Low Young Modulus Research Articles

Investigating the Tribological Properties of the High-Hardness, Low-Young's-Modulus 60NiTi Alloy: A Combined FEM Simulation and Experimental Study

ABSTRACT This study investigates the tribological properties of the 60NiTi alloy, known for its high hardness and low Young's modulus, using a combination of finite element method (FEM) simulations and experimental analysis. A discrete modified Archard model was employed to establish a FEM of a 60NiTi plate paired with a Si3N4 ball, with CSS-42L bearing steel serving as the comparison material. The analysis focused on stress distribution, wear depth, and wear rate to assess the suitability of 60NiTi as a bearing material. The FEM results indicated that, under a 30N load, the peak stress in 60NiTi was reduced by 22.7% compared to CSS-42L, demonstrating the alloy's superior load-bearing capacity. Post-experimentation, both surface and subsurface hardness of the 60NiTi alloy increased, aligning with the stress distribution predicted by FEM, thereby confirming the model's accuracy and reliability. This study highlights the potential of 60NiTi alloy for applications requiring robust wear resistance and stress management under varying load conditions.

Enhancing the Pressure-Sensitive Electrical Conductance of Self-Assembled Monolayers.

The inherent large HOMO-LUMO gap of alkyl thiol (CnS) self-assembled monolayers (SAMs) has limited their application in molecular electronics. This work demonstrates significant enhancement of mechano-electrical sensitivity in CnS SAMs by external compression, achieving a gauge factor (GF) of approximately 10 for C10S SAMs. This GF surpasses values reported for conjugated wires and DNA strands, highlighting the potential of CnS SAMs in mechanosensitive devices. Conductive atomic force microscopy (cAFM) investigations reveal a strong dependence of GF on the alkyl chain length in probe/CnS/Au junctions. This dependence arises from the combined influence of molecular tilting and probe penetration, facilitated by the low Young's modulus of alkyl chains. Theoretical simulations corroborate these findings, demonstrating a shift in the electrode Fermi level toward the molecular resonance region with increasing chain length and compression. Introducing a rigid graphene interlayer prevents probe penetration, resulting in a GF that is largely independent of the alkyl chain length. This highlights the critical role of probe penetration in maximizing mechano-electrical sensitivity. These findings pave the way for incorporating CnS SAMs into mechanosensitive and mechanocontrollable molecular electronic devices, including touch-sensitive electronic skin and advanced sensor technologies. This work demonstrates the potential of tailoring mechanical and electrical properties of SAMs through molecular engineering and interface modifications for optimized performance in specific applications.

Heterogeneous dynamic restoration of Ti–15Mo alloy during hot compression

Near-β titanium alloys have shown low Young's modulus and good strength, making them excellent implant candidates. However, their processing using thermomechanical routes in single phase β region results in heterogeneous microstructures due to high content alloying elements and consequent slow diffusion-controlled processes such as dynamic recovery. This study investigates the deformation behaviour of a Ti–15Mo alloy through hot compression experiments using a Gleeble ® 3800 device in the single β domain at strain rates from 0.01 s−1 to 10 s−1, reaching final strains of 0.50 and 0.85 followed by immediate water quench. The findings show that the material presents a low strain rate sensitivity. The flow curves show significant strain hardening before reaching a steady-state regime, particularly at high strain rates. The strain hardening exponent calculations support the effect of molybdenum on retarding softening mechanisms such as dynamic recovery. Electron backscatter diffraction (EBSD) measurements of deformed samples revealed that dynamic recovery is the primary restoration mechanism, with continuous and geometric dynamic recrystallisation evidence. Due to the slow restoration process, we observe the subgrain formation for different deformation parameters. Therefore, we introduced an EBSD-based method to quantify dynamic recovery and subgrain size. We concluded that for a given deformation, the areas of dynamically recovered and recrystallised regions decrease with increasing strain rate and decreasing temperature, exhibiting negligible variation at higher strain rates.

Electrical Tissue Adhesives for Strain‐Insensitive In‐situ Biosensing

In‐situ biosensing, a rapidly evolving field that focuses on the development of biosensors capable of on‐site detection of biomolecules directly from local tissue regions, holds the potential to revolutionize medicine through real‐time monitoring, personalized diagnosis, and targeted therapies. However, interfacing rigid, nonstretchable biosensors with soft, deformable tissues presents significant challenges due to their fundamentally contradictory properties. Herein, an electrical tissue adhesive featuring an entangled adhesive polymer network interpenetrated with a sacrificial dissipative polymer network is developed, which can rapidly and robustly adhere electrochemical biosensors with biological tissues, enabling strain‐insensitive physiological monitoring. The electrical tissue adhesive achieves a high fracture toughness of up to 3000 J m−2, a low Young's modulus of around 20 kPa, superior stretchability up to 15 times its initial length, and an overall biosensor‐tissue interfacial toughness of up to 500 J m−2. Using an electrochemical glucose sensor as one example, it is demonstrated that the electrical tissue adhesive can maintain resilient glucose sensing under various stress states and stretch levels. Additionally, the application of the electrical tissue adhesive for in‐situ monitoring of exercise and diet in subjects with various BMIs is demonstrated by measuring glucose concentration in sweat.

Enhancement of {110}<001> Texture by Controlling α‐phase and Achievement of Low Young's Modulus and High Strength in Metastable β‐type Ti–Zr‐Based Alloys

Achieving both low Young's modulus and high strength, which are essentially in a trade‐off relationship, is an important challenge in the field of biomaterials. Herein, the effects of oxygen and nitrogen addition on mechanical properties and recrystallization texture of a metastable Ti–18Zr–3Nb–3Sn–2Mo alloy are investigated. Both oxygen and nitrogen additions increase the apparent yield stress and tensile strength. The N‐added alloy exhibits an exceptionally strong {110}<001> texture, commonly referred to as Goss texture, leading to a lower Young's modulus when compared with the O‐added alloy. It is found that the formation and subsequent dissolution of the α‐phase plays an important role in the development of recrystallization texture. The {110}<001> texture can be enhanced in the O‐added alloy by a two‐step heat treatment, the first step to form the α‐phase and the second step to dissolve the α‐phase during recrystallization. An excellent combination of a low Young's modulus and a high yield stress is achieved in the O‐added alloy subjected to the two‐step heat treatment.

Versatile Light-Mediated Synthesis of Degradable Bottlebrush Polymers Using α-Lipoic Acid.

Bottlebrush polymers have a variety of useful properties including a high entanglement molecular weight, low Young's modulus, and rapid kinetics for self-assembly. However, the translation of bottlebrushes to real-world applications is limited by complex, multi-step synthetic pathways and polymerization reactions that rely on air-sensitive catalysts. Additionally, most bottlebrushes are non-degradable. Herein, we report an inexpensive, versatile, and simple approach to synthesize degradable bottlebrush polymers under mild reaction conditions. Our approach relies on the "grafting-through" polymerization of α-lipoic acid (LA)-functionalized macromonomers. These macromonomers can be polymerized under mild, catalyst-free conditions, and due to reversibility of the disulfide bond in LA, the resulting bottlebrush polymers can be depolymerized by cleaving disulfide backbone bonds. Bottlebrushes with various side-chain chemistries can be prepared through the atom transfer radical polymerization (ATRP) of LA-functionalized macromonomers, and the backbone length is governed by the macromonomer molecular weight and solvent polarity. We also demonstrate that LA-functionalized macromonomers can be copolymerized with acrylates to form degradable bottlebrush networks. This work demonstrates the preparation of degradable bottlebrush polymers with a variety of side-chain chemistries and provides insight into the light-mediated grafting-through polymerization of dithiolane-functionalized macromonomers.

Versatile Light‐Mediated Synthesis of Degradable Bottlebrush Polymers Using α‐Lipoic Acid

AbstractBottlebrush polymers have a variety of useful properties including a high entanglement molecular weight, low Young's modulus, and rapid kinetics for self‐assembly. However, the translation of bottlebrushes to real‐world applications is limited by complex, multi‐step synthetic pathways and polymerization reactions that rely on air‐sensitive catalysts. Additionally, most bottlebrushes are non‐degradable. Herein, we report an inexpensive, versatile, and simple approach to synthesize degradable bottlebrush polymers under mild reaction conditions. Our approach relies on the “grafting‐through” polymerization of α‐lipoic acid (LA)‐functionalized macromonomers. These macromonomers can be polymerized under mild, catalyst‐free conditions, and due to reversibility of the disulfide bond in LA, the resulting bottlebrush polymers can be depolymerized by cleaving disulfide backbone bonds. Bottlebrushes with various side‐chain chemistries can be prepared through the atom transfer radical polymerization (ATRP) of LA‐functionalized macromonomers, and the backbone length is governed by the macromonomer molecular weight and solvent polarity. We also demonstrate that LA‐functionalized macromonomers can be copolymerized with acrylates to form degradable bottlebrush networks. This work demonstrates the preparation of degradable bottlebrush polymers with a variety of side‐chain chemistries and provides insight into the light‐mediated grafting‐through polymerization of dithiolane‐functionalized macromonomers.

Amorphous AlOCl Compounds Enabling Nanocrystalline LiCl with Abnormally High Ionic Conductivity.

LiCl is a promising solid electrolyte, providing it possesses high ionic conductivity. Numerous efforts have been made to enhance its ionic conductivity through aliovalent doping. However, aliovalent substitution changes the intrinsic structure of LiCl, compromising its cost-effectiveness and electrochemical stability. Here, we report nanocrystalline LiCl embedded in amorphous AlOCl compounds with a heterogeneous structure to enhance its ionic conductivity. Nanocrystallization enlarges the LiCl unit cell, while amorphization facilitates interfacial ion transport. As a result, the amorphous AlOCl-modified LiCl nanocrystal (AlOCl-nanoLiCl) demonstrates a high ionic conductivity of 1.02 mS cm-1, which is 5 orders of magnitude higher than that of LiCl. Additionally, it exhibits high oxidative stability, low cost ($19.87 US kg-1), and low Young's modulus (2-3 GPa). When AlOCl-nanoLiCl is coupled with Li-rich cathodes (Li1.17Mn0.55Ni0.24Co0.05O2, 4.8 V vs Li+/Li), all-solid-state batteries exhibit remarkable long-term cycling stability (>1000 cycles). This work presents a novel strategy to enhance the ionic conductivity of alkaline chlorides without compromising their intrinsic advantages.

A Highly-Sensitive Omnidirectional Acoustic Sensor for Enhanced Human-Machine Interaction.

Acoustic sensor-based human-machine interaction (HMI) plays a crucial role in natural and efficient communication in intelligent robots. However, accurately identifying and tracking omnidirectional sound sources, especially in noisy environments still remains a notable challenge. Here, a self-powered triboelectric stereo acoustic sensor (SAS) with omnidirectional sound recognition and tracking capabilities by a 3D structure configuration is presented. The SAS incorporates a porous vibrating film with high electron affinity and low Young's modulus, resulting in high sensitivity (3172.9 mVpp Pa-1) and a wide frequency response range (100-20 000 Hz). By utilizing its omnidirectional sound recognition capability and adjustable resonant frequency feature, the SAS can precisely identify the desired audio signal with an average deep learning accuracy of 98%, even in noisy environments. Moreover, the SAS can simultaneously recognize multiple individuals in the auxiliary conference system and the driving commands under background music in self-driving vehicles, which marks a notable advance in voice-based HMI systems.

Super Chloride Ionic Conductivity in CsSnCl3‐Based Perovskite Compound and Its Application for Solid‐State Chloride Batteries

A CsSnCl3‐based solid electrolyte in which 5% of Sn sites are occupied by Y ions, CsSn0.95Y0.05Cl3.05 (CSYC), is developed using a one‐step mechanical ball‐milling method. CSYC exhibits a stable cubic perovskite crystal structure and a high chloride ion conductivity of 4.9 mS cm−1. The relative density of a CSYC pellet following cold pressing without heat treatment is 97.5%. The high relative density and ionic conductivity are considered to originate from the high mechanical plasticity of the pellets, as evidenced by a low Young's modulus of 8.2 GPa. An all‐solid‐state chloride ion battery cell using CSYC as the electrolyte, BiCl3 as the active cathode material, and Sn as the anode is confirmed to operate at room temperature. The cell shows a large initial discharge capacity of 178 mAh g−1, ≈70% utilization, and good capacity retention with a reversible capacity of 100 mAh g−1 after 40 cycles. The mechanical plasticity of CSYC is considered to be a major contributor to its high ionic conductivity and good battery cycling performance.

Robust Strain Sensor with High Sensitivity Based on Polymer-Encapsulated Microfiber Mach-Zehnder Interferometer.

A robust strain sensor is demonstrated based on a microfiber Mach-Zehnder interferometer (MMZI) encapsulated by the polymer polydimethylsiloxane (PDMS). Benefiting from the low Young's modulus of PDMS, both a robust structure and high sensitivity can be realized based on three different encapsulations. In the experiment, the proposed sensors are fabricated and tested with strain sensitivities ranging from -20.95 pm/με to 127.00 pm/με within the wavelength range of 1200-1650 nm. Compared with the bare MMZI sensor, at least one order of magnitude higher sensitivity is reached. To further evaluate the performance of the sensor, the dependences of sensitivity on probing wavelength and the different types and quantities of polymers used in encapsulation are discussed. Results show that the sensitivity of the sensor will increase with the probing wavelength. The type and quantity of polymer used are also very critical to sensitivity. Additionally, a response time of 24.72 ms can be reached. Good recoverability and repeatability of the sensor are also demonstrated by repeated experiments. The strain sensor demonstrated here shows the advantages of simple fabrication, robust structure, high and tunable sensitivity, fast response, good recoverability and repeatability.

Fracture resistance of pottery laminates with intentionally introduced defects

AbstractLaminated ceramics containing layers of pottery materials with high and low Young's moduli were developed to mimic the nacre structure of abalone shells with high resistances against dynamic fractures. The layers with the low Young's modulus moderated crack deflection and impact, thereby exhibiting a high fracture resistance. The ceramic pores were formed by the CO2 gas generated through the oxidation of SiC during firing. The dynamic fracture resistance was enhanced by elastic wave scattering owing to the difference between the Young's moduli of the dense and porous layers. The effect of lamination on the dynamic fracture resistance was observed because the elastic waves were scattered owing to the difference in the elastic modulus between the porous and dense layers, and their propagation to the back sample surface was suppressed. The fracture energy of the 5‐layer laminate was determined to be about four times larger than that of the dense monolayer, which indicates that the introduction of intentional defects is effective in improving the dynamic fracture resistance of the pottery ceramics.

Enhanced Carrier Lifetime and Mobility in Monolayer NbOI2.

The lifetime and mobility of hot carriers are critical parameters for assessing the performance of optoelectronic materials, as they directly impact the response speed and operational efficiency of devices. Combining first-principles calculations with nonadiabatic molecular dynamics (NAMD) simulations, we systematically investigated the electronic properties and carrier dynamics of monolayer NbOI2. Our findings indicate that, at room temperature, this material demonstrates a carrier lifetime of up to ∼13 ns and an electron mobility reaching as high as ∼9 × 103 cm2 V-1 s-1. The low Young's modulus makes it susceptible to deformation under external stress, and we found that the carrier lifetime extends to ∼40 ns under a 4% tensile strain, along with a significant increase in hole mobility. This study elucidates the carrier dynamics in monolayer NbOI2, facilitating its potential application in future flexible optoelectronic devices.

High‐Performance Multipedal Shape Strain Sensors for Human Motion and Electrophysiological Signal Monitoring

AbstractStrain sensors from conducting polymer hydrogel have been widely employed in various wearable devices, electronic skins, and biomedical applications. These sensors provide outstanding flexibility and high sensitivity by integrating conducting polymer with hydrogels, making them particularly suitable for monitoring human motion and physiological signals like heart rate or muscle activity. Despite their extensive application potential, conducting polymer hydrogel face several technical challenges in practical use, including poor mechanical properties, lack of long‐term stability, and difficulty in customizable design. This work introduces a method for fabricating a multipedal strain sensor using poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/polyvinyl alcohol (PVA) dimethyl sulfoxide (DMSO)hydrogels through screen printing and demonstrates its application in human motion monitoring. The multipedal strain sensor demonstrates a low Young's modulus (200 kPa), high stretchability (400%), and excellent mechanical cyclic stability (3000 cycles). Furthermore, this strain sensor is further applied to detect human movements such as chewing, smiling, fist clenching, arm bending, and carotid pulse monitoring. Comparative analysis between the multipedal‐designed sensor and the non‐designed sensor highlights the enhanced sensing capabilities of the multipedal sensor. The design of this multipedal sensor holds the potential to broaden the design concepts for strain sensors and offers new insights for wearable devices and electronic skins.

Improving the electromechanical deformability of MWCNT/silicone composites via encapsulating MWCNT with polyphenols and multilayered structure regulation

AbstractSilicone rubber (SR) is an ideal dielectric elastomer substrate due to its excellent flexibility and fast response speed. However, the innate low dielectric permittivity (ε) of SR generally requires a rather high driving voltage that restricts its widespread application. Typical attempts to increase ε of SR usually deteriorate either its flexibility or electrical stability. Herein, conductive multi‐walled carbon nanotube (MWCNT) were first surface modified with polyphenols (PNs) (MWCNT@PNs), aiming to facilitate its well dispersion within SR matrix, which may maintain the softness and electrical stability of SR via suppressing concentrated physical crosslinking and local leakage current flow. Then, five‐layered MWCNT@PNs/SR composites were prepared with the outer two insulating layers of SR while middle three dielectric layers of MWCNT@PNs filled SR. The multilayered structure further hindered the formation of conductive pathways through the composites, promising a high breakdown strength of the composites. Therefore, the multilayered MWCNT@PNs/SR composites exhibited increased ε, maintained low Young's modulus and electrical breakdown strength compared with pure SR of the same five‐layered structure. Among them, the composite with uniformly distributed MWCNT@PNs (m‐1: 1: 1) showed a highest actuation strain of 11.9% (at 19.6 kV mm−1), which was 4.1 times higher than that of SR (2.9% at 19.1 kV mm−1).

Magnetic elastomer composites with tunable magnetization behaviors for flexible magnetic transducers

AbstractMagnetic elastomer composites are extending the field of soft robotics by integrating the flexibility of elastomers with the versatile performance of magnetic materials. In this work, a series of magnetic elastomers (BaCoxTixFe12–2xO19/PDMS) with tunable magnetic response have been successfully synthesized. In this composite, the magnetic component consists of Co‐Ti co‐doped barium hexaferrite (BaCoxTixFe12–2xO19, BCTF) nano powders, and the matrix is made of polydimethylsiloxane (PDMS). The coercivity (Hc) of BCTF can be reduced from 3950 Oe to 70 Oe, which bestow on the magnetic elastomer different magnetic response behavior. These magnetic elastomer composites obtained by blending have low Young's modulus, approximately 1.5 MPa. Furthermore, when applying the same external magnetic field, BaCo1.2Ti1.2Fe9.6O19/PDMS the magnetic deformation Angle can be as high as 60°. These magnetic elastomers exhibit different magnetic‐induced deformation owing to the adjustable permeability of the magnetic nanoparticles. This research significantly advances the design of applications with specific magnetic characteristics, such as sensors and transducers, thus opening new horizons for innovation in soft robotics and related fields.Highlights All elastomer composite exhibit a low modulus of approximately 1.5 MPa. These composites exhibit different magnetic response behaviors. This research provides a solution for the innovation of transducers.

Composite cellulose/bismuth/PVA nanocrystal for high-performance X-ray radiation shielding

The strong penetrating power of X-rays causes serious health problems. Longer exposure to radiation that penetrates normal cells can result in gene mutations, cancer, and even death. Protection against radiation exposure is necessary to prevent negative impacts from occurring. This research aims to make apron samples using a simple method based on cellulose as a matrix, bismuth as a filler with concentrations of 1 g, 0.75 g, 0.25 g and PVA acts as a binder that helps bind cellulose and bismuth particles into an effective X-ray radiation shield. The characterization carried out includes Fourier transform infrared (FTIR) to determine the functional groups and chemical composition of the sample, x-ray diffraction (XRD) to analyze the crystal size of the sample, and mobile x-ray with energies of 60, 70, and 80 keV to determine the radiation shielding performance. The findings of this study highlight that the optimal shielding properties were attained by employing a sample with the highest concentration of bismuth filler, specifically at 1 g. This material exhibits outstanding characteristics, including a high linear attenuation coefficient and mass attenuation coefficient of 0.68 cm−1 and 2.24 cm2/g respectively for an energy of 60 keV and especially low HVL (1.01 cm) and TVL (3.36 cm) values. These findings have significant implications for developing high-performance X-ray radiation shielding materials, particularly in industries where radiation exposure is a concern, such as the medical industry, research, and laboratories. The high tensile strength (2.83 N/mm2) and elongation (12.09 %) values as well as the low Young's modulus (0.108 N/mm2) values also indicate the flexibility of the resulting material, which could be beneficial for applications that require flexible shielding materials. The practicality of this research makes the audience feel that the findings are applicable and useful in real-world scenarios.

Facile One-Pot Preparation of Polypyrrole-Incorporated Conductive Hydrogels for Human Motion Sensing.

Conductive hydrogels have been widely used in soft robotics, as well as skin-attached and implantable bioelectronic devices. Among the candidates of conductive fillers, conductive polymers have become popular due to their intrinsic conductivity, high biocompatibility, and mechanical flexibility. However, it is still a challenge to construct conductive polymer-incorporated hydrogels with a good performance using a facile method. Herein, we present a simple method for the one-pot preparation of conductive polymer-incorporated hydrogels involving rapid photocuring of the hydrogel template followed by slow in situ polymerization of pyrrole. Due to the use of a milder oxidant, hydrogen peroxide, for polypyrrole synthesis, the photocuring of the hydrogel template and the growing of polypyrrole proceeded in an orderly manner, making it possible to prepare conductive polymer-incorporated hydrogels in one pot. The preparation process is facile and extensible. Moreover, the obtained hydrogels exhibit a series of properties suitable for biomedical strain sensors, including good conductivity (2.49 mS/cm), high stretchability (>200%), and a low Young's modulus (~30 kPa) that is compatible with human skin.

Ti3C2Tx MXene-functionalized Hydroxyapatite/Halloysite nanotube filled poly– (lactic acid) coatings on magnesium: In vitro and antibacterial applications

Magnesium (Mg) stands out in temporary biomaterial applications due to its biocompatibility, biodegradability, and low Young's modulus. However, controlling its corrosion through next-generation polymer-based functional coatings is crucial due to the rapid degradation behavior of Mg. In this study, the function of 2D lamellar Ti3C2Tx (MXene) in Hydroxyapatite (HA) and Halloysite nanotube (HNT) hybrid coatings in biodegradable poly– (lactic acid) (PLA) was investigated. The morphological and structural characterizations of the coatings on Mg were revealed through HRTEM, XPS, SEM-EDX, XRD, FTIR, and contact angle analyses/tests. Electrochemical in vitro corrosion tests (OCP, PDS, and EIS-Nyquist) were conducted for evaluate corrosion resistance under simulated body fluid (SBF) conditions. The bioactivity of the coatings in SBF have been revealed in accordance with the ISO 23,317 standard. Finally, antibacterial disk diffusion tests were conducted to investigate the functional effect of MXene in coatings. It has been determined that the presence of MXene in the coating increased not only surface wettability (131°, 85°, 77°, and 74° for uncoated, pH, PHH, and PHH/MXene coatings, respectively) but also increased corrosion resistance (1857.850, 42.357, 1.593, and 0.085 × 10–6, A/cm2 for uncoated, pH, PHH, and PHH/MXene coatings, respectively). It has been proven that the in vitro bioactivity of PLA-HA coatings is further enhanced by adding HNT and MXene, along with SEM morphologies after SBF. Finally, 2D lamellar MXene-filled coating exhibits antibacterial behavior against both E. coli and S. aureus bacteria.

Stress-Induced Martensitic Transformation in Na3YCl6.

Martensitic transformation with volume expansion plays a crucial role in enhancing the mechanical properties of steel and partially stabilized zirconia. We believe that a similar concept could be applied to unexplored nonoxide materials. Herein, we report the stress-induced martensitic transformation of monoclinic Na3YCl6 with an ∼3.4% expansion. In situ synchrotron X-ray diffraction and atomistic simulations showed that anisotropic crystallographic transformation from monoclinic to rhombohedral Na3YCl6 occurs exclusively under uniaxial pressure; no effect is observed under hydrostatic pressure conditions. The uniaxially pressed powder compact of monoclinic Na3YCl6 showed a large indentation impression and low Young's modulus, in contrast to its high bulk modulus, suggesting that these unique mechanical properties are induced by the martensitic transformation.