Search Results (95)

Wearable sensors have rapidly advanced, enabling applications such as human activity monitoring, electronic skin, and biomimetic robotics. To meet the growing demands of these applications, multifunctional sensing has become essential for wearable devices. However, most existing studies predominantly focus on enhancing single-function sensing capabilities. This study introduces a multifunctional sensor that combines high stretchability for strain and pressure detection with ultraviolet (UV) sensing capability. To achieve simultaneous detection of strain, pressure, and UV light, a multi-sensing approach was employed: a capacitive method for strain and pressure detections and a resistive method utilizing a pn-heterojunction diode for UV detection. In the capacitive method, polyaniline (PANI) served as parallel-plate electrodes, while silicon-based elastomer acted as the dielectric layer. This configuration enabled up to 100% elongation and enhanced operational stability through encapsulation. The sensor demonstrated a strong linear relationship between capacitance value changes reasonably based on the area of PANI, and showed a good linearity with an R-squared value of 0.9918. It also detected pressure across a wide range, from low (0.4 kPa) to high (9.4 kPa). Furthermore, for wearable applications, the sensor reliably captured capacitance variations during finger bending at different angles. For UV detection, a pn-heterojunction diode composed of p-type silicon and n-type zinc oxide nanorods exhibited a rapid response time of 6.1 s and an on/off ratio of 13.8 at −10 V. Durability under 100% tensile strain was confirmed through Von Mises stress calculations using finite element modeling. Overall, this multifunctional sensor offers significant potential for a variety of applications, including human motion detection, wearable technology, and robotics. Full article

Background/Objectives: Thymol, one of the main compounds of thyme essential oil, has shown promising effects in treating various skin disorders owing to its anti-inflammatory, antimicrobial and antioxidative activities. Due to its limited solubility in water, thymol is commonly used in higher concentrations to achieve a suitable therapeutic effect, which can consequently lead to skin irritation. To overcome these limitations, we incorporated thymol into a vesicular phospholipid gel (VPG), a novel semisolid dermal vehicle consisting of highly concentrated dispersion of phospholipid vesicles (liposomes). Methods: Thymol was successfully loaded into two VPGs differing in bilayer fluidity, which were characterized for the physicochemical and rheological properties, storage stability, in vitro release, ex vivo skin permeability, in vitro compatibility with epidermal cells, wound healing potential, and antibacterial activity against skin-relevant bacterial strains. Results: High pressure homogenization method enabled preparation of VPG-liposomes of neutral surface charge in the size range 140–150 nm with polydispersity indexes below 0.5. Both types of VPGs exhibited viscoelastic solid-like structures appropriate for skin administration and ensured skin localization of thymol. Although both types of VPGs enabled prolonged release of thymol, the presence of cholesterol in the VPG increased the rigidity of the corresponding liposomes and further slowed down thymol release. Conclusions: Loading of thymol into VPGs significantly reduced its cytotoxicity toward human keratinocytes in vitro even at very high concentrations, compared to free thymol. Moreover, it facilitated in vitro wound healing activity, proving its potential as a vehicle for herbal-based medicines. However, the antibacterial activity of thymol against Staphylococcus aureus and methicillin-resistant S. aureus was hindered by VPGs, which represents a challenge in their development. Full article

In recent years, flexible piezoresistive sensors based on polydimethylsiloxane (PDMS) matrix materials have developed rapidly, showing broad application prospects in fields such as human motion monitoring, electronic skin, and intelligent robotics. However, achieving a balance between structural durability and fabrication simplicity remains challenging. Traditional methods for preparing PDMS flexible substrates with high porosity and high stability often require complex, costly processes. Breaking through the constraints of conventional material systems, this study innovatively combines the high elasticity of polydimethylsiloxane (PDMS) with the stochastically distributed porous topology of a sponge-derived biotemplate through biomimetic templating replication technology, fabricating a heterogeneous composite system with an architecturally asymmetric spatial network. After 5000 loading cycles, uncoated samples experienced a thickness reduction of 7.0 mm, while PDMS-coated samples showed minimal thickness changes (2.0–3.0 mm), positively correlated with curing agent content (5:1 to 20:1). The 5:1 ratio sample demonstrated exceptional mechanical stability. As evidenced, the PDMS film-encapsulated architecturally asymmetric spatial network demonstrates superior stress dissipation efficacy, effectively mitigating stress concentration phenomena inherent to symmetric configurations that induce matrix fracture, thereby achieving optimal mechanical stability. Compared to the pre-test resistance distribution of 10–248 Ω, after 5000 cyclic loading cycles, the uncoated samples exhibited a narrowed resistance range of 10–50 Ω, while PDMS-coated samples maintained a broader resistance range (10–240 Ω) as the curing agent ratio increased (from 20:1 to 5:1), demonstrating that increasing the curing agent ratio helps maintain conductive network stability. The 5:1 ratio sample displayed the lowest resistance variation rate attenuation—only 3% after 5000 cycles (vs. 80% for uncoated samples)—and consistently minimal attenuation at all stages, validating superior electrical stability. Under 0–6 kPa pressure, the 5:1 ratio device maintained a linear sensitivity of 0.157 kPa⁻¹, outperforming some existing works. Human motion monitoring experiments further confirmed its reliable signal output. Furthermore, the architecturally asymmetric spatial network of the device enables superior conformability to complex curvilinear geometries, leveraging its structural anisotropy to achieve seamless interfacial adaptation. By synergistically optimizing material composition and structural design, this study provides a novel technical method for developing highly durable flexible electronic devices. Full article

Acne vulgaris is one of the most common skin diseases, and its development is closely linked to the overgrowth of the bacterium Cutibacterium acnes. More than half of the strains of this bacterium are resistant to antibiotics, which has prompted scientists to look for alternatives, such as antibacterial peptides, that can replace traditional drugs. Due to its antioxidant properties, ascorbic acid may be a promising ally in the treatment of acne. The aim of our study was to evaluate the effect of peptide (KWK)₂-KWWW-NH₂(P5) in the presence of ascorbic acid (AA) and its derivative (3-O-ethyl-L-ascorbic acid, EAA) on the stability and organization of phosphatidylinositol monolayers (PI) at temperatures of 25–35 °C. This study showed that the monolayers were in the expanded liquid state (35.28–49.95 mN/m) or in the transition between the expanded liquid and condensed phases (51.50–57.49 mN/m). Compression and decompression isotherms indicated the highest flexibility of the PI + P5 system, where the compression reversibility coefficient of isotherm values ranged from 80.59% to 97.77% and increased for each loop with increasing temperature. At 35 °C, the surface pressure of the monolayer in the PI + P5, PI + P5 + AA and PI + P5 + EAA systems changed less with time. Full article

Background: Due to their antibacterial activities, essential oils can be potential alternatives to antibiotics in certain cases. West Indian lemongrass (Cymbopogon citratus) essential oil (LEO) is effective against a broad range of bacteria by inhibiting spore formation, and is considered safe. In this study, we demonstrated its therapeutical potential in the treatment of pitted keratolysis (PK), a superficial skin infection affecting the pressure-bearing areas of plantar surfaces. Methods: For in vitro antibacterial efficacy testing, LEO was mixed into different ointment bases, including Hydrogelum methylcellulose FoNo VIII., Ungentum oleosum FoNo VIII. (Ung. oleoso), Unguentum stearini FoNo VIII. (Ung. stearin), and Vaselinum cholesterinatum FoNo VIII. (Vasel. cholest.), at different concentrations of 1, 3, and 5%. These formulations were tested on representatives of three bacterial species associated with PK: Kytococcus sedentarius, Dermatophilus congolensis, and Bacillus thuringiensis. Results: In the in vitro tests, Hydrogelum methylcellulose (HM) gel best supported the antibacterial effects of LEO, reducing the number of living bacteria on agar plates by 4–5 orders of magnitude in a concentration-dependent manner during the 30 min exposure times. This was also confirmed by the Franz diffusion cell drug release test; after 30 min, several active compounds could be detected in the HM samples, in contrast to the other bases. Shelf-life experiments showed that the HM base supported the antibacterial features of 3% LEO for at least 2 years without significant loss of efficacy. Conclusions: Our study highlights that ointments containing essential oils potentially have a place in the treatment of PK. Therefore, antibiotics may potentially be replaced for the treatment of PK, thereby reducing environmental antibiotic pressure, which is one of the driving forces behind the spread of antibiotic resistance. Full article

Background: Due to rising antibiotic-resistant microorganisms, there is a pressing need to screen approved drugs for repurposing and to develop new antibiotics for controlling infections. Current in vitro and ex vivo models have mostly been unsuccessful in establishing in vivo relevance. In this study, we developed a stringent ex vivo-burned porcine skin model with high in vivo relevance to screen topical antimicrobials. Methods: A 3 cm-diameter thermal injury was created on non-sterilized porcine skin using a pressure-monitored and temperature-controlled burn device. Commensals were determined pre- and post-burn. The burn wound was inoculated with a target pathogen, and efficacies of Silvadene, Flammacerium, Sulfamylon, and Mupirocin were determined. The in vivo relevance of this platform was evaluated by comparing the ex vivo treatment effects to available in vivo treatment outcomes (from our laboratory and published reports) against selective burn pathogens. Results: Approximately 1% of the commensals survived the skin burn, and these commensals in the burn wounds affected the treatment outcomes in the ex vivo screening platform. When tested against six pathogens, both Silvadene and Flammacerium treatment exhibited ~1–3 log reduction in viable counts. Sulfamylon and Mupirocin exhibited higher efficacy than both Silvadene and Flammacerium against Pseudomonas and Staphylococcus, respectively. The ex vivo treatment outcomes of Silvadene and Flammacerium against Pseudomonas were highly comparable to the outcomes of the in vivo (rats). Conclusions: The ex vivo model developed in our lab is a stringent and effective platform for antimicrobial activity screening. The outcome obtained from this ex vivo model is highly relevant to in vivo. 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

Steel/polymer/steel laminates, also known as laminated steels, are composite materials consisting of bonding layers of steel and polymer. The polymer layer acts as a bonding agent between the steel layers, imparting additional properties such as low density, impact resistance, and thermal insulation, while the steel layers provide strength and formability. These laminated steels have found increasing applications in automotive, aerospace, and construction industries to reduce weight and improve fuel efficiency. The bending behavior of this laminates is more complex compared to that of a single layer of metallic sheets. This complexity arises from significant differences in mechanical properties, as well as the thickness ratio between the skin and the core. The flexural properties and behavior of different St14/TPU/St14 laminate sheets that were fabricated using the direct roll bonding (DRB) process were investigated through three-point and hat-shaped bending tests. The direct roll bonding process involves the bonding of steel and semi-melt polymer sheets under the pressure of rollers, ensuring a cohesive and durable composite material. The microscopic analysis of the cross-section of the SPS laminates after the bending processes shows the absence of delamination or slippage between the layers, which indicates the correct selection of materials and the bonding method. The results showed that the springback of three-layer laminates has an inverse relationship with the work-hardening exponent, yield strength, and yield point elongation value, while possessing a direct relationship with normal anisotropy and elastic modulus. Furthermore, the flexural strength and flexural modulus decrease with the increase in the volume fraction of the polymeric core, while the flexural rigidity increases. The findings indicate the DRB technique as a promising method for manufacturing a lightweight metal–polymer laminate with a high formability performance. Full article

Diabetic wounds (DWs) are considered chronic complications observed in patients suffering from type 2 diabetes mellitus (DM). Usually, DWs originate from the interplay of inflammation, oxidation, impaired tissue re-epithelialization, vasculopathy, nephropathy, and neuropathy, all of which are related to insulin resistance and sensitivity. The conventional approaches available for the treatment of DWs are mainly confined to the relief of wound pressure, debridement of the wound, and management of infection. In this paper, we speculate that treatment of DWs with 5-aminosalicylic acid (5-ASA) and subsequent activation of peroxisome proliferator-activated receptor gamma (PPAR-γ) and transforming growth factor beta (TGF-β) via the AhR pathway might be highly beneficial for DW patients. This estimation is based on several lines of evidence showing that 5-ASA and PPAR-γ activation are involved in the restoration of insulin sensitivity, re-epithelialization, and microcirculation. Additionally, 5-ASA and TGF-β activate inflammation and the production of pro-inflammatory mediators. Suitable stabilized formulations of 5-ASA with high absorption rates are indispensable for scrutinizing its probable pharmacological benefits since 5-ASA is known to possess lower solubility profiles because of its reduced permeability through skin tissue. In vitro and in vivo studies with stabilized formulations and a control (placebo) are mandatory to determine whether 5-ASA indeed holds promise for the curative treatment of DWs. Full article

This paper presents an analysis of long, large-diameter bored piles’ behavior under static and dynamic load tests for a megaproject located in El Alamein, on the northern shoreline of Egypt. Site investigations depict an abundance of limestone fragments and weak argillaceous limestone interlaid with gravelly, silty sands and silty, gravelly clay layers. These layers are classified as intermediate geomaterials, IGMs, and soil layers. The project consists of high-rise buildings founded on long bored piles of 1200 mm and 800 mm in diameter. Forty-four (44) static and dynamic compression load tests were performed in this study. During the pile testing, it was recognized that the pile load–settlement behavior is very conservative. Settlement did not exceed 1.6% of the pile diameter at twice the design load. This indicates that the available design manual does not provide reasonable parameters for IGM layers. The study was performed to investigate the efficiency of different approaches for determining the design load of bored piles in IGMs. These approaches are statistical, predictions from static pile load tests, numerical, and dynamic wave analysis via a case pile wave analysis program, CAPWAP, a method that calculates friction stresses along the pile shaft. The predicted ultimate capacities range from 5.5 to 10.0 times the pile design capacity. Settlement analysis indicates that the large-diameter pile behaves as a friction pile. The dynamic pile load test results were calibrated relative to the static pile load test. The dynamic load test could be used to validate the pile capacity. Settlement from the dynamic load test has been shown to be about 25% higher than that from the static load test. This can be attributed to the possible development of high pore water pressure in cohesive IGMs. The case study analysis and the parametric study indicate that AASHTO LRFD is conservative in estimating skin friction, tip, and load test resistance factors in IGMs. A new load–settlement response equation for 600 mm to 2000 mm diameter piles and new recommendations for resistance factors $\mathsf{\phi }$_qp, $\mathsf{\phi }$_qs, and $\phi$_load were proposed to be 0.65, 0.70, and 0.80, respectively. Full article

This research investigates the micro-mechanical and tribological properties of injection-molded parts made from polypropylene. The tribological properties of polymers are a very interesting area of research. Understanding tribological processes is very crucial. Considering that the mechanical and tribological properties of injected parts are not uniform at various points of the part, this research was conducted to explain the non-homogeneity of properties along the flow path. Non-homogeneity can be influenced by numerous factors, including distance from the gate, mold and melt temperature, injection pressure, crystalline structure, cooling rate, the surface of the mold, and others. The key factor from the micro-mechanical and tribological properties point of view is the polymer morphology (degree of crystallinity and size of the skin and core layers). The morphology is influenced by polymer flow and the injection molding process conditions. Gained results indicate that the indentation method was sufficiently sensitive to capture the changes in polypropylene morphology, which is a key parameter for the resulting micro-mechanical and tribological properties of the part. It was proven that the mechanical and tribological properties are not equal in varying regions of the part. Due to cooling and process parameters, the difference in the indentation modulus in individual measurement points was up to 55%, and the tribological properties, in particular the friction coefficient, showed a difference of up to 20%. The aforementioned results indicate the impact this finding signifies for injection molding technology in technical practice. Tribological properties are a key property of the part surface and, together with micro-mechanical properties, characterize the resistance of the surface to mechanical failure of the plastic part when used in engineering applications. A suitable choice of gate location, finishing method of the cavity surface, and process parameters can ensure the improvement of mechanical and tribological properties in stressed regions of the part. This will increase the stiffness and wear resistance of the surface. Full article

Heat transfer coefficients between shower water and human skin could significantly impact occupants’ thermal sensation and energy consumption during showering. A recent study found that heat transfer coefficients varied considerably among showerhead patterns. However, the specific effects of the showering heat transfer process on the showerhead patterns have yet to be determined. Two experiments were conducted to quantify the spray patterns during showering, and the impacts of the patterns’ parameters on the heat transfer coefficient were examined using different statistical methods. Five showerheads with 18 spray patterns were tested in this study. The resistance factor, water supply pressure, and nozzle area ratio of these patterns were measured to qualify their shower performance. The results indicated that all the tested parameters significantly impacted the heat transfer coefficient in general, and using resistance factor and nozzle area ratio could accurately predict the heat transfer performance of the showerhead pattern. Additionally, this study demonstrated that changing to a showerhead with a higher heat transfer coefficient could save considerable energy while maintaining the same thermal sensation during showering. The influence of water spray patterns on the heat transfer coefficient could provide residents with scientific references when selecting showerheads in their bathrooms. Full article

Antimicrobial peptides (AMPs) are key molecules in the innate immune defence of vertebrates with rapid action, broad antimicrobial spectrum, and ability to evade pathogen resistance mechanisms. To date, amphibians are the major group of vertebrates from which most AMPs have been characterised, but most studies have focused on the bioactive skin secretions of anurans (frogs and toads). In this study, we have analysed the complete genomes and/or transcriptomes of eight species of caecilian amphibians (order Gymnophiona) and characterised the diversity, molecular evolution, and antimicrobial potential of the AMP repertoire of this order of amphibians. We have identified 477 candidate AMPs within the studied caecilian genome and transcriptome datasets. These candidates are grouped into 29 AMP families, with four corresponding to peptides primarily exhibiting antimicrobial activity and 25 potentially serving as AMPs in a secondary function, either in their entirety or after cleavage. In silico prediction methods were used to identify 62 of those AMPs as peptides with promising antimicrobial activity potential. Signatures of directional selection were detected for five candidate AMPs, which may indicate adaptation to the different selective pressures imposed by evolutionary arms races with specific pathogens. These findings provide encouraging support for the expectation that caecilians, being one of the least-studied groups of vertebrates, and with ~300 million years of separate evolution, are an underexplored resource of great pharmaceutical potential that could help to contest antibiotic resistance and contribute to biomedical advance. Full article

The new-type stainless steel–concrete–carbon steel double-skin tubular (SCCDST) members, characterized by their exceptional corrosion resistance and mechanical bearing capacity, have promising applications in ocean engineering, particularly in deep-water engineering. The external hydraulic pressure and interfacial action of various materials intensify the complexity of composite performance of SCCDST members. This paper describes an analytical investigation on the concentric compressive performance of SCCDST members under external hydraulic pressure. The full-range mechanism, including load–displacement response, bearing capacity contribution, and contact pressures, was investigated through the finite element (FE) model that was validated by the failure mode, bearing capacity, and response of axial load versus strain. Subsequently, influences of key geometric–physical parameters were analyzed, e.g., diameter-to-thickness ratios (D_o/t_o, D_i/t_i), material strengths (f_yo, f_yi, and f_c), hollow ratios (χ), and water depths (H). Typical results indicate that: the initial active confinement action derived from the hydraulic pressure can enhance the interfacial contact pressure and axial compression capacity of SCCDST members due to the tri-axial compression state; the enhancement of confinement effect is mainly from the interfacial interaction between outer stainless steel tube and concrete infill; influence of water depth on bearing capacity cannot be ignored, e.g., the bearing capacity of an SCCDST member with larger hollow ratio (χ = 0.849) is not enhanced under a higher hydraulic pressure (H = 900 m) because of the cross-sectional buckling failure risk. Finally, a modified method considering the effect of water depth was proposed and verified for SCCDST members under hydraulic pressure. Full article

The emerging field of flexible tactile sensing systems, equipped with multi-physical tactile sensing capabilities, holds vast potential across diverse domains such as medical monitoring, robotics, and human–computer interaction. In response to the prevailing challenges associated with the limited integration and sensitivity of flexible tactile sensors, this paper introduces a versatile tactile sensing system capable of concurrently monitoring temperature and pressure. The temperature sensor employs carbon nanotube/graphene conductive paste as its sensitive material, while the pressure sensor integrates an ionic gel containing boron nitride as its sensitive layer. Through the application of cost-effective screen printing technology, we have successfully manufactured a flexible dual-mode sensor with exceptional performance, featuring high sensitivity (804.27 ${\mathrm{kPa}}^{-1}$), a broad response range (50 kPa), rapid response time (17 ms), and relaxation time (34 ms), alongside exceptional durability over 5000 cycles. Furthermore, the resistance temperature coefficient of the sensor within the temperature range of 12.5 °C to 93.7 °C is −0.17% °C⁻¹. The designed flexible dual-mode tactile sensing system enables the real-time detection of pressure and temperature information, presenting an innovative approach to electronic skin with multi-physical tactile sensing capabilities. Full article