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It is known that BN fibers with functional groups on their surfaces and excellent recyclability are used in the adsorption and removal of antibiotics. However, the antibiotics are difficult to desorb after adsorption, which makes it challenging to continuously use BN fibers on a large scale. In this study, NiO-modified BN fiber composites were prepared through an alkali activation and impregnation process. Among them, uniform loading of NiO on the BN fiber surface was achieved at the NiO content of 7.58% (BN-NiO-0.2), which was due to the generation of hydroxyl groups and B-O-Ni bonds on the fiber surface. Although BN-NiO-0.2 has a low specific surface area of 127.46 m2/g, it exhibited a high adsorption capacity for tetracycline (504.12 mg/g) due to the maximum negative charge (-26.501 mV) on the BN fibers surface. Ni2+ serves as a junction between TC molecules and BN adsorbents to facilitate charge transfer on the surface of BN, thereby forming stable complexes with TC and enhancing its adsorption from theoretical calculations. Notably, the adsorption rate of BN-NiO-0.2 remained above 98% after five cycles, and the release rate of Ni ions (0.0301 mg/L) was extremely low. Furthermore, after five cycles of tetracycline adsorption, the adsorbed tetracycline in BN-NiO-0.2 can rapidly reach 99% desorption by adjusting the pH to reverse the surface charges, enabling quick separation between the adsorbent and tetracycline. This shows excellent environmental friendliness and potential for application. [Display omitted] • Uniformly NiO-decorated BN fiber was obtained by alkali activation and impregnation. • The decoration of BN fiber with a proper NiO maximizes the surface charges. • BN-NiO-0.2 with a low specific surface area achieves highest TC adsorption capacity. • Reversal of surface charge promotes rapid desorption of adsorbed TC. [ABSTRACT FROM AUTHOR]

This paper presents a one-step method for fabricating a PDMS optical lens based on the surface charging and edge pining effects of a PDMS droplet. This method works by electrically lifting the air-liquid PDMS interface initially stabilized by the edge pining effect of a PDMS droplet on a polymethyl methacrylate (PMMA) substrate. The electrical lifting was achieved under the force interaction between the negative surface charges of the PDMS droplet and the non-uniform electric field generated by a needle-plate electrode pair. Experimental results show that the electrical lifting was achieved in about 10 seconds. With the increase of the applied electric field, the magnification of the fabricated lens increases. Fabricating a lens with a resolution of 32 lp/mm and a magnification of 23.92 times was obtained under an averaged electric field of 12500 V/cm. Chlorophyll-fluorescence-based living algae detection with the PDMS lens and a smartphone imaging system was successfully achieved. [Display omitted] [ABSTRACT FROM AUTHOR]

Droplet wetting and manipulation are essential for the efficient functioning of many applications, ranging from microfluidic applications to electronic devices, agriculture, medical diagnosis, etc. As a means of manipulating droplet wetting, the effect of applying an external voltage or surface charge has been extensively exploited and is known as electrowetting. However, there also exist many materials which bear a quasi-permanent surface charge, like electrets, which are widely employed in sensors or energy storage. In addition, other materials in nature can acquire surface charge by the triboelectric effect, like human hair, natural rubber, and polymers. Nevertheless, there do not exist any studies on spreading on this class of charged surfaces. In our work, we for the first time investigate spreading dynamics on lithium niobate (LiNbO 3) as an example of a ferroelectric material with strong instantaneous polarization (0.7 C / m 2 ). We find a spreading behavior that significantly differs from classic surfaces. Spreading times can be significantly enlarged compared to standard surfaces, up to hundreds of seconds. Furthermore, the classic Tanner's law does not describe the spreading dynamics. Instead, the evolution of the droplet radius is dominated by an exponential law. Contact angles and spreading dynamics are also polarization-dependent. They are also influenced by adsorption layers, such as they are left behind by cleaning. Overall, all results indicate that adsorption layers play a significant role in the wetting dynamics of lithium niobate and possibly other charged materials, where such processes are very pronounced. Possible mechanisms are discussed. Our findings are essential for the understanding of wetting on charged surfaces like ferroelectric materials in general. The knowledge of surface charge-based wettability difference, surface charge specific adsorption and its impact on wettability can be utilized in applications like, printing, microfluidics, triboelectric nanogenerators, and to develop biocompatible components for tissue engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

We investigate the mixing and hydrodynamic characteristics computationally for a pure electroosmotic flow of non-Newtonian fluid through a nonuniformly charged micromixer with obstacles arranged in staggered and inline orders. The constitutive behavior of the fluids is described by the power-law model. We present the results by varying the dimensionless zeta potential (| ζ |), Debye parameter (κ), and power-law index (n) in the range of 1 ≤ | ζ | ≤ 8, 0.5 ≤ κ ≤ 100 and 0.5 ≤ n ≤ 1.5, respectively. The mixing is strongly influenced by the rheology of the fluids and the formation of the recirculatory zones. For the overlapped EDL (κ = 0.5), mixing efficiency (ME) decreases with n for lower | ζ | values, while ME increases with n for higher | ζ | values for both the orientation of obstacles. When the obstacles are arranged in a staggered manner, the variation of ME with n follows a decreasing-increasing trend for the intermediate values of | ζ |. The value of ME is higher for the inline arrangement with overlapped EDL (κ = 0.5) and is close to 100%. For thinner EDL (κ = 100), the value of ME is higher for inline arrangement only for | ζ |= 1 and 0.5 ≤ n ≤ 0.6, and for all other cases, it is higher for staggered arrangement. The presence of heterogeneous charged surface always enhances the mixing and the enhancement is always higher for shear-thickening fluid and for the staggered order of the obstacles. The present design of electroosmotic micromixer handling with non-Newtonian fluids provides a higher mixing efficiency as compared to most of the existing designs available in the literature. The values of n , κ and | ζ | are identified for the micromixer with two orientations of the obstacles for quick and efficient mixing and the findings may be helpful to design an efficient micromixer for the point-on care diagnostic applications handling with of non-Newtonian fluids. [Display omitted] [ABSTRACT FROM AUTHOR]

Silica nanoparticles (SNP) with different sizes and surface areas are used in numerous micro/nanofluidic applications, while their surface charge properties play a major role in their function. In many of these applications, SNPs also undergo temperature variation. We present that an increase in temperature yields a substantial increase in SNP surface charge depending on nanoparticle size and surface roughness, which cannot be estimated by existing theory. As a continuation of our earlier work characterizing the deviation of SNP surface charging from theoretical predictions due to curvature and EDL overlap effects, this study presents the differentiation from the theory in temperature dependence under various conditions. As we calculate surface chemistry as a function of local ionic conditions (Charge Regulation), temperature variation changed the equilibrium constants of protonation/deprotonation reactions of the SNP surface, in addition to changes occurring in relative permittivity and ionic mobilities. Results show that variation of SNP surface charge by temperature decreases by decreasing particle size and/or increasing roughness size, compare to theoretical flat plate calculations considering similar temperature-dependent properties and charge regulation on the surface. We characterized these deviations by obtaining an "electrokinetic similarity" between different systems of various size and roughness at various ionic conditions based on the non-dimensional groups of λ/D P and λ/D R. Based on these, we devised a phenomenological model as an extension to the flat plate theory to successfully predict the surface charge of SNPs as a function of the particle size, roughness size, and temperature. The current findings are important for the characterization of SNPs through temperature variations and can also be used to adjust the surface charge of SNPs by tuning the temperature. [Display omitted] • Nanoparticle surface charge increases with increasing temperature. • Temperature effects on surface charge change with particle size and surface condition. • Temperature dependent ionic diffusion and surface charge regulation were considered. • Temperature dependent solution of PNP with charge regulation is presented. • A model for nanoparticle charging is extended from analytical solution. [ABSTRACT FROM AUTHOR]

We theoretically investigate electrostatic properties between two charged surfaces with a grafted polyelectrolyte layer in an aqueous electrolyte solution by using the Poisson-Boltzmann approach accounting for ion partitioning. In order to consider the ion partitioning effect, we focus on changes of electrostatic properties due to the difference in dielectric permittivity of the polyelectrolyte layer and the aqueous electrolyte solution. We find that ion partitioning enhances electrostatic potential in the region between two charged soft surfaces and hence increases the electrostatic interaction between two charged soft surfaces. Ion partitioning effect on osmotic pressure is enhanced not only by an increase in the thickness of polyelectrolyte layer and Debye length but also by a decrease in ion radius. [Display omitted] • Ion partitioning effect involves an increase of electrostatic potential and osmotic pressure. • An increase in surface charge density amplifies the ion partitioning. • A higher thickness of polyelectrolyte layer results in a stronger ion partitioning. • A small radius of ions enhances ion partitioning. [ABSTRACT FROM AUTHOR]