Investigating strain transfer in polymer coated structures for the health monitoring of aerospace vehicles using polymer photonic waveguides

In this work, we present the concept of planar polymer photonic waveguides for the health monitoring of aerospace structures. Here a polymer layer is deposited onto the material/structure to be monitored. Within the polymer layer, waveguides are created after deposition. These waveguides can then be used as 'optical fibres' for optical fibre sensing methodologies. In investigating the use of polymer photonic waveguides the question to be answered is: does the strain in the test material transfer to the polymer layer, such that the value to be measured optically is reliable and indicative of the true strain in the test structure? To answer this question we have conducted a preliminary structural analysis with finite element analysis, utilising ANSYS. A simple aluminium cantilever was used as the test structure, and layers of polyethylene with different thicknesses were added to this. Result show that the thinner the layer of polymer, the more accurate the measured strain will be. For a 100um coating, the difference is strain was observed to be on the order of 3.3%. © 2014 IEEE.

Smartwatch: performance evaluation for long-term heart rate monitoring

Recent advancement in wearable technologies, particularly smart watches embedded with powerful processors, memory subsystems with various built-in sensors such as ac-celerometer, gyroscope and optical sensor in one single package has opened a whole new application space. One of the main applications of interest is the monitoring of movement patterns, heart rate, ECG and PPG particularly for longer duration's in natural environments. In this study, we conducted a performance evaluation on the optical heart rate sensor of the smartwatch with respect to the commonly used ECG and PPG devices. Results have shown that the heart rate acquired from the smartwatch is reasonably accurate with a high degree of correlation. Further, we conducted a preliminary exerise to evaluate sleep quality using the heart rate readings and accelerometer readings captured from the smartwatch and compared with a commercially available and clinically used non-contact sleep sensor, RESMED S+.

Use of optical interferometry to measure gold nanoparticle adsorption on silica

Adsorption of metal nanoparticles is at the heart of many chemical and biosensor techniques, but there are few approaches that can provide quantitative characterisation of individual nanoparticle films fabricated at different times and/or under different conditions. Using synthesised gold nanoparticles (Au NPs) as a model, the nanoparticle films were investigated using an optical interferometry technique known as fringes of equal chromatic order (FECO), which was further systematically validated against both in situ quartz crystal microbalance (QCM) and ex situ atomic force microscopy (AFM) measurements. The results indicate that the FECO wavelengths has a quantifiable red shift with increasing particle densities, making it possible to quantify the degree of surface coverage via the analysis of the fringe shift at a fixed fringe order. Moreover, the calculated formula between the FECO shifts and the surface coverage allows quantitative analysis of the whole adsorption kinetics investigated. Particularly, the as-proposed FECO technique can successfully monitor the Au NP adsorption in situ, which could be a new versatile technology platform for “online” monitoring method, for example in biosensor applications using Au NP-tagged analytes.