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The development of accurate corrosion models from corrosion data is a key requirement for well informed, preemptive actions towards extending the life of water infrastructure systems and reducing maintenance costs. This work presents the development of a custom proof-of-concept system implementation performing water corrosion monitoring using custom integrated corrosion sensing technologies powered by energy harvested through an in-line turbine generator. Implementing a star topology network of wireless corrosion sensor nodes distributed through water infrastructure systems offers an innovative solution for real-time and on-line monitoring of corrosion in water infrastructure systems. The wireless sensor network includes a wireless access point that provides an interface for retrieval of the corrosion data and a nexus for communications. A low-power bidirectional data transfer communications protocol using a form of time-division multiplex access is designed and implemented towards the optimisation of energy efficiency in the network. In an emulated pipeline field setup, the energy harvested and stored provides 125.80 mWh at 4.89 V for an in-pipe flow rate of 13.25 l/min, a typical value for municipal potable water supply in South Africa. The local node ER sensor can of measure changes in resistance values to an accuracy of 1% and will be usable in-system for a year. The access point implements EIS and LPR sensing. The extracted LPR value predicts a corrosion rate is 63.0 um/year in potable water.

An analysis on the viability of implementing non-flow based capacitive biosensing for bulk counting of whole cancer cells is presented. A mathematical model is implemented based on established research to test the validity of the hypothesis that cells are considered to act like parallel electric connections. A finite element analysis model is also presented to investigate the effect of electrode geometry and cell position on the measured capacitance. The electrical interaction between cells is found not to be strictly parallel and in fact dependent on a host of uncontrollable parameters. Bulk sensing of multiple cells is found to be impractical for a single electrode setup due to the unpredictability of cell location and cell interactions. An array-based implementation is proposed, which allows for the use of current models and data of single-cell analyses to be used.

Amitraz is an effective acaricide used in the control of external parasites for livestock. This study investigates the responses of general-purpose metal oxide (MOX) gas sensors to Taktic (a brand name insecticide containing amitraz) in water. An array of MOX sensors is used to design a custom electronic nose (e-nose) device to predict the concentration of Taktic in distilled water. The gases produced by the Taktic show a largely time-dependent response. A neural network is trained on a dataset with 5 concentration levels with time included and excluded as an input variable, and achieves a 100 % training and validation accuracy on different samples from the same sample set. The custom-built device is able to function as an early warning system for when the Taktic concentration falls below the efficacy minimum. The system is used for generalisation analysis of measurements taken from the same sample set at a later time and predicts the concentration correctly for all measured samples. An e-nose can be used for qualitative Taktic detection in water, and is adequately suited to semi-quantitative concentration prediction. Although the system can be further optimised, five levels of Taktic concentration can be discriminated in its current form. The results suggest the need for time-dependent signal conditioning like decay monitoring, as well as individual sensor sensitivity optimisation that include temperature and humidity compensation, to improve the results and practical feasibility of such a system.

The analysis of contact resistance in bottom-gate top-contact thin-film transistors (TFTs) based on nanoparticulate ZnO and a high-k nanocomposite as semiconductor and gate dielectric, respectively, shows that nickel can be used as an alternative to aluminum contacts. Furthermore, an analysis of the morphology of the gate structures and the influence of the work function of the gate metal on the transistor properties is carried out. For this purpose, gate electrodes were made of aluminum (4.28 eV) and gold (5.1 eV). It can be demonstrated that increasing the work function influences the flat-band voltage and thus the turn-on voltage. This effect can also be observed in bottom-gate bottom-contact devices with self-aligned drain/source electrodes.

The need for effective point-of-need health and environmental diagnostics in low and middle income countries (LMICs) is more crucial than ever. This work explores emerging criteria and technologies to address the limitations of current point-of-need solutions. Local developments in South Africa towards this goal are highlighted, utilizing additive manufacturing technologies which combine paper-based diagnostic and printed electronic platforms. Establishment of a pipeline, from undergraduate engineering students and laboratory infrastructure to industry partners using a decentralized manufacturing approach are also discussed as a map for developing novel, low-cost solutions for improving the quality of life of those who need it most.

Thin-film transistors (TFTs) enable low-cost integration of electronic circuits. Due to the low thermal load during manufacturing, flexible substrates can be used, making TFTs suitable for flexible electronic applications such as RFID labels or diagnostic sensors. To achieve mass applications, an increase in the performance of TFTs is required. In this context, the transit frequency f T is an important indicator. This frequency is influenced not only by the charge carrier mobility but also by the overlap of the gate electrode with the drain/source electrodes and by the channel length [1]. For realistic mobilities of about 10 cm2/ Vs and low operating voltages (V D ≤ 10 V), channel lengths in the submicrometer range are required for transit frequencies in the megahertz region [2]. In this work, we report on an integration routine for TFT fabrication in the submicron range by combining a dry etching process for structuring the gate electrode with a self-alignment process for patterning the drain/source electrodes. The self-alignment also minimizes the overlap between the gate and the drain/source electrodes, thus reducing the parasitic capacitances.

According to the UNESCO World Water Development Report 2019 [1], one half of all people with insufficient access to drinking water are located in African states. In the sub-Saharan region the percentage of those with access to clean drinking water is at 24% only. The exploitation of new water sources by means of laboratory water quality analysis may lead to costs of about 30$ each [2]. In view of the above, a low-cost sensor system has been developed that intends to provide a feedback on the general quality of a water probe and gives a statement on the possibility of dissolved chemicals in the probe.

Flexible electronics requires the integration of thin-film transistors (TFTs) at much lower temperatures than traditional Si technology. Here we present an integration routine for complementary inverter structures on a flexible polyethylene terephthalate (PET) substrate, which provides a high degree of freedom in the choice of the individual contact metals for the p-and n-type TFTs. It is therefore suitable for organic, inorganic or hybrid semiconductor systems. The developed integration process enables two different metallization layers to be structured into contact electrodes (drain and source) for thin film transistors on a common flexible substrate. This enables the adaptation of the work function of metals and semiconductors, and thus the performance of the individual TFTs can be optimized. The TFTs are integrated in bottom-gate bottom-contact setup.

The work presented details micro and nano technologies for point-of-need health and environmental diagnostics in resource-limited settings, specifically in Southern Africa. The challenges faced in these settings have limited the effectiveness of point-of-need diagnostic solutions. By combining the growing fields of paper-based diagnostics and printed electronics, the extensive possibilities of functional printing can be utilized to develop novel, low-cost solutions for improving the quality of life of those who need it most. Examples of the research progress made in South Africa are presented, with a map for the way forward, encompassing the different technologies, skills and manufacturing processes required.

This work investigates the properties of conductive circuits inkjet-printed onto the polycarbonate discs used in CD-based centrifugal microfluidics, contributing towards rapidly prototyped electronic systems in smart ubiquitous biosensors, which require sensitive and robust signal readout at low power and cost, and with wireless connectivity. A protocol for inkjet-printing electronic networks on CD substrates is developed. The circuit modeling of conductive tracks is discussed, and validated against experimental results. A design procedure is presented for reliably printing conductive networks with feature dimensions between 150 μm and 2 mm on CDs, and yielding electronic circuits operating with a bandwidth of 1 MHz.

The work presented details the development of a low-cost potentiostat, with the aim of creating an ink-jet printed hybrid paper-based low-cost sensing system for rapid water quality monitoring. Potentiostats exhibit high sensitivities and can be used for a variety of applications. In this application, they use electrochemical techniques to detect heavy metals via stripping analysis. The potentiostat front-end, consisting of an LMP91000 sensing chip, was designed and manufactured on a printed circuit board (PCB) and compared to a laboratory-based potentiostat using cyclic voltammetry performed using an 80 sl sample of 5 mM ferri-ferrocyanide dropped onto a commercial screen-printed electrode. The results obtained from the PCB potentiostat are comparable to those obtained using the development board and the laboratory-based potentiostat. The results highlight the functionality of a low-cost point-of-need potentiostat that can be used for environmental monitoring as well as the feasibility of transferring the design to a paper substrate.

In CMOS, an SRAM cell containing six transistors is generally used. If a smaller number of transistors and fewer connection lines were possible, the packing density of SRAM chips may be improved. A reduce-area four-transistor SRAM cell for implementation in a standard digital CMOS process is proposed in this paper.

In this paper an undergraduate training program for engineers with practical microelectronic experience is presented. The emphasis in this program is on the design of devices and integrated circuits, and the reason for this is expounded. A discussion of the incentives for producing such engineers for the South African context is also furnished.

This paper proposes a programmable integrated circuit (IC) prototyping system. Most IC designs can be implemented by simply programming the device with an appropriate switching map. The device can later be reprogrammed with a modified, or completely different circuit. This allows cheap, rapid prototyping of ICs for the purpose of teaching IC design.

Multiple input floating gate (MIFG) transistors have been found to be very useful in many analogue applications. We extend the existing MIFG models to cover switched operation and charge injection, extending the usefulness of MIFGs to many new applications.