Non‐Swelling and Anti‐Fouling MXene Nanocomposite Hydrogels for Underwater Strain Sensing

Electroconductive hydrogels with stimuli-free self-healing and self-recovery (SELF) properties and high mechanical strength for wearable strain sensors is an area of intensive research activity at the moment. Most electroconductive hydrogels, however, consist of static bonds for mechanical strength and dynamic bonds for SELF performance, presenting a challenge to improve both properties into one single hydrogel. An alternative strategy to successfully incorporate both properties into one system is via the use of stiff or rigid, yet dynamic nano-materials. In this work, a nano-hybrid modifier derived from nano-chitin coated with ferric ions and tannic acid (TA/Fe@ChNFs) is blended into a starch/polyvinyl alcohol/polyacrylic acid (St/PVA/PAA) hydrogel. It is hypothesized that the TA/Fe@ChNFs nanohybrid imparts both mechanical strength and stimuli-free SELF properties to the hydrogel via dynamic catecholato-metal coordination bonds. Additionally, the catechol groups of TA provide mussel-inspired adhesion properties to the hydrogel. Due to its electroconductivity, toughness, stimuli-free SELF properties, and self-adhesiveness, a prototype soft wearable strain sensor is created using this hydrogel and subsequently tested.

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Strain Sensor via Wood Anomalies in 2D Dielectric Array

Nanomaterials ◽

10.3390/nano11041022 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1022

Author(s):

Rashid G. Bikbaev ◽

Ivan V. Timofeev ◽

Vasiliy F. Shabanov

Keyword(s):

Higher Plants ◽

Numerical Study ◽

Reciprocal Lattice ◽

Strain Sensing ◽

Photonic Materials ◽

Sensing Applications ◽

Wide Range ◽

Sensor Structure ◽

Optical Behavior ◽

Chlorophyll Absorption

Optical sensing is one of many promising applications for all-dielectric photonic materials. Herein, we present an analytical and numerical study on the strain-responsive spectral properties of a bioinspired sensor. The sensor structure contains a two-dimensional periodic array of dielectric nanodisks to mimic the optical behavior of grana lamellae inside chloroplasts. To accumulate a noticeable response, we exploit the collective optical mode in grana ensemble. In higher plants, such a mode appears as Wood’s anomaly near the chlorophyll absorption line to control the photosynthesis rate. The resonance is shown persistent against moderate biological disorder and deformation. Under the stretching or compression of a symmetric structure, the mode splits into a couple of polarized modes. The frequency difference is accurately detected. It depends on the stretch coefficient almost linearly providing easy calibration of the strain-sensing device. The sensitivity of the considered structure remains at 5 nm/% in a wide range of strain. The influence of the stretching coefficient on the length of the reciprocal lattice vectors, as well as on the angle between them, is taken into account. This adaptive phenomenon is suggested for sensing applications in biomimetic optical nanomaterials.

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Degradable GO-Nanocomposite hydrogels with synergistic photothermal and antibacterial response

Polymer ◽

10.1016/j.polymer.2021.124018 ◽

2021 ◽

pp. 124018

Author(s):

Jin Han ◽

Yiping Feng ◽

Zhixiong Liu ◽

Qinyue Chen ◽

Yupeng Shen ◽

...

Keyword(s):

Nanocomposite Hydrogels

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Piezoresistive bond lines for timber construction monitoring—experimental scale-up

Wood Science and Technology ◽

10.1007/s00226-021-01305-6 ◽

2021 ◽

Author(s):

Christoph Winkler ◽

Stefan Haase ◽

Ulrich Schwarz ◽

Markus Jahreis

Keyword(s):

Electrical Contact ◽

Scale Up ◽

Strain Analysis ◽

Conductive Filler ◽

Bond Line ◽

Wood Products ◽

Image Correlation ◽

Test Sequence ◽

Strain Sensing ◽

Electrically Conductive

AbstractSeveral laboratory studies and experiments have demonstrated the usability of polymer films filled with electrically conductive filler as piezoresistive material. Applied to adhesives, the glue lines of wood products can achieve multifunctional—thus bonding and piezoresistive/strain sensing—properties. Based on critical load areas in timber constructions, upscaled test setups for simplified load situations were designed, especially with regard to a stress-free electrical contact. In a second step, another upscaling was done to small glulam beams. Based on an experimental test sequence, the piezoresistive reactions as well as the behaviour until failure were analysed. The results show in all cases that a piezoresistive reaction of the multifunctionally bonded specimens was measurable, giving a difference in the extent of relative change. Additionally, measured phenomena like inverse piezoresistive reactions, electrical resistance drift and the absence of a piezoresistive reaction were discussed, based on additional strain analysis by digital image correlation. A model of macroscopic and microscopic strains influencing the piezoresistive reaction of the electrically conductive bond line in wood was used to explain all experimental results. Finally, a first scale-up of piezoresistive bond lines from laboratory samples to glulam beams was possible and successful.

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