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Utilizing Multilayer Design of Organic-Inorganic Hybrids to Enhance Wearable Strain Sensor in Humid Environment

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Chinese Journal of Polymer Science 2023年第7期41卷 1037-1050页

作者： Chen-Chen Lu Wei-Chen Gao Peng li Wei Wu robert k.y.li Hui Zhao Guangxi key Laboratory of Clean Pulp&Papermaking and Pollution Control School of Light Industry and Food EngineeringGuangxi UniversityNanning530004China Guangxi key Laboratory of Calcium Carbonate Resources Comprehensive Utilization College of Materials and Chemical EngineeringHezhou UniversityHezhou542899China Department of Materials Science and Engineering City University of Hong KongTat Chee AvenueKowloonHong Kong999077China

Flexible strain wearable sensors have attracted considerable attention due to their advantages of low cost, lightweight, high sensitivity and good flexibility. However, the strain sensors are easy to be damaged in an extreme humidity environment or by the wearer’s sweat in the process of use, resulting in detection disorder or even a short circuit. Furthermore, preparation of sensors with stable properties under extreme environments is one of the most important research directions. To fill this gap, a flexible sensor was prepared by using polyurethane and carbon nanotubes, then modified by polydopamine and 1H,1H,2H,2H-perfluorodecane-mercaptan. A typical tunnel model was used to explain the working mechanism of the sensor, the sensitivity of the sensor is also explained and evaluated by the tunneling theory. The results show that the sensor has good sensitivity (the sensor has a stable sensing signal output under a strain range from 2% to 300%) and stability over 8500 cycles. At the same time, the sensor has good superhydrophobicity, the water contact angle reaches 152°, and it is still stable in a humid environment. Moreover, this sensor shows excellent performance in monitoring human joint motion (such as finger, elbow, wrist and knee) and physiological signals (such as speaking and drinking). This work provides an effective design method for the sensor which can be applied in a high humidity environment.

关键词： Wearable strain sensor Polyurethane Carbon nanotubes Superhydrophobicity

Facilely prepared layer-by-layer graphene membrane-based pressure sensor with high sensitivity and stability for smart wearable devices

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Journal of Materials Science & Technology 2020年第10期42卷 241-247页

作者： Tao liu Caizhen Zhu Wei Wu kai-Ning liao Xianjing Gong Qijun Sun robert k.y.li Department of Materials Science and Engineering City University of Hong KongTat Chee AvenueKowloonHong KongChina Institute of Low-dimensional Materials Genome Initiative College of Chemistry and Environmental EngineeringShenzhen UniversityShenzhen518060China National Engineering Research Center of Novel Equipment for Polymer Processing Key Laboratory of Polymer Processing Engineering of Ministry of EducationSchool of Mechanical and Automotive EngineeringSouth China University of TechnologyGuangzhou510640China State key Laboratory of Organic-Inorganic Composites College of Materials Science and EngineeringBeijing University of Chemical TechnologyBeijing100029China

With the prosperous development of artificial intelligence,medical diagnosis and electronic skins,wearable electronic devices have drawn much attention in our daily *** pressure sensors based on carbon materials with ultrahigh sensitivity,especially in a large pressure range regime are highly required in wearable *** this work,graphene membrane with a layer-by-layer structure has been successfully fabricated via a facile self-assembly and air-drying(SAAD)*** the SAAD process,air-drying the self-assembled graphene hydrogels contributes to the uniform and compact layer structure in the obtained *** to the excellent mechanical and electrical properties of graphene,the pressure sensor constructed by several layers of membranes exhibits high sensitivity(52.36 kPa……-1)and repeatability(short response and recovery time)in the loading pressure range of 0–50 *** with most reported graphene-related pressure sensors,our device shows better sensitivity and wider applied pressure ***’s more,we demonstrate it shows desired results in wearable applications for pulse monitoring,breathing detection as well as different intense motion recording such as walk,run and ***’s hoped that the facilely prepared layer-by-layer graphene membrane-based pressure sensors will have more potential to be used for smart wearable devices in the future.

关键词： Graphene membrane Self-assembly High sensitivity Wearable devices Human motions

Tailored architecture of composite electrolyte for all-solid-state sodium batteries with superior rate performance and cycle life

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Nano Research 2024年第5期17卷 4171-4180页

作者： Xiang Guan Zhenhua Jian Xingan liao Wenchao liao yanfei Huang Dazhu Chen robert k.y.li Chen liu Shenzhen key Laboratory of Polymer Science and Technology Guangdong Research Center for Interfacial Engineering of Functional MaterialsCollege of Materials Science and EngineeringShenzhen UniversityShenzhen 518055China Department of Materials Science and Engineering City University of Hong KongHong KongChina

Seeking for composite electrolytes reinforced all-solid-state sodium ion batteries with superior long lifespan and rate performance remains a great ***,a unique strategy to tailor the architecture of composite electrolyte via inserting polymer chains into a small quantity of sulfate sodium grafted C_(48)0H_(28)O_(32)Zr_(6)(UIOSNa)is *** intimate contact between polymer segments and UIOSNa with limited pore size facilitates the anion immobilization of sodium salts and reduction of polymer crystallinity,thereby providing rapid ion conduction and reducing the adverse effect caused by the immigration of *** tNa+grafting of-SO_(3)Na groups on fillers allows the free movement of more sodium ions to further improve and ionic ***,even with the low content of UIOSNa fillers,a high ionic conductivity of 6.62×10^(-4) S·cm^(-1) at 60℃ and a transference number of 0.67 for the special designed composite electrolyte are *** assembled all-solid-state sodium cell exhibits a remarkable rate performance for 500 cycles with 95.96%capacity retention at a high current rate of 4 *** corresponding pouch cell can stably work for 1000 cycles with 97.03%capacity retention at 1 C,which is superior to most of the reported composite electrolytes in the literature.

关键词： solid state sodium battery composite electrolyte rate performance cycle life

Confined Crystallization Behaviors of Cross-linked Comb-like Copolymers

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Chinese Journal of Polymer Science 2016年第8期34卷 1039-1046页

作者： Xian-jing Gong 施德安 ying-kui yang Tao Jiang yan-feng Meng robert k.y.li 蒋世春 School of Materials Science andEngineering Tianjin UniversityTianjin 300072China Ministry of Education key Laboratory for the Green Preparation and Application of Functional Materials Hubei Collaborative Innovation Center for Advanced Origanic Chemical MaterialsFaculty of Materials Science and EngineeringHubei UniversityWuhan 430062China School of Chemistry and Materials Science Ludong UniversityYantai 264025China Department of Physics and Materials Science City University of Hong KongHong KongChina

Cross-linked PEG-based copolymers were obtained via synthesis of polyethylene glycol （PEG） and methoxy polyethylene glycol （MPEG） by the bridging and/or cross-linking agent of 2,4-tolylene diisocyanate （TDI） and/or hexamethylene-l,6-diisocyanate homopolymer （HDI trimer）. The effects on the crystallization behaviors of the samples could be found with the changes in molecular weight of MC-PEG and molecular weight of SC-PEG in certain cross-linked density. It is revealed that the samples appear not to crystallize when the molecular weight of MC-PEG and SC-PEG are 1000 g/mol or less than that. The samples begin to crystallize when the molecular weight of either MC-PEG or SC-PEG reaches 2000 g/mol. The crystallinity of crystallized MC-PEG decreases with the increasing molecular weight of uncrystallized SC-PEG and the crystallinity of crystallized SC-PEG declines with the rise of molecular weight of uncrystallizable MC-PEG. The chains of SC-PEG （M_n = 2000 g/mol） can fold and align easilier than those of MC-PEG （M_n = 2000 g/mol）, when the content of PEG is the same.

关键词： PEG-based copolymers Cross-linking Comb-like Confined crystallization behavior.

Surface decoration of Halloysite nanotubes with POSS for fire-safe thermoplastic polyurethane nanocomposites

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Journal of Materials Science & Technology 2022年第6期101卷 107-117页

作者： Wei Wu Wanjing Zhao Xianjing Gong Qijun Sun Xianwu Cao yujun Su Bin yu robert k.y.li Roy A.L.Vellaisamy Department of Materials Science and Engineering City University of Hong KongTat Chee AvenueKowloonHong Kong SARChina National Engineering Research Center of Novel Equipment for Polymer Processing Key Laboratory of Polymer Processing Engineering of Ministry of EducationGuangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced ManufacturingSchool of Mechanical and Automotive EngineeringSouth China University of TechnologyGuangzhou 510640China National-certified Enterprise Technology Center Kingfa Science and Technology Co.Ltd.Guangzhou 510663China Centre for Future Materials University of Southern QueenslandToowoombaQueenslandAustralia James Watt School of Engineering University of GlasgowGlasgow G128QQUnited Kingdom

Halloysite nanotubes(HNTs)have been considered as a promising flame retardant fillers for *** this work,the polyhedral oligomericsilsesquioxane(POSS)containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical *** POSS modified HNTs(HNTs-POSS)dispersed uniformly in the thermoplastic polyurethane(TPU)matrix and endowed TPU nanocomposites with enhanced tensile properties and fire *** calorimeter tests revealed that the introduction of 2 wt%HNTs-POSS to TPU matrix remarkably reduced the peak of heat release rate(PHRR)and total heat release(THR)by 60.0%and 18.3%,*** addition,the peak CO production rate and total smoke release(TSR)could be significantly suppressed by the addition of *** well dispersed HNTs in combination with the ceramified silicon network from the thermal decomposition of POSS contributed to the formation of a continuous and compact char layer,exhibiting a tortuous effect by inhibiting heat diffusion and evaporation of volatile *** addition,the released crystal water from HNTs could dilute the combustible volatiles and then decline the combustion *** tensile tests demonstrated that introduction of 2 wt%HNTs-POSS would enhance the maximum stress of TPU nanocomposite with a slight decrease of elongation at *** combination of HNTs and POSS through the construction of effective interfacial interactions provides a feasible way to effectively enhance the fire safety of TPU nanocomposites without scarifying ductility.

关键词： Thermoplastic polyurethane Halloysite nanotube POSS Flame retardancy Mechanical property

Construction of all-organic low dielectric polyimide hybrids via synergistic effect between covalent organic framework and cross-linking structure

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Nano Materials Science 2023年第4期5卷 429-438页

作者： Wanjing Zhao Zhaoyang Wei Chonghao Lu yizhang Tong Jingshu Huang Xianwu Cao Dean Shi robert kyli Wei Wu key Laboratory of Polymer Processing Engineering of Ministry of Education Guangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced ManufacturingSchool of Mechanical and Automotive EngineeringSouth China University of TechnologyGuangzhou510640China Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials Ministry of Education Key Laboratory for the Green Preparation and Application of Functional MaterialsHubei Key Laboratory of Polymer MaterialsFaculty of Materials Science and EngineeringHubei UniversityWuhan430062China Department of Materials Science and Engineering City University of Hong KongTat Chee AvenueKowloonHong Kong Special Administrative Region of China Jihua Laboratory Foshan528200China

Polyimide(PI)is a promising electronic packaging material,but it remains challenging to obtain an all-organic PI hybrid film with decreased dielectric constant and loss without modifying the ***,a series of allorganic PI hybrid films were successfully prepared by introducing the covalent organic framework(COF),which could induce the formation of the cross-linking structure in the PI *** to the synergistic effects of the COF fillers and the cross-linking structure,the PI/COF hybrid film containing 2 wt%COF exhibited the lowest dielectric constant of 2.72 and the lowest dielectric loss(tanδ)of 0.0077 at 1 *** is attributed to the intrinsic low dielectric constant of COF and a large number of mesopores within the ***,the cross-linking network of PI prevents the molecular chains from stacking and improves the fraction of free volume(FFV).The molecular dynamics simulation results are well consistent with the dielectric properties ***,the PI/COF hybrid film with 5 wt%COF showed a significant enhancement in breakdown strength,which increased to 412.8 kV/mm as compared with pure *** addition,the PI/COF hybrid film achieve to reduce the dielectric constant and thermal expansion coefficient(CTE).It also exhibited excellent thermal,hydrophobicity,and mechanical *** all-organic PI/COF hybrid films have great commercial potential as next-generation electronic packaging materials.

关键词： Polyimide Covalent organic framework All-organic Cross-linking structure Dielectric property Hybrid film

Exercise preconditioning alleviates ischemia-induced memory deficits by increasing circulating adiponectin

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Neural Regeneration Research 2025年第5期20卷 1445-1454页

作者： Meifeng Zheng Borui Zhang Sonata S y yau kwok-Fai So li Zhang Haining Ou Department of Rehabilitation Medicine Guangzhou Medical UniversityGuangzhouGuangdong ProvinceChina Department of Rehabilitation Medicine The Fifth Clinical College of Guangzhou Medical UniversityGuangzhouGuangdong ProvinceChina key Laboratory of CNS Regeneration(Ministry of Education) Guangdong-Hong Kong-Macao Institute of CNS RegenerationJinan UniversityGuangzhouGuangdong ProvinceChina Department of Rehabilitation Sciences The Hong Kong Polytechnic UniversityHong Kong Special Administrative RegionChina State key Laboratory of Brain and Cognitive Science Li Ka Shing Faculty of MedicineThe University of Hong KongHong Kong Special Administrative RegionChina Center for Exercise and Brain Science School of PsychologyShanghai University of SportShanghaiChina Neuroscience and Neurorehabilitation Institute University of Health and Rehabilitation SciencesQingdaoShandong ProvinceChina

Cerebral ischemia is a major health risk that requires preventive approaches in addition to drug *** exercise enhances neurogenesis and synaptogenesis,and has been widely used for functional rehabilitation after *** this study,we determined whether exercise training before disease onset can alleviate the severity of cerebral *** also examined the role of exercise-induced circulating factors in these *** mice were subjected to 14 days of treadmill exercise training before surgery for middle cerebral artery *** found that this exercise pre-conditioning strategy effectively attenuated brain infarct area,inhibited gliogenesis,protected synaptic proteins,and improved novel object and spatial memory *** analysis showed that circulating adiponectin plays a critical role in these preventive effects of *** activation of adiponectin receptors by Adipo Ron mimicked the effects of exercise,while inhibiting receptor activation abolished the exercise *** summary,our results suggest a crucial role of circulating adiponectin in the effects of exercise pre-conditioning in protecting against cerebral ischemia and supporting the health benefits of exercise.

关键词： adiponectin cerebral ischemia exercise pre-conditioning hippocampus memory function middle cerebral artery occlusion prefrontal cortex synaptic proteins treadmill exercise

SyNTHESIS AND MICROSTRUCTURE OF SUPERHARD TiN/SiN_x MULTILAyER THIN FILMS

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 242-248页

作者： Z.F.Zhou y.G.Shen y.W.Mai k.y.li AdvancedCoatingsAppliedResearchLaboratory（ACARL） DepartmentofManufacturingEngineeringandEngineeringManagementCityUniversityofHongKongKowloonHongKongChina CentreforAdvancedMaterialsTechnology（CAMT） SchoolofAerospaceMechanicalandElectronicEngineeringUniversityofSydneySydneyNSW2006Australia

Multilayer thin films of TiN/SiNx have been deposited onto heated Si 100 substra tes (200℃) by reactive dc-magnetron sputtering from Ti and Si targets in an Ar- N2 gas mixture. The rotation speed of the substrate holder was varied from 1 to 20rpm, while target currents were held constant, to produce bilayer periods vary ing from approximately 22 to 0.6nm. These multilayer films were characterized by atomic force microscopy (AFM), cross-sectional transmission electron microscopy (TEM), scanning electron microscopy (SEM), and microhardness measurements. TEM and SEM studies showed elimination of columnar structure in TiN, owing to the in corporation of amorphous SiNx layers. The crystallinity of TiN and amorphous nat ure of SiNx were confirmed by high resolution TEM. An optimum rotation speed was observed, at which hardness was a maximum. The resulting bilayer period was fou nd to be approximately 1.6nm, which resulted in a significant improvement in mic rohardness (~57GPa). The rms surface roughness for this film was less than 1.5nm .

关键词： multilayers hardness supermodulu s stress TiN/SiNx

SyNTHESIS AND THERMAL STABIliTy OF NANOCOMPOSITE nc-TiN/a-TiB_2 THIN FILMS

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 307-312页

作者： y.H.Lu Z.F.Zhou P.Sit y.G.Shen k.y.li H.Chen DepartmentofPhysicsandMaterialsScience CityUniversityofHongKongKowloonHongKongChina／／DepartmentofManufacturingEngineeringg~EngineeringManagementCityUniversityofHongKongKowloonHongKongChina DepartmentofManufacturingEngineering＆EngineeringManagement CityUniversityofHongKongKowloonHongKongChina DepartmentofPhysicsandMaterialsScience CityUniversityofHongKongKowloonHongKongChina

Several nc-TiN/a-TiB2 thin films comprised of nanocrystalline (nc-) TiN and amor phous (a-) TiB2 phases were deposited on Si(100) at room temperature by reactive unbalanced dc magnetron sputtering, followed by vacuum annealed at 400, 600, 80 0 and 1000℃ for 1h, respectively. Effects of B content on microstructure, mecha nical behaviors and thermal microstructure stability have been investigated by X -ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and nanoindentation measurements. The results indicated that B addition greatly affected both microstructure and mechanical behavior of nc-Ti N/a-TiB2 thin films. With increasing B content the grain size decreased. A maxim um hardness value of about 33GPa was obtained at B content of about 19at.%. The improved mechanical properties of nc-TiN/a-TiB2 films with the addition of B int o TiN were attributed to their densified microstructure with development of fine grain size. Only addition of sufficient B could restrain grain growth during an nealing. High B content resulted in high microstructure stability. The crystalli zation of amorphous matrix occurred at about 800℃, forming TiB or TiB2 crystall ite, depending on B content. Before that no change in bonding configuration was found.

关键词： annealing boron reactive unbalanced dc magnetron sputtering ther mal stability nc-TiN/a-TiB2 thin film