Applications In Smart Devices Research Articles

Stretchable Unsymmetrical Piezoelectric BiO2-x Deposited-Hydrogel as Multimodal Triboelectric Nanogenerators for Biomechanical Motion Harvesting.

Enhancing the output performance of triboelectric nanogenerators (TENGs) is essential for increasing their application in smart devices. Oxygen-vacancy-rich BiO2-x nanosheets (BiO2-x NSs) are advanced-engineered nanomaterials with excellent piezoelectric properties. Herein, a stretchable unsymmetrical BiO2-x NSs deposited-hydrogel made of polyacrylamide (PAM) as a multimodal TENG is rationally fabricated, and the performance of TENG can be tailored by controlling the BiO2-x NSs deposition amount and spatial distribution. The alteration of resistance caused by the Poisson effect of PAM/BiO2-x composite hydrogel (H-BiO2-x) can be used as a piezoresistive sensor, and the piezoelectricity of BiO2-x NSs can effectively enhance the density of transfer charge, thus improving the output performance of the H-BiO2-x-based TENG. In addition, the chemical cross-linking between the BiO2-x NSs and the PAM polymer chain allows the hydrogel electrode to have a higher tensile capacity (867%). Used for biomechanical motion signal detection, the sensors made of H-BiO2-x have high sensitivity (gauge factor = 6.93) and can discriminate a range of forces (0.1-5.0 N) at low frequencies (0.5-2.0Hz). Finally, the prepared TENG can collect biological energy and convert it into electricity. Consequently, the improved TENG shows a good application prospect as multimodal biomechanical sensors by combining piezoresistive, piezoelectric, and triboelectric effects.

A Tunable Hydrophilic-Hydrophobic, Stimulus Responsive, and Robust Iridescent Structural Color Bionic Film with Chiral Photonic Crystal Nanointerface.

Bio-inspired in nature, using nanomaterials to fabricate the vivid bionic structural color and intelligent stimulus responsive interface as smart skin or optical devices are widely concerned and remain a huge challenge. Here, the bionic flexible film is designed and fabricated with chiral nanointerface and tunable hydrophilic-hydrophobic by the ultrasonic energy perturbation strategy and crosslinking of the cellulose nanocrystals (CNC). An intelligent nanointerface with adjustable hydrophilic and hydrophobic properties is constructed by the supramolecular assembly using a smart ionic liquid molecule. The bionic flexible film possessed the variable hydrophilic-hydrophobic, stimulus responsive, and robust iridescent structural color. The reflective wavelength and the helical pitch of the film can be easily modulated through the ultrasonic energy perturbation strategy. The bionic flexible film by covalent cross-linking has excellent robustness, good elasticity and flexibility. The tunable brilliant structural color of the chiral nanointerface is attributed to the surface charge change of the CNC photonic crystal, which is disturbed by ultrasonic energy perturbation. The bionic flexible film with tunable structure color has intelligent hydrophilic and hydrophobic stimulus response properties. The chiral bionic materials have potential applications in smart skin, optical devices, bionic materials, robots, anti-counterfeiting, colorful displays, and stealth materials.

Evaluation of a Microcontroller-based Smart Wearable Device in College Students' Sports Forging Application

INTRODUCTION: The widespread use of smart wearable devices in various fields, including healthcare and sports, underscores the importance of their application in enhancing physical exercise among college students. Recent advancements in technology have facilitated the development of sophisticated methods to assess and predict physical activity outcomes, making their evaluation increasingly critical.OBJECTIVES: This study aims to develop a reliable assessment model for smart wearable devices used in college students' sports activities. The objective is to accurately predict and evaluate the effectiveness of these devices in improving students' physical health and promoting lifelong sports habits. Ultimately, the research seeks to integrate advanced computational methods to enhance the accuracy of physical exercise assessments.METHODS: The research introduces a novel assessment model that combines a zebra behavior-based heuristic optimization algorithm with a convolutional neural network (CNN). By analyzing user behavior data from wearable devices, the model constructs an evaluation index system tailored for college sports activities. The approach optimizes the parameters of the CNN using the zebra optimization algorithm, ensuring enhanced prediction accuracy.RESULTS: The evaluation model demonstrated high accuracy, with a significant improvement in predicting the outcomes of physical exercises among college students. Comparative analyses with traditional methods revealed that the new model reduced prediction errors and increased real-time performance metrics. Specifically, the model achieved a lower root mean square error (RMSE) in simulation tests, indicating more precise assessments. Figures and statistical data provided in the study illustrate the model's superior performance across various parameters.CONCLUSION: The developed assessment model significantly advances the application of smart wearable devices in monitoring and enhancing college students' physical activities. By integrating cutting-edge algorithms, the study not only improves the accuracy of exercise assessments but also contributes to the broader understanding of technology's role in health and fitness education. Future research could further refine this model by incorporating additional sensors and data points to expand its applicability and robustness.

Bio-based epoxy resin/carbon nanotube coatings applied on cotton fabrics for smart wearable systems

Electroactive coatings for smart wearable textiles based on a furan bio-epoxy monomer (BOMF) crosslinked with isophorone diamine (IPD) modified with carbon nanotubes (CNTs) are reported herein. The effect of BOMF/IPD molar ratio on the curing reaction, as well as on the properties of the crosslinked resins was first assessed, and it was found that 1.5:1 BOMF/IPD ratio provided higher heat of reaction, glass transition temperature, and mechanical performance. The resin was then modified with CNT to prepare electrically conductive nanocomposite films, which exhibited conductivity values increased by eight orders of magnitude upon addition of 5 phr of CNTs. The epoxy/CNT nanocomposites were finally applied as coatings onto a cotton fabric to develop electrically conductive, hydrophobic and breathable textiles. Notably, the integration of CNTs imparted efficient and reversible electrothermal behavior to the cotton fabric, showcasing its potential application in smart and comfortable wearable electronic devices.

Can the Use of Telemedicine in the Management of Continuous Positive Airway Pressure for the Treatment of Obstructive Sleep Apnea Reduce Clinical Time and Additional Appointments: A Randomized Controlled Trial.

Introduction: Obstructive sleep apnea (OSA) is a common sleep breathing disorder and is associated with increased cardiovascular risk and daytime sleepiness. Continuous positive airway pressure (CPAP) is a treatment for OSA, which splints the airway open. The introduction of telemedicine in CPAP devices offers clinical staff an alternative method of reviewing patients, monitoring treatment, and reducing clinical time. Materials and Methods: A randomized control trial was conducted with patients randomized to one of three arms: Arm 1 (standard care), Arm 2 (modem and a virtual appointment), and Arm 3 (modem, smart device application DreamMapper™, and a virtual appointment). Ninety participants requiring treatment with CPAP following a diagnosis of OSA were recruited and data collected at baseline, 14 days, and 180 days. Additional contacts or appointments were also recorded. Results: Ninety participants (n = 90) were recruited (68% males and 32% females) with an average age of 52.0 ± 13.13 years and apnea/hypopnea index (AHI) 43.5 ± 21.92 (events/h). There was a statistically significant difference between the three arms in the average clinical time taken for the first follow-up appointment (p = 0.001). There was a statistically significant difference between the three arms in the number of additional appointments or contacts required (p = 0.03). Discussion and Conclusion: Telemedicine reduced clinical time at first follow-up, and in patients who received standard care or a smart device application to monitor their own CPAP treatment, there were significantly less additional appointments required when compared with telemedicine support in the form of a modem alone.

Robust ultrahigh electromagnetic interference shielding effectiveness based on engineered structures of carbon nanotube films

High-performance electromagnetic interference (EMI) shielding materials with ultrathin, flexible, and pliable mechanical properties are highly desired for high-end equipments, yet there remain large challenges in the manufacture of these materials. Here, carbon nanotube film (CNTF)/copper (Cu) nanoparticle (NP) composite films are fabricated via a facile electrodeposition method to achieve high electromagnetic shielding efficiency. Notably, a CNTF/Cu NP composite film with 15μm thickness can achieve excellent EMI shielding efficiency of ∼248 dB and absolute EMI shielding effectiveness as high as 2.17×105 dB cm2 g-1, which are the best values for composite EMI shielding materials with similar or greater thicknesses. These engineered composite films exhibit excellent deformation tolerance, which ensures the robust reliability of EMI shielding efficiency after 20,000 cycles of repeated bending. Our results represent a critical breakthrough in the preparation of ultrathin, flexible, and pliable shielding films for applications in smart, portable and wearable electronic devices, and 5G communication.

Reviews on Flexible Force Sensors Based on Fiber Assemblies with Mass Production Efficiency

AbstractFlexible force sensors show great potential applications in smart wearable devices based on their softness and ease of deformation. Textiles are extremely compatible with the human body, where mechanical forces generated by human movements and physiological activities create rich application scenarios for flexible force sensors. Currently, the bottleneck in the development of flexible sensors depends on the breakthrough of mass production efficiency, which has been a research focus in recent years to accelerate the application of smart textiles in various fields. This work reviews the research progress of flexible force sensors based on fiber assemblies with mass production efficiency, which is discussed in four aspects: sensing mechanisms, structure design, preparation methods, and application. Finally, the challenges faced by mass production of flexible force sensors are analyzed and summarized, and a few inspirations for their future development direction are provided.

GO based nanocomposite hydrogel enabled high performance wearable all-solid supercapacitor based on hierarchical structure electrodes derived from ZIF-67

The flexible and wearable supercapacitors have attracted wide interest because of their widespread application in smart electronic devices with rapid charging and discharging. As an important part of supercapacitor, the electrode materials with a hollow structure, especially those with hierarchical structures that provide an array of continuous hollow cages, are considered promising. Because of its porous shell which is rich in redox reaction sites for supercapacitors. In this work, we fabricated a ZIF-67 derived hollow Co3O4 growth on the surface of 1D NiCo2O4 to assemble into a beaded structure. In this case, NiCo precursor acted as a structure-directing agent to grow a ZIF-67, a promising electroactive material of electrochemical capacitors to provide capacitance after calcination. Combined with the grapheneoxide (GO) based high conductivity hydrogel as the solid electrolyte, the capacitance of the flexible supercapacitor exhibited a high specific capacitance of 90F g−1 at 0.5 A/g, and it was sturdy and durable. There was no significant loss of capacitance while suffering from bending and pressing. The outstanding electrochemical properties of the all-solid supercapacitor can be attributed to the unique nanostructure of the electrode that created more reactive active sites, increased the diffusion pathway for electrolyte ions, along with the high conductivity of the hydrogel electrolyte.

Metal oxide-mixed polymer-based hybrid electrochromic supercapacitor: improved efficiency and dual band switching

The inclusion of charge storage properties in electrochromic devices (ECDs) has gained much interest and has evolved into a promising emerging energy-related field due to multifunctional smart device applications. Here, an organic–inorganic solid-state asymmetric electrochromic supercapacitor device (ESCD) containing nano-CoTiO3-mixed poly-3-hexylthiophene and WO3 as two electrodes has been designed to study electrochromic and supercapacitor properties. The electrochemical properties of CoTiO3 show a pseudocapacitive-type charge storage capability, which has been utilized to enhance the electrochromic performance of the ESCD with additional charge storage ability. The device shows charge storage properties with fast charging and slow discharging, giving very high coulombic efficiency with a specific capacitance of 6.4 mF cm−2 at 0.2 mA cm−2 current density. The device shows excellent electrochromic supercapacitive properties with a color contrast of ∼50% and a short switching time of ∼1 s at a 515 nm wavelength with excellent cyclic stability. The device exhibits the capability to cut near infrared wavelength (700 nm and 850 nm) and has a potential application as a heat filtering device. Thus, the addition of pseudocapacitive-type materials in ECDs enhances the capacitive performance along with electrochromic properties, which makes ECDs more suitable for real life applications.

Epoxy resin reinforced high-performance conductive composite foam with ultra-wide pressure sensing range

Flexible piezoresistive sensors based on conductive polymer composites (CPCs) have shown great potential and application in smart wearable devices, sports and health monitoring. Nevertheless, the practical use of many CPCs pressure sensors is often limited by their narrow monitoring range and low sensitivity. Here, a thermoplastic urethane/ epoxy resin/ carbon nanotubes/ polydopamine/ Ti3C2TX MXene (TPU/EP/CNT/PDA/MXene) composite foam was prepared using the commonly used freeze-drying and impregnation methods. Due to the high strength of the EP/TPU foam matrix and CNT@MXene's internal and external synergistic conductive network, the TECPMF has outstanding mechanical and conductive properties. As a result, the foam pressure sensor has an extremely wide monitoring range (0∼300 kPa) and a sensitivity of 2.42 kPa−1 (0∼5 kPa). Furthermore, the superior performance of the foam provides fast response (100 ms) and outstanding durability of more than 8000 cycles. The piezoresistive TECPMF sensor can be used for real-time monitoring of human movement, as well as the magnitude and position of various pressures and air pressures. These promise to enable a wide range of smart wearable and engineering applications. This work opens up a new avenue for the design of more advanced piezoresistive sensors.

Dynamic Photonic Janus Colloids with Axially Stacked Structural Layers.

Diblock copolymer (dBCP) particles capable of dynamic shape and color changes have gained significant attention due to their versatility in programmable shapes and intricate nanostructures. However, their application in photonic systems remains limited due to challenges in achieving a sufficient number of defect-free photonic layers over a tens-of-micrometer scale. In this study, we present a pioneering demonstration of photonic dBCP particles featuring over 300 axially stacked photonic layers with responsive color- and shape-transforming capabilities. Our approach leverages the complex interplay between the macrophase separation of multiple incompatible components and the microphase separation of dBCP from solvent-evaporative microemulsions. Specifically, continuous phase separation of silicone oil from polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP), triggered by solvent evaporation, promotes the anisotropic growth of PS-b-P2VP layers. This results in the formation of Janus colloids, where an oil droplet merges with a nanostructured polymer cone and lamellar structures align along the long axis of the cone. We highlight the capability to precisely adjust the particle morphology and the corresponding orientation, dispersion, and structural color window by modulating both the molecular weight of PS-b-P2VP and the volume ratio between PS-b-P2VP and silicone oil. Furthermore, reversible swelling/deswelling of photonic colloids is visualized and correlated with their structural colors. Finally, we demonstrate the potential of this study by presenting a multicolor-patterned array of photonic colloids, highlighting the possibilities for applications in smart photonic ink and devices.

The use of diffraction techniques for understanding structure–property relationships in Heusler alloys

Heusler compounds are intermetallic alloys that are capable of a wide range of unique properties such as magnetocaloric, thermoelectric, and magnetic-shape-memory effects, antiferromagnetism, superconductivity, and they can even act as topological insulators. These multifunctional behaviors make Heusler alloys prime candidates for numerous smart device applications. However, their specific properties critically depend on their crystalline structures, chemical order, structural phase transformations, and crystallographic texture. Thus, as compositions and processing parameters are varied it becomes essential to be able to accurately characterize the structure of these materials at various scales. This paper provides a brief review of diffraction-based characterization techniques ideally suited for the characterization of Heusler alloys with examples from our previous works including use of synchrotron, neutron, and electron diffraction, especially as a function of temperature and/or magnetic field to explain important phenomena demonstrated by Heusler alloys.

High-Performance Piezoelectric Nanogenerator of BTO-PVDF Nanofibers for Wearable Sensing.

Piezoelectric nanogenerator (PENG) produces stable electrical signals in response to external mechanical stimuli and holds promise in the fields of flexible sensors and smart wearable devices. In practice, a high-performance PENG with a straightforward structure and exceptional reliability is deeply desired. This study optimally synthesizes piezoelectric composites comprising polyvinylidene fluoride (PVDF) incorporated with barium titanate (BTO) nanoparticles (NPs) and fabricated a PENG with heightened sensitivity by using the electrospinning technique. The polar β-phase content of the dual-optimized BTO-PVDF (barium titanate and polyvinylidene fluoride) electrospun fiber reaches up to 82.39%. In the bending mode, it achieves a remarkable maximum open-circuit voltage of 19.152V, a transferred charge of 8.058 nC, and an output voltage per unit area of 2.128Vcm- 2. Under vertical pressure conditions, the BP-PENG exhibits an impressive voltage of 12.361V while the force is 2.156 N, demonstrating a notable pressure sensing sensitivity of 5.159VkPa-1, with an excellent linear relationship. Furthermore, the BP-PENG displays sensitive sensing features in monitoring hand movements. The sensitive response and high performance make it promising for applications in human motion monitoring and smart wearable devices.

High specific capacitance and NTC behavior of substituted cobalt oxide spinels for electrochemical supercapacitor and thermistor applications

Due to the growing importance of low-cost energy storage devices in smart device applications, finding an appropriate electrode material with the least self-discharging, high power, and energy densities is the need of the hour. In this paper, Cu and Mn-modified Co3O4 spinels in the form of CuCo2O4 and MnCo2O4 are reported as the most promising electrode materials for high-performance electrochemical supercapacitors. Modified Co3O4 spinels were prepared by the co-precipitation technique, and the X-ray diffraction (XRD) studies show a single-phase formation with cubic crystal symmetry. The average crystallite size estimated by considering the highest intensity peak of the diffraction pattern using Scherrer’s relation shows the average crystallite size below 30 nm for reported spinels. Scanning electron microscopic (SEM) images stabilize the fact that grains with nanosizes consisting of regular shapes and excellent morphological features. The dc-conductivity measurement establishes the essence of negative temperature coefficient of resistance (NTCR) behavior in nanostructured spinels. The specific capacitance (Cs) of CuCo2O4 and MnCo2O4 estimated using cyclic voltammetry (CV) was found to be 616.074 F g−1 and 1401.16 F g−1 for a scan rate of 10 mV s−1 with verified stability up to 1000 cycles. The low internal resistance value in the range of 0.1 Ω for both the spinels verified by the electrochemical impedance spectroscopy (EIS) graph confirms these spinels as encouraging electrode materials for electrochemical supercapacitors.

Optimization of Higher Education Teaching Methodology System Based on Edge Intelligence

Abstract This study provides an in-depth research on the dynamic allocation of resources in higher education teaching and learning, especially in the application of edge intelligence architecture. In the study, the characteristics of edge intelligence and its application in smart mobile devices (SMDs) are first analyzed, highlighting the role of mobile edge computing (MEC) in reducing latency and improving the quality of user experience. Then, the study adopts a data acquisition method based on deep neural network (DNN) model to optimize the edge training model. The experimental results show that the efficiency of edge computing can be significantly improved by optimizing the allocation of computing resources and reducing the data transmission delay. Specifically, the total training delay and energy consumption of the edge server are reduced under different global iteration numbers in the experiment. In addition, the study also explores the integration of 5G networks and AR/VR technology in education. It proposes a teaching optimization model based on edge intelligence, improving interaction quality and learning efficiency in AR/VR safety education classrooms. The study shows that the teaching model performs well in reducing latency and increasing transmission rate, which is especially suitable for dual-teacher classroom scenarios and provides a new perspective for future higher education teaching.

Phase transition characteristics, electrical and optical properties of AgNbO<sub>3 </sub>crystals grown by flux method

<sec>AgNbO<sub>3</sub>, with the antiferroelectric ordering and huge polarization (>50 μC/cm<sup>2</sup>), has potential applications in smart electronic devices, such as energy storage dielectrics, large displacement actuators, and electrocaloric cooling device. Large electro-strain and excellent energy storage properties have been reported in AgNbO<sub>3</sub>-based ceramics. Nevertheless, the lack of systematic research on the AbNbO<sub>3</sub> single crystals increases the difficulty in further understanding their structure-property relationship.</sec><sec>In this work, <inline-formula><tex-math id="M3">\begin{document}${\left\langle {001} \right\rangle _c}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20230984_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20230984_M3.png"/></alternatives></inline-formula> oriented AgNbO<sub>3</sub> single crystals with a large size (maximum size 5 mm×4 mm×4 mm) and high quality are successfully grown by the flux method. The phase transition characteristics are studied by the X-ray diffraction, temperature dependence of dielectric data and AC impedance, polarized light microscope photos, and differential scanning calorimetry curves. The electrical and optical properties are studied by the ferroelectric response and electro-strain response, optical absorbance spectrum and photo-dielectric effect.</sec><sec>The AgNbO<sub>3</sub> single crystals with the <i>M</i> phase exhibit the same domain structure. When the structure changes from <i>M</i><sub>2</sub> to <i>M</i><sub>3</sub>, the contrast of the PLM image is darkened. Correspondingly, the conductivity and dielectric loss significantly increase, which relates to the dynamic behaviors of the carriers. Interestingly, neither exothermic peak nor endothermic peak relating to the <i>M</i><sub>2</sub>-<i>M</i><sub>3</sub> transition is observed. The active energy for the <i>M</i><sub>3</sub> phase AgNbO<sub>3</sub> single crystal is ~1.24 eV. When the structure changes from orthogonal <i>M</i><sub>3</sub> to paraelectric orthogonal <i>O</i>, the domain structure disappears and the contrast becomes darker. The finding indicates that the anisotropy of the crystals disappears. At the same time, an obvious thermal hysteresis observed in the DSC curve reveals that the <i>M</i><sub>3</sub>-<i>O</i> transition is first-order. At room temperature, the direct band gap of AgNbO<sub>3</sub> single crystal is ~2.73 eV, which is slightly narrower than that of AgNbO<sub>3</sub> ceramic. Below the critical electric field, AgNbO<sub>3</sub> single crystal shows an electro-strain of 0.076% under <i>E</i><sub>m</sub> = 130 kV/cm. The obtained electro-strain value is much higher than that of AgNbO<sub>3</sub> ceramic under the same electric field. The relative permittivity increases from 70 to 73 under the green laser irradiation, showing an apparent photo-dielectric effect. We believe that our study can assist in the further understanding of the phase transition characteristics and physical properties in AgNbO<sub>3</sub> single crystals.</sec>

Plastic phase transitions in tris(hydroxymethyl)aminomethane perchlorate.

Organic crystal materials with metal-free feature and intrinsically low molecular mass are highly desirable for applications in flexible smart devices. Here, we reported a plastic crystal, tris(hydroxymethyl)aminomethane perchlorate (Tris-HClO4), which crystallizes in the R3̄ space group at room temperature and undergoes plastic phase transition at 369 K, showing a large entropy gain of 70.5 J mol-1 K-1, much higher than its fusion entropy gain (12.9 J mol-1 K-1). PXRD measurement indicates that it has cubic lattice symmetry in the high-temperature phase. Moreover, it exhibits excellent dielectric permittivity switching properties and robust cyclic stability. This work could be the pathway for chemical designing multifunctional switchable materials with the motive of combining the idea of symmetry breaking and plastic phase transition.

Gd(III)/Dy(III)-based coordination polymers for luminescent and magnetic properties

Two isostructural lanthanide-based coordination polymers, namely, {[Gd2(H2dhtp)3(DMF)2(H2O)4]·2DMF·H2On (1) and {[Dy2(H2dhtp)3(DMF)2(H2O)4]·2DMF·H2O}n (2) (H4dhtp = 2,5-dihydroxyterephthalic acid, DMF = N, N-dimethylformamide) were synthesized and structurally characterized by single-crystal X-ray diffraction, IR, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and elemental analysis. Compounds 1 and 2 exhibited 3D networks and isostructures, except for the distinction of the metal ion. Magnetic measurements indicated that complex 1 exhibited the dominating contribution at low temperature of zero-field splitting for Gd(III) materials, and the complex 2 shown the depopulation of the excited excited state for Dy(III) material. The solid luminescent properties of H4dhtp, 1, and 2 displayed a blue emission band, while the solution state luminescent properties all demonstrated a green emission band. The combination of luminescence sensing and magnetism in single-phase coordination polymers may offer great potential applications in smart multitasking devices.

Swift 4D printing of thermoresponsive shape-memory polymers using vat photopolymerization

Shape-memory polymers (SMPs) are smart materials that have gained significant attention in recent years owing to their widespread application in smart structures and devices. Digital light processing (DLP), a vat-photopolymerization-based technique, is a significantly faster technology for printing a complete layer in a single step. The current study reports a facile and fast method for the 3D printing of SMP-based smart structures using a DLP 3D printer and a customized resin. A liquid crystal (LC, RM257) was combined with the resin to introduce shape-memory properties. The combination of LCs in photocurable resin provides the opportunity to directly 3D-print thermoresponsive structures, avoiding the complexity of SMP resin preparation. The structures were printed with different geometries, and the shape-memory response was measured. Lattice structures were fabricated and programmed to obtain tunable mechanical properties. Furthermore, the strain-sensing response was measured to demonstrate the utility of these lattice structures as smart patches for joint-movement sensing. The SMPs can be prepared conveniently and can potentially be used for various applications, such as smart tools, toys, and meta-material sensors.

Structure and Properties of TiNi Shape Memory Alloy after Quasi-Continuous Equal-Channel Angular Pressing in Various Aged States

The effect of quasi-continuous (QC) equal-channel angular pressing (ECAP) in various pre-aged states on the structure formation and mechanical and functional properties of a hyper-equiatomic titanium nickelide (TiNi) shape memory alloy is studied. QC ECAP with a channel intersection angle of 110° is carried out at a temperature of 450 °C after aging for 1 and 5 h for three passes. To investigate the obtained structure and properties, the following research methods are applied: transmission electron microscopy, XRD analysis, calorimetric study, tension and hardness tests, and a special technique for the determination of functional properties. QC ECAP allows for the considerable refinement of structural elements and results in obtaining a mixed fine-grade structure, with structural elements of average sizes of 92 nm after pre-aging for 1 h and 115 nm after pre-aging for 5 h. Pre-aging for 5 h before QC ECAP, in combination with QC ECAP and post-deformation aging at 430 °C for 1 h, provides the best combination of mechanical and functional properties: a dislocation yield stress of 1410 MPa, ultimate tensile strength of 1562 MPa, and total recoverable strain of 11.6%. These values are comparable with the best results obtained for titanium nickelide and expand opportunities for the application of smart shape memory devices.