Macroscopic Self-Assembly Realized by Polymer Brush─A Thickness-Dependent Rule for Rapid Wet Adhesion.

Macroscopic self-assembly of µm-to-mm components (dimension from 100 µm to millimeters), is meaningful to realize the concept of "self-assembly at all scales" and to understand interfacial phenomena such as adhesion, self-healing, and adsorption. However, self-assembly at this length scale is different from molecular self-assembly due to limited collision chances and binding capacity between components. Long-time contact between components is requisite to realize µm-to-mm assembly. Even though the recent idea of adding a compliant coating to enhance the molecular binding capacity is effective for such self-assembly, a trade-off between coating thickness (several micrometers) and assembly efficiency exists. Here a new compliant coating of surface-initiated polymer brush to address the above paradox by both realizing fast assembly and reducing the coating thickness to ≈40 nm by two magnitudes is demonstrated. Millimeter-sized quartz cubes are used as components and grafted with oppositely charged polyelectrolyte brushes, enabling assembly in water by electrostatic attraction and disassembly in NaCl solutions. A rule of thickness-dependent assembly chance is obtained and understood by in situ force measurements and a multivalent theory. The polymer brush strategy pushes the thickness limit of requisite compliant coating to the nanoscale for fast µm-to-mm self-assembly and provides insights into rapid wet adhesion.

ON-OFF Control of Marangoni Self-propulsion via A Supra-amphiphile Fuel and Switch.

Marangoni self-propulsion refers to motion of liquid or solid driven by a surface tension gradient, and has applications in soft robots/devices, cargo delivery, self-assembly etc. However, two problems remain to be addressed for motion control (e.g., ON-OFF) with conventional surfactants as Marangoni fuel: (1) limited motion lifetime due to saturated interfacial adsorption of surfactants; (2) in- situ motion stop is difficult once Marangoni flows are triggered. Instead of covalent surfactants, supra-amphiphiles with hydrophilic and hydrophobic parts linked noncovalently, hold promise to solve these problems owing to its dynamic and reversible surface activity responsively. Here, we propose a new concept of 'supra-amphiphile fuel and switch' based on the facile synthesis of disodium-4-azobenzene-amino-1,3-benzenedisulfonate (DABS) linked by a Schiff base, which has amphiphilicity for self-propulsion, hydrolyzes timely to avoid saturated adsorption, and provides pH-responsive control over ON-OFF motion. The self-propulsion lifetime is extended by 50-fold with DABS and motion control is achieved. The mechanism is revealed with coupled interface chemistry involving two competitive processes of interfacial adsorption and hydrolysis of DABS based on both experiments and simulation. The concept of 'supra-amphiphile fuel and switch' provides an active solution to prolong and control Marangoni self-propulsive devices for the advance of intelligent material systems.

A Hydrolyzable Supra-amphiphile as a Marangoni Self-Propulsion Fuel for Efficient Macroscopic Supramolecular Self-Assembly.

Self-assembly of µm-to-mm components is important for achieving all-scale ordering with requirements of extra energy for motion and interaction of components. Marangoni flows caused by surfactants on water provide appropriate energy but have limited lifetimes because of the inevitable interfacial aggregation and difficult decomposition of aggregated covalent surfactants that inactivate Marangoni effects. Here we have synthesized a supra-amphiphile Marangoni "fuel"-sodium-4-(benzylideneamino) benzenesulfonate (SBBS)-that can be hydrolyzed in a timely manner to a species without surface activity to extend the motion time by 10-fold. The motion was optimized at pH=2 by a fine equilibrium between the releasing and removal of interfacial SBBS, leading to the self-assembly of millimeter-scaled ordered dimers. The underlying mechanism was interpreted by motion analyses and simulation. This strategy provides an active solution to self-assembly at the µm-to-mm scale, as well as interactive ideas between miniaturized chemical robots.

Elastic-Modulus-Dependent Macroscopic Supramolecular Assembly of Poly(dimethylsiloxane) for Understanding Fast Interfacial Adhesion.

Macroscopic supramolecular assembly (MSA) is a new concept of supramolecular science with an emphasis on noncovalent interactions between macroscopic building blocks with sizes exceeding 10 µm. Owing to a similar noncovalently interactive nature with the phenomena of bioadhesion, self-healing, etc. and flexible features in tailoring and designing modular building blocks, MSA has been developed as a simplified model to interpret interfacial phenomena and a facile method to fabricate supramolecular materials. However, at this early stage, MSA has always been limited to hydrogel materials, which provide flowability for high molecular mobility to the interfacial binding. The extension to a wide range of materials for MSA is desired. Herein, we have developed a strategy of adjusting intrinsic properties (e.g., elastic modulus) of nonhydrogel materials to realize MSA, which could broaden the material choices of MSA. Using the widely used elastomer of poly(dimethylsiloxane) (PDMS) as building blocks, we have demonstrated the elastic-modulus-dependent MSA of PDMS based on the host/guest molecular recognition between supramolecular groups of ß-cyclodextrin and adamantane. In the varied elastic modulus range of 0.38 to 3.84 MPa, we obtained the trend of the MSA probability decreasing from 100% at 0.38 MPa to 0% at 3.84 MPa. Meanwhile, in situ measurements of interactive forces between PDMS building blocks have supported the observed assembly phenomena. The underlying reasons are interpreted with the low-modulus flexible surfaces favoring for high molecular mobility to achieve interactions between multiple sites at the interface based on the theory of multivalency. Taken together, we have demonstrated the feasibility of directly adjusting the modulus of bulk materials to realize MSA of nonhydrogel materials, which may provide clues to the fast wet adhesion and new solutions to the additive manufacture of elastomer materials.

Influence of Changes in Obesity Indicators on the Risk of Hypertension: A Cohort Study in Southern China.

OBJECTIVES: The objective of this study was to demonstrate the association between changes in different obesity indicators and the risk of incident hypertension by the age-group among community-dwelling residents in southern China. METHODS: A total of 6,959 non-hypertensive participants aged ≥18 years old were enrolled in this cohort study and completed questionnaire interviews and anthropometric measurements at baseline (2010) and follow-up (2017). A time-dependent covariate Cox proportional hazard model considered the changes in obesity indicators during the follow-up period and calculated the hazard ratios (HRs) to analyze the risk of incident hypertension according to different obesity indicators. RESULTS: During a mean follow-up of 7.1 years, 1,904 participants were newly diagnosed with hypertension. The body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were significantly positively associated with an increased future risk of incident hypertension, and BMI was the best predictive indicator of hypertension (obesity in men: HR = 2.65, 95% confidence interval (CI) = 2.20-3.20; obesity in women: HR = 2.80, 95% CI = 2.27-3.45). Compared with the middle-aged and older group, the risk of incident hypertension was highest in the younger group which had the highest baseline obesity indicators. CONCLUSIONS: Changes in obesity indicators were significantly associated with the risk of incident hypertension in all age-groups, and the risk of future incident hypertension increased with the increase in baseline obesity indicators.

The changes in socioeconomic inequalities and inequities in health services utilization among patients with hypertension in Pearl River Delta of China, 2015 and 2019.

BACKGROUND: Assessing inequities in health services utilization contributes to build effective strategies for health equity promotion. This study aimed to evaluate the socioeconomic inequalities and inequities in health services utilization among hypertensive patients and explore the changes between 2015 and 2019 in Pearl River Delta of China. METHODS: The cross-sectional surveys were conducted using the questionnaire. Eight hundred thirty and one thousand one hundred sixty-six hypertensive patients in 2015 and 2019 were interviewed, respectively. The concentration index (CI) and the horizontal inequity index (HI) were used to access the socioeconomic inequalities and horizontal inequities in outpatient and inpatient health services use. The contribution of influential factors to the overall inequalities was estimated via the concentration index decomposition. Oaxaca-type decomposition technique was utilized to measure the changes in socioeconomic inequalities between the observation periods. RESULTS: In 2015 and 2019, the CIs for outpatient and inpatient utilization decreased from 0.1498 to 0.1198, 0.1982 to 0.1648, respectively, and the HIs for outpatient and inpatient utilization decreased from 0.1478 to 0.1078, 0.1956 to 0.1390, respectively. Economic status contributed the maximum ratio of the socioeconomic inequalities in the use of outpatient service (81.05% in 2015, 112.89% in 2019) and inpatient service (82.46% in 2015, 114.68% in 2019) in these 2 years. Oaxaca decomposition revealed that educational level (78.30% in outpatient, 53.79% in inpatient) and time to the nearest health facilities (66.78% in outpatient, 31.06% in inpatient) made the main positive contributions to decline the inequalities. While the main factor pushing the equalities toward deterioration was economic status (- 46.11% in outpatient, -76.56% in inpatient). CONCLUSION: There were certain declines in the socioeconomic inequalities and inequities in health services utilization by hypertensive patients in Pearl River Delta of China over time. The widening economic gap was the largest contribution to the observed inequalities. Interventions to protect the vulnerable group deserve further concern from policy makers.

Precise Macroscopic Supramolecular Assemblies: Strategies and Applications.

Macroscopic supramolecular assembly (MSA) is a new concept in supramolecular science with a focus on interfacial assembly of macroscopic building blocks, which has largely extended the applicable materials of supramolecular assembly and provided new solutions to fabricating tissue scaffolds, soft devices, etc. The precision of the assembled structures is of great interest; unlike molecular assemblies, MSA precision is highly dependent on the matching degree of assembled surfaces because of the large interactive area and group number, which result in remarkably increased kinetic possibilities and metastable assemblies. This Concept introduces the principle, history, and development of MSA, elaborates the low-precision challenge in MSA, summarizes the strategies for precise MSA based on the different thermodynamic stability of precise/imprecise structures and control over assembly kinetics, and finally demonstrates the applications of precise MSA structures in advanced manufacture such as tissue scaffolds.

The mediating effect of pain on the association between multimorbidity and disability and impaired physical performance among community-dwelling older adults in southern China.

AIM: To investigate the association between multimorbidity and disability and impaired physical performance, and to further evaluate the mediating effect of physical pain in this association. METHODS: 1321 community-dwelling older adults, who were over 60 years old in southern China, were regarded as participants in this cross-sectional study. Subjects completed a multi-instrument questionnaire including essential characteristics and physical function assessments. Physical function was assessed by activities of daily living (ADL), instrumental activities of daily living (IADL), index of mobility scale (NAGI), index of basic physical activities scale (RB), and short physical performance battery (SPPB). Multimorbidity was defined as the simultaneous presence of two or more chronic conditions. Multivariable regression and mediation analyses were conducted and gender differences were explored. RESULTS: The prevalence of multimorbidity was 44.6% in our study. In gender stratification analysis, multimorbidity was significantly associated with ADL disability (OR = 2.16), IADL disability (OR = 1.97), NAGI disability (OR = 2.84), RB disability (OR = 2.65) and lower SPPB score (ß = - 0.83) in women. The rate of pain increased with the number of chronic diseases and the multimorbidity patients with higher pain prevalence. Moreover, the presence of pain was also significantly associated with disability and impaired physical performance. Mediation analysis illustrated that pain was accounted for 16.5% to 22.1% of the adverse effects of multimorbidity on disability and impaired physical performance in women. CONCLUSIONS: Multimorbidity was significantly associated with disability and impaired physical performance, and pain might be a mediating factor for adverse effects of multimorbidity on disability and impaired physical performance in women.

A Photowelding Strategy for Conductivity Restoration in Flexible Circuits.

Light-driven micropumps, which are based on electro-osmosis with the electric field generated by photocatalytic reactions, are among most attractive research topics in chemical micromotors. Until now, research in this field has mainly been focused on the directional motion or collective behavior of microparticles, which lack practical applications. In this study, we have developed a photowelding strategy for repeated photoinduced conductivity recovery of cracked flexible circuits. We immersed the circuit in a suspension of conductive healing particles and applied photoillumination to the crack; photocatalysis of a predeposited pentacene (PEN) layer triggered electro-osmotic effects to gather conductive particles at the crack, thus leading to conductivity recovery of the circuit. This photowelding strategy is a novel application of light-driven micropumps and photocatalysis for conductivity restoration.

Constructing a Multiplexed DNA Pattern by Combining Precise Magnetic Manipulation and DNA-Driven Assembly.

There is an urgent demand to construct multiplexed biomolecular patterns to obtain more biological information from a single experiment. However, with only limited reports focusing on defective top-down approaches, challenges remain to develop a bottom-up strategy for multiplexed patterning. To this end, a novel strategy has been proposed to fabricate multiplexed DNA patterns via macroscopic assembly through combined precise magnetic manipulation and DNA hybridization-driven self-assembly. Therefore, a multiplexed DNA pattern composed of glass fibers loaded with multiple specific strands of DNA was constructed, and its potential application in simultaneous detection of multiplex target DNA was demonstrated. Moreover, the fabricated multiplexed DNA pattern shows an erasable behavior because the hybridized DNA can be disassembled by strand displacement.

Macroscopic Supramolecular Assembly through Electrostatic Interactions Based on a Flexible Spacing Coating.

Macroscopic supramolecular assembly (MSA) is a recent advance in supramolecular chemistry that involves associating large building blocks with a size larger than 10 µm through noncovalent interactions. However, until now the applicable material system is rather limited to hydrogels, and MSA of rigid materials with supramolecular interactions widely used in molecular assembly has rarely been reported due to the difficulty in achieving multivalency between rigid surfaces. Herein, the concept of flexible spacing coating is applied with highly flowable properties, and the electrostatic-interaction-driven MSA of relatively rigid polydimethylsiloxane building blocks is demonstrated. With the flexible spacing coating of a polyelectrolyte multilayer, the oppositely charged rigid building blocks can realize MSA under shaking in water for 5 min. The major contribution of the electrostatic interaction is confirmed by both qualitative controlled MSA experiments in other solvents, disassembly in ionic solution and quantitative results with an in situ force measurement method.

Elasticity-Dependent Fast Underwater Adhesion Demonstrated by Macroscopic Supramolecular Assembly.

Macroscopic supramolecular assembly (MSA) is a recent development in supramolecular chemistry to associate visible building blocks through non-covalent interactions in a multivalent manner. Although various substrates (e.g. hydrogels, rigid materials) have been used, a general design rule of building blocks in MSA systems and interpretation of the assembly mechanism are lacking and are required. Herein we design three model systems with varied elastic modulus and correlated the MSA probability with the elasticity. Based on the effects of substrate deformability on multivalency, we have proposed an elastic-modulus-dependent rule that building blocks below a critical modulus of 2.5 MPa can achieve MSA for the used host/guest system. Moreover, this MSA rule applies well to the design of materials for fast underwater adhesion: Soft substrates (0.5 MPa) can achieve underwater adhesion within 10 s with one order of magnitude higher strength than that of rigid substrates (2.5 MPa).

Parallel and Precise Macroscopic Supramolecular Assembly through Prolonged Marangoni Motion.

Macroscopic supramolecular assembly (MSA) is a rising concept in supramolecular science, in which building blocks with sizes exceeding 10 µm self-assemble into larger structures. MSA faces the challenge of developing appropriate self-propulsion strategies to improve the motility of the macroscopic building blocks. Although the Marangoni effect is an ideal driving force with random motion paths, excessive aggregation of the surfactant and fast decay of motion remain challenging problems. Hence, a molecular interference strategy to drive the self-assembly over longer times by finely controlling the interfacial adsorption of surfactants using dynamic equilibria is proposed. Surfactant depletion through molecular recognition in the solution to oppose fast interfacial aggregation efficiently facilitates macroscopic motion and assembly. The resulting motility lifetime is extended remarkably from 120 s to 2200 s; with the improved kinetic energy, the assembly probability increases from 20 % to 100 %.

Chemical and Equipment-Free Strategy To Fabricate Water/Oil Separating Materials for Emergent Oil Spill Accidents.

Oil spill accidents normally have two important features when considering practical cleanup strategies: (1) unexpected occurrence in any situations possibly without specific equipment and chemicals; (2) emergency to be cleaned to minimize the influences on ecosystems. To address these two practical problems regarding removal of spilt oil, we have proposed an in situ, rapid, and facile candle-soot strategy to fabricate water/oil separating materials based on superhydrophobicity/superoleophilicity. The one-step fabrication method is independent of any chemicals or equipment and can be ready for use through short smoking processes within 5 min by using raw materials available in daily life such as textiles. The as-prepared materials perform good durability for repeated separation test and high recovery rate of various oils from water/oil mixtures. This strategy provides possibility of rapid response to sudden oil spill accidents, especially in cases without any equipment or chemicals and in poor countries/areas those could hardly afford transportation and storage of expensive separating materials.

Toward Understanding Whether Interactive Surface Area Could Direct Ordered Macroscopic Supramolecular Self-Assembly.

The mismatching phenomena are ubiquitous in complex and advanced self-assembly, such as hierarchical assembly, macroscopic supramolecular assembly, and so on. Recently, for macroscopic supramolecular assembly, the strategy of maximizing the interactive surface area was used and supposed to handle this problem; however, now there is little understanding of whether interactive surface area is the dominant factor to guide the assembly patterns. Herein by taking millimeter cylinder building blocks with different diameter/height (d/h) ratios as model systems, we have investigated the interactive-surface-area-dependent assembling behaviors in macroscopic supramolecular assembly. The results showed that the increasing d/h ratio of cylinders contributed to selectivity of face-to-face assembled pattern over face-to-side or side-to-side geometries, thus having improved the ordering degree of the assembled structures; however, the mismatching phenomena could not be totally avoided due to high colliding chances in kinetics and the thermally favorable stability of these structures. We further confirmed the above hypothesis by in situ measurements of interactive forces of building blocks with different assembled patterns. This work of macroscopic supramolecular assembly provides an in situ visible platform, which is significant to clarify the influences of interactive surface area on the assembly behaviors.

Surface adhesive forces: a metric describing the drag-reducing effects of superhydrophobic coatings.

Nanomaterials with superhydrophobic properties are promising as drag-reducing coatings. However, debates regarding whether superhydrophobic surfaces are favorable for drag reduction require further clarification. A quantified water adhesive force measurement is proposed as a metric and its effectiveness demonstrated using three typical superhydrophobic coatings on model ships with in situ sailing tests.

pH-responsive on-off motion of a superhydrophobic boat: towards the design of a minirobot.

Combining chemical reactions and stimuli-responsive surfaces as clutch system, a functional cooperating minirobot with on-off locomotion that is responsive to pH changes is fabricated. Its locomotion can be switched on by changing pH value of the solution from 1 to 13, turned off by adjusting the pH back to acidic, and restarted by transforming the solution to basic.

Supramolecular assembly of macroscopic building blocks through self-propelled locomotion by dissipating chemical energy.

Chemical energy supplied by the catalytic decomposition of H2O2 is introduced into macroscopic building blocks, which self-propel, interact with each other, and finally assemble into ordered and advanced structures. The geometry is highly dependent on the way that the catalyst is loaded. The integration of catalyst and building block provides assembling component as well as its energy of motion.

Layer-by-layer self-assembly and disassembly of single charged inorganic small molecules: towards surface patterning.

The patterning of layer-by-layer (LbL) polyelectrolyte multilayers with metal ions is important for the facile fabrication of circuits or selective catalysis. The strategy includes two issues: the incorporation of metal ions and their controlled assembly-disassembly, which require a good understanding of the assembly mechanism. Therefore, we explored the LbL assembly between a polycation, poly-(diallyldimethylammonium chloride) (PDDA) and an inorganic single charged molecule, [AuCl4](-), which could assemble at pH = 3.7 and disassemble at lower pH values. Moreover, we have demonstrated that the driving force in the assembly is a ligand-to-metal charge transfer interaction. Combining the controlled assembly-disassembly of PDDA-[AuCl4](-) multilayers and photolithography, we obtained a surface pattern of PDDA-[AuCl4](-) multilayers.

Polyelectrolyte chain conformation matters in macroscopic supramolecular self-assembly.

We demonstrate molecular-conformation-dependent macroscopic supramolecular self-assembly (MSA) driven by electrostatic interactions. Evidence from single molecular force spectroscopy reveals that polyelectrolytes modified on MSA component surfaces make MSA possible with a loop conformation, while those with a flat conformation lead to no assembly, which is attributed to distinct molecular mobility. We believe that this finding is also applicable in fundamental phenomena such as surface adsorption and adhesion regarding polymers.