Low Young Modulus Research Articles

CORR Insights®: β-type TiNbSn Alloy Plates With Low Young Modulus Accelerates Osteosynthesis in Rabbit Tibiae.

1Section Chief of Orthopedic Surgery, Lower Bucks Hospital, Bristol, PA M. M. Meller ✉, Lower Bucks Hospital, Department of Orthopaedic Surgery 501 Bath Road, Bristol, PA 19007, USA, Email: [email protected] This CORR Insights® is a commentary on the article “β-type TiNbSn Alloy Plates With Low Young Modulus Accelerates Osteosynthesis in Rabbit Tibiae” by Ito et al and colleagues available at: DOI: 10.1097/CORR.0000000000002240. The author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writer, and do not reflect the opinion or policy of CORR® or The Association of Bone and Joint Surgeons®.

Improving the Young's modulus of Mg via alloying and compositing – A short review

Lightweight, high-modulus structural materials are highly desired in many applications like aerospace, automobile and biomedical instruments. As the lightest metallic structural material, magnesium (Mg) has great potential but is limited by its low intrinsic Young's modulus. This paper reviews the investigations on high-modulus Mg-based materials during the last decades. The nature of elastic modulus is introduced, and typical high-modulus Mg alloys and Mg matrix composites are reviewed. Specifically, Mg alloys enhance Young's modulus of pure Mg mainly by introducing suitable alloying elements to promote the precipitation of high-modulus second phases in the alloy system. Differently, Mg matrix composites improve Young's modulus by incorporating high-modulus particles, whiskers and fibers into the Mg matrix. The modulus strengthening effectiveness brought by the two approaches is compared, and Mg matrix composites stand out as a more promising solution. In addition, two well-accepted modulus prediction models (Halpin-Tsai and Rule of mixtures (ROM)) for different Mg matrix composites are reviewed. The effects of reinforcement type, size, volume fraction and interfacial bonding condition on the modulus of Mg matrix composites are discussed. Finally, the existing challenges and development trends of high-modulus Mg-based materials are proposed and prospected.

Interfacial Coordination Interaction Enables Soft Elastomer Composites High Thermal Conductivity and High Toughness.

Soft elastomers have attracted wide applications, such as soft electronic devices and soft robotics, due to their ability to undergo large deformation with a small external force. Most elastomers suffer from poor toughness and thermal conductivity, which limits their use. The addition of inorganic fillers can enhance the thermal conductivity and toughness, but it deteriorates the softness (low Young's modulus and high stretchability). Integrating thermal conductivity, toughness, and softness into one elastomer is still a challenge. Here, we report a strategy of interfacial coordination interaction to achieve soft elastomer composites with high thermal conductivity and high toughness. We demonstrate the strategy by using poly(lipoic acid) elastomer and silver-coated aluminum filler as model, where silver-sulfur coordination cross-links are formed at the interface. The resultant elastomer composite shows high streachability (450%), high thermal conductivity (2.35 W m-1 K-1), low modulus (321 kPa), and high toughness (3496 J m-2), which cannot be achieve in existing elastomers. The time domain thermoreflectance technique demonstrates that the silver-sulfur coordination interaction lowers the interfacial thermal resistance, resulting in enhanced thermal conductivity of the elastomer composites. The excellent softness stems from lower bonding energy of the silver-sulfur coordination cross-links compared with covalent chemical cross-links. The high toughness also benefits from the interfacial silver-sulfur coordination interaction that can dissipate more energy upon deformation. We further demonstrate the potential application of the thermally conductive, tough, and soft elastomer composites for thermal management of chip and soft electronic devices.

Alkali-activated slag (AAS) and OPC-based composites containing crumb rubber aggregate: Physico-mechanical properties, durability and oxidation of rubber upon NaOH treatment

Value-added utilization of waste tires in cementitious materials has been studied for decades, whereas the synergy between rubber and alkali-activated cements deserves more investigations. To this end, we compared physico-mechanical and durability properties of alkali-activated slag (AAS) and OPC-based composites containing NaOH-pretreated/as-received crumb rubber (CR). It was found that the incorporation of CR had both positive and negative effects on specimens due to its special attributes. CR reduced electrical conductivity which was associated with the ion transport ability, since it worked as an electrical insulator and increased hydrophobicity of pore walls. The sulfate expansion decreased with CR content because the flow of sulfate ions was demobilized, and the flexibility of CR relieved the internal stress. CR also improved the freeze-thaw durability of composites if the total CR content was less than 30% in specimens. However, the low Young's modulus of CR impaired the compressive strength and failed to effectively control the total shrinkage upon drying. The composites with CR must avoid high temperature exposure which resulted in the pyrolysis of rubber. In addition, the NaOH pretreatment enhanced adhesion between CR and hydrated cement and improved overall performances of composites. The FTIR spectra confirmed the NaOH-induced accelerated oxidation of CR surface and the generation of polar functional groups including carbonyl and carboxyl groups, increasing the total surface energy of rubber. More importantly, the alkali-activation process for AAS could treat the CR aggregate in the meantime, which means the use of CR in alkali-activated cements does not require the pretreatment of CR before blending.

β duplex phase Ti–Zr–Nb–Ag alloys with impressive mechanical properties, excellent antibacterial and good biocompatibility

In this research, a new series of β duplex phase Ti50Zr25Nb25-xAgx (x = 0, 1, 3 and 5 at. %) alloys were prepared by rapid solidification process. The microstructure, mechanical properties, antibacterial properties, ion release behavior and biocompatibility of the alloys were systematically investigated. The alloys were composed of β main phase and β minor phase, therefor the alloys exhibited a very low Young's modulus of 60-61 GPa, which can effectively reduce the stress shielding effect. The alloys possessed high strength and hardness, which is correlated to the grain refinement strengthening caused by rapid solidification process and solid solution strengthening caused by the addition of Ag. The release of Ag ion increased with the increasing of Ag content. The antibacterial properties also showed the same trend and the Ag5 alloy exhibited 99.1% antibacterial rate. Meanwhile, the alloys possessed good biocompatibilities obtained through cell live and dead staining experiments and cell proliferation experiments.

Numerical simulation of THMC coupling temperature prediction for fractured horizontal wells in shale oil reservoir

In order to study the effects of different parameters in hydraulic fracturing on formation temperature after low-temperature fracturing fluid is injected into high-temperature reservoir, in this paper, considering (1) osmotic pressure and capillary pressure (2) microthermal effect (heat conduction, heat convection, heat expansion, viscous dissipation) (3) the coupling processes of temperature (T), hydraulic, (H) mechanical (M) and chemical (C) in hydraulic fracturing process, and the coupled temperature prediction model of oil-water two-phase THMC based on discrete fractures is established. The effects of fracturing fluid temperature, reservoir temperature, dimensionless conductivity, Young's modulus, injection rate, cluster spacing, and proportion of branch fracture area on reservoir and fracture temperature during the pumping and shut-in stages of shale oil reservoir were studied. The results show (1) For formations with different reservoir temperatures, the temperature drop at the fracture was approximately 97% from the start of the operation to the end of the 30-day shut-in. The saturation change caused by fracturing fluid filtration is much larger than the temperature change caused by heat transfer, and it is found that the temperature and saturation change mainly occur in the early shut-in period (2) Imbibition accelerates the filtration loss of fracturing fluid. During pumping, the bottom hole temperature with imbibition considered is lower than that without imbibition considered. The temperature curve with imbibition considered begins to deviate about 10 min after pumping, but the final temperature tends to be the same, (3) When the fracturing fluid is pumped at high pressure, the fracture and matrix will be deformed, which will improve the porosity and permeability of the near well zone, thus speeding up the heat transfer rate. The high Young's modulus inhibits the increase of permeability. Compared with the young's modulus of 40 GPa and 20 GPa, the increase of permeability decreases by 9% (4) When the well was shut in for 30 days, the cluster spacing was greater than 20 m, and the temperature change around the fracture did not affect the clusters on both sides. The spacing between the clusters was 5 m, and the perforation clusters on both sides had a significant effect on the temperature. The temperature of the reservoir between the two adjacent clusters dropped from 393 K to 385 K. When there is a branch fracture, the small cluster spacing is equivalent to increasing the complexity of the fracture and accelerating the initial heat transfer rate. (5) High injection temperature, high dimensionless conductivity, low Young's modulus and low pumping rate are conducive to the heat transfer of fracturing fluid in the formation.

Structures and properties of biocompatible Ti-Zr-Nb-Fe-Mo medium entropy alloys

Biomedical implants require high yield strength, low Young's modulus and high ductility synergistic effect. The “stress shielding” caused by the high Young's modulus of most existing high-entropy alloys limited their applications. In this work, a body-centered cubic solid solution Ti45Zr37Nb16Fe1Mo1 (at.%) medium entropy alloy with low Young's modulus (~63 GPa), high tensile elongation (~25 %), and good corrosion resistance (Ecorr = −264 mV, Icorr = 0.15 μA·cm−2) was designed and fabricated. The admissible elastic strain of cold rolled alloy has increased 50% compared with as-cast alloy (~1.12 %). Furthermore, the coefficient of friction of the cold rolled alloy was higher than the as-cast alloy due to the stress-induced orthorhombic α'' martensite formation. Their mechanical properties can be achieved by tuning the fraction of β-stabilizing elements to obtain a metastable single body-centered cubic phase.

Machinability performance investigation in CNC turning of Ti–6Al–4V alloy: Dry versus iron-aluminium oil coupled MQL machining comparison

Ti–6Al–4V is the largest useable titanium grade alloy in various engineering components due to its superior inherent properties like high strength to weight ratio, highly corrosive resistance, ability to withstand high temperature, etc. But machining of this alloy is found to be challenging because of having lesser thermal conductivity, highly chemical sensible, more sensitivity in work hardening and low young's modulus. However, the current study offers the use of novel and environment pleasant lubricants like iron aluminium oil with minimum quantity lubrication (MQL) concept to machine this alloy using a low budget hard tool (uncoated carbide) and the performance was compared with dry machining. Severe abrasion, adhesion, diffusion, and chipping were the main cause of tool failure in both cooling strategies. The tool life in MQL was traced to be 280% greater than the dry condition at the same turning parameters. Compared to dry turning, lower tool vibration and superior surface quality were obtained in MQL. The MQL assisted turning exhibited 12.38% lower costs than dry. Overall, with the use of an uncoated carbide tool, the turning of Ti–6Al–4V alloy in MQL was found to be more precise and more economical than dry and recommended for mass production works.

Flexible and Tough Superelastic Co-Cr Alloys for Biomedical Applications.

The demand for biomaterials has been increasing along with the increase in the population of elderly people worldwide. The mechanical properties and high wear resistance of metallic biomaterials make them well-suited for use as substitutes or as support for damaged hard tissues. However, unless these biomaterials also have a low Young's modulus similar to that of human bones, bone atrophy inevitably occurs. Because a low Young's modulus is typically associated with poor wear resistance, it is difficult to realize a low Young's modulus and high wear resistance simultaneously. Also, the superelastic property of shape-memory alloys makes them suitable for biomedical applications, like vascular stents and guide wires. However, due to the low recoverable strain of conventional biocompatible shape-memory alloys, the demand for a new alloy system is high. The novel body-centered-cubic cobalt-chromium-based alloys in this work provide a solution to both of these problems. The Young's modulus of <001>-orientedsingle-crystal cobalt-chromium-based alloys is 10-30 GPa, which is similar to that of human bone, and they also demonstrate high wear and corrosion resistance. They also exhibit superelasticity with a huge recoverable strain up to 17.0%. For these reasons, the novel cobalt-chromium-based alloys can be promising candidates for biomedical applications.

Heterogeneous carbon/silicone composite for ultrasensitive anisotropic strain sensor with loading-direction-perception capability

Anisotropic strain sensors are crucial to accurately detecting the complex strain states in wearable devices and robotics. Large directional sensitivity differences are the key for strain sensors to differentiate loading directions. Here, an ultrasensitive anisotropic strain sensor consisting of orthogonal heterogeneous piezo-resistive composite (HePC) and homogenous piezo-resistive composite (HoPC) is demonstrated for loading direction perception. Benefited by a unique stiff-soft-stiff segment structure design, the HePCs with ultrahigh strain sensitivity were fabricated with carbon black (CB)/silicone nanocomposite with a low Young's modulus as the soft segment (SoS) and carbon-fiber-reinforced CB/silicone nanocomposite with a high Young's modulus as the stiff segment (StS). The HePC with a length ratio (LStS/LSoS) of 14:1 offers an average gauge factor of 70 (ε < 1%), which is increased more than 60 times than that of HoPC, due to the strain concentration effect in the SoS of HePC. Moreover, the anisotropic strain sensor fabricated demonstrates significant directional sensitivity differences due to the heterogeneous structure, and their relative resistance changes (RCR) vary considerably from positive to negative upon the change of loading directions. This makes the sensor highly effective to distinguish strain magnitude and direction simultaneously, and succeeding in monitoring complex human body gestures. Meanwhile, the relation between the loading direction and the measured parameter K (RCR in X-direction over that in Y-direction) is proposed to predict the loading angle. Considering its ultrahigh sensitivity and loading-direction-perception capability, the anisotropic strain sensor with the heterogeneous structure of stiff-soft-stiff segments is promising in wearable devices, robotic systems, artificial intelligence, etc.

Piezoelectric sensing performance of flexible P(VDF-TrFE)/PBDMS porous polymer materials

Polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] polymer materials possess good piezoelectric properties, leading to their use in many practical applications as sensors and transducers. However, pure P(VDF-TrFE) exhibits relatively brittle properties and low thermal resistance. In this work, porous P(VDF-TrFE)/PBDMS flexible materials were designed by embedding a low Young's modulus polyborosiloxane (PBDMS) into the [P(VDF-TrFE)] structure. These P(VDF-TrFE)/PBDMS porous polymer materials exhibit excellent flexibility and piezoelectric response to external stimuli such as bending, shock, vibration, and breathing. The output voltage of these polymer materials can be maintained at a high value of 8.25 V over 6600 cycles of continuous vibration. In addition, the porous polymer materials generate a transient voltage response when in contact with small droplets of water at different temperatures. This work provides a novel approach for designing lightweight and wearable piezoelectric sensors for potential applications in human motion monitoring, mechanical vibration monitoring, and pyroelectric devices. • A porous structured P(VDF-TrFE)/PBDMS composite film was designed to overcome the brittleness of the pure P(VDF-TrFE). • The composite film exhibits an excellent flexibility and piezoelectric sensing to the external stimuli. • A high output voltage of 8.25 V was constantly realized for the composite film over 6600 cycles of continuous vibration. • This work provides a strategy of designing lightweight and wearable piezoelectric sensors for human motion monitoring.

Numerical simulation of proppant embedment in rough surfaces based on full reverse reconstruction

In the hydraulic fracturing process of shale reservoir, proppant will embed and deform under the action of high closure stress. Thus, it is necessary to analyze the mechanical process and influencing factors of proppant embedding in shale. This study reproduced rough fracture surface of real rock slabs based on the reverse reconstruction method and obtained the mechanical parameters of the rock slab and proppant. In this study, a numerical model for the elastoplastic deformation of the proppant embedding in the rough fracture surface, along with mechanical test experiments, is proposed. The reliability of the numerical model is verified by the proppant embedding simulation experiment. Based on this model, the process of proppant embedding in a rough fracture under the action of closing stress and the factors influencing the width of supporting fracture were analyzed. The results show that the embedment degree of the proppant is different in different areas of the rough fracture surface. Furthermore, a stress concentration effect is apparent. The proppant embedment becomes significant after the slab enters the plastic deformation stage under high closure stress. The slabs with high roughness and low Young's modulus or proppants with small particle sizes and high Young's moduli result in a smaller width of the propped fracture.

Photopatternable Poly(dimethylsiloxane) (PDMS) for an Intrinsically Stretchable Organic Electrochemical Transistor.

Patterning elastomers is an essential process for the application of elastomers to stretchable bioelectric devices. In general, replication of a mold and laser ablation are used for patterning elastomers. However, these methods are inefficient and time consuming due to complex patterning procedures and a heat-induced curing mechanism. In this work, we developed a photopatternable elastomer called thiol-ene cross-linked poly(dimethylsiloxane) (TC-PDMS). TC-PDMS showed high-resolution patternability (∼100 μm) through a direct patterning process. It also had high stretchability (∼140%) and low Young's modulus (∼2.9 MPa) similar to conventional PDMS. To demonstrate its practicability in stretchable bioelectric devices, TC-PDMS was applied to a passivation layer of an intrinsically stretchable organic electrochemical transistor (OECT), which showed a low leakage current (∼20 μA) and a high transconductance (0.432 mS) at high strain (60%). The stretchable OECT was able to record electrocardiographic (ECG) signals from human skin, and the measured ECG signals exhibited a high signal-to-noise ratio of 12.2 dB.

β-type TiNbSn Alloy Plates With Low Young Modulus Accelerates Osteosynthesis in Rabbit Tibiae.

β-type TiNbSn Alloy Plates With Low Young Modulus Accelerates Osteosynthesis in Rabbit Tibiae.

Mechanical properties of Li2MoO4 single crystals

Mechanical properties of lithium molybdate single crystals, Li2MoO4, are studied from room temperature to 650 °C. Density functional theory calculations gave the seven elastic constants of the rhombohedral crystal at 0 K. Brillouin light scattering experiments delivered comparable values at room temperature, and measurements up to 650 °C show a linear decrease in the constants with temperature. Nano-indentation results were typical of a brittle material with a low Young modulus and allowed deriving Young's moduli, for c (63 GPa) and m (48 GPa) faces, in agreement with those computed from measured elastic constants. Compressive rupture tests were performed. At 650 °C, the rupture stress was in the range 2–7.5 MPa. No clear evidence of a plastic regime was observed before cracking, even at temperatures close to the melting point.

Mechanisms of near-linear elastic deformation behavior in a binary metastable β-type Ti-Nb alloy with large recoverable strain

A binary metastable β-type Ti-Nb alloy possessing large near-linear recoverable strain was designed to clarify the physical mechanisms responsible for high near-linear elastic deformability in near‑oxygen-free Ti-based alloys. The in situ synchrotron X-ray diffraction (SXRD) investigation reveals that in addition to the inherent elastic deformation, a reversible β↔α'' stress-induced martensitic transformation (SIMT) occurs during the near-linear elastic deformation. During the SIMT, the α'' martensitic variant 5 (V5) forms preferentially due to its maximum phase transformation strains among all 6 equivalent α'' variants. The orientation dependence of phase transformation strains of the preferential V5 leads to the appearance of different α'' diffraction peaks in the loading and Poisson’s directions during the SIMT, which is beneficial for accommodating the external macroscopic deformation to the great extent. Our experimental results show that the high near-linear elastic deformability of present Ti-Nb alloy is attributed to a combined effect of the large inherent elastic deformation arising from low Young's modulus as well as a reversible SIMT that covers a wide stress range and exhibits small phase transformation strains limited by the lattice constants of β and α'' phases. These results could provide a comprehensive understanding of the mechanisms responsible for huge near-linear elastic deformability of β-type titanium alloys.

Design of TiZrNbTa multi-principal element alloys with outstanding mechanical properties and wear resistance

Body-centered cubic (BCC) multi-principal element alloys (MPEAs) have drawn particular attention as orthopedic implant materials recently, due to their high strength and excellent biocompatibility. However, these alloys often exhibit limited tensile ductility and relatively high Young's modulus, which remain challenges for their potential biomedical applications. In this work, a synergistic design of high-performance biomedical MPEAs based on the principles of valence electron concentration theory and average shear modulus mismatch for solid-solution strengthening is reported. Three TiZrNbTa MPEAs (Ti45Zr45Nb5Ta5, Ti42.5Zr42.5Nb5Ta10, Ti40Zr40Nb5Ta15) with different Ta content were designed. All the alloys exhibited single BCC structure and possessed outstanding tensile ductility (≥18.8%), as well as low Young's modulus (59.3±2.1–73.1±1.0 GPa). The yield strengths of these alloys are increasing with the increase of the Ta content, which can be correlated with the average shear modulus mismatch. In particular, Ti40Zr40Nb5Ta15 alloy exhibits the highest yield strength (∼990.0±14.3 MPa) and high wear resistance for biomedical applications. Theoretical calculation suggested that the strength of the TiZrNbTa alloys is mainly attributed to the solid-solution strengthening effect, and increasing the Ta content can effectively enhance this effect.

Highly Skin-Compliant Polymeric Electrodes with Synergistically Boosted Conductivity toward Wearable Health Monitoring.

Despite rapid advances in stretchable electrodes, successful examples of polymeric dry electrodes are limited. Especially in wearable health monitoring, it is urgent to develop biocompatible electrodes that possess intrinsic skin-compliance while maintaining a high conductivity. Herein, a strategy is demonstrated to synergistically regulate the interpenetration behavior and molecular crystallinity in the blend via embedding a novel double network, i.e. physically cross-linked poly(vinyl alcohol) (PVA) and covalently cross-linked polyethylene glycol diacrylate (PEGDA), into the PEDOT:PSS matrix. The favorable interaction energy between PVA and PEGDA enables well-distributed microstructure with finer phase separation in the film, affording a low Young's modulus of 16 MPa with a high conductivity of 442 S/cm. Consequently, the optimal polymeric electrode can acquire high-quality electromyogram (EMG) and electrocardiogram (ECG) signals. Our results provide a feasible approach for producing skin-compliant polymeric electrodes toward next-generation health monitors.

Self-adhesive polyurethane via selective photo-polymerization for biocompatible epidermal soft sensor and thermal heater

Polyurethane (PU) is the most extensively used soft backbone substrate for wearable applications. However, even with biocompatibility and stretchability, PU-based wearable devices are unsuitable for epidermal devices because they lack of adhesive properties. To impart adhesive properties to PU, commercial adhesive additives are required or the mixing ratio of specific materials should be adjusted. Despite PU biocompatibility, additional additives cause skin damage because they are not usually biocompatible due to their toxic ingredient. This study introduces a simple method of fabricating self-adhesive polyurethane (SAPU) without specific adhesive additives for a biocompatible epidermal soft sensor and an attachable epidermal thermal heater. During the selective photo-polymerization of PU resin, the defective crosslinking networks between laser-scanned resin lines enhance the adhesive properties of PU. Adjusting photo-polymerization conditions results in self-adhesive polyurethane with high adhesiveness and low Young's modulus comparable to those of human skin. A mouse skin toxicity test confirms the biocompatibility and highly conformal contact of SAPU. SAPU is then further applied for the fabrication of a biocompatible epidermal soft sensor and an attachable epidermal thermal heater with silver nanowire network. The fabricated self-adhesive epidermal soft sensor successfully detects human motion and bio-signals, whereas the self-adhesive epidermal soft heater efficiently transfers heat to the epidermis due to its excellent conformal contact characteristics on the human skin.

Graphene‐Based Hydrogel Strain Sensors with Excellent Breathability for Motion Detection and Communication

AbstractHydrogels are considered as promising materials in developing next‐generation wearable sensors due to their intrinsic biocompatibility and low Young's modulus. However, there are few reports on their breathability which is very important for wear comfortability of wearable sensors. Here graphene‐based hydrogel is presented with regular pores using microneedles as templates endowing them with excellent breathability (water vapor transmitting rate 2.8 kg d–1 m–2), which is near ten times that of human skin (water vapor transmitting rate less than 0.3 kg d–1 m–2). A high‐performance strain sensor based on this breathable hydrogel is developed. This sensor not only possesses high sensitivity but also has an excellent linearity with strain ranging from 0% to 110%. Based on these performances, this sensor can be applied in monitoring various joint movements and muscle movements. Moreover, it can achieve barrier‐free communication through Morse code.