A fully flexible plasmonic substrate was developed through a scalable, low-cost process that combines ultrathin PDMS membranes with micropatterned amorphous silicon. This configuration enables the stable and localized integration of gold nanoparticles, preserving their distribution during use. Thanks to the stability of the nanoparticles and the engineered design, the platform represents a versatile solution for flexible biosensing applications based on both fluorescence and Raman detection.

In this study, we present a vacuum-driven artificial muscle capable of rapid linear contraction through snap-through instability. The actuator consists of a rigid 3D-printed skeleton enclosed within a sealed membrane. We investigate how material selection influences the instability and bistability behavior of the actuator by comparing two systems: 3D-printed PLA and Flexible 80 A resin. Using a combined experimental and finite element approach, we characterize the snap-through response. In particular, we assess the effects of material selection and loading conditions through a combination of quasi-static and dynamic cyclic testing. Experiments showed that the proposed artificial muscles were able to provide both reversible actuation and self-locking under varying applied loads. Peak performance was achieved with an actuation speed of similar to 325.4 mm s-1 (PLA 100% infill under 0.1 kg load) and an efficiency of similar to 50% (PLA 75% infill under 0.5 kg load) under relatively low vacuum pressures (-39--69 kPa). These results compare favorably with vacuum-driven artificial muscles reported in the literature, highlighting the advantage of incorporating snap-through instability as the actuation mechanism.

This study presents the development of a gold nanoparticle island substrate deposited on a polydimethylsiloxane (PDMS) disk. Metal nanoparticles are known for their strong electromagnetic response when illuminated by incident light. In Raman analysis, this phenomenon leads to a significant signal enhancement from molecules adsorbed on the nanoparticles, known as the Surface-Enhanced Raman Scattering (SERS) effect. In medical applications, this enables the detection of biomarkers in complex biological fluids, such as blood or saliva. In recent years, metallic nanoparticles assembled on silicon substrates have been successfully used for spectroscopic analysis, achieving high sensitivity in detecting trace biomolecules in biological mixtures. However, while these rigid devices offer excellent sensor performance, their lack of flexibility makes them unsuitable for direct application to biological samples, which are inherently soft. Here, we demonstrate a flexible PDMS-based plasmonic device. The fabrication process involves a two-step chemical deposition on a pre-patterned PDMS disk to create gold nanoparticle islands. Using a polymeric soft material instead of a semiconductor offers several advantages, including flexibility, transparency, good mechanical properties, and cost-effectiveness. Most importantly, a soft material can conform to biological tissues, enabling direct, on-site applications. The resulting soft device exhibits promising performance, not only for Raman analysis but also as a versatile platform for soft, metal-decorated materials with potential applications in biosensing and flexible electronics.

This work presents a comprehensive experimental and analytical study of twisted and coiled artificial muscles (TCAMs) fabricated from three types of silver‐coated nylon 6,6 precursor fibers. The coupled thermo‐electromechanical response of these actuators is investigated through systematic characterization and a physics‐based analytical model. Built upon Castigliano's theorem, the model captures nonlinear contraction behavior with high accuracy while remaining computationally efficient compared to more complex formulations. Experimental validation demonstrates maximum contractions up to 19.3%, strongly influenced by precursor type and the applied prestrain. Beyond displacement, actuator performance is quantified through additional metrics. The specific mechanical work per cycle reaches values as high as 8 kJ kg −1 , highlighting the excellent work density achievable with minimal actuator mass. Conversely, electromechanical efficiency is found to be limited (0.15 ± 0.2% under optimized conditions), primarily due to thermal losses resulting from convection, radiation, and conduction. Time‐constant analysis reveals fiber‐dependent trends: Thinner fibers exhibit faster overall dynamics but slower heating than cooling, while thicker fibers display longer relaxation times due to their larger thermal mass. The combined experimental and analytical approach provides both a detailed understanding and a predictive tool for TCAMs, offering insights into their strengths and limitations for future integration into wearable and soft robotic systems.

Using confocal imaging and network topology analysis, we investigated how substrate stiffness affects adhesion and connectivity in hiPSC-derived neuronal cultures grown on polydimethylsiloxane (PDMS). We compared soft (∼12 kPa) and stiff (∼1.5 MPa) substrates with matched surface properties to isolate mechanical effects. Confocal analysis of NCAM expression revealed higher levels on soft PDMS at 10 DIV, indicating enhanced neuronal adhesion and outgrowth. Network topology analysis showed that only soft PDMS supported increased clustering, reduced path length, and higher small-worldness, reflecting more efficient connectivity. These results underscore the importance of substrate compliance in promoting neuronal development and inform scaffold design for neural engineering.

It is well established that the nano-geometry and mechanical properties of a material's interface can significantly influence - and potentially enhance - cell adhesion, growth, proliferation, and migration, collectively referred to as cell behavior. At the same time, these behavioral responses are inherently dependent on the cell's own biological characteristics, including its type, age, cell cycle phase, and whether it is normal or cancerous - as well as, in the latter case, the stage of cancer. In this context, we hypothesize that these material and cellular factors may act synergistically, such that carefully engineered materials can modulate and amplify cellular responses. Specifically, such materials may function as amplifiers, accentuating the behavioral differences between distinct cell lines and thereby improving our ability to distinguish between them. Here, we used this concept to segregate OVCAR-429 ovarian cancer cells silenced for the EXT1 gene (shEXT1) from a control (SCR): i.e. cells infected with an empty lentivirus. EXT1 encodes a glycosyltransferase implicated in the synthesis of heparan sulfate proteoglycans and may play a role in cancer cell invasion and metastasis. We produced polydimethylsiloxane (PDMS) substrates with low values of Young's modulus in the MPa range, and moderate values of roughness of about 20nm. Then, we monitored cell-behavior over time on PDMS substrates and on standard rigid microplates for comparison. Analysis of cell trajectories revealed that shEXT1 cells exhibited significantly reduced motility on PDMS surfaces compared control cells, with cell velocity and diffusivity reduced by more than twofold, whereas no significant differences were observed on standard surfaces. Our results thus indicate the potential of soft biomaterials to reveal biological differences in disease models.

Total Hip Arthroplasty (THA) is a widely used surgical procedure to restore mobility and reduce pain in patients with hip joint disorders. Implant success and longevity are influenced by the selection of appropriate materials. This study presents a comprehensive literature review based on structured searches in Scopus and Web of Science, focusing on material selection criteria and methods in THA. The inclusion criteria targeted original studies and reviews addressing material properties, selection techniques, and clinical performance. A bibliometric analysis and keyword co-occurrence network were used to highlight major research themes. The review examines traditional materials such as Metal-on-Polyethylene (MoP), as well as advanced options like ceramics, composites, and Functionally Graded Materials (FGMs). Key challenges discussed include aseptic loosening, wear resistance, and stress shielding. Selection methodologies such as Multi-Criteria Decision-Making (MCDM), Weighted Properties Methods (WPM), and computational tools like Ashby charts and CES Selector are analyzed. The findings from international arthroplasty registries show that more than half of implant failures are linked to material-related factors. This study therefore aims to guide material selection processes in THA by aligning clinical performance with biomechanical and biological requirements, supporting improved implant outcomes and long-term surgical success. Future developments should focus on patient-specific solutions and continuous innovation.

High-strength polymer fibers such as nylon 6, nylon 6,6, and polyethylene are utilized to produce Twisted and Coiled Artificial Muscles (TCAMs) through the twisting of low-cost fibers. These artificial muscles exhibit high displacement and specific power, particularly under electrothermal actuation, which requires conductive elements. An experimental setup was developed to produce, thermally treat, and characterize commercially available nylon 6,6 fibers coated with silver. The results demonstrate that TCAMs can contract by over 15% and generate forces up to 2.5 N with minimal energy input. Key factors such as motor speed, applied load, and fiber geometry affect the overall performance.

Wearable robotic devices for rehabilitation and assistive applications face a critical challenge: discomfort induced by prolonged pressure at the human–robot interface. Conventional attachment systems with static straps or rigid cuffs frequently exceed pain tolerance thresholds, limiting clinical acceptance and patient adherence. This study presents a novel dynamic pressure modulation system using thermally activated Twisted and Coiled Artificial Muscles (TCAMs). The system integrates a lightweight lattice structure (0.1 kg) with biocompatible silicone coating incorporating two TCAMs fabricated from silver-coated nylon 6,6 fibers (Shieldex 235/36 × 4 HCB). Electrothermal activation via 2 A constant current induces axial contraction, dynamically regulating circumferential pressure from 0.05 kgf/cm2 to 0.50 kgf/cm2 within physiological comfort ranges. Experimental validation on a wrist-worn prototype demonstrates precise pressure control, rapid response (5–10 s), and thermal safety through 8 mm Ecoflex insulation. The system enables on-demand interface stiffening during robotic actuation and controlled pressure release during rest periods, significantly enhancing comfort and device tolerability. This approach represents a promising solution for clinically viable wearable robotic devices supporting upper limb rehabilitation and activities of daily living.

Flexible plasmonic platforms are increasingly sought after for wearable and implantable biosensing, yet current solutions are often costly or mechanically fragile. In this work, we present a scalable and low-cost method to fabricate fully flexible plasmonic substrates by combining ultrathin PDMS membranes with patterned amorphous silicon layers. Nanopatterning, achieved via soft lithography, enables localized growth of gold nanoparticle clusters through electroless deposition, ensuring strong plasmonic activity while maintaining mechanical adaptability. The resulting membranes easily conform to curved surfaces and enable sensitive fluorescence and Raman detection of biomarkers, such as IgG (100 pg/mL) and IL-8 (1 ng/mL). The device also operates effectively in an inverted configuration, which is a key feature for wearable integration. FEM simulations confirm the plasmonic field enhancement, highlighting the robustness of the design.

In recent years, thermoplastic polymers and composites have seen increasing application across various industrial sectors to develop lightweight structures. These materials have gained popularity in the market due to advancements in additive manufacturing. Thermal direct joining serves as an effective solution for integrating such thermoplastic materials into existing or de-novo metal structures. This method enables the creation of lightweight and virtually reversible joints, which foster end-of-life recyclability, thus aligning with the principles of a circular economy. However, these joints are still affected by a low strength, which is mostly related to the poor polymer–metal interaction. The use of surface treatments that promote mechanical interlocking of the polymer within surface asperities in the mating metallic adherend can be an effective strategy to enhance the strength, as well as to improve the toughness and damage tolerance of the joints. In this work, a laser treatment was used to modify the surface texture of an aluminum sheet prior to thermal bonding with 3D-printed polylactic acid (PLA). Different surface textures were analyzed by modifying the main process parameters. Roughness and wettability measurements were performed to identify the most effective processing condition. Finally, mechanical tests were performed to verify the improvement in joint resistance obtained by interface modification.

AbstractThe question of whether material stiffness enhances cell adhesion and clustering is still open to debate. Results from the literature are seemingly contradictory, with some reports illustrating that adhesion increases with surface stiffness and others suggesting that the performance of a system of cells is curbed by high values of elasticity. To address the role of elasticity as a regulator in neuronal cell adhesion and clustering, we investigated the topological characteristics of networks of neurons on polydimethylsiloxane (PDMS) surfaces - with values of elasticity (E) varying in the 0.55–2.65 MPa range. Results illustrate that, as elasticity increases, the number of neurons adhering on the surface decreases. Notably, the small-world coefficient – a topological measure of networks – also decreases. Numerical simulations and functional multi-calcium imaging experiments further indicated that the activity of neuronal cells on soft surfaces improves for decreasing E. Experimental findings are supported by a mathematical model, that explains adhesion and clustering of cells on soft materials as a function of few parameters - including the Young’s modulus and roughness of the material. Overall, results indicate that – in the considered elasticity interval – increasing the compliance of a material improves adhesion, improves clustering, and enhances communication of neurons.

The confined build space of 3D printers often necessitates breaking down larger objects into sub-components for efficient printing. Addressing this challenge, related existing research emphasizes the growing adoption of structural adhesives as a key method for joining 3D printed components. In this context, the present study combines finite element modeling, design exploration, and additive manufacturing, to ascertain the role of the adherends’ architecture on the mechanics of crack growth in adhesive bonded 3D printed materials. Finite element simulations and experiments are carried out using Double Cantilever Beam (DCB) specimens comprising epoxy-bonded selective laser sintered polyamide (PA). In particular, the study includes adherends that feature either sub-surface hollow channels of various shapes (bulk patterns) or sinusoidal interfaces with different aspect ratios (surface patterns). The objective is to demonstrate how the proposed patterning strategies not only promote crack shielding and delayed growth but also unlock energy-absorbing processes, such as interfacial void growth and buckling, that are absent in the control joint (i.e., no patterns). Therefore, customizing the architecture of the adjoined layers ultimately results in toughening and enhanced damage tolerance in adhesive joints that comprise 3D printed materials.

The choice of the proper restorative material is essential for the long-term success of implant-supported rehabilitations. This study aimed to analyze and compare the mechanical properties of four different types of commercial abutment materials for implant-supported restorations. These materials included: lithium disilicate (A), translucent zirconia (B), fiber-reinforced polymethyl methacrylate (PMMA) (C), and ceramic-reinforced polyether ether ketone (PEEK) (D). Tests were carried out under combined bending–compression conditions, which involved applying a compressive force tilted with respect to the abutment axis. Static and fatigue tests were performed on two different geometries for each material, and the results were analyzed according to ISO standard 14801:2016. Monotonic loads were applied to measure static strength, whereas alternating loads with a frequency of 10 Hz and a runout of 5 × 106 cycles were applied for fatigue life estimation, corresponding to five years of clinical service. Fatigue tests were carried out with a load ratio of 0.1 and at least four load levels for each material, and the peak value of the load levels was reduced accordingly in subsequent levels. The results showed that the static and fatigue strengths of Type A and Type B materials were better than those of Type C and Type D. Moreover, the fiber-reinforced polymer material, Type C, showed marked material–geometry coupling. The study revealed that the final properties of the restoration depended on manufacturing techniques and the operator’s experience. The findings of this study can be used to inform clinicians’ choice of restorative materials for implant-supported rehabilitation, considering factors such as esthetics, mechanical properties, and cost.

Plasmonic metal nanomaterials are usually supported by rigid substrates, typically made of silicon or glass. Recently, there has been growing interest in developing soft plasmonic devices. Such devices are low weight, low cost, exhibit elevated flexibility and improved mechanical properties. Moreover, they maintain the features of conventional nano-optic structures, such as the ability to enhance the local electromagnetic field. On account of these characteristics, they show promise as efficient biosensors in biological, medical, and bio-engineering applications. Here, we demonstrate the fabrication of soft polydimethylsiloxane (PDMS) plasmonic devices. Using a combination of techniques, including electroless deposition, we patterned thin membranes of PDMS with arrays of gold nanoparticle clusters. Resulting devices show regular patterns of gold nanoparticles extending over several hundreds of microns and are moderately hydrophilic, with a contact angle of about 80°. At the nanoscale, scanning electron and atomic force microscopy of samples reveal an average particle size of ∼50 nm. The nanoscopic size of the particles, along with their random distribution in a cluster, promotes the enhancement of electromagnetic fields, evidenced by numerical simulations and experiments. Mechanical characterization and the stress-strain relationship indicate that the device has a stiffness of 2.8 MPa. In biological immunoassay tests, the device correctly identified and detected anti-human immunoglobulins G (IgG) in solution with a concentration of 25 μg/ml.

PURPOSE. To examine deformations of the optic nerve head (ONH) deep tissues in response to acute elevation of intraocular pressure (IOP). METHODS. Research-consented brain-dead organ donors underwent imaging by spectral domain optical coherence tomography (OCT). OCT imaging was repeated while the eye was sequentially maintained at manometric pressures of 10, 30, and 50 mm Hg. Radial scans of the ONH were automatically segmented by deep learning and quantified in three dimensions by a custom algorithm. Change in lamina cribrosa (LC) depth and choroidal thickness was correlated with IOP and age by linear mixed-effect models. LC depth was computed against commonly utilized reference planes. RESULTS. Twenty-six eyes from 20 brain-dead organ donors (age range, 22-62 years; median age, 43 years) were imaged and quantified. LC depth measured against a reference plane based on Bruch's membrane (BM), BM opening, and an anterior sclera canal opening plane showed both a reduction and an increase in LC depth with IOP elevation. LC depth universally increased in depth when measured against a sclera reference plane. Choroidal (-0.5222 mu m/mm Hg, P < 0.001) and retinal nerve fiber layer thickness (-0.0717 mu m/mm Hg, P < 0.001) significantly thinned with increasing IOP. The magnitude of LC depth change with IOP was significantly smaller with increasing age (P < 0.03 for all reference planes). CONCLUSIONS. LC depth changes with IOP reduce with age and are significantly affected by the reference plane of choice, which highlights a need for standardizing LC metrics to properly follow progressive remodeling of the loadbearing tissues of the ONH by OCT imaging and for the definition of a reference database.

PurposeTo quantify the effect of negative pressure applied to the anterior surface of the eye on absolute IOP.SubjectsParticipants, and/or Controls. Three eyes from three research-consented brain-dead organ donors.MethodsAir-tight goggles connected to a negative pressure (NP) pump (Mercury Multi-pressure Dial (MPD); Equinox Ophthalmic, Inc., CA) were tested on three research consented brain-dead organ donors. The MPD was set to generate a vacuum of −20mmHg. A baseline IOP of 10, 20, and 30mmHg was sequentially set by adjusting the height of a balanced salt solution bottle connected to the cornea through a 20G needle. IOP was manually annotated at time = 0s, right before turning on the vacuum pump; after a few seconds with the vacuum pump ON; at 60s; at 120s, right before turning the pump OFF; at 240s with the pump OFF (recovery). Three repetitions per each test at varying baseline IOP were taken for a total of nine series of measures per eye.MainOutcomeMeasuresIOP change with exposure to NP.ResultsEye1 and 3 showed an immediate reduction in IOP at all baselines immediately following activation of the MPD NP pump; Eye2 showed an opposite response to NP. Eye1 and 3 showed a reduction in IOP at all baselines with NP pump ON for 60s and 120s, while Eye 2 showed a consistent increase in IOP. After 120s from turning NP OFF (time=240s), IOP partially recovered to its baseline in all eyes.ConclusionsThis study is the first to evaluate changes in manometrically-measured intracameral IOP due to NP applied to the ocular surface in living conditions. The inconsistent response of IOP following exposure to negative pressure warrants further investigations on the mechanism underlaying IOP lowering by NP.

Purpose: To determine if in vivo strain response of the Optic Nerve Head (ONH) to IOP elevation visualized using Optical Coherence Tomography (OCT) video imaging and quantified using novel virtual extensometers was able to be provided repeatable measurements of tissue specific deformations. Methods: The ONHs of 5 eyes from 5 non-human primates (NHPs) were imaged by Spectralis OCT. A vertical and a horizontal B-scan of the ONH were continuously recorded for 60 s at 6 Hz (video imaging mode) during IOP elevation from 10 to 30 mmHg. Imaging was repeated over three imaging sessions. The 2D normal strain was computed by template-matching digital image correlation using virtual extensometers. ANOVA F-test (F) was used to compare inter-eye, inter-session, and inter-tissue variability for the prelaminar, Bruch's membrane opening (BMO), lamina cribrosa (LC) and choroidal regions (against variance the error term). F-test of the ratio between inter-eye to inter-session variability was used to test for strain repeatability across imaging sessions (FIS). Results: Variability of strain across imaging session (F = 0.7263, p = 0.4855) and scan orientation was not significant (F = 1.053, p = 0.3066). Inter session variability of strain was significantly lower than inter-eye variability (FIS = 22.63, p = 0.0428) and inter-tissue variability (FIS = 99.33 p = 0.00998). After IOP elevation, strain was highest in the choroid (-18.11%, p < 0.001), followed by prelaminar tissue (-11.0%, p < 0.001), LC (-3.79%, p < 0.001), and relative change in BMO diameter (-0.57%, p = 0.704). Conclusions: Virtual extensometers applied to video-OCT were sensitive to the eye-specific and tissue-specific mechanical response of the ONH to IOP and were repeatable across imaging sessions.

Most of the researches published on the numerical modeling of laser welding are looking at similar welding, mainly due to the difficulty of simulating the mixing phenomenon that occurs in dissimilar welding. Furthermore, numerical modeling of dissimilar laser welding of titanium and nickel alloys has been rarely reported in the literature. In this study, a 3D finite volume numerical model is proposed to simulate fluid flow, heat, and mass transfer for similar and dissimilar laser welding of Ti-6Al-4V and Inconel 718. The laser source was simulated by volumetric heat distribution, which considers the effects of keyhole and heat transfer on the workpiece. The heat source parameters were calibrated through preliminary experiments, by comparing the simulated and experimental weld pool shapes and dimensions. The model was used to simulate both homogenous and dissimilar laser weldings of Ti-6Al-4V and Inconel 718, and a systematic comparison was carried out through a number of selected experiments. The effects of three distinct levels of laser power (1.25 kW, 1.5 kW, 2.5 kW) on temperature distribution and velocity field in the welds pool were analyzed. Results highlighted the effects of Marangoni forces in the weld pool formation. Furthermore, in order to analyze the mass transfer phenomenon in dissimilar welding, species transfer equations were considered, demonstrating the important role played by the mass mixture in the weld pool formation. Finally, a high level of agreement between simulations and experiments-in terms of weld pool shape and dimensions-was observed in all cases analyzed. This proves the ability of the proposed numerical model to properly simulate both the similar and dissimilar welding of Ti-6Al-4V and Inconel 718 alloys.

In the present paper, authors have demonstrated how a localized induction heat treatment can be advantageously applied, controlled, and mechanically characterized on a specific part—i.e., on steel hose fittings for hydraulic applications. More specifically, the study shows how this specific type of heat treatment facilitates significant localization effects on mechanical properties, and how such a treatment could act as a powerful tool for material optimization in diverse applications. The instrumented micro-indentation test was adopted as the investigation method for mechanical characterization and, due to the reduced amount of material required for the test, has the double advantage of retrieving potential spatial gradients of the mechanical properties without causing permanent damage to the analyzed parts. A measurement of both Vickers hardness and plastic work are required in order to make the indentation necessary to quantify the strength and ductility capability of the parts’ materials. In addition, a customized tensile test, based on a strains measurement obtained through an optical full-field method—i.e., digital image correlation (DIC)—was developed with the aim of identifying and quantifying the correlation between the material properties attainable through a conventional tensile test and those measured by the instrumented micro-indentation test. Finally, it was demonstrated that the proposed customized tensile test, due to the localized heat treatment, is capable of retrieving potential spatial gradients of the material properties.