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1.
Nature ; 600(7890): 664-669, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34937898

RESUMO

More than a decade of research on the electrocaloric (EC) effect has resulted in EC materials and EC multilayer chips that satisfy a minimum EC temperature change of 5 K required for caloric heat pumps1-3. However, these EC temperature changes are generated through the application of high electric fields4-8 (close to their dielectric breakdown strengths), which result in rapid degradation and fatigue of EC performance. Here we report a class of EC polymer that exhibits an EC entropy change of 37.5 J kg-1 K-1 and a temperature change of 7.5 K under 50 MV m-1, a 275% enhancement over the state-of-the-art EC polymers under the same field strength. We show that converting a small number of the chlorofluoroethylene groups in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer into covalent double bonds markedly increases the number of the polar entities and enhances the polar-nonpolar interfacial areas of the polymer. The polar phases in the polymer adopt a loosely correlated, high-entropy state with a low energy barrier for electric-field-induced switching. The polymer maintains performance for more than one million cycles at the low fields necessary for practical EC cooling applications, suggesting that this strategy may yield materials suitable for use in caloric heat pumps.

2.
Allergol Immunopathol (Madr) ; 48(6): 666-674, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33131977

RESUMO

OBJECTIVES: The differences in the expression profiles of colonic miRNAs between ß-lactoglobulin (ß-Lg) allergic mice and normal mice were analyzed to investigate the important role of the miRNA regulation mechanism in the pathogenesis of cow's milk allergy. METHODS: The present study performed Illumina sequencing to characterize the miRNA profile changes in mouse colon responding to ß-Lg challenge. Target genes were predicted by TargetScan 50 and miRanda 3.3a algorithms and assessed by GO and KEGG analysis. The expression levels of selected miRNAs and cytokine production were verified by cell transfection and quantitative RT-PCR. RESULTS: A total of 15 miRNAs were diversely expressed between the colon of the normal and ß-Lg-sensitized mice (P < 0.05, fold change of >1.50 or <0.67), including six up-regulated miRNAs and nine down-regulated miRNAs, among which seven miRNAs were validated using qRT-PCR. GO enrichment and KEGG pathway analyses further revealed that biological process, protein binding, cytoplasm and the pathways of cancer were significantly enriched, which were closely connected to the allergic inflammation development. Additionally, six key functional interaction pairs in ß-Lg allergy were identified in miRNA prediction algorithms and verified using qRT-PCR. CONCLUSIONS: We can conclude that our results suggested that the miRNAs regulation network participated in the pathogenesis of cow's milk allergy.


Assuntos
Colo/patologia , Redes Reguladoras de Genes/imunologia , Lactoglobulinas/efeitos adversos , MicroRNAs/metabolismo , Hipersensibilidade a Leite/genética , Animais , Colo/imunologia , Citocinas/genética , Modelos Animais de Doenças , Feminino , Perfilação da Expressão Gênica , Humanos , Mucosa Intestinal/imunologia , Mucosa Intestinal/patologia , Lactoglobulinas/imunologia , Camundongos , Hipersensibilidade a Leite/imunologia
3.
Allergol Immunopathol (Madr) ; 48(2): 149-157, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31477403

RESUMO

OBJECTIVES: ß-lactoglobulin (ß-Lg)-sensitized mice model was employed to investigate the correlation between Lactobacillus acidophilus KLDS 1.0738 (Lap KLDS 1.0738) modulating gut microbiota and inducting Toll-like receptors (TLRs) expression. METHODS: The alterations of mice fecal microbiota were analyzed by 16S rRNA gene sequencing. The serum cytokines production and TLR4/NF-κB mRNA expression in the colon tissues were measured by ELISA kit and quantitative RT-PCR, respectively. RESULTS: The results showed that Lap KLDS 1.0738 pretreatment attenuated ß-Lg-induced hypersensitivity, accompanied with a diminished expression of TLR4/NF-κB signaling. Moreover, oral administration of Lap KLDS 1.0738 improved the richness and diversity of fecal microbiota, which was characterized by fewer Proteobacteria phylum and Helicobacteraceae family, and higher Firmicutes phylum and Lachnospiraceae family than allergic group. Notably, TLR4/NF-κB expression was positively correlated with the family of Helicobacteraceae in allergic group, but negatively correlated with the family of Lachnospiraceae, Ruminococcaceae and anti-inflammatory cytokines level. A significant positive correlation was observed between TLR4/NF-κB expression and the production of histamine, total IgE and pro-inflammatory cytokines. CONCLUSIONS: Intake of Lap KLDS 1.0738 can influence the gut bacterial composition, which might result in recognizing TLRs signaling so as to inhibit allergic response.


Assuntos
Microbioma Gastrointestinal , Hipersensibilidade a Leite/imunologia , Hipersensibilidade a Leite/microbiologia , Probióticos/farmacologia , Receptor 4 Toll-Like/imunologia , Animais , Modelos Animais de Doenças , Feminino , Microbioma Gastrointestinal/imunologia , Lactobacillus acidophilus , Lactoglobulinas/imunologia , Lactoglobulinas/toxicidade , Camundongos , Camundongos Endogâmicos BALB C
4.
Sens Actuators A Phys ; 3112020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32661455

RESUMO

Noninvasive measurement of liver iron concentration (LIC) is clinically important. Yet, at the present time, it can only be achieved with SQUID technology. However, SQUID based BLS suffers high costs and cumbersome cryogenic requirements that prevent SQUID BLS from being adopted by clinical applications. Recently, we demonstrated that a single channel ME sensor with piezo-single crystals could detect LIC from only 3cc of mouse liver tissue without any magnetic field shielding. The results demonstrated not only the sensitivity of ME sensor system for LIC but also the feasibility for mapping LIC profiles spatially. This investigation further developed ME sensor arrays, exploiting the compact size and room temperature operation. A Dual-Channel 1-D ME sensor array along the vertical, Z-direction, was developed and shown to be sensitive to the skin-liver distance change which can be utilized to calibrate and eliminate the inter-subject variability of the LIC measurement due to skin-liver distance. With phantom having spatially dependent iron concentrations, the 1-D ME sensor array was capable of mapping the one-dimensional profile of the iron concentration in the horizontal X- and Y-directions. The results of the prototype sensor devices show the feasibility of an array ME-sensors for imaging iron profile.

5.
Zhonghua Yi Xue Za Zhi ; 100(5): 345-350, 2020 Feb 11.
Artigo em Chinês | MEDLINE | ID: mdl-32074777

RESUMO

Objective: To compare and analyze the clinical features and potential risk factors of intracranial and extracranial arterial dissection. Methods: A total of 241 consecutive patients with cervicocerebral artery dissection (CAD) in the First Affiliated Hospital of Zhengzhou University from 2010 to 2019 were observed. The 241 CAD patients were divided into extracranial artery dissection group (EAD) (n=81) and intracranial artery dissection group (IAD) (n=160), clinical characteristics and risk factors were compared between the two groups. Results: Compared with EAD, the National Institute of Health Stroke Scale (NIHSS) score was higher in patients with ischemic stroke in the IAD group (P=0.015). Patients with IAD were more likely to present with headache (58.8% vs 37.0%, P<0.001), and dissection Aneurysms (76.3% vs 38.3%, P<0.001). Patients with EAD more likely to have a history of mild head and neck injuries (11.1% vs 4.4%, P=0.047) and often involved the anterior circulation (77.8% vs 20.0%, P<0.001). Multivariate Logistic regression analysis showed differences in a history of minor head and neck trauma (OR=3.53, 95%CI 1.04-11.97, P=0.042), anterior circulation involvement (OR=0.09, 95%CI 0.05-0.19, P<0.001), dissection aneurysms (OR=4.98, 95%CI 2.80-8.84, P<0.001), headache (OR=2.42, 95%CI 1.39-4.20, P=0.002) remained significant, and the NHISS score lost its significance. Conclusions: EAD often involves the anterior circulation and a history of mild injury to the head and neck. IAD is more prone to exhibit headache symptoms, and it is more likely to form a dissection aneurysm, and the symptoms of ischemic stroke are more severe.


Assuntos
Dissecção Aórtica , Cefaleia , Humanos , Fatores de Risco , Acidente Vascular Cerebral
6.
Beijing Da Xue Xue Bao Yi Xue Ban ; 51(4): 665-672, 2019 Aug 18.
Artigo em Chinês | MEDLINE | ID: mdl-31420619

RESUMO

OBJECTIVE: To investigate the impact of preoperative diagnostic ureteroscopy and biopsy (UB) on radical nephroureterectomy (RNU) and the prognosis of upper tract urothelial carcinoma (UTUC). METHODS: The clinical data of UTUC patients receiving RNU between Jan. 2007 and Dec. 2016 were retrospectively collected. The median follow up time was 40 months. The operation time and blood loss of RNU were compared between UB group and non-UB group. Subgroup analyses were conducted according to the time interval between UB and RNU, and surgery methods of lower ureter. The linear regression model was used to adjust for other common factors that impacted operation time. RESULTS: A total of 163 UTUC patients were included in the final analysis. For the lower ureter, open ureterectomies were performed in 91 patients (55.9%), while retroperitoneal laparoscopic ureterectomies were performed in 72 patients (44.1%). A total of 110 (67.5%) patients received preoperative UB. Compared with non-UB group, the average operation time of UB group was significantly longer [(252.5±79.8) min vs. (221.3±79.8) min, P=0.019], but no difference of blood loss was found (median, 50 mL vs. 50 mL, P=0.143). In subgroup analysis, the average operation time of RNU was significantly prolonged when RNU was performed after 1 week of UB (P=0.023). Meanwhile, the median blood loss of RNU increased significantly when it was done after 2 weeks of UB compared with non-UB group (100 mL vs. 50 mL, P=0.012). UB was also significantly prolonged the operation time of RNU in retroperitoneal laparoscopic ureterectomy group (P=0.012). In multivariable analysis, UB (P=0.049), ≥pT3 (P=0.039), pN+ (P=0.018) and ureterectomy method (P=0.005) were independent risk factors of prolonged operation time. The 3-year cancer specific survival (CSS) rate was 87.2% in our cohort. UB had no significant impact on cancer specific survival (P=0.435). CONCLUSION: UB was an independent risk factor of prolonged RNU time, but did not significantly influence cancer specific survival of upper tract urothelial carcinoma patients.


Assuntos
Carcinoma de Células de Transição , Ureter , Neoplasias Ureterais , Biópsia , Carcinoma de Células de Transição/diagnóstico por imagem , Humanos , Nefrectomia , Nefroureterectomia , Estudos Retrospectivos , Neoplasias Ureterais/diagnóstico por imagem , Ureteroscopia
7.
Phys Rev Lett ; 119(13): 137205, 2017 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-29341713

RESUMO

The ground state of the quantum kagome antiferromagnet Zn-brochantite, ZnCu_{3}(OH)_{6}SO_{4}, which is one of only a few known spin-liquid (SL) realizations in two or three dimensions, has been described as a gapless SL with a spinon Fermi surface. Employing nuclear magnetic resonance in a broad magnetic-field range down to millikelvin temperatures, we show that in applied magnetic fields this enigmatic state is intrinsically unstable against a SL with a full or a partial gap. A similar instability of the gapless Fermi-surface SL was previously encountered in an organic triangular-lattice antiferromagnet, suggesting a common destabilization mechanism that most likely arises from spinon pairing. A salient property of this instability is that an infinitesimal field suffices to induce it, as predicted theoretically for some other types of gapless SLs.

8.
Phys Rev Lett ; 117(26): 267202, 2016 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-28059548

RESUMO

We present the ultralow-temperature specific heat and thermal conductivity measurements on single crystals of YbMgGaO_{4}, which was recently argued to be a promising candidate for a quantum spin liquid (QSL). In a zero magnetic field, a large magnetic contribution of specific heat is observed, and exhibits a power-law temperature dependence (C_{m}∼T^{0.74}). On the contrary, we do not observe any significant contribution of thermal conductivity from magnetic excitations. In magnetic fields H≥6 T, the exponential T dependence of C_{m} and the enhanced thermal conductivity indicate a magnon gap of the fully polarized state. The absence of magnetic thermal conductivity at the zero field in this QSL candidate puts a strong constraint on the theories of its ground state.

9.
Phys Rev Lett ; 114(3): 037002, 2015 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-25659015

RESUMO

We report findings of strong anomalies in both mutual inductance and inelastic Raman spectroscopy measurements of single-unit-cell FeSe film grown on Nb-doped SrTiO3, which occur near the temperature where the superconductinglike energy gap opens. Analysis suggests that the anomaly is associated with a broadened ferroelectric transition in a thin layer near the FeSe/SrTiO3 interface. The coincidence of the ferroelectric transition and gap-opening temperatures adds credence to the central role played by the film-substrate interaction on the strong Cooper pairing in this system. We discuss scenarios that could explain such a coincidence.

10.
Genet Mol Res ; 14(4): 12866-71, 2015 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-26505438

RESUMO

A variety of molecular epidemiological studies have been conducted to examine the association between the DNMT3B -149C/T polymorphism and cancer susceptibility; however, there has been no study investigating the association between the DNMT3B -149C/T polymorphism and the risk of laryngeal squamous cell carcinoma (LSCC) until now. To determine the role of the DNMT3B -149C/T polymorphism in LSCC, we genotyped 113 patients with LSCC and 110 controls from a Chinese population using polymerase chain reaction-restriction fragment length polymorphism analysis. The chi-square test was used to examine differences in the distributions of genotypes studied between patients and controls. The association between the DNMT3B -149C/T polymorphism and the risk of LSCC was estimated using ORs and their 95%CIs. Genotypic frequencies in the patients with LSCC were not similar to those of the controls, with the differences being statistically significant (P = 0.001). When the DNMT3B -149 CC genotype was used as the reference group, the CT genotype was not associated with LSCC risk (adjusted OR, 2.12; 95%CI = 0.89-5.19; P = 0.07), but the TT genotype was associated with significantly increased risk for LSCC (adjusted OR = 3.27; 95%CI = 1.79-10.66; P = 0.009). Under the recessive model of inheritance, the TT genotype was associated with significantly increased risk for LSCC (adjusted OR = 1.98; 95%CI = 1.12-5.95; P = 0.012), compared with other genotypes. These results suggested that the DNMT3B -149C/T polymorphism is associated with a genetic susceptibility for developing LSCC in a Chinese population.


Assuntos
Carcinoma de Células Escamosas/genética , DNA (Citosina-5-)-Metiltransferases/genética , Neoplasias de Cabeça e Pescoço/genética , Povo Asiático , Estudos de Casos e Controles , Feminino , Predisposição Genética para Doença/genética , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Polimorfismo de Fragmento de Restrição/genética , Polimorfismo de Nucleotídeo Único , Carcinoma de Células Escamosas de Cabeça e Pescoço , DNA Metiltransferase 3B
11.
Eur J Gynaecol Oncol ; 36(3): 298-303, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26189257

RESUMO

UNLABELLED: Revised manuscript accepted for publication March 5, Objectives: The purpose of this study was to determine the potential of cancer testis antigen OY-TES-1 as a vaccine for ovarian cancer (OC). MATERIALS AND METHODS: A tissue microarray (TMA) containing 107 samples from OC tissues and 48 samples from OC adjacent tissues was analyzed by immunohistochemistry with the OY-TES-1 polyclonal antibody. The correlation between OY-TES-1 and clinic pathological traits of OC was statistically analyzed. RESULTS: The expression of OY-TES-1 protein was found in 81% (87/107) of OC tissues and 56% (27/48) of OC adjacent tissues. The immunostaining intensity of OY-TES-1 in OC tissues was significantly higher than that in OC adjacent tissues tested (p = 0.040). OC adjacent tissues only demonstrated lower immunostaining intensity, whereas some of OC tissues presented higher immunostaining intensity and majority showed the heterogeneity of protein distribution. There was no statistically significant correlation found between OY-TES-1 expression and any other clinicopathological traits such as age, FIGO stage, pathological grade, and histological type. CONCLUSIONS: OY-TES-1 was expressed in OC tissues with a high proportion, and some of OC tissues presented OY-TES-1 expression in high level vs OC adjacent tissues. OY-TES-1 could be an attractive target for immunotherapy for OC in the future.


Assuntos
Adenocarcinoma de Células Claras/metabolismo , Proteínas de Transporte/metabolismo , Disgerminoma/metabolismo , Neoplasias Císticas, Mucinosas e Serosas/metabolismo , Neoplasias Ovarianas/metabolismo , Adenocarcinoma de Células Claras/terapia , Adolescente , Adulto , Idoso , Vacinas Anticâncer , Criança , Disgerminoma/terapia , Feminino , Humanos , Imuno-Histoquímica , Pessoa de Meia-Idade , Terapia de Alvo Molecular , Neoplasias Císticas, Mucinosas e Serosas/terapia , Neoplasias Ovarianas/terapia , Análise Serial de Tecidos , Adulto Jovem
12.
Science ; 380(6645): eadg0902, 2023 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-37167372

RESUMO

Ferroelectric materials are currently some of the most widely applied material systems and are constantly generating improved functions with higher efficiencies. Advancements in poly(vinylidene fluoride) (PVDF)-based polymer ferroelectrics provide flexural, coupling-efficient, and multifunctional material platforms for applications that demand portable, lightweight, wearable, and durable features. We highlight the recent advances in fluoropolymer ferroelectrics, their energetic cross-coupling effects, and emerging technologies, including wearable, highly efficient electromechanical actuators and sensors, electrocaloric refrigeration, and dielectric devices. These developments reveal that the molecular and nanostructure manipulations of the polarization-field interactions, through facile defect biasing, could introduce enhancements in the physical effects that would enable the realization of multisensory and multifunctional wearables for the emerging immersive virtual world and smart systems for a sustainable future.

13.
Lett Appl Microbiol ; 55(3): 210-7, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22725670

RESUMO

AIMS: The aim of this paper is to check the effect of salinity on the bioremediation process of petroleum hydrocarbons in the saline-alkaline soil. METHODS AND RESULTS: In this study, soil salinity was adjusted to different levels by water leaching method and the bioremediation process was conducted for 28 days. Soil pH increased after leaching and decreased during bioremediation process. At initial time, moderate salinity enhanced the biodegradation and addition of microbial consortium was not effective in enhancing degradation rate of petroleum hydrocarbons. At day of 28 days, higher degradation rate was found in treatments with more leaching times with a maximum value of 42·36%. Dehydrogenase activity increased with the progress of bioremediation and positive correlation was found between dehydrogenase activity and degradation rate of petroleum hydrocarbons. Denaturing gradient gel electrophoresis analysis result showed decreased microbial community diversity with increased salt content. CONCLUSIONS: The result suggested that salinity had great impact on bioremediation, and leaching and addition of inoculated consortium were effective in enhancing biodegradation of petroleum hydrocarbons in the saline-alkaline soil. SIGNIFICANCE AND IMPACT OF THE STUDY: The result of this study is important for understanding the bioremediation process of petroleum in contaminated soil. New remediation method of petroleum contaminated soil can be developed based on this study.


Assuntos
Hidrocarbonetos/metabolismo , Petróleo/metabolismo , Salinidade , Microbiologia do Solo , Poluentes do Solo/metabolismo , Biodegradação Ambiental , Concentração de Íons de Hidrogênio , Consórcios Microbianos , Campos de Petróleo e Gás , Oxirredutases/metabolismo
14.
Eur Rev Med Pharmacol Sci ; 26(22): 8523-8533, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36459033

RESUMO

OBJECTIVE: Suanzaoren decoction (SZRD) in Traditional Chinese Medicine is a common prescription for chronic insomnia. This study systematically and accurately evaluated the safety and efficacy of SZRD in the treatment of chronic insomnia, thus providing a reference for its clinical application. MATERIALS AND METHODS: From the establishment of the corresponding database until May 2022, we systematically queried EMbase, PubMed, Cochrane Library, Web of Science, CNKI, VIP, and Wanfang Database. Randomized control trials (RCTs) were included in this study, and the results that qualified for inclusion were screened and cross-checked by two researchers. After the relevant data were extracted, a meta-analysis was performed using RevMan 5.3 software. RESULTS: A total of 1,311 patients with chronic insomnia from 12 RCTs were enrolled in the meta-analysis, showing that the use of SZRD alone or in combination was superior to the control group in improving the clinical effective rate (RR=1.22, 95%CI [1.16, 1.29], p<0.00001), reducing the recurrence rate (RR=0.47, 95%CI [0.28, 0.80], p=0.005), and lowering the Pittsburgh Sleep Quality Index (PSQI) scores (MDSZRD+WM=-3.35,95%CI [-5.22, -1.47], p<0.00001); (MDSZRD=-1.94, 95%CI [-3.80, -0.07], p = 0.04). SZRD also could reduce the adverse effects rate (RR=0.30, 95% CI [0.22, 0.40], p<0.00001). CONCLUSIONS: It was therefore concluded that SZRD alone or in combination with Western medicine can increase the clinical effective rate, reduce the recurrence rate, improve the quality of life of chronic insomnia patients, and decrease the incidence of adverse effects. However, studies included in this analysis varied in quality, and more large-sample, high-quality, multi-center RCTs are still needed to verify the above conclusions.


Assuntos
Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Distúrbios do Início e da Manutenção do Sono , Humanos , Distúrbios do Início e da Manutenção do Sono/tratamento farmacológico , Medicina Tradicional Chinesa , Bases de Dados Factuais , Ensaios Clínicos Controlados Aleatórios como Assunto
15.
Clin Transl Oncol ; 24(2): 266-275, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34318428

RESUMO

PURPOSE: Increasing evidences suggest dysfunctions of microRNAs (miRNAs) are playing important part in tumors. Therefore, the role of miR-802 in osteosarcoma (OS) was exploited. The object was to evaluate the effect of miR-802 and verify its influence on p27 Kip1 (p27) in OS. METHODS: RT-qPCR experiment was used to detect miR-802 and p27 expression in OS tissues and cells. We explored the function of miR-802 through Transwell assays. The phosphoinositide 3-kinase (PI3K)/AKT serine/threonine kinase pathway and epithelial-mesenchymal transition (EMT) was detected by Western blot assays. Luciferase assay was used to testify the target of miR-802. RESULTS: MiR-802 expression was elevated in OS, which was related to poor clinical outcome in OS patients. MiR-802 overexpression promoted OS migration, invasion and EMT. Further, p27 is a direct target of miR-802. P27 elevation counteracted the promotion effect of OS on EMT, migration and invasion induced by miR-802. In addition, miR-802 overexpression inactivated PI3K/AKT pathway via targeting p27 in OS. CONCLUSION: MiR-802 promoted the progress of EMT, migration and invasion in OS via targeting p27. This newly identified miR-802/p27/PI3K/AKT axis may represent potential targets for OS.


Assuntos
Neoplasias Ósseas/etiologia , Inibidor de Quinase Dependente de Ciclina p27/fisiologia , MicroRNAs/fisiologia , Osteossarcoma/etiologia , Fosfatidilinositol 3-Quinases/fisiologia , Proteínas Proto-Oncogênicas c-akt/fisiologia , Adolescente , Neoplasias Ósseas/patologia , Progressão da Doença , Feminino , Humanos , Masculino , Osteossarcoma/patologia , Adulto Jovem
16.
Science ; 375(6587): 1418-1422, 2022 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-35324308

RESUMO

Electromechanical (EM) coupling-the conversion of energy between electric and mechanical forms-in ferroelectrics has been used for a broad range of applications. Ferroelectric polymers have weak EM coupling that severely limits their usefulness for applications. We introduced a small amount of fluorinated alkyne (FA) monomers (<2 mol %) in relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) terpolymer that markedly enhances the polarization change with strong EM coupling while suppressing other polarization changes that do not contribute to it. Under a low-dc bias field of 40 megavolts per meter, the relaxor tetrapolymer has an EM coupling factor (k33) of 88% and a piezoelectric coefficient (d33) >1000 picometers per volt. These values make this solution-processed polymer competitive with ceramic oxide piezoelectrics, with the potential for use in distinct applications.

17.
Polymer (Guildf) ; 52(2): 540-546, 2011 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-21339839

RESUMO

The actuation strain and speed of ionic electroactive polymer (EAP) actuators are mainly determined by the charge transport through the actuators and excess ion storage near the electrodes. We employ a recently developed theory on ion transport and storage to investigate the charge dynamics of short-side-chain Aquivion® (Hyflon®) membranes with different uptakes of ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf). The results reveal the existence of a critical uptake of ionic liquids above which the membrane exhibit a high ionic conductivity (σ>5×10(-2) mS/cm). Especially, we investigate the charge dynamics under voltages which are in the range for practical device operation (~1 volts and higher). The results show that the ionic conductivity, ionic mobility, and mobile ion concentration do not change with the applied voltage below 1 volt (and for σ below 4 volts). The results also show that bending actuation of the Aquivion membrane with 40 wt% EMI-Tf is much larger than that of Nafion, indicating that the shorter flexible side chains improve the electromechanical coupling between the excess ions and the membrane backbones, while not affect the actuation speed.

18.
MRS Adv ; 6(12): 321-326, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33558837

RESUMO

Thermal stability of polypropylene (PP) over a broad temperature is critical for many applications. Hindered phenol (HP) groups have been utilized in PP for thermal-oxidative protection. This paper studies thermal stability of the electret property of PP linked with 0.2 mol% HP. It is observed that small amount of chemically linked HP groups improves electret thermal stability as reflected by the higher peak temperature of the thermally stimulated discharge curve and about 65% increase in the trap level. In addition, the HP groups in PP generate "rigid backbones" which maintain the PP film shapes to temperatures near the melting (~ 150 °C), compared with pristine PP at 70 °C. SUPPLEMENTARY INFORMATION: The online version of this article (10.1557/s43580-021-00016-1) contains supplementary material, which is available to authorized users.

19.
Nanoscale ; 13(24): 10933-10942, 2021 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-34132304

RESUMO

The mechanism of the recently discovered enhancement of dielectric properties in dilute polymer-nanoparticle composites is investigated by experiments and computer simulations. We show that the weakening of the hydrogen bonds between the nanoparticles and the polymer chains reduces the polymer-nanoparticle composite's dielectric enhancement. The subsequent multiscale simulations investigate the attachment of solvated highly dipolar polymers to oxide nanoparticles, which leads to deposition of nanoparticle-polymer blobs during solution casting and a reduced density compared to a neat polymer film. Coarse-grained simulations of nanocomposite morphology are followed by molecular dynamics and density functional theory calculations of permittivities. The increased free volume in the nanocomposite enables easier reorientation of monomer dipoles with an applied electric field, and thus a higher dielectric permittivity. The numerical results are in excellent agreement with experimental data for PEEU and PEI nanocomposites.

20.
Adv Mater ; 33(36): e2103056, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34302386

RESUMO

Energy harvesting from human motion is regarded as a promising protocol for powering portable electronics, biomedical devices, and smart objects of the Internet of things. However, state-of-the-art mechanical-energy-harvesting devices generally operate at frequencies (>10 Hz) well beyond human activity frequencies. Here, a hydrogel ionic diode formed by the layered structures of anionic and cationic ionomers in hydrogels is presented. As confirmed by finite element analysis, the underlying mechanism of the hydrogel ionic diode involves the formation of the depletion region by mobile cations and anions and the subsequent increase of the built-in potential across the depletion region in response to mechanical pressure. Owing to the enhanced ionic rectification ratio by the embedded carbon nanotube and silver nanowire electrodes, the hydrogel ionic diode exhibits a power density of ≈5 mW cm-2 and a charge density of ≈4 mC cm-2 at 0.01 Hz, outperforming the current energy-harvesting devices by several orders of magnitude. The applications of the self-powered hydrogel ionic diode to tactile sensing, pressure imaging, and touchpads are demonstrated, with sensing limitation is as low as 0.01 kPa. This work is expected to open up new opportunities for ionic-current-based ionotronics in electronics and energy devices.

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