Search Results (76)

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 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

With the growing demand for reliable, low-impact deployment systems in small satellite missions, this work introduces an antenna deployment mechanism using fiber-reinforced shape memory polymer composites (SMPC). The mechanism utilized thermally activated SMPCs for stowage and release, configured with different glass transition temperatures (T_g), tuned through the addition of poly(ethylene glycol) (PEG-600), for sequential actuation. The deployment mechanism consisted of three SMPC components with varying PEG concentrations: SMPC-P (0 wt%), SMPC-5 (5 wt%), and SMPC-10 (10 wt%). For component design, three bending angle configurations (BAC) of 20°, 30°, and 40° were tested. The samples exhibited the highest fixity ratio (93.58%, 95.76%, and 96.52% for SMPC-P, SMPC-5, and SMPC-10, respectively) when conformed to the 20° BAC. All samples achieved full recovery within 2 min, with PEG-incorporated composites exhibiting more uniform behavior across cycles, while recovery rates varied by material and BAC. Deployment testing confirmed the antenna was released successfully across all BACs. The 20° BAC exhibited the fastest response, completing deployment 24 s and 30 s ahead of the 30° and 40° BACs, respectively. The proposed mechanism exhibits promising potential for integration in future CubeSat missions. However, further testing under simulated space conditions is necessary to comprehensively assess and validate its performance. Full article

This study presents a novel strategy for designing photocurable resins tailored for the additive manufacturing of smart thermoset materials. A quaternary formulation was developed by integrating bis(2-methacryloyl)oxyethyl disulfide (DADS) with an epoxy/thiol-ene system (ETES) composed of diglycidyl ether of bisphenol A (EP), pentaerythritol tetrakis(3-mercaptopropionate) (PTMP), and 4,4′-methylenebis(N,N-diallylaniline) (ACA4). This unique combination enables the simultaneous activation of four polymerization mechanisms: radical photopolymerization, thiol-ene coupling, thiol-Michael addition, and anionic ring-opening, within a single resin matrix. A key innovation lies in the exothermic nature of DADS photopolymerization, which initiates and sustains ETES curing at room temperature, enabling 3D printing without thermal assistance. This represents a significant advancement over conventional systems that require elevated temperatures or post-curing steps. The resulting hybrid poly(acrylate–co-ether–co-thioether) network exhibits enhanced mechanical integrity, shape memory behavior, and intrinsic self-healing capabilities. Dynamic Mechanical Analysis revealed a shape fixity and recovery of 93%, while self-healing tests demonstrated a 94% recovery of viscoelastic properties, as evidenced by near-overlapping storage modulus curves compared to a reference sample. This integrated approach broadens the design space for multifunctional photopolymers and establishes a versatile platform for advanced applications in soft robotics, biomedical devices, and sustainable manufacturing. Full article

This paper investigates digital comics—particularly webcomics and webtoons—as emerging forms of cultural heritage, analyzing their exponential global influence alongside the limitations of traditional heritage frameworks in systematically preserving them. The UNESCO heritage model, rooted in concepts of physical fixity and authenticity, is shown as inadequate for born-digital works like comics, which derive meaning from technological infrastructure, dynamic platforms, and ongoing community interaction rather than static material forms. Drawing on heritage futures and digital materiality theories, the authors argue that digital comics exemplify "temporal authenticity," evolving through continual transformation and algorithmic curation. The paper details how platform recommendation systems and analytics directly shape which comics achieve cultural visibility and preservation, while community-driven initiatives—such as The Flashpoint Archive—demonstrate effective models for holistic, grassroots digital preservation beyond institutional reach. Ultimately, the study calls for new theoretical and practical approaches to heritage, recognizing digital comics as both cultural artifacts and dynamic, platform-specific vernacular expressions. Full article

Biodegradable and bio-based polymers, such as starch and gelatin, are emerging as an important alternative to the use of conventional polymers. In this work, different proportions (1/1, 1/1.5, 1/2, and 1/2.5) of these bio-based polymers will be investigated, with the primary objective of considering their strong moisture dependence as an advantage instead of a problem, as commonly considered. For this interesting challenge, the humidity-activated shape memory effect has been studied in both neat and plasticized starch. Additionally, for the first time, to the best of our knowledge, the shape-memory behavior activated by humidity in gelatin, as well as in starch/gelatin blends, is reported. In all cases, starch, gelatin, and their plasticized blends show excellent values in terms of strain fixity ratio, obtaining values of about 100% in all cases, and strain recovery ratio, with values higher than 90% for the samples studied. Moreover, considering their potential application as food packaging, mechanical response, wettability, water permeability, water uptake rate, and roughness is also studied in this work, taking into account the effect of the different amounts of gelatin on the final behavior of the materials. Full article

Integrating strong mechanical properties and excellent optical properties for self-healing materials is challenging in both academia and industry. Robust self-healing polyurethane elastomers are expected to have superior mechanical properties, transparency, remarkable healing capability, and shape-memory performance via the adjustment of chemical and microphase separation structure. Herein, a robust transparent self-healable 4,4′-diphenylmethane diisocyanate (MDI)-based polyurethane elastomer containing disulfide bonds and branched structure (MPUE-SS) was synthesized. The chemical and topological structures, compatibility of soft–hard phases, and hard domain size of polyurethane could be adjusted via branched structure and mixed chain extender containing disulfide bonds and 1,4-butanediol (BDO), leading to enhanced self-healing, transparency, and mechanical properties. MPUE-SS exhibited a maximal tensile strength of 40 MPa. The microphase separation structure and reduced crystallinity led to a high transparency of about 91%, close to that of alicyclic polyurethane elastomers. After cutting in half and splicing, the MPUE-SS film recovered more than 95% of the original mechanical properties in 24 h. The shape recovery ratio at 40 °C and shape fixity ratio at −20 °C of MPUE-SS were 96.0% and 99.6%, respectively, higher than those of MPUE without disulfide bonds. Therefore, the chemical, topological structures, and microphase separation of polyurethane could be adjusted to achieve desired self-healing, transparency, shape-memory, and mechanical properties. Full article

This paper critically examines Édouard Glissant’s philosophy of relation through the lens of Watsuji Tetsurō’s theory of fūdo (climate and milieu), arguing that Watsuji’s insights help address some of the tensions and limitations in Glissant’s thought. While Glissant foregrounds relationality as a dynamic process of cultural creolization, his emphasis on fluidity and opacity at times risks obscuring the material and environmental conditions that shape human interactions. In contrast, Watsuji’s fūdo provides a framework for understanding relationality as always embedded in specific climatic and spatial conditions, grounding Glissant’s poetics of relation in a more concrete phenomenological and ecological perspective. By integrating Watsuji’s attention to the reciprocal formation of human subjectivity and milieu, this paper argues for a more nuanced articulation of relational identity—one that does not merely resist fixity but also acknowledges the formative role of an (interconnected) place (or places) and environment (or environments). Ultimately, this comparative approach highlights the potential for a deeper ecological and material grounding of Glissant’s thought, offering a corrective to its occasional indeterminacy while reaffirming its decolonial aspirations. In doing so, it contributes to broader discussions on the intersections of environmental philosophy, postcolonial thought, and theories of intersubjectivity. Full article

The end conditions of columns constitute an important design parameter as they change their stiffness. The degree of restraint of the column modifies its fundamental frequency and mode of vibration. The rotational stiffness at its ends may transform from zero (hinged) to infinite (clamped). For intermediate values, the rotational movement is partially restricted, and it is classified as semi-rigid. In this work, the seismic response for a linearly variable section column and with gradual change in the rotational fixity is studied. A parametric solution is developed using the Rayleigh method, derived for cases of non-prismatic columns, and considering the axially distributed force along the column height. The obtained generalized stiffness and mass are used to perform approximate seismic evaluation at low effort and examine the influence of the changes to the structure. The analysis indicated that with a spring coefficient of 5 EI/l, the displacement drops by 50%, meaning that this range can produce significant influence on the structural response. The relationship between the top load and the column self-weight equal to 0.3 defines the limit for the hinged–hinged boundary condition to exist. As research recommendations, analysis of columns with variable cross-sections and different shapes, different distributed loadings, applying the rotational spring for both ends and over the shape functions, and analysis of buildings by an equivalent system are suggested. Experimental activity is indicated as a possibility for future investigations. Full article

Shape-memory polymer nanocomposites (SMPNCs) have emerged as a transformative class of smart materials, combining the versatility of shape-memory polymers (SMPs) with the enhanced properties imparted by nanostructures. Integrating these nanofillers, this review explores the pivotal role of SMPNCs in addressing critical limitations of traditional SMPs, including low tensile strength, restricted actuation modes, and limited recovery stress. It comprehensively examines the integration of nanofillers, such as nanoparticles, nanotubes, and nanofibers, which augment mechanical robustness, thermal conductivity, and shape-recovery performance. It also consolidates foundational knowledge of SMPNCs, covering the principles of the shape-memory phenomenon, fabrication techniques, shape-recovery mechanisms, modeling approaches, and actuation methods, with an emphasis on the structural parameters of nanofillers and their interactions with polymer matrices. Additionally, the transformative real-world applications of SMPNCs are also highlighted, including their roles in minimally invasive medical devices, adaptive automotive systems, 4D printing, wearable electronics, and soft robotics. By providing a systematic overview of SMPNC development and applications, this review aims to serve as a comprehensive resource for scientists, engineers, and practitioners, offering a detailed roadmap for advancing smart materials and unlocking the vast potential of SMPNCs across various industries in the future. Full article

Using 3D-printed (3DPd) polymers and their composites as shape memory materials in various smart engineering applications has raised the demand for such functionally graded sustainable materials. This study aims to investigate the viscoelastic, shape memory, and fracture toughness properties of the epoxy-based ultraviolet (UV)-curable resin. A UV-based DLP (Digital Light Processing) printer was employed for the 3D printing (3DPg) epoxy-based structures. The effect of the hydrothermal accelerated ageing on the various properties of the 3DPd components was examined. The viscoelastic performance in terms of glass transition temperature (T_g), storage modulus, and loss modulus was evaluated. The shape memory polymer (SMP) performance with respect to shape recovery and shape fixity (programming the shape) were calculated through dynamic mechanical thermal analysis (DMTA). DMTA is used to reveal the molecular mobility performance through three different regions, i.e., glass region, glass transition region, and rubbery region. The shape-changing region (within the glass transition region) between the T_g value from the loss modulus and the T_g value from the tan(δ) was analysed. The temperature memory behaviour was investigated for flat and circular 3DPd structures to achieve sequential deployment. The critical stress intensity factor values of the single-edge notch bending (SENB) specimens have been explored for different crack inclination angles to investigate mode I (opening) and mixed-mode I/III (opening and tearing) fracture toughness. This study can contribute to the development of highly complex shape memory 3DPd structures that can be reshaped several times with large deformation. Full article

This study investigates the fabrication and characterization of heat-responsive PLA/PU/MXene shape memory polymer blend nanocomposites with varying PLA content (10, 20, 30, and 50%) and a fixed MXene content of 0.5 wt.%. The results indicate significant improvements in mechanical properties, with the 50% PLA/PU/MXene blend showing a 300% increase in ultimate tensile strength and a 90% decrease in % elongation compared to pure PU. Additionally, the 50% blend exhibited a 400% increase in flexural strength. Microstructural analysis revealed dispersed pores and sea–island morphology in pure PU and the 50% PLA/PU/MXene blend. Thermal analysis using DSC showed an increase in crystallinity from 33% (pure PU) to 45% for the 50% PLA/PU/MXene blend, indicating enhanced crystalline domains due to the semi-crystalline nature of PLA and MXene’s influence on molecular ordering. TGA demonstrated a significant improvement in thermal stability, with the onset temperature rising from 185 °C (pure PU) to 212 °C and the degradation temperature increasing from 370 °C to 425 °C for the 50% blend, attributed to the rigid structure of PLA and MXene’s stabilizing effect. Shape memory testing revealed that the 30% PLA/PU/MXene blend achieved the best shape fixity and recovery with optimal performance, whereas higher PLA content diminished shape memory behavior. Full article

Poly(lactic acid) (PLA) exhibits excellent shape memory properties but suffers from brittleness and a high glass transition temperature (T_g), limiting its utility in flexible and durable applications. This study explored the modification of PLA properties through the incorporation of poly(ethylene glycol) (PEG), varying in both content (5–20 wt%) and molecular weight (4000–12,000 g/mol), to enhance its suitability for specific applications, such as medical splints. The PLA/PEG blend, containing 15 wt% PEG and with a molecular weight of 12,000 g/mol, exhibited superior shape fixity (99.27%) and recovery (95.77%) in shape memory tests conducted at a programming temperature (T_p) of 45 °C and a recovery temperature (T_r) of 60 °C. Differential scanning calorimetry (DSC) analysis provided insights into the thermal mechanisms driving shape memory behavior of the PLA/PEG blend. The addition of PEG to the PLA blend resulted in a reduction in T_g and an increase in crystallinity, thereby facilitating enhanced chain mobility and structural reorganization. These thermal changes enhanced the shape fixity and recovery of the PLA/PEG blend. Synchrotron wide-angle X-ray scattering (WAXS) was further employed to elucidate the microstructural evolution of PLA/PEG blends during the shape memory process. Upon stretching, the PLA/PEG chains aligned predominantly along the tensile direction, reflecting strain-induced orientation. During recovery, the PLA/PEG chains underwent isotropic relaxation, reorganizing into their original configurations. This structural reorganization highlighted the critical role of chain mobility and alignment in driving the shape memory behavior of PLA/PEG blends, enabling them to effectively return to their initial shape. Mechanical testing confirmed that increasing PEG content and molecular weight enhanced elongation at break and impact strength, balancing flexibility and strength. These findings demonstrated that PLA/PEG blends, especially with 15 wt% PEG at 12,000 g/mol, offer an optimal combination of shape memory performance and mechanical properties, positioning them as promising candidates for customizable and biodegradable medical applications. Full article

In this research, blends of bio-based polybenzoxazine (V-fa) and polycaprolactone (PCL) with different molecular weights (M_n) (14,000, 45,000, and 80,000 Da) were prepared with varying PCL content from 10 to 95 wt%. The spectra measured using Fourier Transform Infrared Spectroscopy (FTIR) may indicate the presence of hydrogen bonding between two polymeric components. The thermograms obtained using a Differential Scanning Calorimeter (DSC) and dynamic mechanical analyzer (DMA) exhibited a shift in glass transition temperature (T_g), which indicated partial miscibility between V-fa and PCL. The thermograms obtained using a thermogravimetric analyzer (TGA) revealed that the addition of PCL led to an increase in the maximum decomposition temperature (T_dmax). The tensile strength and modulus decreased with an increase in PCL, thus indicating a decrease in brittleness. Interestingly, only the samples with an M_n of 80,000 Da were bendable. The blends with 80 wt% PCL were revealed to have shape memory behaviors with a shape fixity of approximately 81%. The shape recovery ratio of the blends with 95 wt% PCL was approximately 78%. Full article