Salivary pellicle, a spontaneously formed, intricate architecture in the human oral cavity, is a high‐performance bio‐lubricant that coats and protects biological surfaces with varying elastic modulus against frictional damage. Although salivary lubrication underpins the fundamentals of human feeding and speech, the peculiar molecular mechanism behind such lubrication properties remains elusive. For the first time, this work demonstrates a binary model comprised of salivary proteins, mucin, and lactoferrin (LF), forming an electrostatically driven, multilayered self‐assembly that exhibits a lubrication behavior closely resembling that of human saliva, from macro to nanoscale. The multiscale tribological analysis with applied forces ranging from 1 N to 1 nN, supported by real‐time self‐assembly monitoring on hydrophilic and hydrophobic substrates differentially resolves the distinct roles played by the salivary proteins of this proposed lubricating model. Evidences reveal that hydrated mucin controls the macromolecular viscous lubrication entrapping water molecules in the mucinous network and LF acts as a “molecular glue” between mucin–mucin and mucin–surface, latter aiding boundary lubrication. This study puts forward an unprecedented molecular model that explains the synergistic lubrication by salivary components. These results can aid into the design routes for synthesizing highly efficacious nature‐inspired aqueous lubricants for future biomedical applications and nutritional technologies.
The remediation of metal and heavy metal contaminants from water ecosystems is a long-standing problem in the field of water management. The development of efficient, cost effective, and environmentally friendly natural polymer-based adsorbents is reported here. Magnetic chitosan (CS) and carboxymethylchitosan (CMC) nanocomposites have been synthesized by a simple one-step chemical coprecipitation method. The nanoparticles were assessed for the removal of Pb 2+ , Cu 2+ , and Zn 2+ ions from aqueous solution. Kinetic and thermodynamic models were used to describe and understand the adsorption process of the ions onto the nanomaterials. The interactions between the ions and the biopolymer-based composites are reversible, which means that the nanoparticles can be regenerated in weakly acidic or EDTA containing solution without losing their activity and stability for water cleanup applications.
Preventing mineral fouling, known as scale, is a long-standing problem for a broad range of industrial applications ranging from oil production to water treatment systems to names 2 but a few. The build-up of inorganic scale such as calcium carbonate on surfaces and facilities is undesirable as it can result in safety risks and associated flow assurance issues. To date the overwhelming amount of research has mainly focused on chemical inhibition of scale bulk precipitation and little attention has been paid to deposition onto surfaces. The development of novel more environmentally-friendly strategies to control mineral fouling will most probably necessitate a multifunctional approach including surface engineering. In this study, we demonstrate that liquid infused porous surfaces provide an appealing strategy for surface modification to reduce mineral scale deposition. Microporous polypyrrole (PPy) coatings were fabricated onto stainless steel substrates by electrodeposition in potentiostatic mode. Subsequent infusion of low surface energy lubricants (fluorinated oil Fluorinert FC-70 and ionic liquid 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIm) ) into the porous coatings results in liquid-repellent slippery surfaces.To assess their ability to reduce surface scaling the coatings were subjected to a calcium carbonate scaling environment and the scale on the surface was quantified using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). PPy surfaces infused with BMIm (and Fluorinert to a lesser extent) exhibit remarkable antifouling properties with the calcium carbonate deposition reduced by 18 times in comparison to untreated stainless steel. These scaling tests suggest a correlation between the stability of the liquid infused surfaces in artificial brines and fouling reduction efficiency. The current work shows the great potential of such novel coatings for the management of mineral scale fouling.
Using the extended-SARA method to fractionate asphaltenes based on their interfacial activity, the current study reports the first results on the estimated size and shape of interfacially active asphaltene (IAA) and remaining asphaltene (RA) nanoaggregates. These fractions have been reported to exhibit distinctly different chemical architectures that influence the size of asphaltene clusters in good and poor solvents. However, little is known about the building blocks, commonly referred to as nanoaggregates, which form these clusters and how those subtle differences in chemical architecture impact aggregation of asphaltenes. The nanoaggregate size and shape of IAA and RA was measured using small-angle neutron scattering (SANS). The characteristic length and asymptotic power-law exponent of whole asphaltenes (WAs) extracted from heavy crude oil and dispersed in deuterated toluene were 28.0 ± 0.2 Å and 2.86 ± 0.01, respectively, showing negligible variations with changing asphaltene concentration, source of asphaltenes (bitumen and heavy crude oil), and solvent aromaticity. For RA fractions, which account for 98.5 wt % of WA, the characteristic length and power-law exponent of 28.8 Å and 2.86 were comparable to that of WA but in contrast to 59.7 Å and 2.20 for IAA. A ∼100% increase in the characteristic length and reduced power-law exponent of the IAA fraction confirms that these two asphaltene subfractions form dissimilar nanoaggregate structures.
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