Search Results (2,155)

Electro-conductive films with excellent flexibility and thermal behavior have great potential in the fields of wearable electronics, artificial muscle, and soft robotics. Herein, we report a super-elastic and electro-conductive composite film with a sandwich structure. The composite film was constructed by spraying Polyvinyl alcohol (PVA) polymers onto a buckled conductive carbon nanotube-polydimethylsiloxane (CNTs-PDMS) composite film. In this system, the PVA and PDMS provide water sensing and stretchability, while the coiled CNT film offers sufficient conductivity. Notably, the composite film possesses high stretchability (205%), exceptional compression sensing ability, humility sensing ability, and remarkable electrical stability under various deformations. The produced CNT composite film exhibited deformation (bending/twisting) and high electro-heating performance (108 °C) at a low driving voltage of 2 V. The developed CNT composite film, together with its exceptional sensing and electrothermal performance, provides the material with promising prospects for practical applications in wearable electronics. Full article

The use of flexible pressure sensors has become increasingly widespread in a variety of applications, including wearable electronics and electronic skin. These sensors need to exhibit high sensitivity, wide detection limits, a fast response time, a linear response, and mechanical stability. In this study, we demonstrate a resistive pressure sensor based on randomly arranged micropyramid polydimethylsiloxane (PDMS) with a conductive poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) thin film with a sensitivity of 391 kPa⁻¹, a response time of 52.91 ms, a recovery time of 4.38 ms, and a limit of detection (LOD) of 0.35 kPa. Electrodes are then connected to a pair of the proposed resistive pressure sensors that face each other to fabricate a pressure sensing device. We examine various characteristics of the fabricated device, including the changes observed when applying loads ranging from 0 to 2.58 kPa. The proposed sensor exhibits high sensitivity and a rapid response time. Full article

Biofouling poses a significant challenge to the marine industry, and silicone anti-biofouling coatings have garnered extensive attention owing to their environmental friendliness and low surface energy. However, their widespread application is hindered by their low substrate adhesion and weak static antifouling capabilities. In this study, a novel silicone polymer polydimethylsiloxane (PDMS)-based poly(urea-thiourea-imine) (PDMS-PUTI) was synthesized via stepwise reactions of aminopropyl-terminated polydimethylsiloxane (APT-PDMS) with isophorone diisocyanate (IPDI), isophthalaldehyde (IPAL), and carbon disulfide (CS₂). Subsequently, a nanocomposite coating (AgNPs-x/PDMS-PUTI) was prepared by adding silver nanoparticles (AgNPs) to the polymer PDMS-PUTI. The dynamic multiple hydrogen bonds formed between urea and thiourea linkages, along with dynamic imine bonds in the polymer network, endowed the coating with outstanding self-healing properties, enabling complete scratch healing within 10 min at room temperature. Moreover, uniformly dispersed AgNPs not only reduced the surface energy of the coating but also significantly enhanced its antifouling performance. The antibacterial efficiency against common marine bacteria Pseudomonas aeruginosa (P.sp) and Staphylococcus aureus (S.sp) was reduced by 97.08% and 96.71%, respectively, whilst the diatom settlement density on the coating surface was as low as approximately 59 ± 3 diatom cells/mm². This study presents a novel approach to developing high-performance silicone antifouling coatings. Full article

Iris taxa are sources of valuable essential oils obtained from aged rhizomes used by various industries, including pharmacy, cosmetic, perfume, and food industry, in which irones are the most important aroma components. In this study, volatile organic compounds (VOCs) obtained from dried rhizomes of three endemics from Croatia, Iris pseudopallida, I. illyrica, and I. adriatica, were studied. The VOCs were isolated by three different methods: headspace solid-phase microextraction (HS–SPME) using divinylbenzene/carboxene/polydimethylsiloxane (DVB/CAR/PDMS) fiber or polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber, and hydrodistillation (HD). The samples were analyzed by gas chromatography–mass spectrometry (GC–MS). In five out of six samples, the main compounds detected by HS–SPME were perilla aldehyde, butan-2,3-diol, acetic acid, 2-phenylethanol, benzyl alcohol, hexanal, and nonanal, while 6-methylhept-5-en-2-one, trans-caryophyllene, and ethanol were common for all studied samples. The former VOCs were absent from the oldest, irone-rich I. pseudopallida sample, mainly characterized by cis-α-irone (43.74–45.76%). When using HD, its content was reduced (24.70%), while docosane prevailed (45.79%). HD yielded predominantly fatty acids, including myristic, common for all studied taxa (4.20–97.01%), and linoleic (40.69%) and palmitic (35.48%) as the major VOCs of I. adriatica EO. The performed GC–MS analyses of EOs, in combination with HS–SPME/GC–MS, proved to be useful for gaining a better insight into Iris VOCs. Full article

Microreactors for process intensification transform chemical synthesis, providing precise control over reactions in compact devices and enhancing efficiency. This review article explores their application in chemical synthesis, emphasizing advantages in mixing, temperature control, and heat transfer. It delves into fundamental aspects, addressing challenges in design, operation, material selection, and scaling. Fundamental microreactor design principles involve scaling strategies such as internal and external numbering up, geometric similarity, and continuous pressure drop procedures. Materials like silicon, steel, and polymers, particularly polydimethylsiloxane (PDMS), play a crucial role in microreactor construction. Fabrication techniques, including microfabrication, are essential for creating complex designs and ensuring reliability. This review addresses challenges and research gaps while showcasing the versatility of microreactors. Challenges include automation, integration, finding optimal configurations, process optimization, and cost analyses. Overcoming these challenges is crucial for widespread adoption in industries like pharmaceuticals and petrochemicals. The future for microreactors will revolve around recent advancements, collaboration between academia and industry, and the integration of automation and sensors. This positions microreactors as key players in revolutionizing chemical production, with potential applications in fuel cells, mini-chemical plants, and next-generation catalysts. Therefore, it is of the utmost importance to address the current challenges and advance research related to this study in order to solidify their role in shaping the future of chemical engineering. Full article

A novel highly sensitive D-shaped photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensor for dual parameters of refractive index and temperature detecting is proposed. A PCF cladding polishing provides a D-shape design with a gold (Au) film coating for refractive index (RI) sensing (Core 1) and a composite film of silver (Ag) and polydimethylsiloxane (PDMS) for temperature sensing (Core 2). Comsol Multiphysics 5.5 is used to design and simulate the proposed sensor by the finite element method (FEM). The proposed sensor numerically provides results with maximum wavelength sensitivities (WSs) of 51,200 and 56,700 nm/RIU for Core 1 and 2 as RI sensing while amplitude sensitivities are −98.9 and −147.6 RIU⁻¹ with spectral resolution of 1.95 × 10⁻⁶ and 1.76 × 10⁻⁶ RIU, respectively. Notably, wavelength sensitivity of 17.4 nm/°C is obtained between −20 and −10 °C with resolution of 5.74 × 10⁻³ °C for Core 2 as temperature sensing. This sensor can efficiently work in the analyte and temperature ranges of 1.33–1.43 RI and −20–100 °C. Due to its high sensitivity and wide detection ranges, both in T and RI sensing, it is a promising candidate for a variety of applications, including chemical, medical, and environmental detection. Full article

The burgeoning development of next-generation technologies, especially the Industrial Internet of Things (IIoT), has heightened interest in predictive maintenance (PdM). Accurate failure forecasting and prompt responses to downtime are essential for improving the industrial efficiency. Traditional PdM methods often suffer from high false alarm rates and inefficiencies in complex environments. This paper introduces a predictive maintenance framework using identity resolution and a transformer model. Devices receive unique IDs via distributed identifiers (DIDs), followed by a state awareness model to assess device health from sensor signals. A sequence prediction model forecasts future signal sequences, which are then used with the state awareness model to determine future health statuses. Combining these predictions with unique IDs allows for the rapid identification of facilities needing maintenance. Experimental results show superior performance, with 99% accuracy for the state awareness model and a mean absolute error (MAE) of 0.062 for the sequence prediction model, underscoring the effectiveness of the framework. Full article

Polydimethylsiloxane (PDMS) is widely used in biomedical applications due to its biocompatibility and flexibility but faces challenges due to its hydrophobicity and limited mechanical strength. This study explores the incorporation of thyme (Thymus vulgaris L.) into PDMS to enhance its properties for wound dressing applications. PDMS composites containing 2.5 wt.% and 5 wt.% of thyme were prepared and evaluated for physical, chemical, mechanical, and biological properties. Scanning electron microscopy, contact angle measurements, absorption tests, Fourier-transform infrared spectroscopy, differential scanning calorimetry, hardness, tensile testing, antibacterial activity, and cell viability assays were conducted. Thyme integration improved mechanical properties with increased absorption and preserved hydrophobicity. FTIR and DSC analyses indicated minimally altered crystallinity and chemical interactions. Hardness decreased with higher thyme content due to terpene-induced polymerization inhibition. Tensile testing showed reduced stress at break but increased elongation, suitable for wound dressings. Enhanced antibacterial activity was observed, with composites meeting bacteriostatic standards. Cell viability exceeded 70%, with optimal results at 2.5 wt.% thyme, attributed to cytokine-inducing compounds. Thyme-incorporated PDMS composites exhibit improved antibacterial and mechanical properties, demonstrating the potential for advanced wound dressings. Full article

This paper presents a photonic crystal fiber (PCF) sensor that can be used to measure the temperature and magnetic field simultaneously, and to monitor the changes in them in the environment. When we designed the fiber structure, two circular channels of the same size were added to the fiber to facilitate the subsequent addition of materials. A gold film is added to the upper channel (ch1), and the channel is filled with a magnetic fluid (MF). The sensor can reflect changes in the temperature and magnetic field strength. The two channels containing MF and PDMS in the proposed fiber are called ch1 and ch2. The structure, mode and properties (temperature and magnetic field) were analyzed and discussed using the finite element method. By using the control variable method, the influence of Ta₂O₅ or no Ta₂O₅, the Ta₂O₅ thickness, the diameter of the special air hole, the distance from the fiber core and the distance between them in the displacement of the loss spectrum and the phase-matching condition of the coupling mode were studied. The resulting maximum temperature sensitivity is 6.3 nm/°C (SPR peak 5), and the maximum magnetic field sensitivity is 40 nm/Oe (SPR peak 4). Because the sensor can respond to temperature and magnetic field changes in the environment, it can play an important role in special environmental monitoring, industrial production and other fields. Full article

Rare earth and transition metal ion-doped CaZnOS has garnered significant attention for its exceptional mechanoluminescence (ML) performance under mild mechanical stimuli and its capability for multicolor emissions. Since powdered phosphors are not directly usable, they require encapsulation within with polymers to create stable structures. This study investigates Mn²⁺-doped CaZnOS (CaZnOS:Mn²⁺) as the ML phosphor, optimizing its performance by varying the Mn²⁺ content, resulting in bright orange-red emissions from the d-d transitions of the Mn²⁺ activator. A quantum efficiency of 59.08% was achieved through the self-sensitization of the matrix lattice and energy transfer to the Mn²⁺ luminescent centers. The enhancement in ML due to Mn²⁺ doping is attributed to the reduced trap depth and increased trap concentration. Encapsulation with four polymers—PDMS, PU, SIL, and RTV-2—was explored to further optimize ML performance. Among these, PDMS provides the best ML output and sensitivity, owing to its slightly cross-linked structure and good triboelectric properties. The optimized CaZnOS:0.03Mn²⁺/PDMS composite, featuring excellent flexibility and recoverability, shows great potential for applications in anti-counterfeiting encryption, stress sensors, and wearable devices. Full article

Due to the extremely low Reynolds number, the mixing of substances in laminar flow within microfluidic channels primarily relies on slow intermolecular diffusion, whereas various rapid reaction and detection requirements in lab-on-a-chip applications often necessitate the efficient mixing of fluids within short distances. This paper presents a magnetic pillar-shaped particle fabrication device capable of producing particles with planar shapes, which are then utilized to achieve the rapid mixing of multiple fluids within microchannels. During the particle fabrication process, a degassed PDMS chip provides self-priming capabilities, drawing in a UV-curable adhesive-containing magnetic powder and distributing it into distinct microwell structures. Subsequently, an external magnetic field is applied, and the chip is exposed to UV light, enabling the mass production of particles with specific magnetic properties through photo-curing. Without the need for external pumping, this chip-based device can fabricate hundreds of magnetic particles in less than 10 min. In contrast to most particle fabrication methods, the degassed PDMS approach enables self-priming and precise dispensing, allowing for precise control over particle shape and size. The fabricated dual-layer magnetic particles, featuring fan-shaped blades and disk-like structures, are placed within micromixing channels. By manipulating the magnetic field, the particles are driven into motion, altering the flow patterns to achieve fluid mixing. Under conditions where the Reynolds number in the chip ranges from 0.1 to 0.9, the mixing index for substances in aqueous solutions exceeds 0.9. In addition, experimental analyses of mixing efficiency for fluids with different viscosities, including 25 wt% and 50 wt% glycerol, reveal mixing indices exceeding 0.85, demonstrating the broad applicability of micromixers based on the rapid rotation of magnetic particles. Full article

One of the most important challenges in polymer science is a rigorous understanding of the molecular mechanisms of rubber elasticity by relating macroscopic deformation to molecular changes and deriving the constitutive stress–strain equation for the elastomeric network. The models developed from the last century to today describe many aspects of the physics of rubber elasticity; although these theories are successful, they are not complete. In this review we analyze the main theoretical and phenomenological models of rubber elasticity, including their assumptions, main characteristics, and stress–strain equations. Then, we compare the predictions of the theories to our experimental data of polydimethylsiloxane (PDMS) rubber, in order to highlight the goodness of the reviewed models. The nonaffine and phenomenological deformation models verify the experimental curves in tension and compression in the whole investigated deformation range λ≤2. On the contrary, the affine deformation hypothesis is rigorously verified only in the deformation range λ≤1. Full article

Flexible, wearable pressure sensors offer numerous benefits, including superior sensing capabilities, a lightweight and compact design, and exceptional conformal properties, making them highly sought after in various applications including medical monitoring, human–computer interactions, and electronic skins. Because of their excellent characteristics, such as simple fabrication, low power consumption, and short response time, capacitive pressure sensors have received widespread attention. As a flexible polymer material, polydimethylsiloxane (PDMS) is widely used in the preparation of dielectric layers for capacitive pressure sensors. The Young’s modulus of the flexible polymer can be effectively decreased through the synergistic application of sacrificial template and laser ablation techniques, thereby improving the functionality of capacitive pressure sensors. In this study, a novel sensor was introduced. Its dielectric layer was developed through a series of processes, including the use of a sacrificial template method using NaCl microparticles and subsequent CO₂ laser ablation. This porous PDMS dielectric layer, featuring an array of holes, was then sandwiched between two flexible electrodes to create a capacitive pressure sensor. The sensor demonstrates a sensitivity of 0.694 kPa⁻¹ within the pressure range of 0–1 kPa and can effectively detect pressures ranging from 3 Pa to 200 kPa. The sensor demonstrates stability for up to 500 cycles, with a rapid response time of 96 ms and a recovery time of 118 ms, coupled with a low hysteresis of 6.8%. Furthermore, our testing indicates that the sensor possesses limitless potential for use in detecting human physiological activities and delivering signals. Full article

Increasing nitrogen use efficiency (NUE) by improving agricultural practices and soil knowledge, and implementing precision agriculture, is essential to reduce the overuse of fertilizers and increase nutrient retention. This study aimed to optimize N management in agriculture by establishing a critical N dilution curve (CNDC) and analyzing variations in NUE and the N nutrition index (NNI) among different crops under various treatments. Using a Bayesian model, the CNDC was determined as %N_c = 3.63 × PDM^−0.71. The results showed that plant dry matter (PDM) and plant N content (PNC) varied significantly with crop type and sampling moments. Strong positive correlations are presented by PDM with N uptake (NUp) (0.89) and NNI (0.88), along with an inverse correlation with critical N concentration (−0.95). The study found that crops under irrigation conditions had higher NUp and higher NNI. This study provides valuable insights into the influence of key management decisions on the N nutritional status of annual ryegrass-based forage crops. The results highlight the critical role of accurate and conscious decision-making in improving NUE and crop yields, emphasizing the complex interactions between biomass production and N dynamics in crops. The conclusions allow significant benefits to be realized, contributing to the sustainability of agricultural systems. Full article

The recent developments in electric vehicle (EV) necessities the requirement of a human intervention free charging system for safe and reliable operation. Wireless power transfer (WPT) technology shows promising options to automate the charging process with user convenience. However, the operation of the WPT system is designed to operate at a high-frequency (HF) range, which requires proper control and modulation technique to improve the performance of power electronic modules. This paper proposes a dead-time (DT) integrated Pulse Density Modulation (PDM) technique to provide better control with minimal voltage and current ripples at the switches. The proposed technique is investigated using a LCC-LCL compensated WPT system, which predominantly affects the high-frequency voltage and current ripples. The performance analysis is studied at different density conditions to explore the impact of the integrated PDM approach. Moreover, the PDM technique gives better control over the power transfer at different levels of load requirement. The simulation and experimental analysis was performed for a 3.7 kW WPT prototype test system under different modes of operation of the high-frequency power converters. Both the simulated and experimental results demonstrate that the proposed PDM technique effectively enhances the efficiency of the HF inverter while significantly reducing output current ripples, power dissipation and improving the overall WPT system efficiency to 92%, and leading to a reduction in the power loss in the range of 10% to 20%. This leads to improved overall system control and performance. Full article