Flagellar-driven locomotion plays a critical role in the bacterial attachment and colonization of surfaces, contributing to the risks of contamination and infection. Extensive efforts to uncover the underlying principles governing bacterial motility near surfaces have relied on idealized assumptions about surrounding artificial surfaces. However, in the context of living systems, the role of cells from tissues and organs becomes increasingly critical, particularly in bacterial swimming and adhesion, yet it remains poorly understood. Here, we propose using biological surfaces composed of vascular endothelial cells to experimentally investigate bacterial motion and interaction behaviors. Our results reveal that bacterial trapping observed on inorganic surfaces is counteractively manifested with reduced radii of circular motion on cellular surfaces. Additionally, two distinct modes of bacterial adhesion were identified: tight and loose adhesion. Interestingly, the presence of living cells enhances bacterial surface enrichment, and imposed flow intensifies this accumulation via a bias-swimming effect. These results surprisingly indicate that physical effects remain the dominant factor regulating bacterial motility and accumulation at the single-cell-layer level in vitro, bridging the gap between simplified hydrodynamic mechanisms and complex biological surfaces with relevance to biofilm formation and bacterial contamination.
It is necessary to study the mechanics performance of thin coating, which composite the prerequisite of coating’s application. The contact stresses are important factors for the design of hard coating/substrate because the failure of the hard coating is usually caused by these stresses. The finite element method is applied to simulate the stress of coating with contact load based on Hertz contact theory. The accuracy of model was initially tested in systems without a film. The contact stresses have been calculated based on various coating/substrate modulus ratios and the coating thickness. Results show that coating thickness changes from 1.5um to 3um, the effects of coating/substrate combination is perfect. The research has important guiding significance for the application of coating.
Regulating the swimming motility of bacteria near surfaces is essential to suppress or avoid bacterial contamination and infection in catheters and medical devices with wall surfaces. However, the motility of bacteria near walls strongly depends on the combination of the local physicochemical properties of the surfaces. To unravel how nanostructures and their local chemical microenvironment dynamically affect the bacterial motility near surfaces, here, we directly visualize the bacterial swimming and systematically analyze the motility of Escherichia coli swimming on ZnO nanoparticle films and nanowire arrays with further ultraviolet irradiation. The results show that the ZnO nanowire arrays reduce the swimming motility, thus significantly enhancing the trapping ability for motile bacteria. Additionally, thanks to the wide bandgap nature of a ZnO semiconductor, the ultraviolet irradiation rapidly reduces the bacteria locomotion due to the hydroxyl and singlet oxygen produced by the photodynamic effects of ZnO nanowire arrays in an aqueous solution. The findings quantitatively reveal how the combination of geometrical nanostructured surfaces and local tuning of the steric microenvironment are able to regulate the motility of swimming bacteria and suggest the efficient inhibition of bacterial translocation and infection by nanostructured coatings.
Abstract Biopolymers with microscale length and nanoscale cross-sections subjected to active forces is a common non-equilibrium phenomenon in living creatures. It is therefore crucial to intuitively present and investigate the detailed dynamics of such flexible filaments in an active bath full of living matter. Hence, by introducing fluorescent actin filament into an active suspension of motile bacteria at different number densities in a quasi-two-dimensional chamber, we directly visualize the detailed interaction processes and find that bacteria deform a fluctuating filament by relative motion perpendicular to its principal axis of the filament and straighten a filament by parallel motions. We analyzed the evolution of bending energy in dilute and dense bacterial baths with gradual compact or coiled shapes. We successfully introduce a dimensionless number μ˜ , named as active elasto-viscous number, which governs the generic deformation of filaments in the bacterial baths by comparing the viscous force generated in the bacterial active baths to the elastic restoring force of filaments. The persistence length measuring the tangential correlation of the flexible filament is found to be proportional to μ˜ . Finally, an effective temperature of the bacterial bath is given through the relation between constant stiffness and loading forces instead of the popularly used Einstein relation. Our findings provide detailed information and specific scaling of flexible filaments interplay with active forces and in response to living and crowded environments.
A new study shows that a moving contact line could be more dangerous for a hydrophobic coating layer on a surface than lamellar flow. The tiny water drops generate a driving force that removes the coating molecules, collecting and depositing them on the substrate as the contact line recedes.
A high-sensitivity optical fiber relative humidity (RH) sensing probe with the ability of temperature calibration is proposed and experimentally demonstrated. It consists of a simple Fabry-Perot interferometer constructed by coating a layer of thin polyimide (PI) film on the end face of single-mode fiber and an upstream fiber Bragg grating (FBG). PI is one of the organic polymer humidity-sensitive materials with good comprehensive properties. The cascaded FBG is used for temperature calibration and elimination of the temperature cross-sensitivity in the process of measuring RH. Experimental results show that this sensing probe can realize simultaneous measurement of temperature and RH. The RH response sensitivity reaches up to 986.25 pm/%RH. This sensing probe with the advantages of simple structure, compact size, high sensitivity, easy packaging, and dual-parameter measurement has an extensive application prospect.
As a renewable energy solution for remote marine environments, marine raft microgrid clusters differ from terrestrial multi-microgrid systems and traditional single-island microgrids. In the absence of large-scale grid support, these marine raft microgrids must maintain the stability and economic efficiency of power supply within a collaborative multi-microgrid context. To address this, a multi-objective optimization approach for energy scheduling is proposed. This study initially constructs a microgrid cluster system model and introduces two economic objective functions. These functions consider both inter-microgrid power scheduling and the economic benefits of power procurement. By applying the Non-dominated Sorting Genetic Algorithm II (NSGA-II) and the Constraint-based Multi-objective Evolutionary Algorithm based on Decomposition (CMOEA/D) to solve the objective functions, the results indicate that the CMOEA/D algorithm demonstrates high efficiency and accuracy in pursuing economically optimal solutions. Compared to the NSGA-II algorithm, CMOEA/D outperforms in terms of the quality of optimal solutions and iteration time, thereby enhancing the economic benefits of the microgrid cluster and validating the effectiveness of the proposed model. This research provides significant theoretical and practical guidance for energy management in remote marine environments, showcasing its profound theoretical significance and application value.
Inspired by a plant leaf, a slippery liquid-infused porous surface (SLIPS) exhibits attractive nonwetting and self-cleaning abilities. However, rigorous requirements for the infused liquid layer and its inevitable loss limit its practical use. Here, we propose a model structure defined as a non-SLIPS by introducing solid nanostructures covered with a discontinuous lubricant film. This non-SLIPS tuned by solid wettability achieves the excellent self-cleaning feature with a small sliding angle comparable to the counterpart of a typical SLIPS. This sliding angle α* can be further reduced to a saturated plateau by a slight enhancement of hydrophobicity of the solid nanostructures. Interestingly, the sliding velocity remains almost constant for all of these non-SLIPS samples at a given tilt angle, independent of solid wettability. We formulate the slippery mechanism by defining an energy barrier responsible for the sliding initiation on the non-SLIPS. This energy barrier of the non-SLIPS is correlated, with a qualitative agreement, to the molecular adsorption on the solid nanostructures. The antibiological contamination is confirmed for this non-SLIPS, indicating its excellent self-cleaning ability. The findings suggest that the new surfaces, even with the gradual depletion of the infused oil layer, exhibit the nondegradation of the self-cleaning performance.
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