Shawn Jeffery Sullivan

Low-cost and disposable pressure sensor mat for non-invasive sleep and movement monitoring applications

Sleep has profound effects on the physical and mental well-being of an individual. The National Institutes of Health (NIH) Sleep Disorder Research Plan gives particular emphasis to non-invasive sleep monitoring methods. Older adults experience sleep fragmentation due to sleep disorders. Unobtrusive non-contact monitoring can be the only realistic solution for long term home-based sleep monitoring. The demand for a low-cost and non-invasive sleep monitoring system for in-home use is more than before due to an increasingly stressful life style. Cost and complexity of current sensor elements hinder the development of low-cost sleep monitoring devices for in-home use. This paper presents the design, development and implementation of a low-cost and disposable pressure sensor mat that could be useful for in-home sleep and movement monitoring applications. The sensor mat design is based on a compressible foam sandwiched between two orthogonal arrays of cPaper capacitance sensors. A low-cost conducting paper has been developed for use as the capacitance sensor electrode. Typical mat design uses a 3 mm thick foam with 5 mm row/column grid array shows that it has a measurement resolution of 0.1 PSI pressure. The resolution can be controlled by both modifying properties of the conducting paper and the foam. Since this pressure mat design is based on low-cost paper, the sensor electrodes are disposable or semi-durable and hence it is ideal for the use in point-of-care physiological monitoring, pervasive healthcare and consumer electronic devices.

Bi-metallic stitched e-textile sensors for sensing salinized liquids

Sensing in e-textiles has generated great interest in a wide range of applications, including wetness detection. A common application for wetness detection sensors is the detection of urine in absorbent products such as diapers. However, unlike water, salinized liquids like urine accelerate the process of chemical reaction of integrated conductors (especially when exposed to electrical current), limiting the lifespan of e-textile sensors. This paper explores an approach to extending the lifespan of conductive thread sensors by blending copper filament with silver threads, and a comparative bench test of the effect of adding copper on the functional lifespan of a wetness sensor when exposed to saline. We find that while the bi-metallic sensor is effective in lengthening the lifespan of the conductive traces, it is likely due to the increased metal content rather than selective reaction of one metal to preserve the other. We make suggestions for further optimizing sensors.