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Graphene-modified PA66 fibers could be used for asthma monitoring and remote warning systems

Time : 2021-06-14 Hits : 10

Intelligent sensors can be divided into pressure sensors, strain sensors, temperature sensors, humidity sensors, gas sensors and other different types. Among them, the non-contact humidity sensor uses the change of humidity field in the air to monitor, which can effectively avoid mechanical contact and bacterial cross-infection. However, the humidity sensor materials commonly used at present are mainly composed of rigid semiconductor, which is difficult to be applied to medical monitoring instruments due to its high stiffness, difficult deformation and poor stability. Therefore, through reasonable material selection and structural design to improve the flexibility and sensitivity of the equipment, to ensure that it can adapt to a variety of deformable occasions.

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Based on this, the research team from Shanghai Jiao Tong University prepared a flexible Mg /PA66 humidity sensor (MPHS) for asthma monitoring by loading multiple layers of graphene (Mg) onto electrospun PA66 fibers, which can be used for asthma monitoring by remote alarm system. The high sensitivity of the flexible MPHS can be attributed to the higher specific surface area and more water-absorbing functional groups of the electrospun PA66 fibre. Experiments have confirmed the effective and reliable non-contact monitoring capability of MPHS, which has a broad application prospect in the field of health care.

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Material preparation

The sensor essentially monitors the exchange of water molecules at the interface between Mphs and the air. Therefore, the specific surface area of the interface and the hydrophilic group content of the structure are two decisive factors. PA66 fibers with a diameter of several hundred nanometers, large specific surface area and size enhancement effect were obtained by electrospinning. Mg was loaded onto the surface of PA66 fibers using ultrasonic treatment, thus creating a conductive path between adjacent Mg fibers, showing supersensitive properties.

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Preparation and characterization of MPHS

Humidity sensitivity

In addition to specific surface area, the characteristics of PA66 fibres themselves are also important factors in improving MPHS sensitivity. PA66 has a large number of amine groups in the molecular chain, which is easy to form hydrogen bonds with water molecules. Moreover, PA66 is a semi-crystalline polymer, and the sensitivity of the humidity sensor can be improved by the synergistic effect of the large specific surface area on the physical structure of the fiber network through the different diffusion of water molecules in the crystal region and the amorphous region.

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Moisture detection in MPHS above water surface

permeability


MPHS also has excellent air permeability and biocompatibility, is able to monitor human breathing and other humidity-related behaviour, and responds to health information in a timely manner. For example, when mounted in a respirator mask used for breathing monitoring, the water vapor molecules carried are captured and absorbed by the PA66 nanofibres as the air exhaled from the mouth or nose passes Mphs, which further stimulates the conductive network, leading to changes in electrical signals that allow monitoring of the corresponding physiological characteristics of the body.

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Application of MPHS in respiratory monitoring and asthma detection in humans

Researchers developed a highly sensitive MPHS for asthma monitoring and non-contact human-computer interaction (HMI) system by loading Mg onto electrospun PA66 fibers. Mphs 'accurate breath monitoring and accurate recognition of finger non-contact sliding gestures ensure monitoring of infant asthma, remote alarm system and non-contact control of HMI, which has broad application prospects in the healthcare sector.

The work was published in Advanced Materials under the title "Flexible Noncontact Sensing for Human-Machine Interaction".

The thesis links: https://onlinelibrary.wiley.com/doi/10.1002/adma.202100218

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