Search Results (676)

This article presents an investigation of the thermomechanical properties of silicone elastomer-based polymer composites modified with carbon nanotubes (CNTs) and mixed fillers (CNTs, bronze, graphite). The primary technique employed was the composite piezoelectric oscillator (CPO) method at approximately 100 kHz. This approach enabled precise measurements of the polymers’ forced oscillation frequency and logarithmic damping decrement (internal friction) across a wide temperature range (80–300 K). The application of this method is novel for this specific class of materials. Scanning electron microscopy confirmed the uniform distribution of the fillers within the polymer matrix. Differential scanning calorimetry (DSC) showed that the fillers modify the thermal stability of the composite. The systematic decrease in the enthalpy of the endothermic decomposition peak suggests a retardation of degradation kinetics, most likely due to a barrier effect of the filler network. Electrical measurements revealed a distinct contrast: the hybrid composite exhibited a frequency-independent conductivity plateau (~1.8 × 10⁻¹ S/m), confirming a robust percolating network, unlike the strong frequency dependence observed for the CNT-only composite. Research shows that the fillers effectively suppress relaxation processes linked to crystallization (205–215 K) and glass transition (165–170 K), as evidenced by a significant reduction in the amplitude of the corresponding internal friction peaks. The most pronounced effect was observed in the composite with mixed fillers, attributable to a synergistic effect between constituents. Furthermore, amplitude-dependent internal friction was found to occur predominantly below the glass transition temperature. The primary objective of the present study is to investigate the dynamic mechanical and damping behavior of CNT-filled silicone composites with mixed fillers under high-frequency loading, using the CPO method. These findings demonstrate the potential for tailoring the stiffness and damping characteristics of these composites for advanced applications in soft robotics and portable electronics. Full article

Underground structures are essential components of modern transportation and infrastructure systems, and evaluating their behavior under extreme dynamic loads such as explosions is critical for urban safety. This study examines the dynamic effects of underground explosions on tunnel–soil–free-field interaction using numerical methods. Finite element-based dynamic analyses are carried out using PLAXIS-2D, in which a single-layer NATM (New Austrian Tunneling Method) tunnel section representing the Eurasia Tunnel is modeled. Blast loads are defined based on closed-space explosion conditions specified in UFC 3-340-02, and force–time histories are generated for different explosion intensities. A parametric study is performed by varying soil type (soft and stiff soil) and tunnel cover depth to investigate wave propagation mechanisms. Response spectra derived from free-field surface acceleration records are compared with the design spectra of the Turkish Building Earthquake Code (TBEC-2018). The results show that increasing explosion intensity significantly amplifies spectral accelerations. Soft soils exhibit longer acceleration wavelengths, whereas stiffer soils result in higher acceleration amplitudes. Shallow explosion depths are found to reduce soil stability and considerably increase surface accelerations. Under unfavorable soil and cover conditions, explosion-induced demands may approach or exceed design-level earthquake spectra. Full article

Continuum robots (CRs) exhibit high compliance and environmental adaptability in confined, tortuous spaces, yet their inherent low stiffness and load capacity limit performance in precise positioning and stable support tasks. To solve the “soft-rigid” paradox, this study proposes and implements a three-segment tendon-driven variable-stiffness CR. Structurally, a segmented constant-curvature model directs the optimization of grid skeletons and notch parameters, enhancing bending consistency and motion predictability. Elongated flat airbag actuators, arranged in annular arrays, enable segment-level stiffness switching through the enhancement of surface properties like axial constraints and friction amplification. A time-sharing drive strategy decouples multi-segment coupling into sequential single-segment subproblems, reducing drivers and kinematic complexity while maintaining dexterity. Experimental results demonstrate that flexible-mode joints maintain near-constant curvature with stable motion (average end-effector trajectory error < 0.9 mm), and in rigid mode, stiffness increases by a factor of 5.77 (rated load: 4.0 N). Shape-locking disturbances during transitions are confined to millimeter levels (remote offset < 1.32 mm), with successful traversal of J/U/S-shaped and irregular paths confirmed in pipeline tests. This work introduces a practical, scalable system for designing variable-stiffness structures and enabling low-complexity multi-segment control, offering valuable insights for minimally invasive devices and industrial endoscopy in confined spaces. Full article

The development of photocurable hydrogel biomaterial inks with suitable rheology, low cytotoxicity, and tuneable mechanical properties is essential for reliable biofabrication. This study aimed to formulate PEGDA–gelatine–collagen inks using lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as photoinitiator. Rheological characterisation and flow-model fitting were performed, mechanical stiffness modulation under different light intensities was evaluated, complex structures were printed using direct extrusion and FRESH methodologies, and PEGDA/LAP extractables were quantified by NMR after controlled washing procedures. In vitro assays assessed cell viability and proliferation on the resulting scaffolds. The Herschel–Bulkley model best described the flow behaviour across formulations; while viscoelastic measurements showed that increasing light intensity progressively enhanced hydrogel stiffness, enabling fine control over final mechanical properties. NMR analysis showed that washing removed a substantial fraction of residual LAP, in agreement with the biological findings: fibroblasts failed to survive on unwashed scaffolds but exhibited robust proliferation and recovered their characteristic elongated morphology on washed constructs. Among all inks, PeGeCol_10_2 provided the best combination of shear-thinning behaviour, structural integrity, low residual photoinitiator, and tuneable mechanics. Using this formulation, we successfully printed large anatomical models with high fidelity and excellent handling properties, underscoring its potential for soft-tissue prosthetics and broader tissue-engineering applications. Full article

Implant science has traditionally treated “biocompatibility” as the master criterion of success, focusing on cytotoxicity, corrosion, immune response, infection control, and the chemical stability of materials in vivo. However, many clinically “biocompatible” devices still fail at the point where the body actually meets the device: the mechanical interface. The interface is not a passive boundary. It is a living, adapting, mechanosensitive microenvironment in which cells integrate stiffness, micromotion, surface roughness, fluid shear, and wear debris with biochemical signals to decide whether to incorporate an implant, wall it off, resorb adjacent tissue, or trigger chronic inflammation. In load-bearing orthopaedics, stiffness mismatch produces stress shielding and maladaptive remodelling; excessive micromotion drives fibrous encapsulation rather than osseointegration; abrasive wear creates particulates that sustain macrophage activation and osteolysis; and design choices that are mechanically adequate in bench tests can still fail in vivo when the implant–tissue system evolves. In soft-tissue implantation, substrate stiffness can be a primary driver of the foreign body response and fibrotic capsule formation through mechanosensitive pathways, such as TRPV4-mediated macrophage–fibroblast signalling. Mechanical compatibility is not a replacement for classical biocompatibility; rather, it should be treated as a co-equal, first-class design requirement in mechanosensitive organisms. Chemically biocompatible materials can still fail through stiffness mismatch, micromotion, fretting and wear debris generation, and mechanobiology-driven fibrosis or osteolysis. We therefore propose a process view of implant success: tissue mechanics should be measured in clinically relevant states, transformed into constitutive models and interface performance envelopes, translated into explicit mechanical-compatibility specifications, and then realised through manufacturing process windows that can reliably reproduce targeted architectures and surface states. Additive manufacturing and microstructural engineering enable the tuning of modulus, the formation of porosity gradients, and the generation of patient-specific compliance fields, but these advances only improve outcomes when coupled to metrology, statistical process control, and validation loops that close the gap between intended and realised interface mechanics through clinical surveillance. Full article

This paper presents a novel two-stage optimization framework for offshore wind turbine jacket structures that integrates gradient-based optimization with comprehensive system verification. The methodology addresses the challenge of balancing structural efficiency with reliability through sequential optimization and validation phases. Applied to a 5 MW reference turbine, the framework achieved a 34% reduction in steel mass while maintaining all structural performance requirements. The optimized structure preserves its fundamental natural frequency at 0.294 Hz within the required soft–stiff frequency band, effectively avoiding resonance with rotor excitations. Structural verification demonstrates significant improvements in joint performance, with a 42.35% reduction in the Maximum unity check value of joint shear. Dynamic analysis confirms consistent performance of OWT under the operational cases before and after optimization, with particular sensitivity to structural modifications observed during parked conditions due to absent operational damping. Full article

Polymers and their composites have introduced significant advancements in engineering and technology. The primary advantages of polymeric materials include their lightweight nature, ease of manufacturing, anti-corrosion properties, reduced power consumption during assembly and integration, as well as enhanced stiffness, durability, and fatigue resistance. Polymer coatings with conductive polymers allow efficient charge transfer and make electrodes more flexible, helping them better match the mechanical properties of soft tissues. In addition, polymer coatings can protect electrodes from corrosion, reduce biofouling, and provide sites for attaching biomolecules, making them essential for reliable and long-term bioelectrode and biosensor performance. Polymer coatings for electrochemical bioelectrodes play a crucial role in enhancing sensor performance and stability in biological environments as they improve the interaction between electronic devices and biological tissues. These coatings enhance biocompatibility by reducing inflammation and tissue damage while also lowering electrode impedance to improve signal quality. The present review focuses on the most recent developments in polymer coatings for electrochemical biosensors and respective applications. The manuscript provides an overview of polymer materials, emerging strategies, coating approaches, and the resulting enhancements in bioelectrochemical applications. Full article

Background/Objectives: The aim of our study was to evaluate the transverse stiffness of selected soft tissues in the knee joint region on the previously injured and uninjured sides of female handball players and non-athlete women, in the lying and standing positions, and to investigate the relationship between stiffness, age, sporting practice, and clinical assessments of the knees. Methods: A total of 25 young female handball players (the SPORT group) and 27 healthy non-athletic individuals (the CONTROL group) were examined. The MyotonPRO device was used to measure the stiffness of the patellar tendon (PT), rectus femoris (RF), and biceps femoris (BF) muscles on both sides and in both positions. The function of the knee joints was clinically assessed using the Knee Outcome Survey—Sports Activities Scale and the Lysholm Knee Scoring Scale. Results: ANOVA indicated a significant effect of group (p < 0.003) on the PT’s stiffness, and a significant effect of position (p < 0.0001) on the PT, RF, and BF muscle stiffness. The SPORT group demonstrated significantly higher PT transverse stiffness when lying down (p < 0.01), but not when sitting up (p > 0.05), compared to the CONTROL group. Significant negative correlations were found between PT stiffness and both clinical scales in the SPORT group (rho from −0.39 to −0.71, p < 0.05). Conclusions: In female handball players, only the patellar tendon transverse stiffness was higher than in the control group. While this higher stiffness could indicate an adaptive rebuilding process, it was negatively correlated with the clinical assessment of joint function, meaning poorer knee joint function. Full article

Background: Wound healing contributes to restoring skin integrity. However, scars affect soft tissue in all its layers, including the superficial and deep fascia; moreover, it has been demonstrated that the fibroblasts leading the scarring process develop from progenitors located in the superficial fascia. In the past, research into scar etiology has focused primarily on the dermal and epidermal layers, leaving the role of the fasciae largely overlooked. Many patients presenting with surgical or traumatic scars complain of the increased stiffness and thickness of the scar, reduced extensibility of the area surrounding it, and chronic pain persisting even after the healing process has been completed. The purpose of this systematic review is to investigate the non-invasive tools and methods employed for the objective evaluation of scars that involve fascial layers. Methods: A systematic literature search was conducted on PubMed and WOS. Registration DOI: 10.17605/OSF.IO/SDR3Q. Results: A total of 11 articles were selected; the etiologies of scars were surgical, traumatic, and other (keloids). The investigations were conducted using ultrasound, magnetic resonance imaging, strain elastography, and shear wave elastography on the visceral fasciae, superficial fascia, hypodermis, and musculoskeletal fasciae. Sliding of fasciae was assessed by ultrasound; thickness of fasciae was assessed by ultrasound and magnetic resonance imaging; stiffness was assessed by shear wave elastography and strain elastography; and the qualitative assessment was performed via ultrasound. Conclusions: Our literature review showed that ultrasound, magnetic resonance imaging, strain elastography, and shear wave elastography are currently adopted for investigating the sliding, thickness, stiffness, and qualitative features of scars involving fascial layers. Moreover, our research showed the existence of a gap in the scientific literature on this topic. Full article

Accurate prediction of subway-induced environmental vibrations for unopened lines remains a significant challenge due to the difficulty in determining appropriate excitation inputs. To address this issue, this study proposes an excitation modification method based on field measurements and numerical simulations. First, field measurements were conducted on a subway line in Shanghai to analyze vibration propagation characteristics and validate a two-dimensional finite element model (FEM). Subsequently, based on the validated model, frequency-band excitation modification formulas were derived. Distinct from existing empirical approaches that often rely on simple statistical scaling, the proposed method utilizes parametric numerical analyses to determine frequency-dependent correction coefficients for four key parameters: tunnel burial depth, tunnel diameter, soil properties, and train speed. The reliability of the proposed method was verified through theoretical analysis and an engineering application. The results demonstrate that the proposed method improves prediction accuracy for tunnels in similar soft soil regions, reducing the prediction error from 10.1% to 5.2% in the engineering case study. Furthermore, parametric sensitivity analysis reveals that ground vibration levels generally decrease with increases in burial depth, tunnel diameter, and soil stiffness, while exhibiting an increase with train speed. This study improves the reliability of vibration prediction in the absence of direct measurements and provides a practical tool for early-stage design and vibration mitigation for unopened lines. Full article

Off-road vehicle control designs often neglect the complex tire–soil interactions inherent to soft terrain. This paper proposes a Variable Impedance Control (VIC) strategy integrated with a high-fidelity terramechanics model. First, a real-time sinkage estimation algorithm is derived using experimentally identified Bekker parameters and the quasi-rigid wheel assumption to capture the nonlinear feedback between soil deformation and vehicle dynamics. Building on this, the VIC strategy adaptively regulates virtual stiffness, damping, and inertia parameters based on real-time suspension states. Comparative simulations on an ISO Class-C soft soil profile demonstrate that this framework effectively balances ride comfort and safety constraints. Specifically, the VIC strategy reduces the root-mean-square of vertical body acceleration by 46.9% compared to the passive baseline, significantly outperforming the Linear Quadratic Regulator (LQR). Furthermore, it achieves a 48.6% reduction in average power relative to LQR while maintaining suspension deflection strictly within the safe range. Moreover, unlike LQR, the VIC strategy improves tire deflection performance, ensuring superior ground adhesion. These results validate the method’s robustness and energy efficiency for off-road applications. Full article

Understanding how primary structural features and secondary material properties adapt to functional loads is essential to determining their effect on changes in joint biomechanics over time. The objective of this study was to map and correlate spatiotemporal changes in primary structural features, secondary material properties, and dentoalveolar joint (DAJ) stiffness with age in rats subjected to prolonged chewing of soft foods versus hard foods. To probe how loading history shapes the balance between the primary and secondary features, four-week-old rats were fed either a hard-food (HF, N = 25) or soft-food (SF, N = 25) diet for 4, 12, 16, and 20 weeks, and functional imaging of intact mandibular DAJs was performed at 8, 12, 16, 20, and 24 weeks. Across this time course, the primary structural determinants of joint function (periodontal ligament (PDL) space, contact area, and alveolar bone socket morphology) and secondary material and microstructural determinants (tissue-level stiffness encoded by bone and cementum volume fractions, pore architecture, and bone microarchitecture) were quantified. As the joints matured, bone and cementum volume fractions increased in both the HF and SF groups but along significantly different trajectories, and these changes correlated with a pronounced decrease in PDL-space from 12 to 16 weeks in both diets. With further aging, older HF rats maintained significantly wider PDL-spaces than SF rats. These evolving physical features were accompanied by an age-dependent significant increase in the contact ratio in the SF group. The DAJ stiffness was significantly greater in SF than HF animals at younger ages, indicating that food hardness-dependent remodeling alters the relative contribution of structural versus material factors to joint function across the life course. At the tissue level, volumetric strains, representing overall volume changes, and von Mises bone strains, representing shape changes, increased with age in HF and SF joints, with volumetric strain rising rapidly from 16 to 20 weeks and von Mises strain increasing sharply from 12 to 16 weeks. Bone in SF animals exhibited higher and more variable strain values than age-matched HF bone, and changes in joint space, degrees of freedom, contact area, and bone strain correlated with joint biomechanics, demonstrating that multiscale functional biomechanics, including bone strain in intact DAJs, are colocalized with anatomy-specific physical effectors. Together, these spatiotemporal shifts in primary (structure/form), and secondary features (material properties and microarchitecture) define divergent mechanobiological pathways for the DAJ and suggest that altered loading histories can bias joints toward early maladaptation and potential degeneration. Full article

Soft robotic grippers provide compliant and adaptive manipulation, but most existing designs address actuation speed, adaptability, modularity, or sensing individually rather than in combination. This paper presents an electro-actuated customizable stacked Fin Ray gripper that integrates these capabilities within a single design. The gripper employs a compact solenoid for fast grasping, multiple vertically stacked Fin Ray segments for improved 3D conformity, and interchangeable silicone or TPU fins that can be tuned for task-specific stiffness and geometry. In addition, a light-guided, vision-based sensing approach is introduced to capture deformation without embedded sensors. Experimental studies—including free-fall object capture and optical shape sensing—demonstrate rapid solenoid-driven actuation, adaptive grasping behavior, and clear visual detectability of fin deformation. Complementary simulations using Cosserat-rod modeling and bond-graph analysis characterize the deformation mechanics and force response. Overall, the proposed gripper provides a practical soft-robotic solution that combines speed, adaptability, modular construction, and straightforward sensing for diverse object-handling scenarios. Full article

Humans could sensitively perceive and identify objects through dense mechanoreceptors distributed on the skin of curved fingertips. Inspired by this biological structure, this study presents a general conformal integration method for flexible tactile sensors on curved fingertip surfaces. By adopting a spherical partition design and an inverse mode auxiliary layering process, it ensures the uniform distribution of stress at different curvatures. The sensor adopts a 3 × 3 tactile array configuration, replicating the 3D curved surface distribution of human mechanoreceptors. By analyzing multi-point outputs, the sensor reconstructs contact pressure gradients and infers the softness or stiffness of touched objects, thereby realizing both structural and functional bionics. These sensors exhibit excellent linearity within 0–100 kPa (sensitivity ≈ 36.86 kPa⁻¹), fast response (2 ms), and outstanding durability (signal decay of only 1.94% after 30,000 cycles). It is worth noting that this conformal tactile fingertip integration method not only exhibits uniform responses at each unit, but also has the preload-free advantage, and then performs well in pulse detection and hardness discrimination. This work provides a novel bioinspired pathway for conformal integration of tactile sensors, enabling artificial skins and robotic fingertips with human-like tactile perception. Full article

Background: Soft tissue tumors (STTs) represent a heterogeneous group of rare lesions that frequently mimic bone sarcomas in both clinical and radiologic appearance. Accurate differentiation between benign and malignant lesions is critical for appropriate treatment planning, yet conventional imaging often remains inconclusive. Ultrasound (US) elastography, a non-invasive method that quantifies tissue stiffness, has recently emerged as a potential adjunct to standard musculoskeletal imaging for improving diagnostic confidence and guiding biopsy. Methods: A systematic review was conducted in accordance with PRISMA guidelines. PubMed, Web of Science, and Cochrane Library were searched using the keywords “elastography”, “sonoelastography”, and “soft tissue tumor”. Twelve studies encompassing 1554 patients met the inclusion criteria, assessing the diagnostic accuracy of strain, compression, and shear wave elastography for differentiating benign from malignant STTs. Results: Elastography alone demonstrated limited specificity when used as a single diagnostic technique. However, its integration into multiparametric ultrasound approaches—combining grayscale, Doppler, and contrast-enhanced imaging—significantly improved diagnostic performance. Several studies reported sensitivities and specificities exceeding 85% when elastographic parameters were incorporated into composite diagnostic scores. Conclusions: Ultrasound elastography shows promise as a quantitative imaging biomarker for the preoperative evaluation of musculoskeletal tumors, particularly in distinguishing soft tissue from bone-related lesions. Although not a substitute for histopathological confirmation, its application within multimodal ultrasound protocols may reduce unnecessary biopsies, enhance diagnostic accuracy, and facilitate tailored management of bone and soft tissue sarcomas. Full article