In this study, a new strategy to achieve high-efficient heat transfer for non-Newtonian fluids with slippage using a stably prepared superhydrophobic coating is presented. A superhydrophobic coating is prepared on the inner surface of a sleeve at specific shear stress. The slippage and heat-transfer processes of the typical non-Newtonian fluid–1% carboxymethyl cellulose solutions on the superhydrophobic coating are investigated simultaneously. A novel porous spherical type of superhydrophobic coating with a contact angle of 168° is obtained. It is found that the shear stress in electrodeposition is a key parameter to control the morphology and wetting ability of the superhydrophobic coating. The slip length and enhancement factor of heat transfer for the non-Newtonian fluid on the coating are found in a range of 20–900 µm and 1.47 experimentally. A new parameter is proposed as Reynolds number Re divided by the dimensionless slip length ls* (Re/ls*) for the heat-transfer enhancement with slippage, which can be used as the guide for designing coating and selecting the operating conditions. The Re/ls* is <4, which can enhance the heat transfer via the slippage.

High-value utilization of biomass has been driven by increasingly growing industrial demands. Herein, we offer a strategy composed of depolymerization and esterification reaction of lignin to transfer to bio-oil with high liquid yield (79.75~85.25%), which is demonstrated as a high performance lubricant. Overall, the bio-oil has the excellent lubrication properties, where a significant wear reduction of 97.6% was observed as compared with polyethylene glycol 200. Meanwhile, the more ether and less acid in bio-oil could improve the anti-wear properties. This work provides a new application of utilizing lignin in advanced lubrication systems.

Polyimide (PI) is one of the most excellent polymers for coating. However, the high friction coefficient and the high wear rate of pure PI limit its further applications. In this work, the hollow inorganic fullerene-like MoS₂/reduced graphene oxide (HIF-MoS₂/r-GO) nanocomposite filled PI coating is prepared by in situ polymerization. Reinforcement in mechanical strength and thermal stability is realized on the PI composite coating with incorporation of HIF-MoS₂/r-GO, which performs better than carbon nanofiber (CNF). Reduced elastic modulus and hardness of HIF-MoS₂/r-GO/PI coating is increased by 8.3% and 4.8%, respectively. The addition of HIF-MoS₂/r-GO also results in 24% higher residual mass at 800 °C than CNF. Tribological study indicates that, HIF-MoS₂/r-GO/PI achieves a wear rate reduction of 79% compared with pure PI under dry sliding condition, which is much more effective than other nanofillers including CNF, r-GO nanosheets and MoS₂ nanoparticles. Under ionic liquid-lubricated condition, the presence of HIF-MoS₂/r-GO in PI results in a 30% reduction in wear rate and 10% reduction in friction coefficient as compared to pure PI. It is thought that the HIF-MoS₂/r-GO in PI can be slowly released to the frictional interface and form a protective film during sliding, in this way the aggregation problem is successfully solved.

Biolubricants refer to eco-friendly, biodegradable, and non-toxic lubricants. Their applications are still limited compared to mineral oils; however, their sustainable credentials are making them increasingly attractive. Vegetable oils are frequently used for this purpose. However, vegetable oils have issues of low lipid productivity, dependence on climatic conditions, and need for agricultural land. Microbial oils represent a more sustainable alternative. To ensure their widespread applicability, the suitability of microbial oils from a physicochemical point of view needs to be de-termined first. In this study, oils obtained from various oleagenic microbes—such as microalgae, thraustochytrids, and yeasts—were characterized in terms of their fatty acid profile, viscosity, friction coefficient, wear, and thermal stability. Oleaginous microalgal strains (Auxenochlorella protothe-coides and Chlorella sorokiniana), thraustochytrids strains (Aurantiochytrium limacinum SR21 and Au-rantiochytrium sp. T66), and yeast strains (Rhodosporidium toruloides and Cryptococcus curvatus) synthesized 64.5%, 35.15%, 47.89%, 47.93%, 56.42%, and 52.66% of lipid content, respectively. Oils from oleaginous microalgae (A. protothecoides and C. sorokiniana) and yeasts (R. toruloides and C. curvatus) possess excellent physicochemical and tribological qualities due to high amount of monounsatu-rated fatty acids (oleic acid C18:1 content, 56.38%, 58.82%, 46.67%, 38.81%) than those from oleaginous thraustochytrids (A. limacinum SR21 and Aurantiochytrium sp. T66; 0.96%, 0.08%, respectively) supporting their use as renewable and biodegradable alternatives to traditional mineral oil-based lubricants. Oil obtained from microalgae showed a lower friction coefficient than oils obtained from yeasts and thraustochytrids.

From one to more, the same raw materials giving rise to multifarious products is one of the goals of researchers to pursue industrial efficiency. Herein, we designed a formula (controlling the content of the matrix) to prepare two functional ionic gels, integrating the excellent lubrication, thermal conductivity, and self-healing ability to meet different industrial demands of the lubrication and biomedical fields. Deep eutectic solvents (DESs) of urea/choline chloride (UCC) and glycerol/choline chloride (GCC) were locked in polyacrylamide (PAM) ionic gel formed by acrylamide (AM) and a photoinitiator by freer-adical polymerization. The unique dual hydrogen bond network in the ionic gel causes the material to exhibit a low wear rate, which can effectively reduce the wear of metal contact. With the addition of PAM, the ionic gel has excellent mechanical strength and good recovery performance. Unexpectedly, this dense hydrogen bond network enhances thermal conductivity by optimizing phonon and electron transfer. The versatile ionic gel has a good application prospect as a substitute for industrial lubricants and medical device materials.

Water-based lubricants are thought to be the next generation green lubricants, however, there are very few developments of aqueous grease lubricants. Here, water-based grease lubricants were developed using the food fat replacers. The concept of using fat replacers was inspired by the historical usage of fat as a lubricant. Dextrins were chosen as the fat replacers and mixture of water and PEG as the base fluid. Dextrins with different molecular weights were selected to study its effect on the rheological, tribological and thermal behavior of the gels. It was found that only higher molecular weight dextrins will form the colloidal gels, whereas low molecular weight dextrins will form the colloidal solution. The SEM images of the dried samples showed the agglomerated micro-spherical network with the void to hold the base fluid. It was found that, at an optimum concentration, the fat replacers showed 35–58% lower friction and 29–41% lower wear than the pure PEG200/water solution regardless of their molecular weight. The spherical shaped colloidal particles will form the film over the metal surface by nano-filling and these particles will act as nano-bearings which will reduce the wear and friction. These gel lubricants can be used where the highly biodegradable and bio-compatible green lubricant is needed.

The capability of sensor systems to efficiently scavenge their operational power from stray, weak environmental energies through sustainable pathways could enable viable schemes for self‐powered health diagnostics and therapeutics. Triboelectric nanogenerators (TENG) can effectively transform the otherwise wasted environmental, mechanical energy into electrical power. Recent advances in TENGs have resulted in a significant boost in output performance. However, obstacles hindering the development of efficient triboelectric devices based on biocompatible materials continue to prevail. Being one of the most widely used polymers for biomedical applications, polyvinyl alcohol (PVA) presents exciting opportunities for biocompatible, wearable TENGs. Here, the holistic engineering and systematic characterization of the impact of molecular and ionic fillers on PVA blends’ triboelectric performance is presented for the first time. Triboelectric devices built with optimized PVA‐gelatin composite films exhibit stable and robust triboelectricity outputs. Such wearable devices can detect the imperceptible skin deformation induced by the human pulse and capture the cardiovascular information encoded in the pulse signals with high fidelity. The gained fundamental understanding and demonstrated capabilities enable the rational design and holistic engineering of novel materials for more capable biocompatible triboelectric devices that can continuously monitor vital physiological signals for self‐powered health diagnostics and therapeutics.

Squalene and docosahexaenoic acid (DHA) have gained substantial market share as dietary supplements and vital nutraceuticals due to their beneficial effects on human health. Marine fish are the main commercial source of these nutraceuticals, but a growing global demand, issues of sustainability, and an expanding vegan and vegetarian population has prompted the search for alternatives. Oils obtained from oleaginous microorganisms such as microalgae, diatoms, certain fungi, and thraustochytrids are alternatives to fish oils for omega-3 fatty acids. Among these, DHA is now being mined from thraustochytrids due to its highest proportion in their lipids, however, this strategy is not cost-effective. One way to offset such elevated production costs is to simultaneously extract other high value-added biological products from these oleaginous microorganisms. Here, we propose a novel biorefinery process based on single-step purification of squalene from total lipids extracted from an oleaginous thraustochytrid cultivated on non-edible forest biomass. To render the process economically feasible and sustainable, additional squalene-free lipids were exploited for enrichment of DHA; whereas leftover lipids generated as by-product during the process were tested as a novel biolubricant.

Developing a fully green lubricant is an urgent need due to the growing consciousness of environmental protection and dwindling resources. In this work, fully green gel lubricants were developed out of cellulose derivatives as gelator and mixture of water and poly(ethylene glycol) 200 (PEG 200) as the base fluid. The non-ionic hydroxyethyl cellulose (HEC) and anionic sodium carboxymethyl cellulose (NaCMC) were chosen to understand the effect of ionic and non-ionic gelators on the thermal, rheological and the tribological properties of the gel lubricant. HEC or NaCMC is demonstrated as effective additive to reduce wear, stabilize friction coefficient and enhance the thermal stability of developed lubricants. It is shown that anionic gelator will result in producing lower friction and wear in comparison to non-ionic gelator, which may be attributed to the possible tribo-film formation due to the negative charge in the NaCMC molecules and its larger molecular weight.