Contact Stability Research Articles

Light Clenching Differentially Affects Balance Ability According to Occlusal Contact Stability

Objectives: The purpose of this study was to determine the stability of occlusal contacts based on the left–right distribution of the occlusal contact area, divide participants into well-balanced and unbalanced groups, and clarify the effect of light clenching on the balance ability. Methods: Forty-one healthy men completed occlusal contact examinations with pressure-sensitive films, and the participants were allocated to the balanced occlusal contact (BOC) group or the unbalanced occlusal contact (UOC) group. The balance ability was measured using a center of gravity sway meter. The static balance in standing and dynamic balance using the cross test were assessed. Measurements were performed in the mandibular rest position (RP) or with light clenching (LC). Differences in the balance ability between the participant groups due to clenching and correlations between the static and dynamic balance were analyzed. Results: Differences in the balance ability due to clenching were observed only in the BOC group, with the static balance higher with LC, and the dynamic balance higher in the RP condition (p < 0.01). Significant correlations were observed between the static and dynamic balance except for the UOC group with LC (p < 0.01, p < 0.05). Conclusions: The results of this study suggested that occlusion affects the postural control when occlusal contact is stable but does not affect the postural control when occlusal contact is unstable.

Robust Shared Control With Stable Contact Servoing for Enhanced Object Transportation by Telerobotic Bimanual Mobile Manipulators

ABSTRACTBimanual mobile manipulation significantly enhances the capabilities of field robots that interact with diverse dynamic environments and expands the range of possible manipulation actions. This paper introduces a robust shared control architecture for remote manipulation of the Collaborative Dual‐arm Robot Manipulator (CURI), aimed at stable object transportation. Given that stable contact is pivotal for successful object transportation, our focus is on stabilizing the contact between the robot end‐effectors and the object using a contact servoing strategy. To maintain stable contact, it is essential that the contact wrenches consistently stay within the predefined friction cones throughout the task. We propose a novel shared control strategy to stabilize the contact using the contact parameterization model. This model formulates the contact stability manifold using a set of unconstrained reparameterized variables through a bijective mapping function, ensuring that the controller derived from these unconstrained reparameterized variables consistently maintains contact stability. The efficacy of the proposed approach is convincingly demonstrated through a series of experiments involving representative bimanual transportation tasks within a logistics context. Both theoretical analysis and experimental validations confirm that our proposed control strategy not only ensures the stable transportation of objects by CURI but also substantially enhances the overall robustness of the shared control system.

Effects of Interfacial Imperfections on Nanoscale Adhesive Contact for Layered Medium

Depending on processing technologies and working conditions, imperfect bonding at the layer-substrate interface may occur, resulting in diverse mechanical responses compared to a perfectly bonded layer-substrate system. This study focuses on an imperfect interface under force-like conditions and incorporates it into a nanoscale adhesive contact model to explore the influences of interfacial imperfection on the adhesive contact behaviors of the layered medium. The adhesive contact model is formulated based on the Lennard-Jones (LJ) potential and the Hammaker summation method. The adhesive contact problem is addressed by solving the nonlinear surface gap equations between the contact bodies. The deformation within the gap equations, accounting for the influence of imperfections, is computed using the fast Fourier transform (FFT) algorithm. This study explores the influence of three stress jumping coefficients t1,t2 and t3, which quantitatively characterize the interfacial imperfection, and their coeffects with material parameters, including imperfection depth (layer thickness), adhesion work, and elastic modulus, on the adhesive contact behaviors of the layered medium. The findings underscore that the normal stress jumping coefficient t3 exerts the most significant impact, wherein a higher t3 value corresponds to a smaller adhesive force and a larger absolute contact approach, while tangential stress jumping coefficients t1 and t2 exhibit negligible influence. Decreasing t3 values correspond to varying interaction force-contact approach responses and contribute to alleviating contact stability in cases with large Tabor parameters. Interfacial imperfections manifest their influence by modifying the pressure-displacement response, with noticeable effects only within a specific imperfection depth range h¯<40. While the introduction of interfacial imperfections does not alter the fundamental impact of material parameters—such as imperfection depth, adhesion work ratios, and elastic modulus ratios—on adhesive force and contact approach, it does modify the magnitude of these effects. Furthermore, imperfections alter stress distribution, increasing maximal von Mises stress and causing stress concentration within the layer and at the interface. In summary, force-like imperfections reduce surface displacement, resulting in a smaller region of positive pressure and ultimately contributing to a larger adhesive force. However, this effect is accompanied by increased stress concentration at the imperfect interface. This heightened stress level poses a potential risk to the system's reliability.

Substituted Indole Derivatives against Leucine Transporter (LeuT) as SSRI Antidepressant: Molecular Dynamics Study

Molecular docking and molecular dynamics on substituted indole derivatives-Leucine Trasporter had been performed. Indole derivatives with methoxy and fluorine group are chosen and specific amino acid residue Arg30 and Asp404 are π-alkyl and π-cation interactions. The suggested molecule containing methoxy groups has an RMSD value of 1.95 Å, a binding energy of-4.00 kcal mol-1, and an inhibition constant of 1.17 μM. The hypothesized fluorine-containing compound's RMSD value, binding energy, and inhibition constant were each 1.88 Å; -5.97 kcal mol-1; and 41.88 μM, respectively. The substituted indole derivative with the methoxy group was stable, according to the findings of a 200-ns molecular dynamics simulation, while the substituted indole derivative with the fluorine group was less stable. Based on the examination of RMSD, RMSF, RoG, the quantity of hydrogen, and the level of contact stability of the ligands with the particular amino acid residues for the antidepressant drug, the dynamical interaction of ligands against LeuT was determined.

Synergistic Dual Electrolyte System of LATP and In‐ Situ Solod‐State PDOL System and its Improvement on the Performance of NCM811 Batteries

Abstract1,3‐Dioxolane (DOL) can undergo in‐situ polymerization in batteries to form solid‐state organic electrolyte PDOL. When applied to NCM811||Li battery system, PDOL electrolyte helps optimize the contact and interface stability between electrolyte and electrodes. This study explores the effects of PDOL with PE separators coated with Li1.3Al0.3Ti1.7(PO4)3(LATP) on the performance of NCM811||Li batteries. 2,2,2‐trifluoroethyl phosphite (DETFPi), was mixed with DOL at a 1 : 35 mass ratio. Then, LiBF4 was used to initiate in‐situ polymerization and thereby obtained DETFPi‐PDOL electrolyte after 24 h at room temperature. The composite electrolyte exhibits enhanced ion conductivity (1.59×10−4 S cm−1), high lithium ion transference number (0.78), wide electrochemical stability window (4.53 V), and high critical current density (2.2 mA cm−2). Li||PDOL@LATP||Li battery shows extremely low overpotential (35 mV) after a constant current stable cycle of 500 h at 1.0 mA cm−2. After 500 cycles at 1 C, the remaining capacity is 153.9 mAh g−1 with a capacity retention of 82.1 % in NCM811||PDOL@LATP||Li batteries. This indicates that the LATP coating on the surface of the PE separator plays an important role in optimizing the performance of DETFPI‐PDOL electrolyte batteries. LATP and DETFPI‐PDOL are effective in improving the cycling stability, rate performance, and interface state of NCM811 batteries.

Construction of a superhydrophobic surface with long-term durability on 5052 Aluminium for corrosion protection

Superhydrophobic surfaces have been demonstrated to offer exceptional corrosion protection for metal surfaces. However, long-term stability issues have plagued superhydrophobic surfaces. In this study, a durable superhydrophobic surface on aluminum (SHC-Al) was created using etching combined with anodizing followed by polydimethylsiloxane (PDMS) modification. To optimize the multi-scale rough structures, the optimal anodizing conditions were explored in detail. The superhydrophobic surfaces were analyzed using Field emission scanning electron microscopy (FESEM), Confocal laser microscopy (CLSM), X-ray energy spectrometry (EDS), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), contact angle (CA) measurements, stability tests, and electrochemical analysis. The results reveal the successful preparation of a nest-like micro-nano composite structure on metal surface, and the contact and sliding angles of SHC-Al were measured at 157.6° and 6°, demonstrating the formation of excellent superhydrophobic surface. Electrochemical tests showed a corrosion current density of only 1.38 × 10–9 A∙cm-2 for SHC-Al, with a corrosion inhibition efficiency of 99.97 %, highlighting its outstanding anti-corrosion performance. Furthermore, stability tests demonstrated the SHC-Al surface had long-term durability. This study not only provides new evidence for the preparation of long-lasting superhydrophobic surfaces, but also provides a new solution for the practical application of superhydrophobic surfaces.

Maximizing interface stability in all-solid-state lithium batteries through entropy stabilization and fast kinetics

The positive electrode|electrolyte interface plays an important role in all-solid-state Li batteries (ASSLBs) based on garnet-type solid-state electrolytes (SSEs) like Li6.4La3Zr1.4Ta0.6O12 (LLZTO). However, the trade-off between solid-solid contact and chemical stability leads to a poor positive electrode|electrolyte interface and cycle performance. In this study, we achieve thermodynamic compatibility and adequate physical contact between high-entropy cationic disordered rock salt positive electrodes (HE-DRXs) and LLZTO through ultrafast high-temperature sintering (UHS). This approach constructs a highly stable positive electrode|electrolyte interface, reducing the interface resistance to 31.6 Ω·cm2 at 25 °C, making a 700 times reduction compared to the LiCoO2 | LLZTO interface. Moreover, the conformal and tight HE-DRX | LLZTO solid-state interface avoids the transition metal migration issue observed with HE-DRX in liquid electrolytes. At 150 °C, HE-DRXs in ASSLBs (Li|LLZTO | HE-DRXs) exhibit an average specific capacity of 239.7 ± 2 mAh/g at 25 mA/g, with a capacity retention of 95% after 100 cycles relative to the initial cycle—a stark contrast to the 76% retention after 20 cycles at 25 °C in conventional liquid batteries. Our strategy, which considers the principles of thermodynamics and kinetics, may open avenues for tackling the positive electrode|electrolyte interface issue in ASSLBs based on garnet-type SSEs.

Junctionless Structure Indium-Tin Oxide Thin-Film Transistors Enabling Enhanced Mechanical and Contact Stability.

In recent years, considerable attention has focused on high-performance and flexible crystalline metal oxide thin-film transistors (TFTs). However, achieving both high performance and flexibility in semiconductor devices is challenging due to the inherently conductive and brittle nature of crystalline metal oxide. In this study, we propose a facile way to overcome this limitation by employing a junctionless (JL) TFT structure via oxygen plasma treatment of the crystalline indium-tin oxide (ITO) films. The oxygen plasma treatment significantly reduced oxygen vacancies in the ITO films, contributing to the significant reduction in the carrier concentration from 4.67 × 1020 to 1.39 × 1016. Importantly, this reduction was achieved without inducing any noticeable structural changes in the ITO, enabling the successful realization of ITO JL TFTs with an adjustable threshold voltage. Furthermore, the ITO JL TFTs demonstrate good stability and reliability under various bias stress conditions, aging in the air atmosphere, and high-temperature processes. In addition, the ITO JL TFTs exhibit low light sensitivity due to the wide bandgap of ITO and further suppression of Vo defects, making them suitable for applications requiring stable performance under light exposure. To compare and analyze the flexibility of the JL structure and conventional structure with additional source/drain (S/D) junction in ITO TFTs with nonencapsulation, we utilized mechanical simulations and transmission line method (TLM). By employing the JL structure in ITO TFT through carefully optimized oxygen plasma treatment, we successfully mitigated stress concentration at the S/D-channel interface. This resulted in a JL ITO TFT that exhibited a change in contact resistance of less than 20% even after 20,000 bending cycles. Consequently, a stable and flexible ITO TFT with field-effect mobility (μFE) of 12.74 cm2/(V s) was realized, outperforming conventionally structured ITO TFTs with additional S/D junction, where the contact resistance nearly tripled.

Improved Accuracy and Contact Stability in Robotic Contouring With Simultaneous Registration and Machining

Improved Accuracy and Contact Stability in Robotic Contouring With Simultaneous Registration and Machining

Interface-reinforced solid-state electrochromic Li-ion batteries enabled by in-situ liquid-solid transitional plastic glues

The electrochromic Li-ion batteries (ELIBs) combine the functions of electrochromism and energy storage, realizing the display of energy-storage levels by visual signals. However, the accompanying interfacial issues including physical contact and (electro)chemical stability should be taken into account when the conventional liquid/gel electrolytes are replaced with solid-state counterparts. Herein, the in-situ liquid-solid transitional succinonitrile (SCN) plastic glues are constructed between electrodes and poly(ethylene oxide) (PEO) polymer electrolytes, enabling an interface-reinforced solid-state ELIB. Specifically, the liquid SCN precursor can adequately wet electrode/PEO interfaces at high temperature, while it returns back to solid state at room temperature, leading to seamless interfacial contact and smooth ionic transfer without changing the solid state of the device. Moreover, the SCN interlayer suppresses the direct contact of PEO with electrodes containing high-valence metal ions, evoking the improved interfacial stability by inhibiting the oxidation of PEO. Therefore, the resultant solid-state ELIB with configuration of LiMn2O4/SCN-PEO-SCN/WO3 delivers an initial discharge capacity of 111 mA h g−1 along with a capacity retention of 88.3% after 200 cycles at 30 °C. Meanwhile, the electrochromic function is integrated into the device by distinguishing its energy-storage levels through distinct color changes. This work proposes a promising solid-state ELIB with greatly reinforced interfacial compatibility by introducing in-situ solidified plastic glues.

Localized high concentration polymer electrolyte enabling room temperature solid-state lithium metal batteries with stable LiF-rich interphases

Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) based polymer electrolyte shows mechanical flexibility, soft and intimidate physical contact and good electrochemical stability, however, low ionic conductivity at room temperature and unstable interphases against Li metal hinder its application. In this article, we propose a universal strategy to prepare localized high concentration polymer electrolytes (LHCPE) in which high concentration lithium salt (LiTFSI) dissolved in tiny residual solvent (DMF) and the PVDF-HFP serves as solid dilution. The LHCPE regulates the solvation structure of lithium ions with anions instead of DMF solvent, allowing more anions to coordinate with Li+ and forming amount contact ion pairs (CIPs) and aggregates (AGGs). As a result, high ionic conductivity (5.9 × 10−4 S cm−1) and low activation energy (0.10 eV) achieved. The LHCPE also induces the decomposition of anions-derived LiF-rich interphases, that is ionic conducive and mechanical robust, thereby greatly improving the charge transfer kinetics and stability towards Li metal anodes. Consequently, at 0.5 mA cm−2 and 0.25 mAh cm−2, stable and long-term cycling over 2000 h obtained under room temperature in Li//Li symmetric cells achieved. The full solid-state LFP//LHCPE//Li cells further exhibit excellent capacity retention of 82.83 % even after 1200 cycles at room temperature and a high rate of 8 C (1C=170 mA·g−1). Our work shed light on the design of high-performance polymer-based composite electrolytes by manipulating the Li solvation structure.

Drug-Modified Contact Lenses-Properties, Release Kinetics, and Stability of Active Substances with Particular Emphasis on Cyclosporine A: A Review.

The following review focuses on the manufacturing and parameterizing of ocular drug delivery systems (DDS) using polymeric materials to create soft contact lenses. It discusses the types of drugs embedded into contact lenses, the various polymeric materials used in their production, methods for assessing the mechanical properties of polymers, and techniques for studying drug release kinetics. The article also explores strategies for investigating the stability of active substances released from contact lenses. It specifically emphasizes the production of soft contact lenses modified with Cyclosporine A (CyA) for the topical treatment of specific ocular conditions. The review pays attention to methods for monitoring the stability of Cyclosporine A within the discussed DDS, as well as investigating the influence of polymer matrix type on the stability and release of CyA.

Treefrog-Inspired Flexible Electrode with High Permeability, Stable Adhesion, and Robust Durability.

Long-term continuous monitoring (LTCM) of physiological electrical signals is an effective means for detecting several cardiovascular diseases. However, the integrated challenges of stable adhesion, low impedance, and robust durability under different skin conditions significantly hinder the application of flexible electrodes in LTCM. This paper proposes a structured electrode inspired by the treefrog web, comprising dispersed pillars at the bottom and asymmetric cone holes at the top. Attachment structures with a dispersed pillar improve the contact stability (adhesion increases 2.79/13.16 times in dry/wet conditions compared to an electrode without structure). Improved permeable duct structure provides high permeability (12 times compared to cotton). Due to high adhesion and permeability, the electrode's durability is 40 times larger than commercial Ag/AgCl electrodes. The treefrog web-like electrode has great advantages in permeability, adhesion, and durability, resulting in prospects for application in physiological electrical signal detection and a new design idea for LTCM wearable dry electrodes.

Halogenated Hole Selective Contact Enhances Interfacial Weak Bonding of Perovskite Solar Cells

AbstractWeak bonding between the perovskite and charge transport layers can lead to interfacial defects, hindering charge transfer and limiting the efficiency and stability of perovskite solar cells (PSCs). To address this issue, two halogenated spiro[fluorene‐9,9′‐xanthene]‐based molecules (SFX‐DM‐F and SFX‐DM‐Cl) are designed as an interfacial layer between perovskite and hole transport materials (HTMs). Both first‐principles simulations and experimental results are used to demonstrate that these halogenated interfacial layers improve the contact stability between perovskite's Pb(II) and HTMs, increasing the efficiency of charge transfer. The similar structure of interlayer to HTM also enhances the interfacial hole transfer integral, favoring effective hole transport. The PSCs based on SFX‐DM‐Cl achieve power conversion efficiencies of 24.8% (0.0625 cm2) and 23.1% (1 cm2). Even after 2000 h at a relative humidity of 15–20%, the unencapsulated PSC retains 94% of its initial efficiency. This work proposes the halogenated homologous HTMs as interfacial molecular bridges to optimize weak chemical bonds and hole transfer, thereby enabling efficient and stable PSCs.

Electrolyte design to regulate the electrode–electrolyte interface on the electrochemical performance for K0.5MnO2||graphite-based potassium-ion batteries

The system of layered-metal-oxide||carbon-anode cells with carbonate electrolytes is highly promising for constructing potassium-ion batteries (PIBs). However, this system faces serious issues of poor compatibility between the electrolyte and electrode, particularly with conventional ethylene carbonate (EC)-based electrolytes. Herein, owing to the regulated coordination environment of cation–anion-solvent and the formed KF-rich interface, a superior rate performance of graphite anode was achieved. The designed 4 M KFSI EC/DEC electrolyte demonstrates superior performance in graphite||K cells, exhibiting a high reversible capacity of approximately 200 mAh g−1 at a high current density of 700 mA g−1, surpassing many reported high-concentration and weak solvation PIB electrolytes. Meanwhile, it exhibits low polarization and maintains stable contact stability with active K metal. Furthermore, it demonstrates great compatibility with Mn-based layered metal oxide cathodes. Remarkably, we reveal a unique formation mechanism of the solvent-anion co-derived solid electrolyte interface (SEI) through a two-stage XPS deep analysis, which has the KF-deficient inorganic inner and KF-rich outer. This SEI can protect the graphite structure and enable great rate performance of graphite anode. This work holds significant reference value for the design of commercial electrolytes.

Evaluation on Mechanical Properties and Electrical Contact Behaviors for Au/Ni Composite Coating by Experiment and Finite Element Method

Gold coatings are the most widely used protective layer for resisting surface oxidization and corrosion in various complex environments. However, the extremely low hardness, inferior load‐bearing capacity, and lack of an effective strategy for evaluating the elastic‐plastic behavior of gold coatings have greatly limited their further application. The main aim of this work is to investigate the effect of Ni doping on the microstructure, mechanical properties, and electrical contact stability of a coating based on an experimental method and finite element simulation. The strain‐hardening exponent model of the coating is established by employing a reverse analysis method based on the nanoindentation experiment until the reverse and forward loading curves are consistent, thereby determining the yield strength. The results indicate that Ni doping is conducive to enhancing the mechanical properties under the premise of ensuring low contact resistance. The hardness (3.3–4.2 GPa) and yield strength (524.3–689.8 MPa) of the Au1−xNix composite coating with a Ni content of 4 at–8 at% is more than twice as high as that of pure Au. The electrical contacts deposited by the Au1−xNix coatings maintain a low contact resistance range (1.12–3.29 mΩ) at a contact force of 10 gf.

An In Situ Gelled Polymer Electrolyte to Stabilize Lithium–Air Batteries

AbstractGel polymer‐based lithium batteries exhibit a unique combination of advantageous properties, including the favorable interfacial contact characteristic of liquid‐state batteries and the inherent stability of solid‐state batteries. For Li–air batteries operated in the semi‐open atmosphere, implementing in situ synthesized gel polymer electrolytes (GPEs) is effective in mitigating the environment‐induced challenges. In this study, a dimethyl sulfoxide (DMSO)‐based GPE in situ initiated by the toluene‐2,4‐diisocyanate (TDI) and 1,4‐benzenediboronic acid (BDBA) is designed to enable the stable operation of lithium–air batteries. The integration of in situ polymerization and polyvinyl alcohol's functional group engineering not only brings benefits to the interfacial contact and electrochemical stability of the battery but also mitigates the moisture sensitivity and volatility of the DMSO electrolyte in the ambient environment. In addition, the GPE can promote the formation of a robust protection film on the lithium surface. As a result, the designed GPE makes the batteries fully leverage their outstanding cycling stability in the ambient environment (241 cycles at 500 mA g−1 and 1000 mAh g−1). Moreover, an optimized Li–air pouch cell structure incorporating the GPE achieves a boasted energy density of 757.5 Wh kg−1, providing a significant technical pathway to bring Li–O2 batteries to practical Li–air batteries.

Mathematical modeling of contact tracing and stability analysis to inform its impact on disease outbreaks; an application to COVID-19

We develop a mathematical model to investigate the effect of contact tracing on containing epidemic outbreaks and slowing down the spread of transmissible diseases. We propose a discrete-time epidemic model structured by disease-age which includes general features of contact tracing. The model is fitted to data reported for the early spread of COVID-19 in South Korea, Brazil, and Venezuela. The calibrated values for the contact tracing parameters reflect the order pattern observed in its performance intensity within the three countries. Using the fitted values, we estimate the effective reproduction number Re and investigate its responses to varied control scenarios of contact tracing. Alongside the positivity of solutions, and a stability analysis of the disease-free equilibrium are provided.

Sealing Performance of Ethylene Propylene Diene Monomer Seals for Proton Exchange Membrane Fuel Cells

The reliability of the sealing system of a proton exchange membrane fuel cell (PEMFC) is a prerequisite for ensuring the efficient and safe operation of the cell stack. In consideration of the actual assembly process, a local model of single‐cell sealing structure is constructed using a rounded corner rectangular sealing gasket structure. Apart from that, the effects of fluid pressure, bipolar plate offset, sealing gasket size, steady‐state temperature field, and seal structure on the sealing performance of PEMFC are investigated. As shown by results, with the increase of fluid pressure and sealing gasket width, the contact pressure is increased and the sealing performance is also improved. However, the increase of sealing gasket height is unfavorable to the stability and sealing performance of the stack. Meanwhile, excessive offset error leads to a sharp decrease in contact length and contact pressure at the sealing interface, which reduces the stability of the stack. With the increase of the operating temperature, the thermal expansion of the gasket increases and the contact performance improves significantly. Seals with rectangular structure have some advantages in terms of contact stability and standard deviation of contact pressure.

Effect of Water Adsorption on Lubricating Film Stability in Slippery Coatings.

The absorption of water by slippery coatings is a ubiquitous phenomenon that arises due to small but finite water dissolution during the contact of aqueous media with lubricants. In this study, using the concept of surface forces, we have analyzed the influence of trace amounts of water in lubricants on the stability of slippery coatings for both coatings with hydrophilic porous bases, prone to form hydrogen bonds with water, and those with hydrophobic porous bases. To perform such analysis, we have considered for the first time the electrostatic problem of the distribution of the electric potential and electric field strength in stratified films that contain two thin dielectric layers imitating the lubricant and a hydrophobic layer sandwiched between the porous substrate and air or water. Based on the developed approach, the equations for the calculation of the excess free energy and the disjoining pressure, associated with water dissolution in the lubricant film, were derived. An analysis of the excess film energy and the contribution of the image interaction to the disjoining pressure isotherm indicates that the dissolved water can both stabilize and destabilize the oil film, depending on the ratio of the static and dynamic dielectric permittivities of the lubricant and the phases confining the film. The results of calculations and simple experiments carried out here indicate much better water contact stability of silicone films impregnating a hydrophobized porous substrate than films impregnating a hydrophilic porous substrate. The obtained results indicate the preference for using the hydrophobic bases for the fabrication of long-lived slippery coatings characterized by better preservation of slippery functional properties under conditions of lubricant depletion and prolonged contact with water.