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Lanzhou Chemical has made a series of progress in the field of flexible strain (friction) sensing
[ Instrument R&D of Instrument Network ] Flexible sensors are one of the core components of wearable electronic devices. With the advent of the 5G era, flexible sensors are receiving more and more attention. However, flexible sensor materials face environmental temperature constraints in practical applications. For example, the currently reported elastomer substrate materials have low dynamic characteristics that make the assembled sensors poor in low-temperature self-healing performance, and there is an urgent need to improve the rapid self-healing capabilities of flexible strain sensor materials in low-temperature applications.
Recently, the research team of Wang Jinqing, a researcher at the State Key Laboratory of Solid Lubrication of the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, based on the work of achieving rapid self-healing polyurethane elastomers at room temperature (ACS Applied Materials & Interfaces, 2019, 11, 7387-7396; Journal of Colloid and Interface Science, 2020, 559, 152-161), using a binary collaborative cross-linking strategy (Figure 1), first introduced toluene diisocyanate-terminated polypropylene glycol (PPG) into modified polydimethylsiloxane ( PDMS) skeleton, obtained PPG-PDMS ligand with high dynamic characteristics; subsequently, the introduction of double hydrogen bond and zinc coordination bond into PPG-PDMS ligand, successfully prepared with high toughness and low temperature rapid self-healing Capability of PPG-PDMS-Zn supramolecular elastomer material.
The material's self-healing efficiency is as high as 98% after 8 hours in an environment with a temperature as low as -20°C (Figure 2), mainly because the introduction of PPG segments can significantly reduce the crosslink density of the polymer and promote molecular chains It quickly migrates to the fracture interface for self-healing, and the unique dynamic exchange characteristics of zinc coordination bonds and the low-temperature dissociation effect of hydrogen bonding can effectively enhance the low-temperature self-healing ability of the polymer network. When this elastomer material is used in a multi-functional coating, it exhibits excellent anti-icing characteristics. Related work was published online in the Chemical Engineering Journal (2020, 398, 125593) recently.
In addition, the research group has also made a series of progress in the design and preparation of three-dimensional graphene flexible sensing materials and the assembly of flexible strain (friction) sensor devices. The researchers compounded graphene oxide with conductive polymers, biomass glucomannan or carbon nanotubes, etc., to prepare a three-dimensional graphene composite material with long-range structure, high conductivity and adjustable density. The sensitivity of the flexible strain sensor assembled with this kind of material has been significantly improved, which can realize real-time, accurate measurement and monitoring of human facial expressions, pulse beats and joint movements and other physiological signals. At the same time, inspired by the tactile sensing function of human fingertips, researchers through the clever sensor array design, the assembled friction sensor can effectively distinguish and recognize the surface roughness, hardness and other information of the object (Figure 3). A series of research results were published in Nanoscale (2019, 11, 1159-1168), ACS Applied Materials & Interfaces (2018, 10, 8180-8189; 2018, 10, 39009-39017), Journal of Materials Chemistry C (2018, 6, 8717 -8725; 2019, 7, 7386-7394; 2019, 7, 9008-9017) and Journal of Physical Chemistry C (2019, 123, 3781-3789) and other journals.
Relevant research work was supported by the National Natural Science Foundation of China, Lanzhou Institute of Chemistry, and the State Key Laboratory of Solid Lubrication.