment..Geneva,.Switzerland:.Safety, 1984. [10] S. Chakraborty et al., Investigating the quasi-oscillatory behaviour of electrical parameters with the concentration of D-glucose in its aqueous solution at room temperature by employing impedance spectroscopy technique. Journal of Electrical Bioimpedance, 6(1), pp.10-17, 2015. Figures used in the abstract Figure 1: Circular CSRR resonance shift due to relative permittivity changes (0 to 20) in skin in contact with CSRR sensor Figure 2: Circular CSRR resonance shift due to relative permittivity changes (20 to 40) in skin in contact with CSRR sensor

Globally, chronic kidney disease (CKD) burden healthcare systems. Current treatment systems in many countries have presented a serious socioeconomic situation for low- to middle-income countries. As such, monitoring mechanisms present a clinical need for effective diagnosis, prevention and treatment of numerous non communicable diseases, such as CKD. Non-invasive, continuous monitoring of renal function using a complementary split ring resonator (CSRR) microwave sensor confers potential benefits to meeting this clinical need. The sensor was sensitive to changes in the relative permittivity of a material under test with the electrical properties of blood, for the frequency range investigated in COMSOL Multiphysics®. The correlation of the electrical parameters with relative permittivity changes highlights the applicability of CSRRs as a sensor module for CKD monitoring.

In this paper magnetically-coupled human body communications (MHBC) is investigated. In human body communications (HBC) the human body is the transmission medium through which wireless sensors and actuators in, on or in close proximity to the human body exchange information. MHBC, unlike the more common galvanic and capacitive coupled HBC, is less affected by the proximity to the surrounding environment, with the exception of materials with high permeability. Therefore, MHBC offers tremendous potential for the implementation of personalised healthcare systems. In this work MHBC is investigated using finite element analysis through COMSOL. A communications scenario involving the human arm is explored for investigating transmission parameters. COMSOL simulation results demonstrate the MHBC technique and highlight the importance of finite element analysis as a powerful tool for investigating the performance of MHBC systems.

This work investigates the effects of variations in skin-topology on the non-invasive measurement of blood glucose levels using an interdigital electrode. Several models of varying skin topologies were built and analysed within the COMSOL Multiphysics® 4.3 software environment. The deviations in blood glucose readings for the varying skin topologies were quantised. Finally the authors propose and model an alternative interdigital electrode structures. Variations in skin-topology can occur due to movement of the patient during readings and common variations in the skin surface from one person to the next or even different locations on the same person. Non-invasive measurement methods offer improved patient quality of care by reducing the pain and risk associated with testing.

One challenge faced in the engineering education, is the need to imbue both technical competence and critical thinking skills within the bounds of academic program delivery. While technical competence can be built and assessed using structured and/or quantitative exercises, critical thinking is a skill that is both difficult to cultivate and to assess. Critical thinking involves the possession of both an expert mental model as well as the ability to leverage this model in various tasks. In engineering education, these tasks include making and justifying design choices, system optimization, and predicting system performance. Prior work, by one of the authors, explored the role of graphic organizers in the development of student's mental models. This paper describes action research underway, to explore the use of the argument map, as a structured means of leveraging mental models to promote critical thinking. In this paper, interactive smallgroup tasks based on argument maps are presented, and outputs generated by the initial cohort of undergraduate senior learners on these tasks are examined for evidence of critical thinking. These items form the basis of a longer-term longitudinal study in which the most effective means of deploying argument maps for promoting critical thinking will be examined.

This paper explores whether engaging embedded electronic systems students in the creation of, as opposed to simply the use of, lab equipment improves their motivation to practice, and thereby their ability to acquire, discipline-specific skills. The specific piece of laboratory equipment considered is the Microchip In Circuit Debugger, inclusive of header, for PIC16F mid-range micro-controllers. A printed circuit board related teaching activity guided students through design of the ICD header (both 2011/12 and 2013/14), and physical assembly of a pre-designed ICD unit (2011/12 only). Three student cohorts subsequently used the in-house ICDs. Increased availability of units allowed each student to take the equipment outside of the lab and conduct studies at their convenience. The impact of the intervention was measured through the use of a survey; the survey instrument and response summaries are presented. Deliberate use of equipment construction as teaching activity could be an innovative way to improve skills acquisition by leveraging student motivation. Follow-up work will establish whether such activities yield reduction in time to minimal skill levels, and/or an improvement in final skill levels.