DUBLIN CITY UNIVERSITY

This material is based upon work supported by the Irish Research Council for Science, Engineering & Technology.

Wireless-based Monitoring of Body Movements Using Wearable Sensors.

Shirley Coyle, Sarah Brady, Yanzhe Wu, Gordon Wallace, Dermot DiamondAdaptive Sensors Group, School of Chemical Sciences, National Centre for Sensor Research,

Dublin City University, Dublin 9, Ireland

IntroductionThe world is becoming more health conscious and as a result healthcare is evolving in many ways. Wearable technologies are taking physiological testing out of the lab and into the realistic lifestyle of the wearer. Traditionally electronic components are hard and brittle which lends to an inharmonious integration into the soft textile substrate. A more seamless integration is possible by intrinsically making the textile the sensor. This may be done by opting for conducting polymer sensors rather than inflexible, brittle silicon-based components. This work is focused on the use of foam-based pressure sensors and similar textile-based strain gauges for monitoring the ambulatory movements of the wearer. Characterization of the molecular nature of the materials and their environment are presented. We find these sensors to be successful in detecting the movement events without imposing on the daily activity of the wearer.

MethodsPolyurethane foam or lycra® coated with polypyrrole has a conductance that changes linearly with respect to the force applied. When pressure or strain is applied to the modified material it causes an increase in the contacting surface area that is coated with polypyrrole. This shortens the conducting path length and results in an increase in bulk conductivity.

Results/DiscussionCadence, stride time, step time and pressure distribution may be measured using the smart insoles. This has applications in sports assessments, clinical analysis and remote patient monitoring. The smart insoles incorporated two sensors to monitor heel strike and front foot lift-off. This measure is significant when performing different movement activities, e.g. normal walking steps or shuffling of the feet. The graphs clearly show the phase shift between heel and toe pressure during these two types of

movements.

Conclusions

Acknowledgements: We gratefully acknowledge the financial support of Science Foundation Ireland (Grant no. 03/IN.3/I361), Irish Research Council for Science Engineering and Technology (RS/2002/765-1) and the European Union (Biotex FP6-2004-IST-NMP-2 – 016789).

The sensing fabric is integrated into a strap that may be positioned around the thoracic cavity. The expansion of the chest causes the lycra to stretched, increasing its conductivity. Motion artefacts affect the signal depending on the sports activity. Graph on right shows sensor response during high speed walking. The signal is filtered to extract the breathing rate.

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Wearable technologies expand the functionality of our clothing, giving us more intuition about our health and physiology. Combining conductive polymer technology with textiles can provide this additional functionality in a seamless manner - the textiles themselves become the sensors, without compromising comfort. Wireless data transfer in imperative to allow free movement of the wearer. Need for wireless!

Smart insoles

Crossbow mote and foam sensor

Coated foam

Uncoated foam Uncoated lycra

Coated lycra

Wearable?

Resistance changes of foam due to compression

Breathing patterns measured using lycra

sensor

Smart shoe