Alexander P. Mazzolini

A new sensor for monitoring chest wall motion during high-frequency oscillatory ventilation.

The recently developed technique of fibre optic respiratory plethysmography (FORP) has been modified to monitor the rapid, small amplitude movements of the chest wall during high-frequency oscillatory ventilation (HFOV). The FORP sensor is an expandable belt encircling the chest, in which is housed a fibre optic loop that alters its radius of curvature as a function of chest perimeter. These curvature changes cause variations in macrobending losses of light transmitted through the fibre, which are proportional to the chest perimeter. Dynamic measurement of transmitted light intensity can hence be used to monitor chest wall motion (CWM). For application to HFOV, the design of the FORP belt was altered to increase sensitivity and the materials were chosen to maximise macrobending effects induced by the CWM. FORP was tested in four piglets ventilated with HFOV, both in the normal and surfactant-deficient lung. Measurement of CWM was possible over the full range of tidal volumes and ventilation frequencies used during HFOV. In all cases, the measured frequency of the CWM fell within 3% of the applied ventilation frequency. In addition, the technique was sufficiently sensitive to detect changes in the amplitude of CWM in response to changes in applied tidal volume. It is anticipated that application of this new non-invasive measurement device will lead to an increased understanding of the dynamics of chest and abdominal wall motion during HFOV.

Optic fibre bundle contact imaging probe employing a laser scanning confocal microscope

A small diameter (600 µm) fused optic fibre imaging bundle was used as a probe to compare fluorescent specimens by direct contact imaging using both a conventional fluorescence microscope and a laser scanning confocal microscope (LSCM) system. Green fluorescent polyester fibres placed on a green fluorescent cardboard background were used to model biological tissue. Axial displacement curves support the hypothesis that pinhole size in the LSCM system reduces the contribution of non‐focal plane light. Qualitative comparison showed that the LSCM system produced superior image quality and contrast over the conventional system. The results indicate that the new LSCM–probe combination is an improvement over conventional fluorescence–probe systems. This study shows the feasibility of employing such a small diameter probe in the investigation of biological function in difficult to access areas.

A roadmap for forming successful interdisciplinary education research collaborations: a reflective approach

Current literature about interdisciplinary education research is focused on three points: conceptual definitions of interdisciplinarity, the need for interdisciplinary research to tackle the advent of problem-based research and the positive curriculum outcomes to be gained from interdisciplinary research. While this research is important, it does not always include an account of the often complex and politicised interactions that might affect the outcomes of interdisciplinary research groups. This paper provides one possible ‘roadmap’ for successful interdisciplinary collaboration. It is based on a reflective case study of the authors’ own formation of an interdisciplinary research group and the practical resolutions to both the theoretical and the practical issues involved in achieving interdisciplinarity in education research.

Active learning in optics and photonics: experiences in Africa

The UNESCO Active Learning in Optics and Photonics project is designed for the benefit of teachers of introductory university physics from developing countries. Initial implementation has taken place in two African nations, Ghana and Tunisia. The training curriculum includes student materials to teach topics in geometrical and physical optics in an active way with a high level of student involvement in the learning process. The curriculum makes use of simple, inexpensive materials. A conceptual learning assessment instrument is being developed as part of the project. Follow-up activities are planned. Experiences of the international group of workshop trainers are reported.

Collection efficiency of scattered light in single-ended optical fiber sensors.

Optical fibers allow a variety of spectroscopic sensing methods to be implemented in a single-ended backscattering geometry. Taking multimode fibers with surface-enhanced Raman scattering active tips as a model system, it is shown that the remote single-ended collection geometry can be relatively inefficient in comparison to the performance of the underlying sensor structure. Therefore the performance of the single-ended geometry has been compared to the analogous sensor structure on a nonguiding silica glass substrate. While part of the reduction in collection efficiency can be attributed to mismatches between the numerical aperture of the collection optics and that of the fiber, this study suggests that there can be an additional loss due to a mismatch between the confocal area of the collection optics and the area of the fiber core. This effect is most significant for high numerical aperture objectives. However, the collection efficiency is somewhat higher than would be expected from a simple area ratio analysis. This can be attributed to the graded-index fiber used in the model system and the relaxation of confocal requirements in the longitudinal direction.

The Effect of the Cladding Refractive Index on an Optical Fiber Evanescent-Wave Sensor

Evanescent field interactions can be used to provide a variety of sensing modalities in optical fibers with a modified cladding. However, the evanescent field interaction with the surrounding environment is strongly dependent on the refractive index of the modified cladding region. This can lead to difficulties due to dispersion in the refractive index, particularly in fluorescence based sensors where the excitation and emission wavelengths are separated. Here, a broadband supercontinuum light source has been used to characterize the refractive index dependence of the sensor response over a wide wavelength range. The critical effect of the cladding refractive index on the performance of an optical fiber evanescent wave sensor is demonstrated for both amplitude and wavelength modulated situations. In principle, this approach can be used to predict the performance of the sensor over the full wavelength range of the broadband source. The results also suggest that residues from the original cladding of the fiber cause an intrinsic loss, which reduces the sensitivity at low levels of extrinsic absorption. The integrity of the interface between the core and the modified cladding is therefore an important parameter to be addressed in practical sensing applications.

A simple, low-cost demonstration of wavelength division multiplexing

Optics and photonics can be used to motivate students in physics courses at the high school, college, or university level. Many fundamental ideas and concepts can be taught by exploring wavelength division multiplexing as used in optical fiber communication systems. We describe a safe, simple, low-cost experimental apparatus that can be used to demonstrate the key concepts of wavelength division multiplexing. The apparatus can form the basis of several hands-on, active-learning activities.

Chemical sensors based on nanoparticle arrays

The size-dependent properties of nanomaterials are currently attracting a great deal of interest in the research community because of the many important potential applications in microelectronic, data storage and sensing devices. The signature optical property of metal nanoparticles is the localized surface plasmon resonance (LSPR), which occurs when collective oscillations of the conduction electrons are excited by light. The LSPR results in wavelength-selective photon absorption, scattering and local electromagnetic field enhancement. The latter contributes to the significant enhancements observed in surface-enhanced Raman scattering (SERS) and other surface-enhanced spectroscopies. Several groups have already demonstrated the enormous potential of compact, integrated SERS sensors for a broad range of chemical and biological sensing applications. However, the systems described so far have generally utilized substrates with a wide range of feature sizes and irregular spatial distributions. These factors contribute to relatively poor reproducibility between sensors. Fabrication techniques based on ordered, self-assembled arrays of nanospheres appear to offer a convenient and inexpensive means for generating uniform structures. Progress in applying these methods to the fabrication of reproducible SERS microsensors will be described.

The Use of Active Learning Methods in Introductory Electronics Deliver Positive Learning Outcomes, Yet Some Academics Still Resist Change

At Swinburne University of Technology, we incorporate Interactive Lecture Demonstrations (ILDs), which are a form of Active Learning (AL), into our introductory electronics course. The ILDs are used in a blended learning approach, and used as revision to consolidate important concepts after the completion of traditional (passive) lectures. The analysis of our education research data indicates that: (a) traditional lectures do little to improve students’ conceptual understanding, (b) ILDs can improve students’ conceptual understanding significantly, (c) the ILD learning cycle, where students actively engage in discussions about the ILD activities, can improve conceptual understanding significantly, and (d) students’ exam performance can be significantly better in sections that have been taught by traditional lectures plus ILDs, compared to sections that have been taught by traditional lectures alone. This evidence from our studies at Swinburne, and similar validated results from Physics Education Research (PER) throughout the world, appears to have had only limited impact on improving the teaching practices of many science and engineering academics. The reasons for this reluctance to upgrade teaching practices, even when confronted with compelling evidence, may be associated with each academic’s deeply-rooted conceptions about the effectiveness of their own traditional teaching methods. These conceptions need to be identified and adapted in order to improve teaching practices for these academics.

Fibre Bragg grating sensor for respiratory monitoring

A temperature sensor based on fibre Bragg gratings has been used to monitor human respiration. We discuss the thermodynamic properties of the sensor and present the general performance characteristics of the system.