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Abstract Although lubricants play an essential role in reducing wear and friction in mechanical systems, environmental issues persist. In the past decades, Ionic Liquids (ILs) have arisen as environmentally friendly alternatives to conventional lubricants and additives. ILs are low-volatile and non-flammable salts that possess low melting points (below 100 °C). Their tunable properties, achieved by selecting the appropriate cation and anion, make them ideal candidates for different applications, including lubricants. In recent times, Protic Ionic Liquids (PILs) have attracted attention in the tribological community as a cost-effective alternative to conventional aprotic counterparts. In this work, a choline-amino acid ionic liquid, derived only from renewable, biodegradable, and biocompatible products, was synthesized, and investigated as both neat lubricant and additive to non-polar oil. The lubricating properties of [CHO][GLY] were studied both as a neat lubricant and as a 1 wt. % additive to a polyalphaolefin (PAO) oil using a ball-on-flat reciprocating friction tester. AISI 52100 steel disks were tested against AISI 52100 steel balls using either [CHO][GLY] or the mixture of PAO+[CHO][GLY]. For comparison purposes, the commercially available base oil, PAO, was also tested. Preliminary results showed no major differences in friction between the lubricants used. Nevertheless, the addition of 1 wt.% to the PAO demonstrated a remarkable 30% reduction in wear on the steel disk. This encouraging improvement in anti-wear characteristics raises the potential advancement of lubrication technology with the choline-amino acid ionic liquid, coupled with its environmentally friendly nature. Energy-dispersive X-ray (EDX) spectroscopy, non-contact profilometry, and scanning electron microscopy (SEM) were used to study the worn steel surfaces and elucidate the wear mechanisms. 

Abstract Functional oxides have extensively been investigated as a promising class of materials in a broad range of innovative applications. Harnessing the novel properties of functional oxides in micro‐ to nano‐scale applications hinges on establishing advanced fabrication and manufacturing techniques able to synthesize these materials in an accurate and reliable manner. Oxidative scanning probe lithography (o‐SPL), an atomic force microscopy (AFM) technique based on anodic oxidation at the water meniscus formed at the tip/substrate contact, not only combines the advantages of both “top‐down” and “bottom‐up” fabrication approaches, but also offers the possibility of fabricating oxide nanomaterials with high patterning accuracy. While the use of self‐assembled monolayers (SAMs) broadened the application of o‐SPL, significant challenges have emerged owing to the relatively limited number of SAM/solid surface combinations that can be employed for o‐SPL, which constrains the ability to control the chemistry and structure of oxides formed by o‐SPL. In this work, a new o‐SPL technique that utilizes room‐temperature ionic liquids (RTILs) as the functionalizing material to mediate the electrochemistry at AFM tip/substrate contacts is reported. The results show that the new IL‐mediated o‐SPL (IL‐o‐SPL) approach allows sub‐100 nm oxide features to be patterned on a model solid surface, namely steel, with an initiation voltage as low as −2 V. Moreover, this approach enables high tunability of both the chemical state and morphology of the patterned iron oxide structures. Owing to the high chemical compatibility of ILs, which derives from the possibility of synthesizing ILs able to adsorb on a wide variety of solid surfaces, IL‐o‐SPL can be extended to other material surfaces and provide the opportunity to accurately tailor the chemistry, morphology, and electronic properties within nanoscale domains, thus opening new pathways to the development of novel micro‐ and nano‐architectures for advanced integrated devices. 

While ionic liquids (ILs) have attracted much attention as potential next-generation lubricant additives, their implementation in oil formulations has been hindered by their limited solubility in hydrocarbon fluids and corrosivity. Here, we encapsulate an oil-insoluble IL that has been studied in lubrication science, namely 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([HMIM][TFSI]), within poly(ethylene glycol dimethacrylate-buytl methacrylate copolymer) (poly(EGDM-c-BMA)) microshells using a mini-emulsion polymerization process. The synthesized poly(EGDM-c-BMA)-encapsulated [HMIM][TFSI] microparticles are shown to be dispersible in a non-polar, synthetic oil (i.e., poly-α-olefin). Tribological experiments indicated that the microcapsules act as an additive reservoir that reduces friction by releasing the encapsulated IL at the sliding interface following the mechanical rupture of the polymer shell. X-ray photoelectron spectroscopy (XPS) measurements provided evidence that [HMIM][TFSI] does not tribochemically react on steel surfaces to create a reaction layer, thus suggesting that this IL reduces friction by generating a solid-like, layered structure upon nanoconfinement at sliding asperities, as proposed by previous nanoscale studies. The results of this work do not only provide new insights into the lubrication mechanism of ILs when used as additives in base oils in general, but also establish a new, broadly-applicable framework based on polymer encapsulation for utilizing ILs or other compounds with limited solubility as additives for oil formulations. 

Ionic liquids (ILs) have attracted considerable attention in several sectors (from energy storage to catalysis, from drug delivery to separation media) owing to their attractive properties, such as high thermal stability, wide electrochemical window, and high ionic conductivity. However, their high viscosity and surface tension compared to conventional organic solvents can lead to unfavorable transport properties. To circumvent undesired kinetics effects limiting mass transfer, the discretization of ILs into small droplets has been proposed as a method to increase the effective surface area and the rates of mass transfer. In the present review paper, we summarize the different methods developed so far for encapsulating ILs in organic or inorganic shells and highlight characteristic features of each approach, while outlining potential applications. The remarkable tunability of ILs, which derives from the high number of anions and cations currently available as well as their permutations, combines with the possibility of tailoring the composition, size, dispersity, and properties ( e.g. , mechanical, transport) of the shell to provide a toolbox for rationally designing encapsulated ILs for next-generation applications, including carbon capture, energy storage devices, waste handling, and microreactors. We conclude this review with an outlook on potential applications that could benefit from the possibility of encapsulating ILs in organic and inorganic shells.