Constructing flexible,
high-sensitivity strain sensors with large
working ranges is an urgent task in view of their widespread applications,
including human health monitoring. Herein, we propose a self-compensated
two-order structure strategy to significantly enhance the sensitivity
and workable range of strain sensors. Three-dimensional printing was
employed to construct highly stretchable, conductive polymer composite
open meshes, in which the percolation network of graphene sheets constitutes
a deformable conductive path. Meanwhile, the graphene layer coated
on the open mesh provides an additional conductive path that can compensate
spontaneously for the conductivity loss of the percolation network
at large strains, through new conductive paths formed by the graphene
sheets in the coating layer and the inner networks. At strains lower
than 20%, the sliding and disconnection of graphene sheets coated
on the mesh surface largely enhance the sensitivity of the sensor,
a 20 times increase as opposed to that of the non-two-order structure
sensor. The resulting sensor reveals high gauge factors (from 18.5
to 88 443) in a strain range of 0–350% and the exceptional
capability to monitor a wide range of human motions, from the subtle
pulse, acoustic vibration to breathing and arm bending.
For infants admitted at neonatal intensive care unit, the continuous monitoring of health parameters is critical for their optimal treatment and outcomes. So it's crucial to provide proper treatment, accurate and comfortable monitoring conditions for newborn infants. In this paper, we propose wearable sensor systems integrated with flexible material based non-invasive sensors for neonatal monitoring. The system aims at providing reliable vital signs monitoring as well as comfortable clinical environments for neonatal care. The system consists of a smart vest and a cloud platform. In the smart vest, a novel stretching sensor based on Polydimethylsiloxane-Graphene (PDMS-Graphene) compound is created to detect newborns' respiration signal; textile-based dry electrodes are developed to measure Electrocardiograph (ECG) signals; inertial measurement units (IMUs) are embedded to obtain movement information including accelerated speed and angular velocity of newborn wrists. Experiments were conducted to systematically test the sensing related characteristics of the aforementioned flexible materials and the performance of the proposed multi-sensor platform. The results show that the proposed system can achieve high quality signals. The wearable sensor platform is promising for continuous long term monitoring of neonates. The multi-modal physiological and behavioral signals measured by the platform can be further processed for clinical decision support on the neonatal health status.
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