Stick-slip is typically associated with high friction and wear, whereas superlubricity is characterized by ultralow friction and negligible wear. Can these two seemingly opposite phenomena coexist? Here, we present an experimental observation of stick-slip behavior that exhibits structural superlubric characteristics, in a microscale single-crystalline Au mesa sliding against a single-crystalline graphite substrate. This behavior emerges when the applied sliding velocity falls below a critical threshold. Unlike traditional ones, this observed stick-slip phenomenon originates from the inherently superlubric Au/graphite interface and exhibits key structural superlubric features: near zero coefficient of friction and wear-free long-distance sliding. Theoretical analysis attributes this duality to the distinctive nature of Au/graphite interface: a globally atomically flat incommensurate van der Waals interface, yet locally weakly pinned by discrete point vacancy defects. Bond formation and rupture at these sites underpin the static-dynamic friction asymmetry that drives stick-slip. These findings not only deepen our understanding of stick-slip and structural superlubricity, but also open pathways for stable, long-lasting control of superlubric interfaces in micro/nanoscale actuators and sensors.

Intelligent tire systems enable real-time measurement of tire forces, offering new opportunities for improving vehicle state estimation. This paper proposes a state estimation approach that integrates longitudinal, lateral, and vertical tire force information obtained from a PVDF-based intelligent tire system. An optimal in-tire sensor layout is determined using global sensitivity analysis, and tire forces are estimated from in-tire voltage signals via Gaussian Process Regression. To effectively utilize the estimated forces, a tire force update frequency compensation strategy and a vehicle parameter estimation method are incorporated into an adaptive cubature Kalman filter framework. Simulation and experimental results demonstrate that the proposed approach significantly improves the accuracy of vehicle speed and sideslip angle estimation and enhances robustness against variations in vehicle and tire parameters, including tire-road friction.

Artificial neural network (ANN) techniques have emerged as powerful data-driven tools for their effectiveness in analysis, modeling, and simulation. These supervised learning approaches are designed to reduce the error between predicted and observed data, providing accurate approximations of complex physical systems. To improve training performance, the Levenberg-Marquardt algorithm (LMA) is widely adopted due to its fast convergence and suitability for nonlinear problems. The objective of this study is to develop an ANN-based computational framework using the LMA to accurately predict the flow and heat transfer characteristics of an MHD nanofluid over a thin needle based on Buongiorno's model. The novelty of the present work lies in applying an ANN-based predictive framework to the Buongiorno nanofluid model over a moving thin needle, which has received limited attention in the existing literature. The impacts of transverse magnetic field, Brownian motion, and thermophoresis are contained in the mathematical model. The governing equations for fluid flow are converted to ordinary differential equations (ODEs) and numerically solved. The results are also predicted by using Artificial Neural Networks (ANNs) techniques. The effect of physical parameters like magnetic parameter ( M ), Prandtl number ( Pr ), thermophoresis parameter ( Nt ), Brownian motion parameter ( Nb ), and Schmidt number ( Sc ) on velocity, temperature and concentration profiles are explored. The outcomes indicate that the velocity of the fluid decreases with the upsurge of the magnetic parameter while the temperature increases. Higher values of Pr and Sc reduce the temperature and concentration profiles, correspondingly. The Brownian motion parameter boosts the temperature but lowers the concentration, while the thermophoresis parameter rises both temperature and concentration. It is also observed that the magnetic field increases the skin friction coefficient but decreases the heat and mass transfer rates. The ANN results are very close to the numerical results, showing that ANN is an accurate and reliable method for predicting complex nanofluid flow problems.

To address the balance between reactivity and safety in nano-HNS, this study presents a green composite molding strategy that facilitates the self-assembly of nano-HNS into micro-nano-structured microspheres within confined spaces. This approach utilizes confined spaces to precisely control the morphology and size of the resultant microspheres. The effects of process parameters on the morphology and size of microspheres were systematically investigated, and the underlying formation mechanisms were elucidated. Comprehensive characterizations encompassing morphology, crystal structure, mechanical sensitivity, thermal behavior, and impact properties were conducted. The results demonstrate that the synthesized HNS microspheres possess high sphericity, an average particle size of 224.2 µm, and exhibit favorable fluidity and bulk density. This approach effectively reduces the mechanical sensitivity of the material while preserving the crystal structure and thermal stability of HNS-IV (impact sensitivity: 12 J vs. 20 J; friction sensitivity: 216 N vs. 240 N). Furthermore, it enhances the initial sensitivity to short duration shock, as evidenced by reductions in the 50% and 99.9% initiation voltages by 18 and 48 V, respectively. This approach facilitates the synergistic stimulation of selective sensitization and passivation. This methodology is straightforward and applicable, providing a versatile and eco-friendly approach for the multi-structural modification of nano-HNS.

A unified constitutive framework is developed for dense fine-granular mixtures exhibiting apparent shear thinning and continuous or discontinuous shear thickening in the macro-viscous flow regime. The effective granular stress is decomposed into viscoplastic structural and suspension-stress contributions. The former is obtained from a hypoplastic model combined with a Herschel-Bulkley rheology, whereas the latter encompasses the μ (I m) rheology and the Wyart-Cates frictional-contact transition, and shows stress-dependent jamming state. Benchmark calculations show that the proposed formulation captures the transition between shear-thinning and shear-thickening behaviour. A depth-averaged long-wave analysis further shows that non-monotonicity induced by discontinuous shear thickening may persist to promote instability in the macro-viscous flow regime.

Liquid crystalline elastomers (LCEs) are soft materials capable of large, reversible deformations in response to external stimuli, making them promising alternatives to rigid actuators where compliance and untethered motion are crucial. However, adoption of LCEs in real-world systems has been hindered by the lack of practical modeling techniques that describe their functional behavior. Here, we present an analytical continuum framework based on decomposition of the actuation and elastic strains. Paired with existing hyperelastic models, this decomposition yields closed-form constitutive expressions which describe LCE behavior over a broad range of operating conditions. We experimentally validate the framework by showing it successfully predicts the stress state of an LCE across a variety of actuation sequences with low bias and error, indicating path independence for processes where elasticity dominates behavior. We further demonstrate the framework's flexibility by applying it to LCE fibers of different chemistry, and to a fiber having a complex hierarchical architecture; a capability crucial to employing LCE actuators in practical systems. Finally, we illustrate the utility of the resulting closed-form solutions through two design applications: quantitatively determining the coefficient of friction for a low-friction material, and a qualitative procedure for designing an LCE-actuated bistable mechanism. This work provides designers and researchers in soft robotics, microactuators, and compliant systems with a practical, rapidly deployable framework for characterizing and comparing thermoactive soft actuators.

Diabetic non‑healing wounds pose a clinical challenge due to persistent inflammation, dysregulated immunity, and poor integration of dressings with the skin. Conventional hydrogel dressings have proven effective in providing physical barriers, moisture retention, and local drug delivery. Further optimization is still feasible for precise immune regulation and dynamic skin interfacial matching. In non-healing wound therapy, enantiomerically defined chiral hydrogels have emerged as a promising platform for targeted immune remodeling. By selectively steering macrophage polarization from pro-inflammatory M1 to pro-healing M2, they facilitate a smooth inflammatory-to-proliferative transition and accelerate wound closure. With rational network design, chiral hydrogels achieve favorable interfacial compatibility with the moist, dynamic wound environment, supporting cell adhesion, reducing friction induced microtrauma, sustaining bioactive signal delivery, and avoiding overt foreign body reactions. By integrating chiral topography, biomimetic mechanical properties, and moderate tissue adhesion, these hydrogels help establish an "immune-friendly" dermal interface. This review discusses structure-activity relationships linking chiral chemistry to immune cell behavior and outlines design principles for clinically translatable wound dressings. Collectively, chiral hydrogels that synergistically remodel immune microenvironment and ensure skin compatibility could redefine diabetic wound therapy, enabling a new paradigm of precision, immune‑instructive the wound management that transcends conventional dressing functions.

This study investigates the effectiveness of bio-inspired barbed geometries applied to curved needles for percutaneous procedures. The geometries of insect stingers, such as honeybees and mosquitoes, have been applied to straight needles to reduce insertion forces, tissue deformation, and tissue damage during linear insertion. However, whether these benefits extend to curved needles undergoing curvilinear base manipulation remains unclear. In this study, mosquito-inspired barb geometry was adapted onto bevel-tip curved needles with bent angles of 7.5°, 15°, 22.5°, and 30°. The effect on transverse and axial insertion forces, bending moments, and needle-tip trajectories was evaluated. The regular and bio-inspired curved needles were fabricated using high-resolution 3D printing and tested in tissue-mimicking gel under curvilinear insertion. Force and moment data were recorded at the needle base, and the needle tip paths were quantified using radius of curvature analysis from video tracking. No statistically significant reductions were found in insertion forces or bending moments under curvilinear insertion. These findings suggest that, for curved needles following predefined trajectories under the tested conditions, the measured forces did not change significantly with the addition of barbed surface features under curvilinear insertion. This suggests that the tested surface modification does not substantially alter the overall mechanical response under these conditions. This work highlights that friction-reducing surface features effective in linear insertion may not directly translate to curvilinear insertion, and that optimization strategies for curved needle applications may benefit from prioritizing geometric and trajectory-based design considerations.

In the human cardiovascular system, the flow of fluid through blood vessels is important in many biological and biomedical fields. Stenosis & thrombosis are vascular disorders that can block many blood vessels. To clear constrictions in an artery, various types of catheters are used, which generate frictional forces between the clot's wall and the catheter. This paper presents an analysis of blood flow and heat transfer during the initial phase of axisymmetric stenosis and thrombosis in a vessel containing a catheter. Blood's rheological behaviour is described by a non-Newtonian K-L fluid model. In the proposed model, the nonlinear momentum equation is simplified under various assumptions to find an analytical solution. Exact solutions are obtained using boundary conditions. The novelty of this work is that the velocity & temperature profile has not yet been analysed in conjunction with stenosis, thrombosis, and catheter presence, using the non-Newtonian K-L fluid model. An explicit expression for velocity, temperature, and flow resistance has been obtained. The obtained results have been shown for flow characteristics through graphs for various values of stenosis height, clot height, plasma viscosity, and different catheter radii. The highest velocity is found at the centre and diminishes at the wall. Velocity decreases as the constriction height increases. It is observed that using a larger radius catheter, velocity quickly decreases in the core compared with the central region due to the narrowing of the flow passage area. The temperature of the fluid increases in a stenotic artery with thrombosis in the presence of the catheter, and also increases as the radius of the catheter increases.

Gastrointestinal fluid sampling plays a pivotal role in early detection of gastrointestinal diseases, yet conventional methods are invasive, uncomfortable, and susceptible to sample contamination. Here, we developed a self-driven superlubricated capsule (GFSCap) that achieved autonomous gastric fluid sampling and sealing. A chemical-fluidic-mechanical cascade was implemented, in which dissolution of a trigger film opened the sampling pathway, while a mechanically precompressed collector facilitated fluid uptake. Subsequently, hydrogel swelling drove a piston to close the sampling channels and retain the collected sample. Furthermore, the capsule surface was modified with a superlubricated copolymer, which substantially reduced interfacial friction and cell adhesion. Under in vitro conditions, the GFSCap collected approximately 230 mg of simulated gastric fluid within 30 min, while the proof-of-concept in vivo experiment in an anesthetized pig yielded approximately 127 mg of native gastric fluid. Simulated esophageal retrieval experiments showed that the sealed capsule retained most of the collected sample. Additionally, DNA recovery remained above 93.8% after exposure to individual GFSCap material extracts and reached 98.7% after exposure to combined material extracts, supporting the compatibility of the GFSCap material system with representative downstream nucleic acid analysis. Overall, the GFSCap provided a self-driven platform integrating gastric fluid sampling, sealing, lubrication, and controllable retrieval.

Tissue adhesion and thermal injury remain major challenges in high-frequency electrosurgery because carbonized residues can accumulate on the electrode surface and reduce cutting stability. To address this issue, a coating-free bio-inspired electrosurgical knife was designed and fabricated from 316L stainless steel by selective laser melting. Inspired by loach-skin lubrication and anti-fouling characteristics, a porous-groove blade surface was designed for lubricant storage and transport. Inspired by crab-chela serrations, a micro-serrated cutting edge was introduced to reduce cutting resistance. Fluid-flow simulation showed that the porous-groove surface promoted lubricant retention and local recirculation, reducing near-wall resistance by up to 20.73%. Friction tests indicated that Dp = 350 μm and Lp = 800 μm produced the lowest lubricated friction coefficient of 0.362 among the tested porous-groove surfaces. Static cutting simulation and cutting-force tests confirmed that the micro-serrated edge reduced cutting resistance, with the lowest peak cutting force of approximately 0.605 N obtained at H1 = 300 μm. Powered electrosurgical tests showed that the sample with Dp = 350 μm, Lp = 800 μm, and H1 = 300 μm achieved the lowest apparent adhesion mass of 2.07 ± 0.67 mg, corresponding to a 61.5% reduction compared with the DT401 commercial smooth control electrode. The thermal damage areas on the upper and lateral tissue surfaces were reduced by 56.75% and 54.44%, respectively. These results demonstrate an effective engineering strategy for improving the anti-adhesion and thermal-safety performance of electrosurgical knives.

BACKGROUND: Falls are a leading cause of morbidity, functional decline, and premature care entry among older adults. Assistive living technologies (ALTs) are increasingly used for fall prevention, detection, and risk monitoring, but their value depends on how older adults, caregivers, and care staff experience them in practice.

NiP-graphene oxide (GO) composite coatings were fabricated by ultrasonic-assisted pulse electrodeposition using a horn-type ultrasonic processor operating at 20 kHz and equipped with an 8 mm-diameter titanium probe. The non-sonicated condition was designated as 0 W, while nominal generator power readings of approximately 50 and 100 W were obtained under the selected sonication conditions; the corresponding calorimetric power dissipated in 400 mL of electrolyte was determined experimentally. The calorimetric powers measured at nominal settings of 50 and 100 W were 34.67 and 49.64 W, corresponding to volumetric power densities of 0.0867 and 0.1241 W mL[-][1], respectively. The effects of acoustic energy input and GO concentration on coating morphology, crystallographic structure, hardness, tribological behavior, and corrosion resistance were systematically evaluated using FESEM, EDS, Raman spectroscopy, XRD, microhardness testing, ball-on-disc wear testing, potentiodynamic polarization, and electrochemical impedance spectroscopy. Increasing the calorimetric power density promoted cavitation-assisted mass transport, GO deagglomeration, heterogeneous nucleation, and hydrogen-bubble removal from the cathode surface. Consequently, the crystallite size decreased from 33.8 to 24.5 nm, while the hardness increased from 623 to 679 HV. Further optimization of the GO concentration revealed that the coating produced with 300 mg L[-][1] GO at a nominal ultrasonic power of 100 W exhibited the highest hardness of approximately 704 HV, together with the lowest coefficient of friction, wear rate, and corrosion current density. The optimized coating was subsequently tested under different normal loads and sliding speeds, and a wear-mechanism map was constructed to identify transitions among mild abrasive wear, abrasive-fatigue wear, and oxidation-assisted delamination. These findings establish a quantitative acoustic energy-microstructure-property relationship and demonstrate the potential of ultrasonic-assisted pulse electrodeposition for producing NiP-GO composite coatings with enhanced wear and corrosion resistance.