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.

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.

Bioinspired rotary flight of light-driven composite films.

Light-driven actuators have great potential in different types of applications. However, it is still challenging to apply them in flying devices owing to their slow response, small deflection and force output and low frequency response. Herein, inspired by the structure of vine maple seeds, we report a helicopter-like rotary flying photoactuator (in response to 0.6 W/cm2 near-infrared (NIR) light) with ultrafast rotation (~7200 revolutions per minute) and rapid response (~650 ms). This photoactuator is operated based on a fundamentally different mechanism that depends on the synergistic interactions between the photothermal graphene and the hygroscopic agar/silk fibroin components, the subsequent aerodynamically favorable airscrew formation, the jet propulsion, and the aerodynamics-based flying. The soft helicopter-like photoactuator exhibits controlled flight and steering behaviors, making it promising for applications in soft robotics and other miniature devices.

A Multi-engine Marangoni Rotor with Controlled Motion for Mini-Generator Application.

Marangoni rotors are smart devices that are capable of self-propulsive motions based on the Marangoni effect, namely interfacial flows caused by a gradient of surface tension. Owing to the features of untethered motions and coupled complexity with fluid, these Marangoni devices are attractive for both theoretical study and applications in biomimicking, cargo delivery, energy conversion, etc. However, the controllability of Marangoni motions dependent on concentration gradients remains to be improved, including the motion lifetime, direction, and trajectories. The challenge lies in the flexible loading and adjustments of surfactant fuels. Herein, we design a multi-engine device in a six-arm shape with multiple fuel positions allowing for motion control and propose a strategy of diluting the surfactant fuel to prolong the motion lifetime. The resulting motion lifetime has been extended from 140 to 360 s by 143% compared with conventional surfactant fuels. The motion trajectories could be facilely adjusted by changing both the fuel number and positions, leading to diverse rotation patterns. By integrating with a coil and a magnet, we obtained a system of mini-generators based on the Marangoni rotor. Compared with the single-engine case, the output of the multi-engine rotor was increased by 2 magnitudes owing to increased kinetic energy. The design of the above Marangoni rotor has addressed the problems of concentration-gradient-driven Marangoni devices and enriched their applications in harvesting energy from the environment.

Robust Electrostatically Interactive Hydrogel Coatings for Macroscopic Supramolecular Assembly via Rapid Wet Adhesion.

A macroscopic supramolecular assembly (MSA) refers to non-covalent interactions between building blocks over a micrometer scale, which provides insights into bio-/wet adhesion, self-healing, and so on and new fabrication strategies to heterogeneous structures and bio-scaffolds. The key to realize the MSA of rigid materials is pre-modifying a compliant coating known as a "flexible spacing coating" beneath the interactive moieties. However, available coatings are limited to polyelectrolyte multilayers with shortcomings of tedious fabrication, weak adhesion to substrates, susceptibility to external reagents, and so on. Here, we develop a facile method to induce a new "flexible spacing coating" of a poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel with electrostatic interactions to achieve MSA of diverse rigid materials (quartz, metal, rubber, and plastics). Selective self-assembly of positive-negative charged surfaces is observed by the naked eye under 3 min of shaking in water, providing strategies to rapid wet adhesion. The interfacial binding force between positive-negative interacted surfaces is 1018.1 ± 299.2 N/m2, which is over two magnitudes larger than that of control groups, that is, positive-positive (24.4 ± 10.0 N/m2) and negative-negative (67.5 ± 16.7 N/m2) interacted surfaces. In situ force measurements and control experiments of identically charged building blocks have strongly supported the improved binding strength and chemical selectivity between interactive building blocks. The coating is advantageous with a simple fabrication, strong adhesion to materials, robust solvent tolerance to assembly solutions, and feasibility of photo-patterning. We envision that the above strategy would broaden the material choices of flexible spacing coatings for efficient MSA and new methods for rapid interfacial adhesion.

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.

Macroscopic Supramolecular Assembly of Rigid Building Blocks Facilitated by Layer-By-Layer Assembled Microgel Film.

Macroscopic supramolecular assembly (MSA) of building blocks larger than 1 µm provides new methodology for fabrication of functional supramolecular materials and a platform for mechanism investigation of interfacial phenomena. Most reports on MSA are restricted to soft hydrogels, and supramolecular groups can be directly integrated into a hydrogel matrix to generate sufficient attraction for maintaining macroscopic assemblies. For non-hydrogel stiff building blocks, two layer-by-layer modification processes consisting of flexible spacing coating and additional interacting groups are necessary to enable MSA, which is laborious and time-consuming. Approaches for highly efficient MSA based on flexible spacing coating are desired. In this work, MSA of polydimethylsiloxane (PDMS) building blocks is demonstrated by inducing microgel films that serve as both flexible spacing coating and surface functional groups, thus avoiding a two-step LbL modification process. By the varying bilayer number of microgel films, the MSA probability of modified PDMS increases from 54% at 3 bilayers to 100% at 6 bilayers. Control experiments and in situ force measurement strongly support the obtained MSA results and verify the dominant role of the microgel film as a flexible spacing coating and a supramolecularly interactive layer in achieving MSA. Moreover, the underlying mechanism is interpreted as low Young's modulus microgel films rendering surface groups highly mobile to enhance the multivalent interfacial binding. Taken together, this work has demonstrated the feasibility of MSA of rigid building blocks assisted by microgel films as flexible spacing coating and supramolecularly interactive layer simultaneously, which may extend the application fields of microgel materials to interfacial adhesion and advanced manufacturing with MSA methodology.

Self-sorting in macroscopic supramolecular self-assembly via additive effects of capillary and magnetic forces.

Supramolecular self-assembly of µm-to-mm sized components is essential to construct complex supramolecular systems. However, the selective assembly to form designated structures at this length scale is challenging because the short-ranged molecular recognition could hardly direct the assembly of macroscopic components. Here we demonstrate a self-sorting mechanism to automatically identify the surface chemistry of µm-to-mm components (A: polycations; B: polyanions) based on the A-B attraction and the A-A repulsion, which is realized by the additivity and the competence between long-ranged magnetic/capillary forces, respectively. Mechanistic studies of the correlation between the magnetic/capillary forces and the interactive distance have revealed the energy landscape of each assembly pattern to support the self-sorting results. By applying this mechanism, the assembly yield of ABA trimers has been increased from 30%~40% under conventional conditions to 100% with self-sorting. Moreover, we have demonstrated rapid and spontaneous self-assembly of advanced chain-like structures with alternate surface chemistry.

Macroscopic Supramolecular Assembly Strategy to Construct 3D Biocompatible Microenvironments with Site-Selective Cell Adhesion.

Three-dimensional (3D) scaffolds with chemical diversity are significant to direct cell adhesion onto targeted surfaces, which provides solutions to further control over cell fates and even tissue formation. However, the site-specific modification of specific biomolecules to realize selective cell adhesion has been a challenge with the current methods when building 3D scaffolds. Conventional methods of immersing as-prepared structures in solutions of biomolecules lead to nonselective adsorption; recent printing methods have to address the problem of switching multiple nozzles containing different biomolecules. The recently developed concept of macroscopic supramolecular assembly (MSA) based on the idea of "modular assembly" is promising to fabricate such 3D scaffolds with advantages of flexible design and combination of diverse modules with different surface chemistry. Herein we report an MSA method to fabricate 3D ordered structures with internal chemical diversity for site-selective cell adhesion. The 3D structure is prepared via 3D alignment of polydimethylsiloxane (PDMS) building blocks with magnetic pick-and-place operation and subsequent interfacial bindings between PDMS based on host/guest molecular recognition. The site-specific cell affinity is realized by distributing targeted building blocks that are modified with polylysine molecules of opposite chiralities: PDMS modified with films containing poly-l-lysine (PLL) show higher cell density than those with poly-d-lysine (PDL). This principle of selective cell adhesion directed simply by spatial distribution of chiral molecules has been proven effective for five different cell lines. This facile MSA strategy holds promise to build complex 3D microenvironment with on-demand chemical/biological diversities, which is meaningful to study cell/material interactions and even tissue formation.

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.

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.

Fabrication of 3D Ordered Structures with Multiple Materials via Macroscopic Supramolecular Assembly.

Integration of diverse materials into 3D ordered structures is urgently required for advanced manufacture owing to increase in demand for high-performance products. Most additive manufacturing techniques mainly focus on simply combining different equipment, while interfacial binding of distinctive materials remains a fundamental problem. Increasing studies on macroscopic supramolecular assembly (MSA) have revealed efficient interfacial interactions based on multivalency of supramolecular interactions facilitated by a "flexible spacing coating." To demonstrate facile fabrication of 3D heterogeneous ordered structures, the combination of MSA and magnetic field-assisted alignment has been developed as a new methodology for in situ integration of a wide range of materials, including elastomer, resin, plastics, metal, and quartz glass, with modulus ranging from tens of MPa to over 70 GPa. Assembly of single material, coassembly of two to four distinctive materials, and 3D alignment of "bridge-like" and "cross-stacked" heterogeneous structures are demonstrated. This methodology has provided a new solution to mild and efficient assembly of multiple materials at the macroscopic scale, which holds promise for advanced fabrication in fields of tissue engineering, electronic devices, and actuators.

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.

Interaction of lipid accumulation product and family history of hypertension on hypertension risk: a cross-sectional study in the Southern Chinese population.

OBJECTIVES: This study aimed at investigating the applicability of a novel index based on waist circumference (WC) and triglyceride (TG) which was named lipid accumulation product (LAP) in the Southern Chinese population, and compared the predictive effects of LAP and other obesity indicators on hypertension risk. Moreover, this study investigated the interactive effects of LAP and family history of hypertension. METHODS: A total number of 2079 of community-dwelling adults in Southern China were enrolled in this cross-sectional study. The participants underwent questionnaire surveys, anthropometric tests and laboratory examinations. Themultinomial logistic regression model and receiver operating characteristic curves, including LAP, body mass index (BMI), waist-to-hip ratio (WHR), WC and TG, were used to assess the association between hypertension risk and obesity indexes. The interaction effects were evaluated by relative excess risk of interaction (RERI), attributable proportion due to interaction (AP) and synergy index (SI). RESULTS: Higher LAP levels have a relatively higher risk of having hypertension in both sexes (males: adjusted OR=2.79 per SD increase, 95% CI 1.43 to 5.44, p<0.001; females: adjusted OR=3.15, 95% CI 1.56 to 6.39, p<0.001). LAP (area under the curve=0.721; 95% CI 0.680 to 0.761) is a better indicator in identifying hypertension risk than BMI, WHR and TG in females, but WC performed better in males. A significant interaction between LAP and family history of hypertension was observed in males (RERI=1.652, 95% CI 0.267 to 3.037; AP=0.516, 95% CI 0.238 to 0.794; SI=3.998, 95% CI 0.897 to 17.820), but there is no statistically significant difference in females. CONCLUSIONS: LAP significantly associates with hypertension risk in the Southern Chinese population. It has better performance than BMI, WHR and TG on predicting hypertension risk of the Southern Chinese female population. Moreover, LAP and family history of hypertension might synergistically increase the risk of hypertension.

Mini-Generator Based on Reciprocating Vertical Motions Driven by Intracorporeal Energy.

Most implantable devices rely on a power supply from batteries and require replacement surgeries once the batteries run low. Mini-generators that harvest intracorporeal energy available in the human body are promising replacements of batteries and prolong the lifetime of implantable devices, thus reducing surgery pain, risks, and cost. Although various sources of energy available in the human body are used for electricity generation using piezoelectric and triboelectric materials or intravascular turbines, concerns about material durability or thrombus risks remain, and developing novel strategies to fabricate a mini-generator to harvest the intracorporeal energy is still challenging. Herein, a mini-generator system is designed by exporting the systolic/diastolic blood pressure from the femoral artery of a sheep to trigger the pressure-responsive reciprocating vertical motions of a conductor. By applying a magnetic field, an induced voltage of 0.32 V and a stable output power of 13.86 µW are obtained, which is promising to power a state-of-the-art pacemaker (8-10 µW). The noncontact electricity generation strategy provides a novel avenue to sustainable power supply for implantable devices.

Removal of Oil Spills through a Self-Propelled Smart Device.

Oil/water separation through superhydrophobic/superoleophilic materials has attracted considerable interest over the past decades; however, dealing with oil spills on broad waters through an active way remains a challenge. Herein, we report a self-propelled smart device driven by the decomposition of hydrogen peroxide that can spontaneously move on the water surface and collect floating oil droplets inside with superhydrophobic and superoleophilic properties. Moreover, the self-propelled smart device exhibits excellent stability and high efficiency for oil/water separation. We believe this study may provide a promising strategy for fabricating smart aquatic devices that have potential applications in water remediation.

Macroscopic supramolecular assembly of rigid hydrogels assisted by a flexible spacing coating.

To address the difficult challenge of realizing macroscopic supramolecular assembly (MSA) of high-modulus hydrogels, we propose a strategy of introducing a flexible spacing coating to improve the surface compliance for efficient MSA, which holds promise to develop versatile MSA methods for fabricating hydrogel-based tissue scaffolds, and to provide insight into the MSA mechanism.