A mechanically robust, ultraelastic foam with controlled multiscale architectures and tunable mechanical/conductive performance is fabricated via 3D printing. Hierarchical porosity, including both ...macro‐ and microscaled pores, are produced by the combination of direct ink writing (DIW), acid etching, and phase inversion. The thixotropic inks in DIW are formulated by a simple one‐pot process to disperse duo nanoparticles (nanoclay and silica nanoparticles) in a polyurethane suspension. The resulting lightweight foam exhibits tailorable mechanical strength, unprecedented elasticity (standing over 1000 compression cycles), and remarkable robustness (rapidly and fully recover after a load more than 20 000 times of its own weight). Surface coating of carbon nanotubes yields a conductive elastic foam that can be used as piezoresistivity sensor with high sensitivity. For the first time, this strategy achieves 3D printing of elastic foam with controlled multilevel 3D structures and mechanical/conductive properties. Moreover, the facile ink preparation method can be utilized to fabricate foams of various materials with desirable performance via 3D printing.
Mechanically robust hierarchical foam with unprecedented elasticity, controllable structure, and performance is fabricated by 3D printing using concentrated nanofiller‐based inks. Combination of direct ink writing, acid etching, and phase inversion produces pores in three different length scale, which are tunable through ink formulation or computer‐designed geometries. Surface coating of carbon nanotubes yields a highly sensitive stress sensor with excellent recoverability.
Realizing solid‐state lithium batteries with higher energy density and enhanced safety compared to the conventional liquid lithium‐ion batteries is one of the primary research and development goals ...set for next‐generation batteries in this decade. In this regard, polymer electrolytes have been widely researched as solid electrolytes due to their excellent processability, flexibility, and low weight. With high cationic transference numbers (tLi+ close to 1), single‐ion conducting polymer electrolytes (SICPEs) have tremendous advantages compared to polymer electrolyte systems (tLi+ < 0.4) because of their potential to reduce the buildup of ion concentration gradients and suppress growth of lithium dendrites. The current review covers the fundamentals of SICPEs, including anionic unit synthesis, polymer structure design, and film fabrication, along with simulation and experimental results in solid‐state lithium–metal battery applications. A perspective on current challenges, possible solutions, and potential research directions of SICPEs is also discussed to provide the research community with the critical technical aspects that may advance SICPEs as solid electrolytes in next‐generation energy storage systems.
This review covers the fundamentals of single‐ion conducting polymer electrolytes (SICPEs), including anionic unit synthesis, structure design, and film fabrication, along with simulation and experimental results in solid‐state lithium‐metal batteries. A perspective on current challenges, possible solutions, and research directions of SICPEs is also discussed to provide critical aspects that may advance SICPEs as solid electrolytes in lithium‐metal batteries.
Highly elastic silicone foams, especially those with tunable properties and multifunctionality, are of great interest in numerous fields. However, the liquid nature of silicone precursors and the ...complicated foaming process hinder the realization of its three‐dimensional (3D) printability. Herein, a series of silicone foams with outstanding performance with regards to elasticity, wetting and sensing properties, multifunctionality, and tunability is generated by direct ink writing. Viscoelastic inks are achieved from direct dispersion of sodium chloride in a unique silicone precursor solution. The 3D‐architectured silicone rubber exhibits open‐celled trimodal porosity, which offers ultraelasticity with hyper compressibility/cycling endurance (near‐zero stress/strain loss under 90% compression or 1000 compression cycles), excellent stretchability (210% strain), and superhydrophobicity. The resulting foam is demonstrated to be multifunctional, such that it can work as an oil sorbent with super capacity (1320%) and customizable soft sensor after absorption of carbon nanotubes on the foam surface. The strategy enables tunability of mechanical strength, elasticity, stretchability, and absorbing capacity, while printing different materials together offers property gradients as an extra dimension of tunability. The first 3D printed silicone foam, which serves an important step toward its application expansion, is achieved.
Multi‐functional, hyper‐elastic silicone foam is three‐dimensionally (3D) printed from a viscoelastic ink. Trimodal porosity is achieved to offer extreme compressibility/cyclic endurance and remarkable stretchability. The resulting foam is multi‐functional, serving as a super oil‐sorbent and soft sensor after surface‐absorption of carbon nanotubes. Tuning ink composition, designing 3D architecture, and printing different materials together afford multi‐dimensional control over foam performance.
Self‐healable elastomers are extremely attractive due to their ability to prolong product lifetime. An additional function that could further expand their applications is strong adhesion force to ...clean and dusty surfaces. This study reports a series of autonomous self‐healable and highly adhesive elastomers (ASHA‐Elastomer) that are fabricated via a simple, efficient, and scalable process. The obtained elastomers exhibit outstanding mechanical properties with elongation at break up to 2102% and toughness (modulus of toughness) of 1.73 MJ m–3. The damaged ASHA‐Elastomer can autonomously self‐heal with full recovery of functionalities, and the healing process is not affected by the presence of water. The elastomers are found to possess an ultrahigh adhesion force up to 3488 N m−1, greatly outperforming previously reported self‐healing adhesive elastomers. Furthermore, the adhesion force of the ASHA‐Elastomer is negligibly affected by dust on the surface, in stark contrast with regular adhesive polymers that have adhesion strengths extremely sensitive to dust. The successful development of high‐toughness, autonomous self‐healable, and ultra‐adhesive elastomers will enable a wide range of applications with enhanced longevity and versatility, including their use in sealants, adhesives, and stretchable devices.
A series of self‐healing adhesive elastomers are fabricated via a simple, efficient, and scalable process. The obtained elastomers exhibit outstanding mechanical properties (extensibility 2102%, toughness 1.73 MJ m–3), and the damaged areas can autonomously self‐heal with full recovery. They also possess an ultrahigh adhesion force (3488 N m−1), greatly exceeding the reported self‐healing adhesive elastomers.
Dementia is a severe neurodegenerative disorder and it can be categorized into several subtypes by different pathogenic causes. We sought to comprehensively analyzed the prevalence of dementia from ...perspectives of geographic region (Asia, Africa, South America, and Europe/North America), age, and gender. We searched PubMed and EMBASE for relevant articles on dementia published from January 1985 to August 2019. In these studies, analyses were stratified by geographic region, age, and gender. Meta-regression was conducted to identify if there were significant differences between groups. We included forty-seven studies. Among the individuals aged 50 and over in the community, the pooled prevalence for all-cause dementia, Alzheimer's disease, and vascular dementia were 697 (CI95%: 546-864) per 10,000 persons, 324 (CI95%: 228-460) per 10,000 persons, and 116 (CI95%: 86-157) per 10,000 persons, respectively. In our study, the prevalence of all-type dementia in individuals aged 100 years and older (6,592 per 10,000 cases) is 244 times higher than in those aged 50-59 (27 per 10,000 cases). The number of people living with dementia approximately doubles every five years. The prevalence was greater in women than in men (788 cases versus 561 cases per 10,000 persons) in overall analysis. In individuals aged 60 to 69 years, AD prevalence in females was 1.9 times greater than that in males (108 cases versus 56 cases per 10,000 persons), while the prevalence of VaD was 1.8 times greater in males than in females (56 cases versus 32 cases per 10,000 persons). Prevalence rate was higher in Europe and North America than in Asia, Africa, and South America.
Abstract
Background
Since December 2019, SARS-CoV-2 has extended to most parts of China with >80 000 cases and to at least 100 countries with >60 000 international cases as of 15 March 2020. Here we ...used a household cohort study to determine the features of household transmission of COVID-19.
Methods
A total of 105 index patients and 392 household contacts were enrolled. Both index patients and household members were tested by SARS-CoV-2 RT-PCR. Information on all recruited individuals was extracted from medical records and confirmed or supplemented by telephone interviews. The baseline characteristics of index cases and contact patients were described. Secondary attack rates of SARS-CoV-2 to contact members were computed and the risk factors for transmission within the household were estimated.
Results
Secondary transmission of SARS-CoV-2 developed in 64 of 392 household contacts (16.3%). The secondary attack rate to children was 4% compared with 17.1% for adults. The secondary attack rate to the contacts within the households with index patients quarantined by themselves since onset of symptoms was 0% compared with 16.9% for contacts without quarantined index patients. The secondary attack rate to contacts who were spouses of index cases was 27.8% compared with 17.3% for other adult members in the households.
Conclusions
The secondary attack rate of SARS-CoV-2 in household is 16.3%. Age of household contacts and spousal relationship to the index case are risk factors for transmission of SARS-CoV-2 within a household. Quarantine of index patients at home since onset of symptoms is useful to prevent the transmission of SARS-Co-2 within a household.
The secondary transmission rate of SARS-CoV-2 in households is 16.3%. Age of contacts and spousal relationship to the index case are risk factors for transmission of coronavirus disease 2019. Quarantine of index patients since onset of symptoms is helpful to prevent COVID-19 spread.
Self-healing materials open new prospects for more sustainable technologies with improved material performance and devices’ longevity. We present an overview of the recent developments in the field ...of intrinsically self-healing polymers, the broad class of materials based mostly on polymers with dynamic covalent and noncovalent bonds. We describe the current models of self-healing mechanisms and discuss several examples of systems with different types of dynamic bonds, from various hydrogen bonds to dynamic covalent bonds. The recent advances indicate that the most intriguing results are obtained on the systems that have combined different types of dynamic bonds. These materials demonstrate high toughness along with a relatively fast self-healing rate. There is a clear trade-off relationship between the rate of self-healing and mechanical modulus of the materials, and we propose design principles of polymers toward surpassing this trade-off. We also discuss various applications of intrinsically self-healing polymers in different technologies and summarize the current challenges in the field. This review intends to provide guidance for the design of intrinsic self-healing polymers with required properties.
Display omitted
Lithium (Li) metal has been considered as the ultimate anode material for next-generation rechargeable batteries due to its ultra-high theoretical specific capacity (3860 mAh g−1) and ...the lowest reduction voltage (−3.04 V vs the standard hydrogen electrode). However, the dendritic Li formation, uncontrolled interfacial reactions, and huge volume variations lead to unstable solid electrolyte interphase (SEI) layer, low Coulombic efficiency and hence short cycling lifetime. Designing artificial solid electrolyte interphase (artificial SEI) films on the Li metal electrode exhibits great potential to solve the aforementioned problems and enable Li–metal batteries with prolonged lifetime. Polymer materials with good ionic conductivity, superior processability and high flexibility are considered as ideal artificial SEI film materials. In this review, according to the ionic conductive groups, recent advances in polymeric artificial SEI films are summarized to afford a deep understanding of Li ion plating/stripping behavior and present design principles of high-performance artificial SEI films in achieving stable Li metal electrodes. Perspectives regarding to the future research directions of polymeric artificial SEI films for Li–metal electrode are also discussed. The insights and design principles of polymeric artificial SEI films gained in the current review will be definitely useful in achieving the Li–metal batteries with improved energy density, high safety and long cycling lifetime toward next-generation energy storage devices.
Utilization of self‐healing chemistry to develop synthetic polymer materials that can heal themselves with restored mechanical performance and functionality is of great interest. Self‐healable ...polymer elastomers with tunable mechanical properties are especially attractive for a variety of applications. Herein, a series of urea functionalized poly(dimethyl siloxane)‐based elastomers (U‐PDMS‐Es) are reported with extremely high stretchability, self‐healing mechanical properties, and recoverable gas‐separation performance. Tailoring the molecular weights of poly(dimethyl siloxane) or weight ratio of elastic cross‐linker offers tunable mechanical properties of the obtained U‐PDMS‐Es, such as ultimate elongation (from 984% to 5600%), Young's modulus, ultimate tensile strength, toughness, and elastic recovery. The U‐PDMS‐Es can serve as excellent acoustic and vibration damping materials over a broad range of temperature (over 100 °C). The strain‐dependent elastic recovery behavior of U‐PDMS‐Es is also studied. After mechanical damage, the U‐PDMS‐Es can be healed in 120 min at ambient temperature or in 20 min at 40 °C with completely restored mechanical performance. The U‐PDMS‐Es are also demonstrated to exhibit recoverable gas‐separation functionality with retained permeability/selectivity after being damaged.
Urea‐functionalized poly(dimethyl siloxane)‐based elastomers with extremely high stretchability, self‐healing mechanical properties, and recoverable gas‐separation performance are fabricated. Tailoring the molecular weights of poly(dimethyl siloxane) offers tunable mechanical properties, such as ultimate elongation (from 984% to 5600%), Young's modulus, toughness, and elastic recovery. After mechanical damage, the elastomers can be healed in 2 h at ambient temperature with completely restored mechanical properties and recovered gas‐separation functionalities.
Silicon (Si) is a promising candidate for high‐capacity anode materials owing to its high theoretical capacity (3579 mAh g−1), low working voltage, and wide natural abundance, although its huge ...volume variation during charge/discharge processes always results in a short cycling life. Polymer binders play a vital role in improving the cycling performance of Si‐based anodes, although traditional polyvinylidene difluoride cannot fulfil the requirements owing to its weak van der Waals forces with the Si surface. Recently, polymer binders constructed by dynamic bonds have been developed, which are reported to allow high‐energy‐density electrodes with improved electrochemical performance. With dynamic bonds including hydrogen bonding, ionic bonding, and host–guest interactions, these polymer binders possess self‐healing capabilities and enhanced mechanical performance, achieving a tremendous advance in addressing the capacity fading of Si‐based anodes. In this review, we will summarize the research progress of polymer binders constructed with dynamic bonds, and the challenges for their real applications in advanced Li‐ion batteries will also be discussed.
In a bind: Polymer binders constructed through dynamic noncovalent bonds for Si‐based electrodes in lithium‐ion battery applications are summarized. Their dynamic nature makes them especially attractive owing to their ability to in situ repair conductive networks. Recent progress of polymer binders with hydrogen bonding, ionic bonding, host–guest interactions, and multidynamic bonds are discussed, followed by their challenges for practical applications (see figure).
PDF
