Search Results (432)

This study examines how the sense of home for people with dementia is shaped not only by physical settings but by dynamic atmospheric compositions emerging through memory, sensation, and everyday practices. Building on a preliminary literature mapping that identified three dimensions of home in later-life care environments—safe space, small world, and connection—we developed a multisensory co-design toolkit combining key-element cards and curated olfactory prompts. The study was conducted in a dementia-friendly residential care facility in Italy. Nine residents with mild–moderate dementia (aged 75–84) participated in two group sessions and six individual sessions, facilitated by two design researchers with care staff present. Data consist of audio-recorded and transcribed interviews, guided olfactory sessions, and researcher fieldnotes. Across sessions, participants articulated “small worlds” as micro-environments composed of meaningful objects, bodily comfort, routines, and sensory cues that supported emotional regulation and identity continuity. Olfactory prompts, administered through a low-intensity and participant-controlled protocol, supported scene-based autobiographical recall for some participants, often eliciting memories of domestic rituals, places, and relationships. Rather than treating home-like design as a fixed architectural style, we interpret home as continuously re-made through situated sensory–temporal patterns and relational practices. We translate these findings into atmospheric design directions for dementia care: designing places of self and refuge, staging accessible material memory devices, embedding gentle olfactory micro-worlds within daily routines, and approaching atmosphere as an ongoing process of co-attunement among residents, staff, and environmental conditions. The study contributes a methodological and conceptual framework for multisensory, narrative-driven approaches to designing home-like environments in long-term care. Full article

To develop a cost-effective shape memory alloy fiber-reinforced engineered cementitious composite (SMAF-ECC) with excellent mechanical properties, polypropylene (PP) fibers were used to partially replace polyvinyl alcohol (PVA) fibers to prepare the ECC matrix, and superelastic shape memory alloy fibers (SMAFs) were incorporated to fabricate a novel SMAF-ECC. Uniaxial tensile tests were systematically performed to characterize the tensile mechanical properties of the composites, focusing on the effects of SMAF volume content and diameter. The results indicate that the optimal base ECC mix proportion is 0.8 vol.% PP fibers and 1.2 vol.% PVA fibers, achieving an ultimate tensile strain of 4.88% (only a 4.69% reduction compared to pure PVA-ECC) while significantly reducing material cost without sacrificing superior ductility. SMAF volume content and diameter notably influence the tensile performance of SMAF-ECC, with the specimen containing 0.2 mm diameter SMAFs at 0.2 vol.% exhibiting the best performance: initial cracking stress, ultimate tensile stress, and ultimate tensile strain are enhanced by 16.79%, 20.85%, and 2.87%, respectively, compared to pure ECC. This study provides a theoretical basis and parametric guidance for the engineering popularization and application of cost-effective SMAF-ECCs. Full article

Biocompatible poly(lactic acid) (PLA) was plasticized with poly(ethylene glycol) (PEG) added at concentrations of 10, 15, and 20 wt.% relative to PLA, and then processed into gyroid triply periodic minimal surface (TPMS) scaffolds using fused filament fabrication (FFF) 3D printing. The influence of PEG concentration and gyroid structure (50% infill density) on thermal transitions, crystallinity, and low–temperature shape-memory performance was systematically investigated. The shape-memory effect (SME) of the PLA–based scaffolds was tailored through compositional control and structural design. Shape recovery under thermal activation at 40 °C and 50 °C was examined to reveal the correlation between composition and structure in governing low–temperature shape-memory behavior. The optimal composition (PLA/10 PEG, 50% gyroid infill) achieved shape recovery with a recovery ratio (R_r) of 97 ± 1% at 40 °C within 6 ± 1 min, demonstrating optimal shape-memory activation close to physiological temperature. Structural and morphological changes were characterized using ATR–FTIR, Raman spectroscopy, DSC, XRD, and SEM, providing comprehensive insight into the plasticization of the PLA matrix and its impact on structure–property relationships relevant to bone tissue engineering. Full article

To address poor seismic performance, large residual displacement, and insufficient self-centering capacity of prefabricated frame joints in building industrialization, this study proposes a novel self-centering prefabricated frame joint reinforced with shape memory alloy fiber (SMAF)–engineered cementitious composite (ECC) composites (SMAF-ECC). A validated finite element model of the proposed joint was established using ABAQUS, with comparative analyses conducted against conventional reinforced concrete (RC) and ECC-strengthened (RC-E) joint models to explore the effect of SMAF volume content on seismic performance. Results show that replacing the joint core zone concrete with SMAF-ECC significantly enhances the joint’s seismic and self-centering capabilities, reducing residual displacement and optimizing hysteretic behavior. SMAF volume content is a key factor affecting performance, with an optimal value identified and excessive content leading to fiber agglomeration and degraded self-centering ability. This study provides a feasible solution to improve the seismic resilience of prefabricated frame joints, laying a foundation for the application of SMAF-ECC in prefabricated structures. Full article

Background: Soft actuation relies on materials that are lightweight, flexible, and responsive to external stimuli. In biomedical applications, miniaturization and biocompatibility are key requirements for developing smart devices. Thermoplastic polyurethane (TPU) is particularly attractive due to its elasticity, processability, and biocompatibility; however, an improvement in its shape-recovery performance would significantly enhance its suitability for actuation systems. This study aims to develop TPU-based shape memory polymer (SMP) composites with improved functional behavior for biomedical applications. Methods: TPU was modified with aluminum nanoparticles (AlNPs) and multi-walled carbon nanotubes (MWCNTs), incorporated individually (1 wt.% and 3 wt.%) and in hybrid combinations (MWCNT:AlNP ratios of 2:1, 5:1, and 10:1). Samples were produced by compression molding and characterized through thermal, mechanical, electrical, and shape-recovery tests, supported by morphological analysis. Results: AlNPs moderately improved thermal conductivity, while MWCNTs significantly enhanced electrical conductivity and doubled the recovery force compared with neat TPU. Hybrid composites showed intermediate properties, with the 5:1 MWCNT:AlNP ratio offering the best balance between recovery force and activation speed. Conclusions: The synergistic combination of MWCNTs and AlNPs effectively enhances TPU’s multifunctional behavior, demonstrating strong potential for soft actuation in biomedical devices. Full article

Ionomers are promising materials because ionic interactions and their reversible clustering provide sensitivity to stimuli and facilitate energy dissipation, polymer miscibility, and ion transport. The existence of a wide variety of interacting ionic groups and their associated macromolecular structures provides the basis for considering the supramolecular organization of ionic polymeric materials as a factor determining the emergence of specific properties. The main structural elements of ionomers are ionic clusters, and the properties of ionomers are determined by their sizes and size distribution. Ionomers are attractive for use in composites, actuators, coatings, dyed textiles, adhesives, shape-memory and self-healing materials, water purification membranes, and ion-exchange membranes for fuel cells and batteries. This paper presents a review of the macromolecular structure and supramolecular organization of ionomers and their properties, depending on the basis of their ionic functionalization. The ionic functions of ionomers are determined primarily by the type of ion (cations or anions) that serves as the basis for their functionalization. Ionomers containing both anionic and cationic pendant ions are considered, with attention given to the influence of the nature of the counterions used on the properties of ionomers. Full article

Over the last decade, laser powder bed fusion (LPBF) received increased attention as a method of producing complex-shaped products from various materials. Recent results indicate the potential of this technology for the production of intermetallic NiTi alloys with shape memory. Several studies have demonstrated a strong influence of the LPBF process conditions on the resulting material properties, i.e., the martensitic phase transformation temperatures, reversible/irreversible strain after cyclic loading, phase composition, chemical composition, etc. However, the mechanisms of functional properties altering during LPBF consolidation remain unexplored in the present state-of-the-art. This study aims to advance the knowledge about tailoring material properties of NiTi under laser influence. In this work, thin-walled samples were manufactured from pre-alloyed NiTi powder via LPBF in a wide window of laser power and scanning speed, excluding hatch spacing by employing a single track-based scanning strategy to reveal the pure effect of the laser’s influence. NiTi samples were characterized by various methods such as differential scanning calorimetry, X-ray diffraction, and mechanical tests. Established relationships between NiTi properties and the LPBF process conditions provide the basis for the development of NiTi production protocols with controlled functional properties. Full article

In this study, surface alloying technology based on Gas Tungsten Arc Welding (GTAW) was used to synthesize in situ NiTiTa coatings on a NiTi substrate using commercially pure Ta foils. The influence of different Ta contents (0.91, 1.42, and 2.91 at.%) on the microstructure, phase formation, hardness, corrosion resistance, and X-ray visibility of the prepared coatings were systematically studied. These results show that the NiTiTa coatings fabricated by GTAW were free of microcracks with good surface quality and superior adhesion to the NiTi substrate. The NiTiTa coatings are mainly composed of columnar austenitic NiTi (B2), and martensitic NiTi (B19’) with (Ti, Ta)2Ni precipitating at the grain boundaries. The proportion of B19’ martensite and the Ta content dissolved in the NiTi matrix increases with the increasing addition of Ta. In addition, β-Ta appeared in the coating formed with 1.42 at.% Ta and precipitated abundantly when the Ta amount was increased to 2.91 at.%. Changes in phase composition and secondary phases lead to a decrease in the material nanohardness. To simulate the body fluid environment, corrosion tests were conducted in Hank’s solution at a rate of 0.5 mV/s. Electrochemical tests show that the NiTiTa coatings exhibit superior corrosion resistance, where the corrosion potential, Ecorr, increased with increasing Ta content. The enhanced X-ray visibility of the newly formed coatings was also revealed. This work provides a cost-effective method for in situ synthesis of NiTiTa coatings on NiTi alloys, highlighting its potential for improving the corrosion resistance and X-ray visibility of NiTi shape memory alloys. Full article

This study explores the development of 4D-printed smart structures based on PLA/PETG (75/25) polymer blends reinforced with nanocellulose (0–3 wt%), processed using fused filament fabrication (FFF). Both conventional U-shaped specimens and anti-tri-chiral auxetic architectures were fabricated to evaluate the effects of nanocellulose on mechanical performance and shape memory behavior. Tensile tests demonstrated that nanocellulose reinforcement enhanced both strength and stiffness, with the highest values observed at 2 wt% (tensile strength of 56 MPa and Young’s modulus of 3.3 GPa). In standard U-shaped samples, all compositions showed excellent shape fixity and recovery (100%). For auxetic structures, shape memory behavior and deformation response varied with nanocellulose content. Notably, 2 wt% nanocellulose yielded the highest shape recovery ratio (90.8%) and fixity (99.8%), indicating improved elasticity and structural responsiveness. Meanwhile, 1 wt% nanocellulose resulted in the highest energy absorption and more controlled deformation under compression, suggesting enhanced energy dissipation and stress distribution. A slight decrease in performance at 3 wt% is attributed to nanocellulose agglomeration and reduced polymer chain mobility. These findings highlight nanocellulose as a multifunctional additive that enables fine-tuning of mechanical and functional properties in 4D-printed structures. Depending on the intended application whether focused on energy absorption, mechanical strength, or shape recovery nanocellulose content can be strategically adjusted. This approach opens pathways for designing responsive materials suited for biomedical engineering, adaptive devices, and advanced environmental technologies. Full article

Shape memory polymers (SMPs) are a class of smart materials that exhibit unique shape-fixing and recovery abilities, attracting wide attention for applications in electronics, aerospace, and biomedical engineering. Chitosan (CS) as a renewable biopolymer, possessing good biocompatibility, biodegradability, and antimicrobial properties; its use as a matrix enhances the environmental compatibility and bio-adaptability of SMPs. MXene, as a novel two-dimensional material, is characterized by high electrical conductivity, abundant surface functional groups and good hydrophilicity, showing potential in energy storage, electromagnetic shielding and sensing. In this work, CS and poly (vinyl alcohol) (PVA) were used as the polymer matrix, and carbon nanotubes (CNTs) together with MXene were introduced as co-fillers to construct multifunctional composites. The effect of the CNTs/MXene hybrid fillers on mechanical properties, electromagnetic shielding and multi-stimuli-responsive shape memory behavior was systematically investigated. After ratio optimization, the composites showed excellent comprehensive performance: tensile strength reached up to 20.0 MPa, Young’s modulus up to 292.2 MPa, and maximum elongation at break of 23.2%; electromagnetic interference shielding effectiveness (SE_T) in the X-band (8.2–12.4 GHz) reached a maximum of 10.6 dB; shape fixation rates exceeded 90%; under thermal stimulation, a shape recovery ratio of 98.3% was achieved within 41.7 s; light-driven recovery rate reached 86.5% with a minimal recovery time of 82.3 s; under electrical stimulation the highest recovery rate was 94.1% with a shortest recovery time of 30 s. This study successfully prepared functional multi-stimuli-responsive shape memory composite films and provided a new strategy for the design of green smart materials. Full article

Shape-memory polymers (SMPs) are a unique class of smart materials capable of recovering their original shape upon external stimuli, with thermoresponsive polyurethane (PU) being one of the most widely studied systems. However, the relatively low mechanical strength, thermal stability, and durability of PU limit its broader functional applications. PU/ND composites containing 0.1–0.5 wt.% ND were fabricated via melt blending and injection molding method. The objective was to evaluate the effect of ND reinforcement on the mechanical, scratch, thermal, rheological, and shape-memory properties. Results show that tensile strength increased up to 114% and Young’s modulus by 11% at 0.5 wt.% ND, while elongation at break decreased due to restricted chain mobility. Hardness improved by 21%, and scratch resistance was significantly enhanced, with the coefficient of friction reduced by 56% at low loads. Thermal stability was improved, with the maximum degradation temperature shifting from 350 °C (pure PU) to 362 °C (0.5 wt.% PU/ND) and char yield increasing by 34%. DSC revealed an increase in glass transition temperature from 65 °C to 68.6 °C. Rheological analysis showed an 89% reduction in damping factor (tan δ), indicating enhanced elasticity. Shape-memory tests confirmed notable improvements in both shape fixity and recovery ratios across successive cycles compared to neat PU, with the highest enhancements observed for the 0.5 wt.% PU/ND nanocomposite—showing up to 7.6% higher fixity and 32% higher recovery than pure PU. These results demonstrate that ND reinforcement effectively strengthens PU while preserving and improving its shape-memory behavior, making the composites promising candidates for high-performance smart materials in sensors, actuators, and aerospace applications. Full article

Shape memory polymer composites (SMPCs) are promising materials in aerospace thanks to their light weight and ability to provide an actuation load during shape recovery, the magnitude of which depends on the laminates design. In this work, SMPCs were manufactured by alternating carbon fiber prepregs with a SM interlayer of epoxy resin. The number of composite plies ranged from 2 to 8 and two interlayer thicknesses were selected (100 μm and 200 μm in the lamination stage). Compression molding was performed for consolidation, and the interlayer’s thickness was reduced by edge bleeding. A thermo-mechanical cycle was applied for memorization. The shape fixity and the shape recovery of the vast majority of the SMPCs were above 90%, with the 200 μm/six-ply laminate recording the highest combination of values (94.8% and 95.7%, respectively). A significant effect due to the presence of a thicker interlayer was not evident, underlying the need to determine specific manufacturing procedures. Starting from these results, a lab-scale procedure was implemented to manufacture a smart device by embedding a microheater in the 200 μm/two-ply architecture. The device was memorized into a L-shape (90° bending angle), and a voltage of 24 V allowed it to recover 86.2° in 90 s, with a maximum angular velocity of 1.55 deg/s. Full article

The field of 4D printing has seen rapid advancement in recent years, making it a highly dynamic research domain. This new technology is promising for the development of brand-new lightweight, smart and reliable devices. This article is a literature review of the latest research in 4D printing, focusing on electroconductive thermosensitive Shape Memory Polymers. They are promising thanks to their high strength-to-weight ratio and their large deformability. However, devices made of such materials are difficult to embed into larger systems because of the triggering mechanism needed to actuate them. Electroconductive Shape Memory Polymers can be stimulated by the Joule effect, but the intricacies and interdependence of their properties make them a great scientific challenge. The first part of this article provides a clear explanation of the main concepts of 4D printing. Afterwards, it focuses on Fused Filament Fabrication due to its high customisability and ease of use. A description of the properties of thermosensitive 4D printed specimens is provided in the third part. Finally, their main challenges and intricacies are discussed. Full article

This study investigates the control of the phase-structural state in Ni–45Ti–xCu (x = 5, 7 at.%) shape memory alloys fabricated via a shortened powder metallurgy route: mechanical activation → spark plasma sintering (SPS) → heat treatment. Compact samples were produced from mechanically alloyed powders (650–750 rpm, up to 5 h) and sintered at 900 °C. The structure and microstructure were characterized using X-ray diffraction (to identify B2/B19′/Ni₄Ti₃ phases and assess ordering) and SEM–BSE/EDS (to analyze morphology, porosity, and Ni-rich precipitates). Two post-processing treatments were applied: single-stage annealing (500 °C, 2 h) and a three-stage treatment (900 °C/30 min → water quenching → 300 °C/20 min). Mechanical alloying transformed the initial elemental powder mixture (fcc-Ni, hcp-Ti, fcc-Cu) into a supersaturated fcc-(Ni, Cu, Ti) solid solution with emerging NiTi phases, with a minimum particle size achieved after ~300 min at 750 rpm. SPS compaction yielded a high-density matrix consisting predominantly of the B2 phase. Single-stage annealing preserved B19′ martensite and Ni₄Ti₃ precipitates, particularly in the 5 at.% Cu alloy. In contrast, the three-stage treatment dissolved the Ni₄Ti₃ precipitates, suppressed the formation of B19′ and R phases, and stabilized a highly ordered B2 matrix. Increasing the Cu content from 5 to 7 at.% significantly enhanced the B2 phase fraction, reduced secondary nickel-rich phases, and improved structural homogeneity, evidenced by a continuous neck network and closed porosity. The optimized condition—7 at.% Cu combined with the three-stage annealing—produced a microstructure with >95% B2 phase, <1% Ni₄Ti₃, and ~98% relative density. This forms the prerequisite microstructural state for a narrow transformation hysteresis and high functional cyclic stability. Full article

This paper focuses on the vibration analysis of a prototype helicopter rotor test stand, with particular attention to the dynamic response of its electric propulsion system. The stand is driven by an induction motor and equipped with composite rotor blades of various geometries, including blades with shape memory alloy (SMA)-based torsion actuators for angle of attack (AoA) adjustment. These variable geometries significantly influence the system’s dynamic behavior, where resonance phenomena may pose risks to structural integrity. The objective was to investigate how selected operational parameters specifically motor speed and AoA affect the vibration response of the propulsion system. Structural vibrations were measured using a tri-axial piezoelectric accelerometer system integrated with calibrated signal conditioning and high-resolution data acquisition modules. This setup enabled precise, time-synchronized recording of dynamic responses along all three axes. Fast Fourier Transform (FFT) and Power Spectral Density (PSD) methods were applied to identify dominant frequency components, including those associated with rotor harmonics and SMA activation. The highest vibration amplitudes were observed at an AoA of 16°, but all results remained within the vibration limits defined by MIL-STD-810H for rotorcraft drive systems. The study confirms the importance of sensor-based diagnostics in evaluating electromechanical propulsion systems operating under dynamic loading conditions. Full article