Ion-Exchange Enabled Dual-Functional Swarms with Reconfigurability and Magnetic Controllability.

In nature, many organisms are capable of self-organizing into collective groups through local communications to perform complex tasks that individuals cannot complete. To date, the reported artificial microswarms either rely on toxic chemical reactions for communication or lack the hierarchical controllability and functionality, which is unfavorable for practical applications. To this end, this exploits the ion-exchange reaction enabled hierarchical swarm composed of cationic ion exchange resin and magnetic microspheres of internal information exchange. The swarm is reconfigurable under magnetic fields, generating ordered structures of controllable mobilities and even reversed hierarchy, able to navigate in confined and complex environments. Moreover, the swarm shows interesting communications among each other, such as merging, splitting, and member exchange, forming multi-leader groups, living crystals, and complex vortices. Furthermore, the swarm functions as a dual-functional microreactor, which can load, transport, and release drugs in a pH-enhanced manner, as well as effectively degrade antibiotics via light-enhanced Fenton-like reaction in polluted water. The organized structure of the swarm greatly improves the drug loading/transport efficiency and the local concentration of catalysts for fast pollutant removal. This design lays the foundation for the design of dual-functional micro/nanorobots for intelligent drug delivery and advanced environmental remediation.

Writing Into Water.

Writing is an ancient communication technique dating back at least 30 000 years. While even sophisticated contemporary writing techniques hinge on solid surfaces for engraving or the deposition of ink, writing within a liquid medium requires a fundamentally different approach. The study here demonstrates the writing of lines, letters, and complex patterns in water by assembling lines of colloidal particles. Unlike established techniques for underwater writing on solid substrates, these lines are fully reconfigurable and do not require any fixation onto the substrate. Exploiting gravity, an ion-exchange bead (pen) is rolled across a layer of sedimented colloidal particles (ink). The pen evokes a hydrodynamic flow collecting ink-particles into a durable, high-contrast line along its trajectory. Deliberate substrate-tilting sequences facilitate pen-steering and thus drawing and writing. The experiments are complemented with a minimal model that quantitatively predicts the observed parameter dependence for writing in fluids and highlights the generic character of writing by line-assembly. Overall, the approach opens a versatile route for writing, drawing, and patterning fluids-even at the micro-scale.

Efficient Fabrication of Micro/Nanostructured Polyethylene/Carbon Nanotubes Foam with Robust Superhydrophobicity, Excellent Photothermality, and Sufficient Adaptability for All-Weather Freshwater Harvesting.

The integration of fog collection and solar-driven evaporation has great significance in addressing the challenge of the global freshwater crisis. Herein, a micro/nanostructured polyethylene/carbon nanotubes foam with interconnected open-cell structure (MN-PCG) is fabricated using an industrialized micro extrusion compression molding technology. The 3D surface micro/nanostructure provides sufficient nucleation points for tiny water droplets to harvest moisture from humid air and a fog harvesting efficiency of 1451 mg cm-2 h-1 is achieved at night. The homogeneously dispersed carbon nanotubes and the graphite oxide@carbon nanotubes coating endow the MN-PCG foam with excellent photothermal properties. Benefitting from the excellent photothermal property and sufficient steam escape channels, the MN-PCG foam attains a superior evaporation rate of 2.42 kg m-2 h-1 under 1 Sun illumination. Consequently, a daily yield of ≈35 kg m-2 is realized by the integration of fog collection and solar-driven evaporation. Moreover, the robust superhydrophobicity, acid/alkali tolerance, thermal resistance, and passive/active de-icing properties provide a guarantee for the long-term work of the MN-PCG foam during practical outdoor applications. The large-scale fabrication method for an all-weather freshwater harvester offers an excellent solution to address the global water scarcity.

Weak Ion-Exchange Based Magnetic Swarm for Targeted Drug Delivery and Chemotherapy.

Swimming microrobots that are actuated by multiple stimuli/fields display various intriguing collective behaviors, ranging from phase separation to clustering and giant number fluctuation; however, it is still chanllenging to achieve multiple responses and functionalities within one colloidal system to emulate high environmental adaptability and improved tasking capability of natural swarms. In this work, a weak ion-exchange based swarm is presented that can self-organize and reconfigure by chemical, light, and magnetic fields, showing living crystal, amorphous glass, liquid, chain, and wheel-like structures. By changing the frequency and strength of the rotating magnetic field, various well-controlled and fast transformations are obtained. Experiments show the high adaptability and functionality of the microrobot swarm in delivering drugs in confined spaces, such as narrow channels with turns or obstacles. The drug-carrying swarm exhibits excellent chemtherapy for Hela and CT26 cells due to the pH-enhanced drug release and locomotion. This reconfigurable microswarm provides a new platform for biomedical and environmental applications.

Cost-Effective Fabrication of Micro-Nanostructured Superhydrophobic Polyethylene/Graphene Foam with Self-Floating, Optical Trapping, Acid-/Alkali Resistance for Efficient Photothermal Deicing and Interfacial Evaporation.

Solar evaporation is one of the most attractive and sustainable approaches to address worldwide freshwater scarcity. Unfortunately, it is still a crucial challenge that needs to be confronted when the solar evaporator faces harsh application environments. Herein, a promising polymer molding method that combines melt blending and compression molding, namely micro extrusion compression molding, is proposed for the cost-effective fabrication of lightweight polyethylene/graphene nanosheets (PE/GNs) foam with interconnected vapor escape channels and surface micro-nanostructures. A contact angle of 155 ± 2°, a rolling angle of 5 ± 1° and reflectance of ≈1.6% in the wavelength range of 300-2500 nm appears on the micro-nanostructured PE/GNs foam surface. More interestingly, the micro-nanostructured PE/GNs foam surface can maintain a robust superhydrophobic state under dynamic impacting, high temperature and acid-/alkali solutions. These results mean that the micro-nanostructured PE/GNs foam surface possesses self-cleaning, anti-icing and photothermal deicing properties at the same time. Importantly, the foam exhibits an evaporation rate of 1.83 kg m-2 h-1 under 1 Sun illumination and excellent salt rejecting performance when it is used as a self-floating solar evaporator. The proposed method provides an ideal and industrialized approach for the mass production of solar evaporators suitable for practical application environments.

Green Synthesis of Carbon Nitride-Based Conjugated Copolymer for Efficient Photocatalytic Degradation of Tetracycline.

Upcycling waste plastics into advanced semiconductor photocatalysts provides a new strategy to reasonably and economically solve the huge amount of waste plastics, which remains challenging. Herein, a carbon nitride-based donor-acceptor (D-A) conjugated copolymer by copolymerization of dicyandiamide and terephthalic acid from discarded polyethylene terephthalate (PET) using Zn(OH)2 as catalyst and template at 360-440 °C is synthesized. The morphology and structure of the conjugated copolymer are well regulated by the calcination temperature. The resultant conjugated copolymer exhibits merits of high light absorption and low electron-hole recombination probability. Consequently, it works excellently in the persulfate-based advanced oxidation process for visible light-driven photocatalytic degradation of tetracycline. The kinetic constant (3.4 × 10-2  min-1 ) is 40.5 and 2.3 times that of the conjugated copolymer system and persulfate system, respectively. Furthermore, the reactive species (including •OH, SO4 •- , •O2 - , 1 O2 , and h+ ) and degradation intermediates of tetracycline are analyzed to expound its degradation process. This work not only pioneers design guidelines on upcycling of waste plastics in a sustainable manner, but also provides a facile strategy to synthesize carbon nitride-based D-A conjugated copolymers for the efficient activation of persulfate-based advanced oxidation process in wastewater treatment.

Upcycling Waste Polyethylene into Carbon Nanomaterial via a Carbon-Grown-on-Carbon Strategy.

Upcycling waste plastics (e.g., polyethylene (PE)) into value-added carbon products is regarded as a promising approach to address the increasingly serious waste plastic pollution and simultaneously achieve carbon neutrality. However, developing new carbonization technology routes to promote the oxidation of PE at low temperature and construct the stable cross-linking network remains challenging. Here, a facile carbon-grown-on-carbon strategy is proposed using carbon black (CB) to convert waste PE into core/shell carbon nanoparticles (CN) in high yields at low temperature. The yield of CN remarkably increases when the heating temperature decreases or the dosage of CB increases. The obtained CN displays turbostratic structure and closely aggregated granular morphology with a size of ≈80 nm. It is found that, prior to the oxidation and carbonization of PE, CB forms a 3D network architecture in the PE matrix. More importantly, CB not only catalyzes the partial oxidation of PE to form PE macromolecular radicals and introduce oxygen-containing groups at low temperature in the early stage, but also favors for the construction of a stable cross-linking network in the latter stage. This work offers a facile sustainable strategy for chemical upcycling of PE into value-added carbon products without post-treatments or usage of metallic catalysts.

Negative emotional status and influencing factors among young employees in center of disease control and prevention.

BACKGROUND: Negative emotions among employees have become a public problem that increase the risk of developing the disease and accelerate its progression. This study aimed to investigate the status and influencing factors of negative emotions among young employees in center of disease control and prevention. METHODS: Participants included 6099 employees aged 40 or below in center of disease control and prevention (CDC) of 32 province of China were interviewed by online questionnaire survey. The emotional conditions of anxiety and depression, and their influencing factors were analyzed. RESULTS: A total of 5353 valid questionnaires were collected with the recovery rate of 87.77%. 2871 cases of young employees had different degrees of negative emotions at work, accounting for about 53.60%. Regression analysis showed that gender, professional title, educational level, job satisfaction, chronic diseases, daily sleep duration, average weekly overtime, physical activity time, and sugary beverage intake were the influencing factors of negative emotions (P < 0.05). Male, primary and below, never working overtime and daily physical activity time more than 30 min were protective factors for negative emotions (OR vale were 0.79, 0.68, 0.39 and 0.63, respectively, P < 0.05). Bachelor degree or above, poor job satisfaction, chronic disease, daily sleep duration less than 8 h and drinking one to three sugary drinks a week were the risk factors for negative emotion (OR vale were1.21, 4.32, 2.16, 2.75 and 1.20, respectively, P < 0.05). CONCLUSION: Due to the influence of work pressure, lifestyle, chronic diseases and other factors, young employees in CDC have a certain degree of negative emotions at work, which should be paid enough attention. Meanwhile, corresponding measures should be taken according to the influencing factors to reduce the occurrence of negative emotions.

Magnetic handshake materials as a scale-invariant platform for programmed self-assembly.

Programmable self-assembly of smart, digital, and structurally complex materials from simple components at size scales from the macro to the nano remains a long-standing goal of material science. Here, we introduce a platform based on magnetic encoding of information to drive programmable self-assembly that works across length scales. Our building blocks consist of panels with different patterns of magnetic dipoles that are capable of specific binding. Because the ratios of the different panel-binding energies are scale-invariant, this approach can, in principle, be applied down to the nanometer scale. Using a centimeter-sized version of these panels, we demonstrate 3 canonical hallmarks of assembly: controlled polymerization of individual building blocks; assembly of 1-dimensional strands made of panels connected by elastic backbones into secondary structures; and hierarchical assembly of 2-dimensional nets into 3-dimensional objects. We envision that magnetic encoding of assembly instructions into primary structures of panels, strands, and nets will lead to the formation of secondary and even tertiary structures that transmit information, act as mechanical elements, or function as machines on scales ranging from the nano to the macro.

[Secular trends in food intakes among the elderly aged 60 and older in nine provinces in China from 1991 to 2015].

OBJECTIVE: To analysis the status and trend of food intake of elderly aged 60 and older years old in nine provinces of China. METHODS: The data of China Health and Nutrition Survey from 1991 to 2015 were used, which elderly ≥60 years old were selected as the subjects. The dietary survey used compared. The 3-consecutive day-24-hour dietary recall was used to collect information on food intake, the condiment intake was collected by weighting and bookkeeping method. RESULTS: The intakes of cereals and tubers and vegetables among the elderly were 363.3 g/d and 249.1 g/d, respectively in 2015, decreased by 65.4 g/d and 17.6 g/d as compared with those in 1991. The intakes of meat, egg, and edible oil were 56.7 g/d, 19.2 g/d and 27.5 g/d respectively and increased by 7.5 g/d, 19.2 g/d and 2.5 g/d as compared to those with 1991. The intakes of eggs, soybeans and nuts were higher among the elderly people having high income or living in urban areas. In 2015, the proportion of elderly in nine provinces of China whose intake of vegetables, fruits, soybeans, milk and dairy products was lower than the recommended amount was relatively high. The proportion of meat higher than the recommended value is higher than that of aquatic products and eggs. Oil, salt and other limited flavoring intake of less than and above the limit was nearly 50 percent of the population. CONCLUSION: There are three problems in the diet of the elderly in nine provinces in China: the structure of diet is not rational; low intake of the food rich in high quality protein and low fat such as aquatic products, eggs, dairy products and so on; the problem of excessive oil and salt in food.

The modification effect of temperature on the relationship between air pollutants and daily incidence of influenza in Ningbo, China.

BACKGROUND: Although exposure to air pollution has been linked to many health issues, few studies have quantified the modification effect of temperature on the relationship between air pollutants and daily incidence of influenza in Ningbo, China. METHODS: The data of daily incidence of influenza and the relevant meteorological data and air pollution data in Ningbo from 2014 to 2017 were retrieved. Low, medium and high temperature layers were stratified by the daily mean temperature with 25th and 75th percentiles. The potential modification effect of temperature on the relationship between air pollutants and daily incidence of influenza in Ningbo was investigated through analyzing the effects of air pollutants stratified by temperature stratum using distributed lag non-linear model (DLNM). Stratified analysis by sex and age were also conducted. RESULTS: Overall, a 10 µg/m3 increment of O3, PM2.5, PM10 and NO2 could increase the incidence risk of influenza with the cumulative relative risk of 1.028 (95% CI 1.007, 1.050), 1.061 (95% CI 1.004, 1.122), 1.043 (95% CI 1.003, 1.085), and 1.118 (95% CI 1.028, 1.216), respectively. Male and aged 7-17 years were more sensitive to air pollutants. Through the temperature stratification analysis, we found that temperature could modify the impacts of air pollution on daily incidence of influenza with high temperature exacerbating the impact of air pollutants. At high temperature layer, male and the groups aged 0-6 years and 18-64 years were more sensitive to air pollution. CONCLUSION: Temperature modified the relationship between air pollution and daily incidence of influenza and high temperature would exacerbate the effects of air pollutants in Ningbo.

[Study on infant and young children complementary feeding in poor rural regions in China].

OBJECTIVE: To analyze complementary feeding status and issues among 6-23 month infants and young children(IYC) in poor rural regions in China to figure out actions further IYC nutrition in China. METHODS: Using 2018 monitoring data from Project of Children Nutrition Improvement in Poor Rural Regions, 6-23 months infants were sampled with the method of a combination of provincial stratification, multi-stage stratified cluster, PPS and random equidistant. Complementary feeding practices were collected by 24 hours diet recall method and and parental knowledge on IYC feeding was collected by KAP questionnaire. Complementary diet was analyzed according to the World Health Organization& apos; s definition of infant and young child feeding indicators. Logistic regression model was used to analyze the influencing factors of minimum acceptable diet(MAD). RESULTS: A total of 40 910 infants(boys 21 153, girls 19 757) completed the survey. The proportion of infants 6-8 months of age who receive solid, semi-solid foods was 83.8%, the percentage of IYC who get minimum dietary diversity(MDD), minimum meal frequency(MMF), and MAD was 67.8%, 71.4% and 39.7%, respectively. The age of months, mother& apos; s educational level and parent& apos; s nutrition and feeding knowledge had significant impact on the outcome of MAD. The OR for month& apos; s age were 1.990 and 1.905(P& lt; 0.001), OR for mother education level was 1. 545(P& lt; 0.001) and OR for parent knowledge were 1.114 and 1.346(P& lt; 0.001). CONCLUSION: Complementary feeding practices were poor in terms of the proportion of infants 6-8 months of age who introduced complementary foods, MDD, MMF and MAD in poor region of China.

[Current status of nutrition work in Chinese disease control institutions].

OBJECTIVE: To investigate the basic nutrition working status in Chinese CDCs. METHODS: The questionnaire of nutritional working ability of CDC was designed for investigation. The questionnaire was filled in by all disease control institutions of 31 provinces, autonomous regions, municipalities and Xinjiang Production and Construction Corps(excluding Hong Kong, Macao and Taiwan). Data was inputted by each institution through a questionn aire-survey platform called 'wenjuanxing& apos; , and the quality control was carried out by the provincial CDCs according to their jurisdiction. RESULTS: A total of 3150 valid questionnaires were collected. 35.97% of the institutions surveyed had never undertaken nutrition-related work, and only 4.19% of them had set up an independent department for nutrition-related work. The average number of people engaged in nutrition work was 2.5(P50=1.0); The average number of full-time staff was 0.2(P50=0.0). The average number of full-time staff in provincial, municipal and county CDCs was 3.6, 0.4 and 0.2, respectively. In terms of the nutrition work, by 2020 the China Nutrition and Health Surveillance and the National Food Nutrition Surveillance have covered 31 provinces, autonomous regions and municipalities. Besides Shanghai, Zhejiang and Fujian, provincial CDCs implemented the Nutrition Improvemeat Program for Compulsory Education Students in Rural Area. As to the scientific research, only 9.08% of the institutions have carried out nutrition-related projects in the past five years. Particularly, there were little nutrition-related scientific research funds for municipal and county disease control institutions, while 96.57% of the institutions do not have special funds for nutrition work. From 2015 to 2019, the proportion of the institutions that published nutrition-related papers, published nutrition-related books, won nutrition-related awards, and participated in the formulation of nutrition-related standards was 3.81%, 1.27%, 5.65% and 0.70%, respectively. With regard to the implementation of the six major actions of the National Nutrition Plan(2017-2030), only 29.81% of CDCs have organized and carried out related actions. CONCLUSION: Disease control institutions are short of nutrition professional posts, professional personnel, nutrition work funds and scientific research investment, lack of regular nutrition work tasks. Therefore, the nutrition capacity of the CDCs needs to be strengthened, and more efforts will be needed to meet the requirements of the National Nutrition Plan(2017-2030) and the Healthy China Action(2019-2030)-Healthy Diet Campaign.

[Perceived stress level and its related factors in Chinese adult residents aged 18-65 in 15 provinces (autonomous regions and municipalities) in 2015].

OBJECTIVE: To investigate the perceived stress prevalence of adult residents aged 18-65 in 15 provinces(autonomous regions and municipalities) and its related factors. METHODS: Adults aged 18 to 65 years, with middle school education or above and complete demographic and socioeconomic characteristics, lifestyle, disease history and physical measurements were selected as study subjects from the database of Nutritional Status and Health Transition of Chinese Residents Project in 2015. Chinese perceived stress scale(CPSS) was used to evaluate the perceived stress level of participants, and percentile regression model was used to analyze the correlation between related factors and perceived stress. RESULTS: A total of 6679 subjects were enrolled in this study. The mean and median of perceived stress scores were 22. 6 and 24. 0, respectively. The percentile regression model showed that age was positively associated with perceived stress in the 5 th, 25 th, 50 th and 95 th percentiles, and the difference between the two groups decreased with the increase of perceived stress score(P5, ß=1. 31, 95%CI 0. 38-2. 24; P25, ß=0. 91, 95%CI 0. 28-1. 53). Compared with the control group, adults with junior high school education had a high level of perceived stress in higher percentiles(P50, ß=0. 81, 95%CI 0. 32-1. 30; P75, ß=0. 42, 95%CI 0. 11-0. 72; P95, ß=0. 62, 95%CI 0. 06-1. 18). Perceived stress levels in the 50 th, 75 th and 95 th percentiles were lower in the married adults than in the control group(P50, ß=-0. 81, 95%CI-1. 40--0. 23; P75, ß=-0. 39, 95%CI-0. 68--0. 10; P95, ß=-0. 95, 95%CI-1. 79--0. 12). In the 5 th, 25 th, 50 th and 75 th percentiles, the perceived stress level of no workers is higher than that of workers, and the difference decreases with the increase of perceived stress score(P5, ß=1. 31, 95%CI 0. 32-2. 31; P75, ß=0. 53, 95%CI 0. 35-0. 71). Income level showed a positive association with perceived stress across the entire conditional perceived stress distribution(P<0. 05). People with low levels of physical activity had higher levels of perceived stress in the 25 th, 50 th, and 75 th percentiles than the control group(P25, ß=1. 15, 95%CI 0. 41-1. 90; P50, ß=1. 09, 95%CI 0. 62-1. 56; P75, ß=0. 28, 95%CI 0. 07-0. 49). Urbanization level and alcohol consumption and other factors had influence on perceived stress in different percentile(P<0. 05). No significant correlation was found between housing ownership, smoking, sleep duration and perceived stress. CONCLUSION: The perceived stress level of adult residents aged 18 to 65 in 15 provinces of China is on the high level on the whole, which is correlated with age, marital state employment, annual per capita income, physical activity level and other factors.

Seedless assembly of colloidal crystals by inverted micro-fluidic pumping.

We propose a simple seedless approach to assemble millimeter sized monolayer single colloidal crystals with desired orientations at predetermined locations on an unstructured charged substrate. This approach utilizes the millimeter-ranged fluid flow on the bottom glass substrate induced by an ion exchange resin (IEX) fixed on top of the closed sample cell. The fluid flow increases with decreasing height of the sample cell and increasing radius R of the IEX. For a single inverted pump, millimeter sized monolayer single crystals of hexagonal close packing can be obtained. For two closely spaced (D ∼ 4R) pumps, the formed crystals have a predefined orientation along the line connecting the two IEX. By patterning IEX into different structures, colloidal crystals of different complex patterns form. The present method paves a convenient way for fabricating high quality monolayer colloidal crystals for a variety of applications.

Modular approach to microswimming.

The field of active matter in general and microswimming in particular has experienced a rapid and ongoing expansion over the last decade. A particular interesting aspect is provided by artificial autonomous microswimmers constructed from individual active and inactive functional components into self-propelling complexes. Such modular microswimmers may exhibit directed motion not seen for each individual component. In this review, we focus on the establishment and recent developments in the modular approach to microswimming. We introduce the bound and dynamic prototypes, show mechanisms and types of modular swimming and discuss approaches to control the direction and speed of modular microswimmers. We conclude by highlighting some challenges faced by researchers as well as promising directions for future research in the realm of modular swimming.

Correction: Seedless assembly of colloidal crystals by inverted micro-fluidic pumping.

Correction for 'Seedless assembly of colloidal crystals by inverted micro-fluidic pumping' by Ran Niu et al., Soft Matter, 2018, 14, 3435-3442.

Colloidal electro-phoresis in the presence of symmetric and asymmetric electro-osmotic flow.

We characterize the electro-phoretic motion of charged sphere suspensions in the presence of substantial electro-osmotic flow using a recently introduced small angle super-heterodyne dynamic light scattering instrument (ISASH-LDV). Operation in integral mode gives access to the particle velocity distribution over the complete cell cross-section. Obtained Doppler spectra are evaluated for electro-phoretic mobility, wall electro-osmotic mobility and particle diffusion coefficient. Simultaneous measurements of differing electro-osmotic mobilities leading to asymmetric solvent flow are demonstrated in a custom made electro-kinetic cell fitting standard microscopy slides as exchangeable sidewalls. The scope and range of our approach are discussed demonstrating the possibility of an internal calibration standard and using the simultaneously measured electro-kinetic mobilities in the interpretation of a microfluidic pumping experiment involving an inhomogeneous electric field and a complex solvent flow pattern.

Self-Assembly of Colloidal Molecules due to Self-Generated Flow.

The emergence of structure through aggregation is a fascinating topic and of both fundamental and practical interest. Here we demonstrate that self-generated solvent flow can be used to generate long-range attractions on the colloidal scale, with subpiconewton forces extending into the millimeter range. We observe a rich dynamic behavior with the formation and fusion of small clusters resembling molecules. The dynamics of this assembly is governed by an effective conservative energy that for large separations r decays as 1/r. Breaking the flow symmetry, these clusters can be made active.

Assembly and Speed in Ion-Exchange-Based Modular Phoretic Microswimmers.

We report an experimental study on ion-exchange-based modular microswimmers in low-salt water. Cationic ion-exchange particles and passive cargo particles assemble into self-propelling complexes, showing self-propulsion at speeds of several micrometers per second over extended distances and times. We quantify the assembly and speed of the complexes for different combinations of ion-exchange particles and cargo particles, substrate types, salt types and concentrations, and cell geometries. Irrespective of the experimental boundary conditions, we observe a regular development of the assembly shape with increasing number of cargo. Moreover, the swimming speed increases stepwise upon increasing the number of cargo and then saturates at a maximum speed, indicating the active role of cargo in modular swimming. We propose a geometric model of self-assembly to describe the experimental observations in a qualitative way. Our study also provides some constraints for future theoretical modeling and simulation.