High-Speed Parallel Plasmonic Direct-Writing Nanolithography Using Metasurface-Based Plasmonic Lens

Simple and efficient nanofabrication technology with low cost and high flexibility is indispensable for fundamental nanoscale research and prototyping.Lithography in the near field using the surface plasmon polariton(i.e.,plasmonic lithography)provides a promising solution.The system with high stiffness passive nanogap control strategy on a high-speed rotating substrate is one of the most attractive highthroughput methods.However,a smaller and steadier plasmonic nanogap,new scheme of plasmonic lens,and parallel processing should be explored to achieve a new generation high resolution and reliable efficient nanofabrication.Herein,a parallel plasmonic direct-writing nanolithography system is established in which a novel plasmonic flying head is systematically designed to achieve around 15 nm minimum flying-height with high parallelism at the rotating speed of 8–18 m·s^(-1).A multi-stage metasurface-based polarization insensitive plasmonic lens is proposed to couple more power and realize a more confined spot compared with conventional plasmonic lenses.Parallel lithography of the nanostructures with the smallest(around 26 nm)linewidth is obtained with the prototyping system.The proposed system holds great potential for high-freedom nanofabrication with low cost,such as planar optical elements and nano-electromechanical systems.

Recent advances in ocular lubrication

The ocular lubrication,where the eyelid constantly slides on the curved corneal surface,is considered as one of primary lubrication systems in bio-tribology.Under reliable lubrication conditions,sensitive ocular tissues remain intact from fatigue damage during spontaneous blink cycles.The tear film,evenly filled between cornea and conjunctiva,is a biological fluid with dynamic adjustment ability,which provides superior lubrication with the friction coefficient of below 0.01.However,the lubrication failure may result in a variety of uncomfortable symptoms such as inflammatory reactions,tissue damage and neurological abnormalities.Therefore,it is essential to clarify the fundamental mechanism of ocular lubrication,which helps to alleviate and even recover from various ocular symptoms.This review firstly demonstrates that the ocular components,containing lipids and mucins,contribute to maintaining the lubrication stability of tear film.Furthermore,the ocular lubrication state in various physiological environments and the physical effect on tear film dynamics are further discussed.As typical applications,the therapeutic agents of dry eye syndrome and contact lens with superior lubrication effects are introduced and their lubrication mechanisms are clarified.Finally,this review summarizes a series of the latest research inspired by ocular lubrication.Overall,this work will provide a valuable guidance on the theoretical research and extensive applications in the field of biological lubrication.

Simple and effective:Superlubricity behaviour of the G-quadruplex hydrogel with high selectivity for K+ions based on the ocular environment

Hydrogels have been the subject of significant research in the field of friction due to their exceptional lubricating properties.In this study,the G-quadruplex hydrogel with high selectivity for K+ions was formed by introducing a mixture of G,2-formylphenylboronic acid,and polyethylene glycol diamine into simulated artificial tears solution with high transparency,and an ultra-low coefficient of friction(COF)of about 0.004 was obtained based on the simulated ocular environment,thus achieving macroscopic superlubricity.In friction pairs simulating the ocular environment,to assess the frictional performance of the G-quadruplex hydrogel as both a lubricant and a friction pair based on the simulated ocular environment,we conducted experiments considering various factors such as concentration,sliding speed,and stress.Through these experiments,it was found that superlubricity was achieved when the G-quadruplex hydrogel was applied as lubricant or friction pair.This effect was attributed to the three-dimensional network structure and hydrophilicity of the hydrogel,which facilitated the formation of a highly bearing and flowing hydration layer,promoting macroscopic superlubricity.Compared to the G-quadruplex hydrogel with low concentration,the high concentration hydrogel(75 mM)exhibited increased mechanical strength and robustness in superlubricity.Combined with biocompatibility experiments,our synthesized G-quadruplex hydrogel has excellent biocompatibility and offers a novel approach to achieve superlubricity in ocular drug delivery.

Hierarchical self-assembled structure and frictional response of phthalocyanine molecules

Solid evidence is needed to demonstrate the effect of molecular orientation and structure on the frictional property of boundary lubricants.In this work,the frictional properties of phthalocyanine self-assembled monolayers(SAMs)with face-on(aromatic cores parallel to the substrate)and edge-on(aromatic cores stand on the substrate)orientations have been compared and the in situ structural variation of edge-on SAMs under frictional shear has been revealed by atomic force microscope(AFM).Face-on oriented SAMs show lower adhesion,lower friction,and stronger wear resistance,compared with edge-on oriented SAMs.Hierarchical structures of edge-on oriented SAMs have been revealed by frictional topography,which are consisted of nanoscale columns,micron-scale stripes,and centimeter-scale monolayer.The column structure deforms under increasing load force,leading to a stepwise friction force curve and a transition among three friction states(ordered friction,collapsed friction,and worn friction).The structural deformation depends on both the order degree and anisotropic stiffness of columns.Columns in phthalocyanine SAMs show a larger stiffness when shearing against molecular plane than shearing along the molecular plane.The presented study on the interfacial structure and frictional mechanism promisingly supports the designing of novel boundary lubricants and their application in engineering.

Achieving ultrafast superlubricity with layered double hydroxides

Layered double hydroxides(LDHs)have the potential to be superlubricated materials due to their strong adsorption effect and weak internal interaction.However,obtaining stable superlubricity during the ultrafast time(<10 s)is still a challenge.Here,we demonstrated macroscale superlubricity based on LDHs of multiple metal ions at high surface roughness,achieving superlow friction coefficients(0.006)and ultrafast wearing-in time(<7 s),which mainly originated from tribochemical reactions and the formation of nanostructured adsorption layers.Through cross-sectional analysis and density functional theory,we revealed the properties of the protective tribofilm to achieve ultrafast superlubricity.LDHs strongly adsorbed on the surface of the bearing steel,the sliding interface transformed into a heterogeneous interface between the polytetrafluoroethylene and LDH,leading to macroscale superlubricity.These findings demonstrate that tribochemical treatment of surfaces produces tribofilm that effectively reduces wearing-in time and promotes ultralow friction.

Adjustable superlubricity system using polyalkylene glycol with various acid aqueous solutions

Polyalkylene glycol(PAG)aqueous solutions have recently been demonstrated to exhibit an ultralow friction coefficient(COF,μ<0.01).However,the prolonged running-in period and low bearing capacity have limited its widespread application.In this study,we determined that the running-in period can be decreased by more than 75%when the pH value of the lubricant is controlled at 3 by introducing various acid solutions.Additionally,less time was required to realize stable superlubricity with inorganic acid at lower pH values.This was mainly attributed to the acceleration effect of hydrogen ions around the contact region.In case of PAG aqueous solution with organic acid,the wear loss between sliding solid surfaces was reduced,and thus the bearing pressure during the superlubricity period was significantly improved from approximately 30 to 160 MPa.Furthermore,the organic acid molecules were considered to form strong hydrogen bonds with PAG macromolecules and solid surfaces.This in turn strengthened the structure of the adsorption layers.The unique effect of different acids in aqueous polymer lubrication can potentially significantly aid in advancing the study of polymer tribology and broadening industrial applications.

Construction and experimental verification research of a magnetic detection system for submarine pipelines based on a two-part towed platform

With the acceleration of the investigation and development of marine resources,the detection and location of submarine pipelines have become a necessary part of modern marine engineering.Submarine pipelines are a typical weak magnetic anomaly target,and their magnetic anomaly detection can only be realized within a certain distance.At present,a towfish or an autonomous underwater vehicle(AUV)is mainly used as the platform to equip magnetometers close to the submarine pipelines for magnetic anomaly detection.However,the mother ship directly affects the towfish,thus causing control interference.The AUV cannot detect in real time,which affects the magnetic anomaly detection and creates problems regarding detection efficiency.Meanwhile,a two-part towed platform has convenient control,thus reducing the interference of the towed mother ship and real-time detection.If the platform can maintain constant altitude sailing through the controller,the data accuracy in the actual magnetic anomaly detection can be guaranteed.On the basis of a two-part towed platform,a magnetic detection system with constant altitude sailing ability for submarine pipelines was constructed in this study.In addition,experimental verification was conducted.The experimental verification research shows that the constant altitude sailing experiment of the two-part towed platform verifies that the platform has good constant altitude sailing ability in both a hydrostatic environment and the actual marine environment.Meanwhile,the offshore magnetic anomaly detection experiment of submarine pipelines verifies the stable measurement function of the magnetic field and the function of the system to detect magnetic anomaly of submarine pipelines.

Superlubricity achieved with two-dimensional nano-additives to liquid lubricants

The topic of superlubricity is attracting considerable interest around the world while humanity is facing an energy crisis.Since various liquid superlubricity systems can be commonly achieved on the macroscale in ambient conditions,it is considered an effective solution to reduce unnecessary energy and material losses.However,certain practical problems such as low load-bearing pressure,dependence on hydrogen ions,and relatively long running-in processes still limit its widespread application.Two-dimensional(2D)nano-additives with ultrathin longitudinal dimensions can lower the shear resistance between sliding solid surfaces,and thus further optimize the applied conditions.In this review,the latest studies on 2D nano-additives with a combination of various water-based lubricants in the state of superlubricity are reported,typically including black phosphorus(BP),graphene oxide(GO),and layered double hydroxide.During the sliding process,composite lubricants effectively improved the load capacity(up to 600 MPa),reduced wear,and accelerated the running-in period(within 1,000 s)of the liquid superlubricity system.Both macromechanical experiments and microscopic tests are conducted to precisely analyze various interactions at the interfaces of the nano-additives and solid surfaces.These interactions can be described as tribochemical reactions,physical protection,and adsorption enhancement,and improved wear resistance.This review provides better guidance for applying 2D nanomaterials in liquid superlubricity systems.

Tribological properties of novel palygorskite nanoplatelets used as oil-based lubricant additives

Layered palygorskite(PAL),commonly called attapulgite,is a natural inorganic clay mineral composed of magnesium silicate.In this study,an aqueous miscible organic solvent treatment method is adopted to prepare molybdenum-dotted palygorskite(Amo-PMo)nanoplatelets,which greatly improved the specific surface area of PAL and the dispersion effect in an oil-based lubricant system.Their layered structure and size were confirmed using transmission electron microscopy(TEM)and atomic force microscopy.Following a tribological test lubricated with three additives(PAL,organic molybdenum(SN-Mo),and Amo-PMo),it was found that the sample of 0.5 wt%Amo-PMo exhibited the best tribological properties with a coefficient of friction of 0.09.Moreover,the resulting wear scar diameter and wear volume of the sliding ball surface were 63%and 49.6%of those lubricated with base oil,respectively.Its excellent lubricating performance and self-repairing ability were mainly attributed to the generated MoS2 adsorbed on the contact surfaces during the tribochemical reaction,thereby effectively preventing the direct collision between asperities on sliding solid surfaces.Thus,as-prepared Amo-PMo nanoplatelets show great potential as oil-based lubricant additives,and this study enriches the existing application of PAL in industry.

Macroscale superlubricity under ultrahigh contact pressure in the presence of layered double hydroxide nanosheets

It is difficult to achieve macroscale superlubricity under high contact pressures and high normal loads.Layered double hydroxide(LDH)nanoadditives were introduced into an ionic liquid alcohol solution(IL(as))with contact pressures up to 1.044 GPa,which resulted in a friction coefficient(COF)of 0.004 and a robust superlubricity state lasting for 2 h.Compared with the LDH particles(LDH-Ps)with ca.90-nm widths and 18-nm thickness,micron-scale LDH nanosheet(LDH-N)additives with ca.1.5-pm width and 6-nm thickness increased the load-bearing capacity by approximately three times during superlubricity.The lubricant film thickness and the ultrathin longitudinal dimension of the LDH-N additives did not influence the continuity of the fluid film on the contact surface.These improvements resulted from the protective adsorption layer and ion distribution formed on the contact interface,as revealed by detailed surface analyses and simulation studies.In particular,the sliding energy barrier and Bader charge calculation revealed that weak shear sliding between the nanosheet and the solid surface formed easily and the anions in the liquid adsorbed on the solid surface exhibited electrostatic repulsion forces,which generated stable tribological properties synergistically.This research provides a novel method for obtaining macroscale superlubricity for practical industrial applications.