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We describe a ‘clock control unit’ based on a dual-axis cubic cavity (DACC) for the frequency stabilisation of lasers involved in a strontium optical lattice clock. The DACC, which ultimately targets deployment in space applications, provides a short-term stable reference for all auxiliary lasers—i.e. cooling, clear-out, and optical lattice—in a single multi-band cavity. Long-term cavity drift is compensated by a feed-forward scheme exploiting a fixed physical relation to an orthogonal second cavity axis; either by reference to an ultrastable 698 nm clock laser, or by exploiting the differential drift between orthogonal axes extracted by a single laser in common view. Via a change of mirror set in the cavity axis accessed by the clock laser, the system could also provide stabilisation for sub-Hz linewidths at the 698 nm clock wavelength, fulfilling all stabilisation requirements of the clock.

A non-invasive and portable bioimpedance method and a device for detecting superior to inferior closure of the pharynx during swallowing have been developed. The 2-channel device measures electric impedance across the neck at two levels of the pharynx via injected currents at 40 and 70 kHz. The device has been trialled on both healthy and dysphagic subjects. Results from these trials revealed a relationship (r = 0.59) between the temporal separation of the second peaks in the bioimpedance waveforms and descending pressure sequence in the pharynx as measured by pharyngeal manometry. However, these features were only clearly visible in the bioimpedance waveforms for 64% of swallows. Further research is underway to improve the bioimpedance measurement reliability and validate waveform feature correlation to swallowing to maximise the device's efficacy in dysphagia rehabilitation.

We develop a model of single spherical cell electroporation and simulate spatial and temporal aspects of the transmembrane potential and pore radii as an effect of any form of applied electric field. The extent of electroporation in response to sinusoidal electric pulses of two different frequencies in a range of extracellular conductivity for two different cell radii are compared. Results show that pore radii tend to be more normalized for AC fields. The relative difference in fractional pore area is reduced by the use of a 1 MHz sinusoidal applied electric field over a 100 kHz field.

The University of Canterbury has embedded design projects into each of the three professional education years (years 2-4 of the degree) in its new Mechatronics programme. The goal is to create an educational mechanism that links engineering sciences and individual class topics to integrated applications. A series of application-oriented laboratory projects using a Programmable Logic Controller is built into the second-year (1st professional year) curriculum. In the third year (2nd professional), a mobile robotic system design project encompasses electromechanical design, embedded control, software development and system integration. In the fourth and final year (3rd professional), students advance to working on mechatronics research projects that address real-life complex engineering problems facing the industrial sponsors. Embedding design projects progressively into multidisciplinary engineering education has proven to be an effective pedagogy to reinforce students' systems thinking, hands-on abilities, and cross-course linkage.

To hasten the process of saving lives after disasters in urban areas, autonomous robots are being looked to for providing mapping, hazard identification and casualty location. These robots need to maximise time in the field without having to recharge and without reducing productivity. This project aims to improve autonomous robot navigation through allowing comparison of algorithms with various weightings, in conjunction with the ability to vary physical parameters of the robot and other factors such as error thresholds/limits. The lack of a priori terrain data in disaster sites, means that robots have to dynamically create a representation of the terrain from received sensor range-data in order to path plan. To reduce the resources used, the affect of input data on the terrain model is analysed such that some points may be culled. The issues of identifying hazards within these models are considered with respect to the affect on safe navigation.

Lab-on-a-chip micro-devices utilizing electric field-mediated particle movement provide advantages over current cell rotation techniques due to the flexibility in configuring micro-electrodes. Recent technological advances in micro-milling, three-dimensional (3D) printing and photolithography have facilitated fabrication of complex micro-electrode shapes. Using the finite-element method to simulate and optimize electric field induced particle movement systems can save time and cost by simplifying the analysis of electric fields within complex 3D structures. Here we investigated different 3D electrode structures to obtain and analyse rotational electric field vectors. Finite-element analysis was conducted by an electric current stationary solver based on charge relaxation theory. High-resolution data were obtained for three-, four-, six- and eight-cylindrical electrode arrangements to characterize the rotational fields. The results show that increasing the number of electrodes within a fixed circular boundary provides larger regions of constant amplitude rotational electric field. This is a very important finding in practice, as larger rotational regions with constant electric field amplitude make placement of cells into these regions, where cell rotation occurs, a simple task – enhancing flexibility in cell manipulation. Rotation of biological particles over the extended region would be useful for biotechnology applications which require guiding cells to a desired location, such as automation of nuclear transfer cloning.

Many applications of electroporation, especially those utilizing electrofusion and in-vivo electroporation, involve cell environments that include close cell-to-cell proximity and a wide range of target cell size. It is important to understand how this kind of environment may alter optimum electroporation electrical parameters for any given application. A physical, electrically equivalent model of biological cell electroporation, based on aqueous solution filled thin latex rubber membrane spheroids, was used to investigate membrane permeabilization behaviour where there is both close cell-to-cell proximity and different cell radii. Cell model arrangements were pulsed using either a 50 micros or 10 micros, 1/e decay time constant dc capacitive discharge electric field, with peak amplitudes of 160-500 kV m(-1). Results indicate that, compared to cells in isolation, electroporation initiates at substantially decreased applied electric field magnitudes in regions of close cell-to-cell proximity where the external media conductivity is lower than the cell interior conductivity, and the membrane is maximally polarized. Additionally, the use of shorter time constant, higher peak magnitude pulse parameters should reduce the relative difference in threshold membrane permeabilization in regions of close cell-to-cell proximity for cells of different size so that the degree of electroporation is more uniform for variable size and shape target cell populations.

Recent advances have resulted in the availability of a new generation of silicon carbide (SiC) junction field effect transistors (JFETs), which unlike previous generations, exhibit highly desirable normally off characteristics. Normally off SiC JFETs are characterised with particular focus on previously unknown reverse conduction characteristics. Refinements are proposed to JFET gate driving circuits that allow their implementation as a single-chip solution. Reverse recovery characteristics of SiC JFETs were measured using diode testing techniques and found to be significantly faster than typical silicon metal oxide semi-conductor field effect transistor (MOSFET) body diodes. SiC JFETs are compared with silicon MOSFETs in power factor correction boost converters, including a real-world application where superior power conversion efficiency utilising SiC JFETs is demonstrated.