Group-Graded By-Product Construction and Group Double Centralizer Properties

For a group π with unit e, we introduce and study the notion of a π-graded Hopf algebra. Then we introduce and construct a new braided monoidal category HHeYDπ over a π-graded Hopf algebra H. We introduce the notion of a π-double centralizer property and investigate this property by studying a braided π-graded Hopf algebra U(gln(V))⋉πH, where V is an n-dimensional vector space in HHeYDπ and U(gln(V)) is the braided universal enveloping algebra of gln(V) which is not the usual Hopf algebra. Finally, some examples and special cases are given

A New Approach to Braided T-Categories and Generalized Quantum Yang–Baxter Equations

We introduce and study a large class of coalgebras (possibly (non)coassociative) with group-algebraic structures Hopf (non)coassociative group-algebras. Hopf (non)coassociative group-algebras provide a unifying framework for classical Hopf algebras and Hopf group-algebras and Hopf coquasigroups. We introduce and discuss the notion of a quasitriangular Hopf (non)coassociative π-algebra and show some of its prominent properties, e.g., antipode S is bijective. As an application of our theory, we construct a new braided T-category and give a new solution to the generalized quantum Yang–Baxter equation

A New Approach to Braided T-Categories and Generalized Quantum Yang–Baxter Equations

We introduce and study a large class of coalgebras (possibly (non)coassociative) with group-algebraic structures Hopf (non)coassociative group-algebras. Hopf (non)coassociative group-algebras provide a unifying framework for classical Hopf algebras and Hopf group-algebras and Hopf coquasigroups. We introduce and discuss the notion of a quasitriangular Hopf (non)coassociative π-algebra and show some of its prominent properties, e.g., antipode S is bijective. As an application of our theory, we construct a new braided T-category and give a new solution to the generalized quantum Yang–Baxter equation

Robust Super‐Lubricity for Novel Cartilage Prototype Inspired by Scallion Leaf Architecture

The simultaneous achievement -under physiologically high contact pressures- of ultra-low friction, nearly zero surface wear, and long lifetime in the development of human cartilage prosthetics is still a big challenge. In this work, inspired by the unique lubrication mechanism of scallion leaves resulting from the synergy of oriented surface micro-topography and mucus hydration, a novel layered soft hydrogel as cartilage prototype is developed by chemically embedding thick hydrophilic polyelectrolyte brush chains into the sub-surface of a high strength anisotropic hydrogel bulk. It exhibits an anisotropic polymer network with unique mechanical properties (tensile strength: 8.3 to 23.7 MPa; elastic modulus 20.0 to 30.0 MPa), anisotropic hydrated surface texture, super-lubricity, and excellent wear resistance. Thydrogel architecture can exhibit low coefficient of friction (COF) less than approximate to 0.01 under a wide range of contact stresses (0.2 to 2.4 MPa) and maintain cartilage-like long-lasting (50k sliding cycles) robust super-lubricity (COF approximate to 0.006) and nearly-zero wear under high contact pressure (approximate to 2.4 MPa) condition. Theoretical underpinning reveals how multiscale surface anisotropy, mechanics, and hydration regulate super-low friction generation. This work provides a novel design paradigm for the fabrication of robust soft materials with extraordinary lubricity as implantable prototypes and coatings.A novel anisotropic layered lubrication hydrogel (ALLH) is engineered by mimicking the architecture and lubrication mechanism of natural scallion leaf (NSL). The ALLH exhibits low coefficient of friction (COF) less than approximate to 0.01 under a wide range of contact stresses and demonstrates long-lasting (50k sliding cycles) robust super-lubricity (COF approximate to 0.006) along with nearly-zero wear under high contact pressure (approximate to 2.4 MPa).imag

3D Printing of an Oil/Water Mixture Separator with In Situ Demulsification and Separation

Currently, many meshes, membranes, and fabrics with extreme wettability of superhydrophobicity/superoleophilicity, or superhydrophilicity and underwater superoleophobicity are promising candidates for oil/water mixture separation. Nevertheless, a facile yet effective way to design and fabricate porous mesh still remains challenging. In this work, fused deposition modeling (FDM) 3D printing of Fe/polylactic acid (PLA) composites was employed to fabricate superhydrophilic and underwater superoleophobic mesh (S-USM) with hydrogel coatings via the surface polymerization of Fe(II)-mediated redox reaction. In addition, salt of aluminum chloride was incorporated within the hydrogel coating, which was attributed to strengthening the demulsification of oil-in-water emulsions, resulting in efficient separation of oil-in-water mixtures. The S-USM was efficient for a wide range of oil-in-water mixtures, such as dodecane, diesel, vegetable oil, and even crude oil, with a separation efficiency of up to 85%. In this study, the flexible design and fabrication of 3D printing were used for the facile creation of spherical oil skimmers with hydrogel coatings that were capable of removing the floating oil. Most importantly, this work is expected to promote post-treatment processes using 3D printing as a new manufacturing technology and, in this way, a series of devices of specific shape and function will be expanded to satisfy desired requirements and bring great convenience to personal life

Esophagus‐Inspired Actuator for Solid Transportation via the Synergy of Lubrication and Contractile Deformation

Directional transportation of objects has important applications from energy transfer and intelligent robots to biomedical devices. Although breakthroughs in liquid migration on 2D surfaces or 3D tubular devices have been achieved, realizing smooth/on-demand transportation of constrained solids within a 3D cavity environment under harsh pressurized environment still remains a daunting challenge, where strong interface friction force becomes the main obstacle restricting the movement of solids. Inspired by typical feeding mechanism in natural esophagus system which synergistically couples a lubricating mucosa surface with the peristaltic contraction deformation of the cavity, herein, this challenge is addressed by constructing an esophagus-inspired layered tubular actuator with a slippery inner surface and responsive hydrogel matrix to realize spherical solid propulsion by photo(thermo)-induced cavity deformation. The as-constructed tubular actuator containing Fe3 O4 nanoparticles exhibits local volumetric shrinkage upon NIR-irradiation, which can generate large hydrodynamic pressure and considerable mechanical extrusion force (Fdriving force ≈ 0.18 N) to overcome low interface friction force (ffriction force ≈ 0.03 N), enabling on-demand transportation of constrained (pressure: 0.103 MPa) spherical solids over a long distance in an arbitrary direction. This actuator is anticipated to be used as bionic medicine transportation devices or artificial in vitro esophagus simulation systems, for example, to help formula eating-related physiotherapy plans for patients and astronauts

The Weak Interaction of Surfactants with Polymer Brushes and Its Impact on Lubricating Behavior

We study the weak interaction between polymers and oppositely charged surfactants and its effect on the lubricating behavior and wettability of polymer brush-covered surfaces. For cationic (PMETAC) and anionic (PSPMA) brushes, a gradual transition from ultralow friction to ultrahigh friction was observed upon adding oppositely charged surfactant as a result of the electrostatic and hydrophobic interactions between surfactant and polymer. The surfactant exchange led to a strong dehydration of the brush and a concomitant increase in friction. Upon adding surfactant above the CMC, we find a reduction in friction for the anionic brushes, while the cationic brushes maintain a high friction. This difference between the two lubrication systems suggests a different interaction mechanism between the polymers and the surfactants. For zwitterionic (PSBMA) and neutral (POEGMA) polymer brushes, where electrostatic and hydrophobic interactions could be negligible, there is nearly no surfactant uptake and also no effect of surfactant on lubrication

Interfacial mechanism of hydrogel with controllable thickness for stable drag reduction

Abstract Surface wettability plays a significant role in reducing solid-liquid frictional resistance, especially the superhydrophilic/hydrophilic interface because of its excellent thermodynamic stability. In this work, poly(acrylic acid)-poly(acrylamide) (PAA–PAM) hydrogel coatings with different thicknesses were prepared in situ by polydopamine (PDA)-UV assisted surface catalytically initiated radical polymerization. Fluid drag reduction performance of hydrogel surface was measured using a rotational rheometer by the plate-plate mode. The experimental results showed that the average drag reduction of hydrogel surface could reach up to about 56% in Couette flow, which was mainly due to the interfacial polymerization phenomenon that enhanced the ability of hydration layer to delay the momentum dissipation between fluid layers and the diffusion behavior of surface. The proposed drag reduction mechanism of hydrogel surface was expected to shed new light on hydrogel-liquid interface interaction and provide a new way for the development of steady-state drag reduction methods