Magnetically induced micropillar arrays for an ultrasensitive flexible sensor with a wireless recharging system

This research introduces an idea of producing both nanoscale and microscale pores in piezoelectric material, and combining the properties of the molecular β-phase dipoles in ferroelectric material and the space charge dipoles in order to increase the sensitivity of the sensor and modulate the response frequency bandwidth of the material. Based on this idea, a bi-nano-micro porous dual ferro-electret hybrid self-powered flexible heart sound detection sensor is proposed. Acid etching and electrospinning were the fabrication processes used to produce a piezoelectric film with nanoscale and microscale pores, and corona poling was used for air ionization to produce an electret effect. In this paper, the manufacturing process of the sensor is introduced, and the effect of the porous structure and corona poling on improving the performance of the sensor is discussed. The proposed flexible sensor has an equivalent piezoelectric coefficient d33 of 3312 pC/N, which is much larger than the piezoelectric coefficient of the common piezoelectric materials. Experiments were carried out to verify the function of the flexible sensor together with the SS17L heart sound sensor (BIOPAC, Goleta, CA, USA) as a reference. The test results demonstrated its practical application for wearable heart sound detection and the potential for heart disease detection. The proposed flexible sensor in this paper could realize batch production, and has the advantages of flexibility, low production cost and a short processing time compared with the existing heart sound detection sensors.

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Preparation of Laser‐Induced Graphene Fabric from Silk and Its Application Examples for Flexible Sensor

Advanced Engineering Materials ◽

10.1002/adem.202100195 ◽

2021 ◽

pp. 2100195

Author(s):

Zehong Li ◽

Longsheng Lu ◽

Yingxi Xie ◽

Wentao Wang ◽

Zhiran Lin ◽

...

Keyword(s):

Flexible Sensor

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Flexible and Transparent Polymer-Based Optical Humidity Sensor

Sensors ◽

10.3390/s21113674 ◽

2021 ◽

Vol 21 (11) ◽

pp. 3674

Author(s):

Katerina Lazarova ◽

Silvia Bozhilova ◽

Sijka Ivanova ◽

Darinka Christova ◽

Tsvetanka Babeva

Keyword(s):

Humidity Sensor ◽

Amphiphilic Copolymer ◽

Poly Vinyl Alcohol ◽

Optical Monitoring ◽

Optical Contrast ◽

Successful Development ◽

Flexible Sensor ◽

Surface Profiling ◽

Humidity Range ◽

Different Levels

Thin spin-coated polymer films of amphiphilic copolymer obtained by partial acetalization of poly (vinyl alcohol) are used as humidity-sensitive media. They are deposited on polymer substrate (PET) in order to obtain a flexible humidity sensor. Pre-metallization of substrate is implemented for increasing the optical contrast of the sensor, thus improving the sensitivity. The morphology of the sensors is studied by surface profiling, while the transparency of the sensor is controlled by transmittance measurements. The sensing behavior is evaluated through monitoring of transmittance values at different levels of relative humidity gradually changing in the range 5–95% and the influence of up to 1000 bending deformations is estimated by determining the hysteresis and sensitivity of the flexible sensor after each set of deformations. The successful development of a flexible sensor for optical monitoring of humidity in a wide humidity range is demonstrated and discussed.

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Ultra‐Stretchable Monofilament Flexible Sensor with Low Hysteresis and Linearity based on MWCNTs/Ecoflex Composite Materials

Macromolecular Materials and Engineering ◽

10.1002/mame.202100113 ◽

2021 ◽

pp. 2100113

Author(s):

Yanlin Zhang ◽

Xubin Zhu ◽

Yitao Liu ◽

Li Liu ◽

Qiang Xu ◽

...

Keyword(s):

Composite Materials ◽

Flexible Sensor

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Wettability control of polymeric microstructures replicated from laser-patterned stamps

Scientific Reports ◽

10.1038/s41598-020-79936-1 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Yangxi Fu ◽

Marcos Soldera ◽

Wei Wang ◽

Stephan Milles ◽

Kangfa Deng ◽

...

Keyword(s):

Contact Angle Hysteresis ◽

Contact Angles ◽

Spatial Period ◽

Structured Surfaces ◽

High Adhesion ◽

Direct Laser ◽

Periodic Microstructures ◽

Structure Height ◽

Direct Laser Interference Patterning ◽

Micropillar Arrays

AbstractIn this study, two-step approaches to fabricate periodic microstructures on polyethylene terephthalate (PET) and poly(methyl methacrylate) (PMMA) substrates are presented to control the wettability of polymeric surfaces. Micropillar arrays with periods between 1.6 and 4.6 µm are patterned by plate-to-plate hot embossing using chromium stamps structured by four-beam Direct Laser Interference Patterning (DLIP). By varying the laser parameters, the shape, spatial period, and structure height of the laser-induced topography on Cr stamps are controlled. After that, the wettability properties, namely the static, advancing/receding contact angles (CAs), and contact angle hysteresis were characterized on the patterned PET and PMMA surfaces. The results indicate that the micropillar arrays induced a hydrophobic state in both polymers with CAs up to 140° in the case of PET, without modifying the surface chemistry. However, the structured surfaces show high adhesion to water, as the droplets stick to the surfaces and do not roll down even upon turning the substrates upside down. To investigate the wetting state on the structured polymers, theoretical CAs predicted by Wenzel and Cassie-Baxter models for selected structured samples with different topographical characteristics are also calculated and compared with the experimental data.

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