Mechanical Robustness Research Articles

SiO2/polydopamine photothermal superhydrophobic coating with good anti-icing performance

The icing phenomenon has become a safety hazard for the normal operation of equipment. In this work, we report a strategy for simply obtaining photothermal anti-icing coatings by spraying acrylic resin, polydimethylsiloxane and polydopamine modified SiO2 particles on a steel plate substrate. The prepared icephobic AR/PDMS/SiO2@PDA composite coating not only has excellent superhydrophobicity (WCA = 162°). It also shows good anti- and de-icing performances. The superhydrophobic surface was able to delay freezing for 614 s at −20°C, and the ice adhesion of its surface was 54 kPa. In addition, PDA-modified SiO2 particles endow the coating with photothermal properties. Under the irradiation of simulated sunlight, the photothermal coating rapidly reached 61°C within 3 min, and the ice droplets completely melted in 155 s. Besides, it's able to withstand a wide range of chemical attacks and mechanical impacts. After 15 icing-de-icing cycles and 40 sandpaper abrasions cycles test, the prepared coatings can still maintain remarkable ice-removal performance, demonstrating excellent mechanical robustness and stability in harsh environments.

Silicon dioxide incorporated cellulose acetate-mixed matrix membranes for Safranin-O removal from aqueous solutions.

Nanoparticle incorporated-mixed matrix membranes are renowned for their multifaceted advantages, including improved hydrophilicity, elevated solute rejection, enhanced mechanical robustness, and augmented chemical and thermal stability. The inherent hydrophilicity of silicon dioxide (SiO2) nanoparticles, due to silanol groups (Si-OH), along with their high porosity and surface area, renders them an ideal reinforcing filler within polymer matrices, significantly strengthening structural integrity of membranes. In this work, SiO2 nanoparticles were incorporated in a cellulose acetate (CA) matrix to prepare CA/SiO2 adsorptive membranes using phase inversion method. The performance of the membranes was assessed on the removal of Safranin-O (Sf-O) from aqueous solution. The physicochemical characterization of the synthesized membranes was assessed using contact angle, XRD, FE-SEM, EDS, FTIR, TGA, and tensile strength studies. The optimization studies on novel CA/SiO2 membrane revealed that the membrane with 2.5 wt.% of SiO2 in the CA matrix was the best in terms of Sf-O removal (approximately 100% dye removal) when the operating pH, initial dye concentration, and operating pressure were 9, 50 ppm, and 1 bar respectively. It is also found that 2.5 wt.% CA/SiO2 membrane has higher water permeability than other membranes. Incorporating SiO2 nanoparticles into a polymer matrix augments the structural, mechanical, and thermal properties of the resulting membranes while also enhancing water permeability, selectivity, and dye removal efficacy.

Micro-integrated crossed-beam optical dipole trap system with long-term alignment stability for mobile atomic quantum technologies

Quantum technologies extensively use laser light for state preparation, manipulation, and readout. For field applications, these systems must be robust and compact, driving the need for miniaturized and highly stable optical setups and system integration. In this work, we present a micro-integrated crossed-beam optical dipole trap setup, the µXODT, designed for trapping and cooling 87Rb. This fiber-coupled setup operates at 1064 nm wavelength with up to 2.5 W optical power and realizes a free-space crossed beam geometry. The µXODT precisely overlaps two focused beams (w0 ≈ 33 µm) at their waists in a 45° crossing angle, achieving a position difference of ≤3.4 µm and a 0.998 power ratio between both beams with long-term stability. We describe the design and assembly process in detail, along with optical and thermal tests with temperatures of up to 65 °C. The system’s volume of 25 ml represents a reduction of more than two orders of magnitude compared to typically used macroscopic setups while demonstrating exceptional mechanical robustness and thermal stability. The µXODT is integrated with an 87Rb 3D MOT setup, trapping 3 × 105 atoms from a laser-cooled atomic cloud, and has shown no signs of degradation after two years of operation.

Flexural Behavior of 3D-Printed Carbon Fiber-Reinforced Nylon Lattice Beams.

This study investigates the flexural behavior of 3D-printed multi-topology lattice beams, with a specific emphasis on octet and cube lattice geometries created through fused deposition modeling (FDM). The mechanical properties of these beams were evaluated through quasi-static three-point bending tests. A comparative analysis of load-carrying capacity, energy absorption, and specific energy absorption (SEA) indicates that octet lattice beams exhibit superior performance to cube lattice beams. The octet lattice beam in the triple-layer double-column (TL-DC) arrangement absorbed 14.99 J of energy, representing a 38% increase compared to the 10.86 J absorbed by the cube lattice beam in the same design. The specific energy absorption (SEA) of the octet beam was measured at 0.39 J/g, which exceeds the 0.29 J/g recorded for the cube beam. Two distinct types of deformations were identified for the struts and the beam layers. Octet struts exhibit enhanced performance in stretch-dominated zones, whereas the cube system demonstrates superior efficacy in compressive-dominated regions. The results highlight the enhanced efficacy of octet lattice structures in energy absorption and mechanical stability maintenance. The investigation of sandwich lattice topologies integrating octet and cube structures indicates that while hybrid designs may exhibit efficiency, uniform octet structures yield superior performance. This study provides valuable insights into the structural design and optimization of lattice systems for applications requiring high-energy absorption and mechanical robustness.

Tailoring ZrWNb-Based Refractory High Entropy Alloys: A Multidirectional Characterization Through Elemental, Physical, Thermodynamic, and Nuclear Radiation Attenuation Properties

This study explores the development and characterization of 18 novel ZrWNb[(X)(Y)] (where XY are Hf, Ta, Mo, V, Ti) refractory high entropy alloys (RHEAs) designed to enhance mechanical robustness, thermodynamic stability, and radiation shielding effectiveness. Through a rigorous analysis, we evaluated the elastic modulus, entropy, and enthalpy of mixing, atomic size difference, valence electron concentration, and the omega parameter to understand the alloys’ phase behavior and structural integrity. Our findings revealed a broad range of elastic modulus values, indicating diverse mechanical adaptability suitable for high-stress applications. The thermodynamic assessment highlighted several RHEAs with favorable phase stability, particularly ZrWNbTaHf and ZrWNbTiTaHf, which are poised for high-performance usage due to their balanced mixing entropy and enthalpy. This study also benchmarks the RHEAs against conventional alloys, with sample R1 exhibiting the lowest fast neutron effective removal cross section, underscoring its superior neutron shielding capabilities. Additionally, R1 demonstrated exceptional photon attenuation, as evidenced by its competitive half-value layer performance across an extensive energy spectrum. Collectively, these results position R1 as a standout candidate, offering a significant advancement in materials science for applications demanding stringent radiation shielding, such as in nuclear reactor environments and space exploration.

Ti3C2Tx-UHMWPE Nanocomposites-Towards an Enhanced Wear-Resistance of Biomedical Implants.

There is an urgent need to enhance the mechanical and biotribological performance of polymeric materials utilized in biomedical devices such as load-bearing artificial joints, notably ultrahigh molecular weight polyethylene (UHMWPE). While two-dimensional (2D) materials like graphene, graphene oxide (GO), reduced GO, or hexagonal boron nitride (h-BN) have shown promise as reinforcement phases in polymer matrix composites (PMCs), the potential of MXenes, known for their chemical inertness, mechanical robustness, and wear-resistance, remains largely unexplored in biotribology. This study aims to address this gap by fabricating Ti3C2Tx-UHMWPE nanocomposites using compression molding. Primary objectives include enhancements in mechanical properties, biocompatibility, and biotribological performance, particularly in terms of friction and wear resistance in cobalt chromium alloy pin-on-UHMWPE disk experiments lubricated by artificial synovial fluid. Thereby, no substantial changes in the indentation hardness or the elastic modulus are observed, while the analysis of the resulting wettability and surface tension as well as indirect and direct invitro evaluation do not point towards cytotoxicity. Most importantly, Ti3C2Tx-reinforced PMCs substantially reduce friction and wear by up to 19% and 44%, respectively, which was attributed to the formation of an easy-to-shear transfer film.

Ultrathin Copper Monosulfide Films for an Optically Semitransparent, Highly Selective Ammonia Chemosensor.

Transition-metal sulfides are emerging as promising materials for chemiresistive gas sensors─a field still dominated by semiconducting metal oxides. Despite the availability of materials with tunable electronic, optical, physical, and chemical properties, few studies have moved beyond synthesis to provide strategies for enhancing gas sensing performance through material modification. Here, we present a simple, scalable synthetic strategy for developing an optically semitransparent, flexible NH3 gas sensor with a highly uniform, ultrathin CuS (covellite) active sensing layer. The optical and chemical properties of the CuS were precisely controlled near the percolation threshold of thin-film formation by varying key experimental parameters such as the Cu film thickness (<10 nm) and the sulfurization time (∼90 s) under ambient conditions. Experimental and computational studies of CuS and its NH3 sensing characteristics identify key physicochemical properties. The controlled surface chemistry and morphology of the ultrathin CuS layer demonstrate its effectiveness in functional NH3 sensing devices, which achieve a calculated detection limit of 1.38 ppm for NH3 gas at 150 °C, along with exceptional mechanical robustness and optical semitransparency in the visible-light spectrum.

Electrospinning Aligned SF/Magnetic Nanoparticles-Blend Nanofiber Scaffolds for Inducing Skeletal Myoblast Alignment and Differentiation.

In the realm of skeletal muscle tissue engineering, anisotropic materials that emulate natural tissues show substantial promise. Electrospun scaffolds, mimicking the fibrillar structure of the extracellular matrix, are commonly employed but often fall short in achieving optimal alignment and mechanical strength. Silk fibroin has emerged as a versatile material in tissue engineering, valued for its biocompatibility, mechanical robustness, and biodegradability. However, conventional electrospinning methods of SF result in randomly oriented fibers, limiting their efficacy. In this work, we developed a straightforward method to fabricate directional tissue scaffolds using silk fibroin. By integrating a magnetic field collecting device and incorporating Fe3O4 nanoparticles into the spinning solution, we successfully produced well-aligned silk nanofiber scaffolds. These aligned fibers not only improved scaffold orientation and mechanical properties but also exhibited magnetic responsiveness. The aligned SF scaffolds effectively guided the adhesion, proliferation, and differentiation of mesenchymal stem cells along the fiber direction. Cultured on these scaffolds, myoblast C2C12 cells demonstrated oriented growth, highlighting the potential of aligned SF fibers in advancing skeletal muscle engineering for biomedical applications.

Ultra-Thin Highly Sensitive Electronic Skin for Temperature Monitoring.

Electronic skin capable of reliable monitoring of human skin temperature is crucial for the advancement of non-invasive clinical biomonitoring, disease diagnosis, and health surveillance. Ultra-thin temperature sensors, with excellent mechanical flexibility and robustness, can conformably adhere to uneven skin surfaces, making them ideal candidates. However, achieving high sensitivity often demands sacrificing flexibility, rendering the development of temperature sensors combining both qualities a challenging task. In this study, we utilized a low-cost drop-casting technique to print ultra-thin and lightweight (thickness: approximately 3 µm, weight: 0.61 mg) temperature sensors based on a combination of vanadium dioxide and PEDOT:PSS at room temperature and atmospheric conditions. These sensors exhibit high sensitivity (temperature coefficient of resistance: -5.11%/°C), rapid response and recovery times (0.36 s), and high-temperature accuracy (0.031 °C). Furthermore, they showcased remarkable durability in extreme bending conditions (bending radius = 400 µm), along with stable electrical performance over approximately 2400 bending cycles. This work offers a low-cost, simple, and scalable method for manufacturing ultra-thin and lightweight electronic skins for temperature monitoring, which seamlessly integrate exceptional temperature-measuring capabilities with optimal flexibility.

Theoretical investigation on crash performance of bamboo-inspired energy absorption systems based on systematic experimental and numerical analysis

The need for energy-absorbing devices with adaptable crashworthiness is increasingly urgent in various engineering fields with diverse load environments. For this aim, bamboo-inspired modular energy absorption systems have recently been proposed to integrate mechanical efficiency, tunability, and robustness. However, their mechanical responses under varying load velocities have not been systematically studied, which limits the effective prediction and optimization of their crashworthiness. In this study, quasi-static and dynamic experiments were performed on bamboo-inspired systems, discretely assembled using 3D printed steel tube specimens. Matched finite element simulations were conducted using ABAQUS/Explicit. Specific energy absorption and efficiency of these systems respectively exceeded 12.9 J/g and 47 %, surpassing existing discretely assembled systems and rivaling typical cellular materials. Efficient deformation mode with self-locking capability was observed, and sharp impact peak was avoided when the crash velocity was less than 50 m/s. Building upon these findings, a modified spherical shell theory under crashing was developed to predict energy absorption performance of bamboo-inspired system based on the traveling plastic hinge model. The average relative error between the analytical solution and finite element results was found less than 6.5 %. The mean effective stress of the system could exceed 35 MPa under thickness-to-diameter ratio of 5 %. This work presents an efficient and effective approach for optimizing and estimating the crash performance of modular protective devices.

Synergistic Dual-Cross-Linking Gelation: Exploring the Impact of Metal-Ligand Complexation on Ionogel Performance.

Owing to the growing interest in wearable ionotronics, the demand for ionogels with outstanding mechanical and electrochemical characteristics has increased dramatically. Nevertheless, it remains challenging to simultaneously enhance the mechanical robustness and conductivity of ionogels because of their trade-off relationship. In this work, we propose physically/chemically dual-cross-linked ionogels designed to improve the mechanical strength without reducing ionic conductivity by introducing metal-ligand complexation only within the physically cross-linked domains. In particular, the impact of metal-ligand complexation, a crucial parameter in this strategy, on ionogel performance is systematically examined using various metal ions. The mechanical resilience and thermal stability of ionogels are effectively enhanced with Co3+ having the highest coordination number, which can be explained by the highest metal-ligand complexation (i.e., chemical cross-linking) density. Additionally, there is no degradation in ionic conductivity when compared to the pristine ionogel because these complexations occur within physically cross-linking domains that are irrelevant to the ion conductive channels. The dual-cross-linked ionogels are successfully applied to alternating-current electroluminescent displays (ACEDs). Moreover, a versatile mixed-emitter strategy is suggested to improve practicality, enabling the realization of frequency-controlled multicolor ACEDs.

Agile robotic fish based on direct drive of continuum body

Fish-like agile movements, such as fast swimming and rapid turning, are essential for biomimetic underwater robots but challenging to achieve simultaneously. We present a self-contained robotic fish capable of swimming at a speed of 6.3 body length per second and pivot turning at an angular speed of 1450° per second. These fast motions, comparable to real fish, are realized by directly oscillating a flexible body using an electromagnetic motor, eliminating the need for transmission parts and simplifying the structure. This direct-drive (DD) method improves mechanical robustness and generates fish-like deformations and subsequent rapid swimming. The Strouhal and swimming numbers of the robot match typical values observed in nature. Moreover, the observed frequency peaks in swimming are similar to computed values using a model, which guides the design of the robot. These results illustrate the DD method as a promising framework for the creation of highly versatile biomimetic underwater robots.

Hierarchically‐Interlocked, Three‐Axis soft Iontronic Sensor for Omnidirectional Shear and Normal Forces

AbstractArtificial tactile sensing capable of measuring shear and normal forces is crucial for the diverse human‐machine interactions and dexterous robotic manipulations. However, existing soft multi‐axis force sensors usually suffer from limited detectable directions and complex coupling mechanisms, limiting their applications in realistic wearable and robotic systems. Here, a hierarchically‐interlocked, three‐axis soft iontronic sensor is presented with an asymmetrical electrode pattern that leverages the mortise‐and‐tenon structure and ultracapacitive principle to detect omnidirectional shear and normal forces. The designed sensor facilitates the decoupling process and achieves enhanced sensing performances including high accuracy, fast response ability, and mechanical robustness. Prototypical integration and application of the sensor are demonstrated to perform wearable telecontrol of virtual platforms and assist robot gripper through closed‐loop force feedback. A sensing array is further developed to construct a touch panel and identify handwriting based on the continuously measured directions of applied forces. This work may offer a potentially promising solution for the next‐generation intelligent electronic skins requiring multimodal tactile sensing information.

Robust conductive hydrogel advances self-powered intelligent sports monitoring and fair judging

Currently, combining multimodal perceptual ability with mechanical robustness poses a significant challenge for developing hydrogel-based flexible electronics. Herein, a robust conductive hydrogel was successfully synthesized by introducing cellulose nanocrystals (CNC) as nanofillers and lithium chloride (LiCl) as the conductive component into the copolymer network through a one-pot crosslinking procedure in a water-dimethyl sulfoxide binary solvent. Besides excellent stretchable, self-adhesive, anti-freezing, self-healing, and anti-swelling properties, tunable and reversible optical property was realized due to the polarity-induced microphase separation of the hydrophilic and hydrophobic group in the zwitterionic sulfobetaine chains, enabling cyclic information encryption and decryption. An all-weather wearable sensor array was thus developed for multi-modal sensing of various environmental stimuli, including mechanical, and thermal variations. Specifically, the intensity and spatial distribution of strain can be detected almost in real time within a broad strain range, thus realizing speech recognation, text-to-speech and human electrocardiogram signal acquisition and underwater non-contact sensing functions. Notably, the CPAMD-based triboelectric nanogenerator demonstrates impressive temperature tolerance (−40 °C and 60 °C), and remarkable material identification capability. A non-contact proximity sensing sensor and a foul detection system were thus developed by coupling the piezoresistive, triboelectric and capacitive sensing metrics to serve as an electronic referee for identifying foul in curling. This work provides a valuable reference toward combining excellent mechanical robustness with balanced electrical performance for tactile perception and intelligent sports monitoring.

Utilization of the Resonance Behavior of a Tendon-Driven Continuum Joint for Periodic Natural Motions in Soft Robotics

Continuum joints use structural elastic deformations to enable joint motion, and their intrinsic compliance and inherent mechanical robustness are envisioned for applications in which the robot, the human, and the environment need to be safe during interaction. In particular, the intrinsic compliance makes continuum joints a competitor to soft articulated joints, which require additional integrated spring elements. For soft articulated joints incorporating rigid and soft parts, natural motions have been investigated in robotics research to exploit this energy-efficient motion property for cyclic motions, e.g., locomotion. To the best of the author’s knowledge, there is no robotic system to date that utilizes the natural motion of a continuum joint under periodic excitation. In this paper, the resonant behavior of a tendon-driven continuum joint under periodic excitation of the torsional axis is experimentally investigated in a functional sense. In the experiments, periodic inputs are introduced on the joint side of a tendon driven continuum joint with four tendons. By modulating the pretension of the tendons, both the resonant frequency and the gain can be shifted, from 3 to 4.3 Hz and 2.8 to 1.4, respectively, in the present experimental setup. An application would be the rotation of a humanoid torso, where gait frequencies are synchronized with the resonant frequency of the continuum joint.

Effect of Ta–TiO2 Nanoparticles in Anion Exchange Membranes: Improved Hydroxide Ion Conductivity and Mechanical Strength for Alkaline Water Electrolysis Cells

AbstractTo improve the properties of quaternized QPAF‐4 copolymers as anion exchange membranes, compositing with hydrophilic Ta–TiO2 particles are investigated. Flexible QPAF‐4/Ta–TiO2 composite membranes are obtained using solution‐casting and die coating methods. Cross‐sectional scanning electron microscopy reveals that the die coating method produces a more homogenous and uniform distribution of Ta–TiO2 particles in the composite membranes than the solution‐casting method. The Ta‐TiO2 particles promotes the suppression of water absorbability and dimensional swelling of the composite membranes which is more pronounced in the die coated membranes. The Ta–TiO2 increase hydroxide ion conductivity to 116.9 mS cm−1 at 80 °C for the die‐coated membrane, surpassing that of the pristine QPAF‐4 membrane (92 mS cm−1). Ta–TiO2 with the composite membranes survive in 4 m KOH at 80 °C for 1000 h, maintaining 96–112 mS cm−1 (88–99% remaining) of initial conductivity. All composite membranes exhibit higher mechanical robustness (elongation of &gt;200%), with the die‐coated composite membranes. The optimized die coated composite membrane is fabricated in an alkaline water electrolysis cell achieving 1.63 V at 1.0 A cm−2 (75.5% efficiency).

Breathable and Stretchable Epidermal Electronics for Health Management: Recent Advances and Challenges.

Advanced epidermal electronic devices, capable of real-time monitoring of physical, physiological, and biochemical signals and administering appropriate therapeutics, are revolutionizing personalized healthcare technology. However, conventional portable electronic devices are predominantly constructed from impermeable and rigid materials, which thus leads to the mechanical and biochemical disparities between the devices and human tissues, resulting in skin irritation, tissue damage, compromised signal-to-noise ratio (SNR), and limited operational lifespans. To address these limitations, a new generation of wearable on-skin electronics built on stretchable and porous substrates has emerged. These substrates offer significant advantages including breathability, conformability, biocompatibility, and mechanical robustness, thus providing solutions for the aforementioned challenges. However, given their diverse nature and varying application scenarios, the careful selection and engineering of suitable substrates is paramount when developing high-performance on-skin electronics tailored to specific applications. This comprehensive review begins with an overview of various stretchable porous substrates, specifically focusing on their fundamental design principles, fabrication processes, and practical applications. Subsequently, a concise comparison of various methods is offered to fabricate epidermal electronics by applying these porous substrates. Following these, the latest advancements and applications of these electronics are highlighted. Finally, the current challenges are summarized and potential future directions in this dynamic field are explored.

Strengthening Transformer Tank Structural Integrity through Economic Stiffener Design Configurations Using Computational Analysis

Power transformers play a vital role in adjusting voltage levels during transmission. This study focuses on optimizing the structural design of power transformer tanks, particularly high-voltage (HV) tank walls, to enhance their mechanical robustness, performance, and operational reliability. This research investigates various stiffener designs and their impact on stress distribution and deformation through finite element analysis (FEA). Ten different configurations of stiffeners, including thickness, width, type, and position variations, were evaluated to identify the optimal design that minimizes stress and deflection while considering weight constraints. The results indicate that specific configurations, particularly those incorporating 16 mm thick H beams, significantly enhance structural integrity. Experimental validation through pressure testing corroborated the simulation findings, ensuring the practical applicability of the optimized designs. This study’s findings have implications for enhancing the longevity and reliability of power transformers, ultimately contributing to more efficient and resilient power transmission systems.

Organic polymer composite with inorganic SiO2 particles for mechanical robustness and self-cleaning anti-reflective coatings

Anti-reflective coatings prepared from SiO2 nanoparticles have excellent anti-reflective properties, but the coating's poor mechanical properties and low self-cleaning performance limit its practical application. In this work, SiO2 nanoparticles were modified into hydrophobic particles using surface modification, and then organic polymer were added as a binder to formulate SiO2 sols, which were coated onto a glass substrate to form a anti-reflective coating. The coating can enable the glass substrate to achieve a transmittance of 99.1 % at 580 nm, and it can increase the average transmittance of the glass substrate from 89.6 % to 96.2 % in the 400–1100 nm band. In addition, the coatings prepared from hydrophobic SiO2 nanoparticles composite organic polymers have a water contact angle of 136°, resulting in good self-cleaning properties. The organic polymers can connect the SiO2 nanoparticles together, increasing the mechanical properties of the coating. This multifunctional anti-reflective coating with high transmittance, good mechanical properties and self-cleaning is beneficial in many applications, such as photovoltaic glass, architectural glass, displays and more.

Four-Dimensional Printing of Multi-Material Origami and Kirigami-Inspired Hydrogel Self-Folding Structures.

Four-dimensional printing refers to a process through which a 3D printed object transforms from one structure into another through the influence of an external energy input. Self-folding structures have been extensively studied to advance 3D printing technology into 4D using stimuli-responsive polymers. Designing and applying self-folding structures requires an understanding of the material properties so that the structural designs can be tailored to the targeted applications. Poly(N-iso-propylacrylamide) (PNIPAM) was used as the thermo-responsive material in this study to 3D print hydrogel samples that can bend or fold with temperature changes. A double-layer printed structure, with PNIPAM as the self-folding layer and polyethylene glycol (PEG) as the supporting layer, provided the mechanical robustness and overall flexibility to accommodate geometric changes. The mechanical properties of the multi-material 3D printing were tested to confirm the contribution of the PEG support to the double-layer system. The desired folding of the structures, as a response to temperature changes, was obtained by adding kirigami-inspired cuts to the design. An excellent shape-shifting capability was obtained by tuning the design. The experimental observations were supported by COMSOL Multiphysics® software simulations, predicting the control over the folding of the double-layer systems.