Search Results (839)

To address prevalent industrial challenges, including the high cost of fabricating microstructures via photolithography and 3D printing, impurity residues easily generated by conventional physical/chemical pore-forming techniques, and the limited sensitivity of regular capacitive sensors, this paper innovatively proposes an integrated low-temperature in situ gas foaming strategy using ammonium bicarbonate for the fabrication of porous TPU-based ionic gels. Relying on the complete gaseous decomposition property of ammonium bicarbonate upon heating, a three-dimensionally interconnected continuous porous network is spontaneously constructed inside the polymer matrix. Thermoplastic polyurethane (TPU) is selected as the continuous polymer phase, and [EMIM][TFSI] imidazolium ionic liquid is blended as the ion source to synthesize composite ionic gel substrates. A PDMS composite slurry filled with graphene is employed to prepare flexible substrates, followed by low-temperature oxygen plasma surface modification to introduce polar functional groups such as hydroxyl and carboxyl onto electrode surfaces. A standard sandwich-structured ionic pressure sensor with the configuration of “top modified electrode—porous ionic gel dielectric layer—bottom modified electrode” is finally assembled. The porous framework and modified electrodes constitute a dual synergistic enhancement system: the porous structure markedly reduces the equivalent elastic modulus of the gel and improves its compressive deformation capacity; polar-modified electrodes optimize the interfacial compatibility between electrodes and gels, shorten ion migration paths and lower interfacial contact resistance. Systematic calibration of multiple batches of parallel samples reveals that the as-fabricated sensor achieves a high sensitivity of 25.3 kPa⁻¹ across the full measuring range from 0 to 1000 kPa with a linear fitting coefficient R² = 0.992. The loading response time and unloading recovery time of the device are 60 ms and 80 ms respectively, with a performance degradation of less than 3% after 1000 consecutive loading–unloading cycles, featuring low hysteresis error and excellent signal repeatability. Multi-scenario in vivo wearable tests on human subjects verify that the device can precisely capture subtle fluctuations of radial artery pulse and periodic laryngeal deformation during swallowing, distinguish characteristic waveform patterns of various English words according to differences in vocal cord vibration, and accurately detect bending motions when attached to finger joints. The entire fabrication process adopts common chemical raw materials and standard laboratory equipment without expensive micro-nano processing facilities, featuring convenient raw material procurement and high process fault tolerance, which enables large-area coating-based mass production. This work delivers a novel technical route for the low-cost large-scale production of high-performance ionic flexible sensors and bears significant industrialization reference value for applications in wearable medical monitoring, bionic robotic electronic skin, flexible human–machine interactive touch panels and other related fields. Full article

Optics is the science of light, which supports disciplines like biology, medicine, engineering, materials science, chemistry, physics and more. Optics helps to improve diagnostic speed, portable and user-friendly devices, cost efficiency, and sensitivity. Through time, optical components have been made with hard and non-deformable materials. However, traditional optical elements can no longer meet the needs of the market, and new optical elements are needed, such as materials with higher degrees of freedom. A candidate that has been proposed to replace traditional optical materials is polydimethylsiloxane (PDMS or silicone) because it presents suitable characteristics like biocompatibility, nontoxicity, flexibility, non-biodegradability, high transparency in the UV–visible range, low scattering and absorption, easy fabrication, cost-effective relation and more. Many articles have reported the fabrication of optical components with silicone and the use of these components in optical devices. Unfortunately, there is no review that comprehensively covers the field of optics in relation to the application of silicone. The present work is intended as a descriptive overview to provide a clear and accessible review of the topic, rather than a comparative analysis. Articles describing the use of silicone in the fabrication of optical components during the past 20 years were reviewed. Full article

Triboelectric nanogenerators (TENG) show significant potential in pressure sensing by converting mechanical disturbances into electrical signals positively correlated with the magnitude of the applied force, yet their development as practical pressure sensors is severely hindered by the major drawback of only detecting transient mechanical inputs. Additionally, traditional dual-mode pressure sensors have typically required complex multilayer structures and time-consuming fabrication processes. Here, a simple dual-mode pressure sensor of novel structure integrated with TENG and anodic aluminum oxide (AAO) for both dynamic and static pressure detection is proposed. Nanoporous AAO is directly grown on an aluminum substrate to simplify the traditionally complex multi-layer structure of dual-mode pressure sensors. The AAO layer serves a dual functionality by acting as an active triboelectric layer that significantly enhances the triboelectric output performance while concurrently functioning as the capacitive dielectric layer. A polydimethylsiloxane (PDMS) film is employed as the elastic counterpart to pair with the AAO substrate. The influence of PDMS thickness on the charge accumulation and extraction of the TENG mode is investigated to optimize the device output. Under optimal configurations, the streamlined Al-AAO/PDMS sensor demonstrates good sensitivity and linearity (R² > 0.99) for both dynamic triboelectric voltage (1.05 V/kPa) and static capacitance (5.56 pF/kPa) over a wide sensing range of 1–73 kPa. This dual-mode sensor effectively overcomes the transient limitation of conventional single-mode TENGs and shows significant potential for future smart tactile applications. Full article

Flexible capacitive pressure sensors have garnered significant attention in wearable electronics and robotic tactile sensing due to their high flexibility and simple structure. However, non-uniform distribution of conductive fillers in composite dielectric layers often compromises dielectric stability and sensing performance. In this work, a Cu/PDMS composite dielectric layer was fabricated using ultrasonic-assisted homogenization to enhance Cu particle dispersion and suppress sedimentation. A theoretical model and finite element simulations were employed to investigate the effects of particle distribution on permittivity, capacitance, electric field, and current density. The results indicate that uniform Cu dispersion improves dielectric stability and mitigates local electric-field concentration. Compared with conventionally prepared sensors, the ultrasonically treated sensor demonstrated higher sensitivity, enhanced dielectric stability, and a broader working range. Specifically, the sensor achieved a sensitivity of 0.157 kPa⁻¹ within 0–1 kPa and maintained stable performance over 1000 loading cycles. These findings confirm that ultrasonic-assisted homogenization is an effective approach for improving the dielectric and sensing performance of flexible capacitive pressure sensors. Full article

To elucidate the mechanisms responsible for high friction in micro-pillared soft tribo-contacts under wet conditions, this study investigates the liquid migration behavior across elasticity interfaces featuring bionic surface textures and examines the influence of this migration on interfacial friction properties. Micro-pillar bionic surface textures were fabricated on polydimethylsiloxane (PDMS) substrates. In situ observation of liquid migration and corresponding friction tests were systematically conducted using custom-built experimental setups on soft interfaces textured with micro-pillars of varying area densities. The results demonstrate that both geometrical shape and area density of surface textures play a critical role in regulating liquid migration behavior. Surface textures with circular and hexagonal geometries exhibit optimal migration rates, attributed to their smooth structural profiles, which reduce flow resistance within the microchannels. Liquid migration efficiency is effectively improved with increasing area density of the bionic surface texture owing to strengthened capillary forces. Correspondingly, bionic surface textures exhibiting superior liquid migration characteristics show the smallest relative reduction in friction force during transitions from dry to wet frictional states. This behavior is primarily attributed to the surface’s exceptionally rapid drainage capability, which effectively mitigates the adverse effects of interfacial liquid films on friction. Specifically, rapid liquid removal increases the effective solid–solid contact area and enhances mechanical interlocking at the interface. Consequently, these surfaces maintain outstanding frictional performance even under humid or wet conditions. These findings provide important theoretical support for the rational design of surface microstructures and the optimized regulation of friction and liquid film in wet contact conditions. Full article

Superhydrophobic antibacterial coatings offer an effective approach to overcoming the limitations of single anti-adhesion or bactericidal strategies; however, it remains a great challenge to develop such coatings with long-term durability and high bactericidal performance. In this study, a ZT/PDMS composite coating was successfully fabricated by directly mixing ZnO@TiO₂ with PDMS. Benefiting from the low surface energy of polydimethylsiloxane (PDMS) and the coral-like micro/nanostructured rough morphology generated by the incorporation of ZnO@TiO₂ nanoparticles, the coating exhibited excellent superhydrophobic properties, with a water contact angle of 153.5°. The proposed fabrication method showed good adaptability to various substrates, and the resulting coating demonstrated outstanding durability and self-cleaning performance. Notably, the coating retained superhydrophobicity after six abrasion cycles, and the water contact angle remained above 140° after immersion in solutions with pH ranging from 1 to 13 for 7 days. The ZT/PDMS composite coating achieved an antibacterial adhesion rate of 87.98% and 80.11% against Acinetobacter baumannii (A. baumannii) and Staphylococcus aureus (S. aureus), respectively. Under UV and visible light irradiation, its bactericidal efficiency exceeded 90%. The excellent antibacterial performance of the coating was attributed to the synergistic effects of anti-adhesion, active sterilization (Zn²⁺ release and ROS generation), and self-cleaning. This study provides a facile and effective strategy for the development of efficient and durable multifunctional antibacterial coatings. Full article

Background: A transdermal drug delivery system has significant benefits over conventional routes; however, its effectiveness is limited by the barrier properties of the stratum corneum. Dissolving microneedles (DMNs) have emerged as a minimally invasive strategy to enhance drug permeation while improving patient compliance. The integration of advanced fabrication techniques such as 3D printing enables precise control over microneedle geometry and reproducibility. Objective: This study aimed to fabricate and characterize pregabalin-loaded PVA/PVP dissolving microneedle arrays using a 3D-printing-assisted mold fabrication approach for efficient transdermal drug delivery. Methods: Microneedle master molds were fabricated using 3D printing, followed by replication using polydimethylsiloxane (PDMS) to obtain negative molds. Pregabalin-loaded bilayer microneedles were prepared using a micromolding technique with PVA/PVP polymers. The formulation was evaluated through rheological analysis, scanning electron microscopy (SEM), mechanical strength testing, insertion studies, swelling behavior, drug loading efficiency, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and in vitro drug release studies. Results: The fabricated microneedles exhibited uniform geometry with sharp tips and no structural defects. Rheological analysis confirmed shear-thinning behavior suitable for mold filling. The microneedles demonstrated adequate mechanical strength (~3.3 N/needle) and efficient insertion into the parafilm model. Drug loading efficiency was high (92.4%), indicating effective encapsulation. FTIR analysis confirmed compatibility between drug and polymers, while DSC and XRD results indicated partial amorphization of pregabalin within the polymer matrix. The formulation showed a biphasic drug release profile with an initial burst followed by sustained release, achieving ~96.8% cumulative release over 24 h. Conclusions: The study successfully demonstrates a robust and reproducible 3D-printing-assisted approach for fabricating pregabalin-loaded dissolving microneedles. The developed system exhibited desirable mechanical, physicochemical, and drug release properties, highlighting its potential as an effective transdermal drug delivery platform. Full article

Magnetically actuated catheters have attracted increasing attention for minimally invasive interventions because they enable remote, non-contact steering in confined and tortuous anatomical environments. However, integrating magnetic actuation, electroablation capability, and high structural compliance into a single soft catheter remains challenging. Here, we present a coaxially printed magnetically actuated electroablation catheter (MEC). The MEC is fabricated via a coaxial 3D printing process, combining a highly flexible PDMS outer sheath with a continuously deformable eutectic gallium–indium (eGaIn) conductive core, followed by the distal assembly of a magnetic ring and a copper electrode. This structural design preserves intrinsic mechanical flexibility while maintaining stable electrical conductivity under bending deformation. To achieve active catheter steering, an eight-axis electromagnetic actuation system was developed to generate controllable magnetic fields for tip deflection and guidance. The MEC exhibited effective navigation and manipulation in maze traversal and selective navigation within a 3D-printed vascular model. Furthermore, ex vivo porcine liver and in vivo rat liver electroablation experiments verified that the MEC could be magnetically navigated to designated sites for localized electroablation. This work provides a new strategy for precise, minimally invasive ablation of target tissues in confined and difficult-to-access anatomical environments. Full article

Patterned lead-halide perovskite microstructures are promising for integrated optoelectronics, photonics, and polarization-sensitive devices, but the practical growth behavior of compositionally tunable microcrystals under simple static confinement remains insufficiently understood. Here, we investigate template-assisted confined crystallization of MAPbBr₃ and MAPbBr_3−xCl_x microstructures using patterned polydimethylsiloxane (PDMS) stamps. MAPbBr₃ was first examined as a reference system to evaluate pattern transfer, morphology, substrate compatibility, and characteristic growth imperfections. Periodic microstructures with template spacings from 0.8 to 10 μm were obtained on Si/SiO₂, ITO, PDMS, and MAPbBr₃ macrocrystal substrates. Static stamping creates strong edge–center morphological divergence: thick patterned microcrystals and coalesced domains formed preferentially near the sample edges, whereas thinner isolated microcrystal arrays were more common in central regions. XRD, AFM, SEM, SAED, EDX, HRTEM, PL microscopy, and TRPL analyses show that the method can generate well-crystallized and optically active perovskite domains while also producing multidomain aggregates, incomplete pattern transfer, pressure-induced wrinkling, and nanoscale secondary crystallites. Extension to MAPbBr_3−xCl_x demonstrates that patterned mixed-halide microstructures can be obtained with composition-dependent structural and optical properties. Nevertheless, XRD, EDX, PL, and TRPL results indicate that Cl-rich samples are not fully described by a simple homogeneous solid-solution model, likely involving compositionally heterogeneous crystallization and a Br-rich emissive component. Preliminary MAPbCl₃-on-MAPbBr₃ experiments further show that PDMS-confined patterning can be coupled with substrate-mediated halide exchange or interfacial recrystallization. Overall, static PDMS-confined crystallization is established as a simple exploratory platform for producing diverse patterned perovskite microstructures. This approach is well-suited for the manual selection of suitable crystals and the fabrication of individual microdevices; however, improved control over pressure, mass transport, nucleation localization, and composition will be required when the uniformity of produced patterned microcrystals is desired. Full article

Polymeric membranes are widely investigated for CO₂ separation; however, their performance is often limited by the permeability–selectivity trade-off. Incorporating metal–organic frameworks (MOFs) and designing composite membrane architectures are promising strategies to overcome these limitations. This study aims to evaluate the effect of incorporating MOF-74 (Cu and Ni variants) into a polydimethylsiloxane (PDMS) selective layer supported on a polysulfone (PSF) membrane for enhanced CO₂/N₂ separation performance. Dual-layer PDMS/PSF composite membranes were fabricated via phase inversion for the PSF support, followed by solution casting of the PDMS/MOF layer. The developed membrane architecture introduces a synergistic design that combines the mechanical robustness of PSF with the selective transport capability of PDMS and the strong CO₂ affinity of MOF-74, offering an effective strategy for improving gas separation efficiency. Gas permeation performance was assessed using single-gas CO₂ and N₂ measurements at feed pressures of 2–5 bar. The incorporation of MOF-74 improved CO₂ transport properties, with the 1 wt.% Cu-MOF-74 composite membrane achieving a CO₂ permeance of 912.5 GPU and a CO₂/N₂ ideal selectivity of 94.75. The dual-layer configuration significantly enhanced permeance compared with unsupported mixed-matrix membranes while maintaining selectivity. Additionally, the composite membranes exhibited improved mechanical strength due to the PSF support layer. The findings demonstrate that dual-layer PDMS/PSF composite membranes incorporating MOF-74 provide a promising proof-of-concept approach for improving CO₂ separation performance. Further studies involving mixed-gas testing and long-term stability are required to assess their practical applicability. Full article

Superhydrophobic photothermal coatings have great potential in anti-icing and de-icing applications. However, how to construct superhydrophobic coatings with high photothermal conversion performance and an appropriate rough structure is still a challenge. In this study, we first constructed the photothermal nanosphere coating by in situ co-deposition of tannic acid (TA) and (3-aminopropyl) triethoxysilane (APTES) and then by the coordination of iron ions (Fe³⁺). A superhydrophobic photothermal coating with a micro–nano–nano hierarchical rough structure was constructed by further applying a polydimethylsiloxane (PDMS)/hydrophobic fumed silica (SiO₂) coating. The coating has excellent superhydrophobic (water contact angle (WCA) of 158°) and efficient photothermal conversion performance (75 °C). Based on this, the coated fabric shows ideal performance in passive anti-icing and active de-icing tests. At the same time, the coated fabric also has an ideal UV shielding effect, which can ensure the long-term and efficient operation of the coated fabric in the outdoor sunlight. This preparation strategy provides an innovative method for the development of superhydrophobic photothermal coating materials and has broad application prospects in the field of flexible anti-/de-icing applications. Full article

To overcome the inherently low temperature sensitivity of fiber Bragg gratings (FBGs) in engineering applications under low-temperature conditions, a sensitivity-enhanced FBG temperature sensor based on a polytetrafluoroethylene (PTFE) encapsulation sleeve was developed. Four adhesive materials—silicone thermal grease, polydimethylsiloxane (PDMS), epoxy resin, and modified acrylic ester—were employed to package the FBG within the PTFE sleeve to improve its temperature sensitivity. Thermal stress simulations of the proposed sensor structure were carried out using COMSOL Multiphysics^® 6.2, and the simulation results showed good agreement with the experimental data. Based on the experimental results, the sensitivity-enhancement effects of PTFE combined with different adhesives, as well as the influences of the PTFE sleeve length and wall thickness, were systematically investigated. The results indicate that, within the temperature range of −35 °C to 15 °C, increasing both the length and thickness of the PTFE sleeve can effectively improve the temperature sensitivity of the sensor. When epoxy resin was used as the encapsulating adhesive, the sensor achieved a maximum sensitivity of 117.4 pm/°C, corresponding to a 13.19-fold increase compared with that of a bare FBG sensor. This sensitivity-enhancing packaging structure significantly improves both the temperature sensitivity and linearity of FBG temperature sensors, while also substantially reducing fabrication costs. Full article

To address the issues of complex fabrication and poor mechanical stability associated with traditional light-controlled interfaces, we developed a highly durable photothermal surface based on a polydimethylsiloxane (PDMS)—carbon black (CB) composite using spin-coating and laser ablation techniques. Under 600 W/m² illumination, the 3 wt% PDMS-CB surface achieves a rapid photothermal response, reaching 104.7 °C within 150 s. Driven by a localized 0.5 W near-infrared laser, a 10 μL droplet exhibits high-speed transport at 6.53 mm/s. Uniquely, the platform enables flexible, programmable multi-modal maneuvers, including dynamic obstacle avoidance, controlled merging, and induced splitting by presetting the laser spot trajectory. At the same time, the coating surface exhibits excellent durability when subjected to external mechanical damage. Notably, because the photothermal-active CB is uniformly embedded within the durable PDMS matrix rather than superficially coated, the surface maintains reliable actuation performance (4.17 mm/s) even after multiple cyclic actuation experiments. This study provides a simple, robust solution with potential for multifunctional integration for advanced non-contact microfluidic control and lab on chip applications. Full article

Solid rocket motor (SRM) is a reliable and cost-effective aerospace propulsion system, by virtue of its advantages in terms of simple structure, long storage life, low cost, and ease of manufacturing. However, cracks and interfacial delamination may occur at the interface owing to the interface stress resulting from the complex service scenarios throughout the entire life cycle of the SRM. Therefore, it is crucial to monitor the interface stress for health assessment of the SRM. To achieve non-destructive in situ monitoring of interface stress, this paper proposes a novel embedded wireless flexible sensor (EWFS). Through theoretical analysis, the expression of the relationship between the input and output signals of EWFS is formulated. The response patterns of the output signals under different interface stresses are investigated. A prototype of the EWFS comprising the flexible printed circuit board (FPCB) and polydimethylsiloxane (PDMS) is fabricated, along with an interface stress-testing system established for experiments. The experimental results indicate that the EWFS exhibits a sensitivity of 27.2 mV·MPa⁻¹, a linearity error of 1.73%, a maximum hysteresis error of 2.67%, and a stability error of 0.023%. Full article

Soil adhesion and abrasive wear severely degrade the performance and service life of soil-covering rollers in no-tillage seeders, particularly in the heavy clay black soil regions of Northeast China. To address the critical issues of soil adhesion and wear on soil-covering rollers used in no-tillage seeders within black soil regions, this study presents a surface engineering strategy that integrates a bionic micro-texture with a functional composite coating. Inspired by the crescent-shaped pits on the body surface of Procambarus clarkii, a bionic texture was designed and combined with a PTFE/PDMS/TiO₂ composite coating. Key parameters were optimized using response surface methodology, yielding a TiO₂ mass fraction of 6%, coating thickness of 40 μm, remaining texture depth of 50 μm, and texture spacing of 250 μm. A prototype was fabricated and evaluated through orthogonal field experiments in two distinct soil environments. In clay soil (15–25% moisture content), soil moisture and vertical load significantly influenced anti-adhesion performance, with recommended operating parameters of 600 N vertical load and a speed range of 10.8–14.4 km·h⁻¹. In sandy soil (8–18% moisture content), vertical load and operating speed had significant effects on wear resistance, with optimal parameters identified as 600 N vertical load and 10.8 km·h⁻¹. Verification tests confirmed stable low-adhesion and low-wear performance under varying moisture conditions. Compared to conventional and PTFE-coated rollers, the bionic roller reduced soil adhesion by 82.62% and 74.02%, respectively, in high-moisture clay soil, and reduced wear loss by 36.81% and 28.97%, respectively, in dry sandy soil. These results demonstrate that the synergistic “structure–material” design, which leverages stress dispersion and storage from the bionic texture alongside low surface energy and enhanced wear resistance from the composite coating, offers a promising approach for improving the durability and performance of soil-engaging agricultural components. Full article