Contact Mode Research Articles

Silk Flocked Flexible Sensor Capable of Wide-Range and Sensitive Pressure Perception.

In recent years, there have been advancements in high-performance soft sensors with simultaneous moderate sensitivity and wide linearity. However, it remains challenging to combine high-efficiency production and high performance for soft sensors. The skin and hair structure provide an elegantly simple sensing model, where hair acts as signal receptors and basal skin acts as signal processors. Herein, we used efficient electrostatic flocking and extrusion printing to engineer comb-shaped electrodes with conductive polydimethylsiloxane (PDMS) flocked with conductive silk fibers as a biomimetic flexible sensor. The mechanical and electrical properties of modified PDMS and silk fibers were characterized to optimize the functionalization process. The sensor unit exhibited a high linear range up to 2,000 kPa and a competitively good sensitivity of 0.0285 kPa-1 in the contact mode with conductive materials, as well as good resolution in the noncontact mode. Such sensors and a sensor array demonstrated potential applications for detecting pressure disturbances from acoustic activity and for human-robot interactions. We anticipate that the straightforward design and facile fabrication of soft sensors with vertical fibrous morphology for perception will open new avenues for the next generation of high-performance soft sensors integrated with artificial intelligence.

Strong Bonding of Robust Lubricating Hydrogels to Porous Substrates for Joint Replacement.

Hydrogels with excellent mechanical and lubrication properties have been developed rapidly, laying the foundation for their application in cartilage replacement. However, the combination of robust hydrogels and substrates under different forms of movement is a great challenge. In addition, due to differences in modulus, the stress shielding effect caused by implantable artificial joint metal materials can lead to bone resorption. Here, we proposed to combine a 3D printed porous titanium alloy with a high-strength lubricating hydrogel to construct an integrated joint substitute material. The porous titanium alloy TC4 substrate constructed by 3D printing possesses a modulus similar to that of human bone. The strong bonding of the hydrogel and TC4 was achieved through two strategies: mechanical interlocking and chemical bonding. The combination of the alloy substrate and hydrogel realizes the construction of a bionic lubricating cartilage layer on the surface of traditional artificial joint materials. The hydrogel has excellent bonding properties with the porous substrate under different test conditions. Truly human-like joint sockets were prepared for the first time with soft-soft and soft-hard contact modes. Under conditions simulating human motion, the hydrogel maintains a low friction coefficient and still has excellent substrate adhesion after 100,000 cycles. This study further pushes the application of hydrogels in biolubrication into practice.

Kinetic Modeling of Brilliant Blue Discoloration by Ozonation

This paper presents the results of investigations on the kinetic modeling of Brilliant Blue FCF (BB) discoloration reactions in aqueous solutions with different ozone concentrations and pH conditions. Kinetic studies involve knowledge of the structure and properties of dye and ozone, as well as of the experimental conditions. In general, scientists admit that the predominant oxidation pathway is direct (by free oxygen atoms) or indirect (by free hydroxyl radicals); this will depend on influencing factors such as the physicochemical properties of the dye, the pH of the aqueous solution, ozone concentration, reaction time, and the contact mode with/without stirring. In this experimental research, two pathways were chosen following CBB = f(t)—1. a constant dye concentration and different ozone concentrations, in the concentration range of 100–250 mg/L, in three pH media (acidic, neutral, and basic), with and without stirring; 2. a constant concentration of ozone and different dyes in the concentration range of 2.5–10 mg/L, under the conditions of point 1. With the obtained experimental data, the curves CBB = f(t) were drawn and processed according to the integral method of classical kinetics, based on first- and second-order equations. Unfortunately, this simple procedure did not give any results for the pH values studied. The rate constants were negative, and/or the reaction order depended on the initial conditions. Due to its structure, the BB dye has several chromophore groups, and thus multiple attack centers, resulting in several oxidation by-products, which is why the 1H-NMR spectrum was recorded for the discoloration of BB with ozone. Since the stoichiometry of the overall oxidation reaction, as well as the relationship between the rate constant and the reaction conditions mentioned above, is not known, a kinetic model based on mass transfer coupled with a chain reaction in the bulk liquid phase was proposed and successfully tested at pH = 7. This research approach also involves the consolidation of the theoretical bases of the ozonation process through the kinetic study carried out, as well as the proposal of a kinetic model. These systematics lead to results that are applicable to other aqueous systems that are impure with dyes, allowing for generalizations and the development of the field, ensuring the sustainability of the research.

Bacterial film-based degradable triboelectric nanogenerator for both contact and non-contact sensing

As an emerging environmentally friendly energy conversion device, degradable triboelectric nanogenerators (TENGs) play an important role in self-powered sensing, health care and human–machine interaction. However, traditional degradable materials used in TENGs often suffer from limited material sources and complex preparation processes, restricting large-scale production for widespread applications. Here, we propose a simple and efficient way to prepare degradable TENGs with inactivated bacterial film, taking advantage of wide source, self-proliferation and easy culture properties of bacteria. The prepared bacterial film-based TENG (BF-TENG) has stable electrical output, good durability and fatigue resistance, along with superior capabilities in both contact and non-contact sensing. In contact mode, the BF-TENG can generate a peak voltage of up to 83.3 V, which is employed for accurate Morse code transmission. In non-contact mode, the BF-TENG is capable of effectively perceiving the target polymer at a distance of 150 cm. The non-contact LED control circuit and a sensing array based on BF-TENG further demonstrate its practical potential for gesture recognition and spatial position perception. Furthermore, the fully degradable nature of BF-TENG ensures effortless disposal after use without environmental impact, serving as a promising solution for the new generation of eco-friendly and sustainable sensing devices.

Investigating the role of internal electric fields on interfacial charge transfer dynamics in 2D MoSTe/WSeTe heterojunction for photocatalytic water splitting

Introducing the degrees of freedom brought by intrinsic dipole moments into heterojunctions allows for effective manipulation through the combination of different interfaces, thus offering more possibilities for designing high-performance photocatalysts. The influence of internal electric fields (EIN) in Janus materials on heterojunction interface charges is a crucial aspect of understanding the intrinsic mechanisms of charge transfer at interfaces. To address this, we construct four contact modes of MoSTe/WSeTe heterojunctions, considering the work function difference as a mediator to quantify two different electric fields. It is estimated that the influence of the interfacial electric field (EIF) on interfacial charge transfer is approximately 1.6 times that of the EIN (pointing outwards the interface). Moreover, the direction of the EIN varies, resulting in different impacts on interface charges. Subsequently, we also discuss the conditions under which different charge transfer modes are formed at different contact surfaces. On the other hand, the heterojunction of the Te-S mode can serve as a direct Z-Scheme photocatalyst for overall water splitting, and the presence of vacancies is necessary to address the issue of surface passivation. Our study not only refines the intrinsic mechanism of interfacial charge transfer in Janus-based heterojunctions but also predicts a direct Z-Scheme photocatalyst capable of achieving overall water splitting.

Selective Reduction of Nitroarenes via Noncontact Hydrogenation.

In traditional hydrogenation, where H2 and substrates with unsaturated bonds are activated on the same catalyst (contact mode), competitive hydrogenation of multiple reducible groups often occurs. We employ an unbiased H-cell for selective hydrogenation of the nitro group when multiple reducible groups are present. The setup spatially separates H2 and nitroarenes into two chambers connected by a proton-exchange membrane, thus adding barriers for a Langmuir-Hinshelwood-type mechanism that is common in thermocatalytic hydrogenation. Through a unique proton/electron transfer pathway that is specific to nitro functional group reduction to hydroxylamine, side reactions like C═C, C═O, and C≡C bond hydrogenation are fully avoided. Using Pd/C for H2 activation, and CNT for selective proton/electron transfer to -NO2 groups while being inert to C≡C, C═C, and C═O hydrogenation, the system effectively eliminates the competitive hydrogenation, achieving 100% nitro-group reduction selectivity in the hydrogenation of various nitroarenes, in sharp contrast to negligible selectivity over the same catalysts in a batch reactor under contact mode. This device enables selectivity control in hydrogenation reactions, moving beyond the traditional focus on catalyst active site engineering.

Multi-energy harvesting: Integrating contact-mode and slide-mode triboelectric nanogenerators, and solar technologies for efficient power generation in small electronic

Harvesting energy from the environment is getting more attention daily to drive small electronics. This paper presents a hybrid energy harvesting module that uses contact-mode triboelectric nanogenerator, slide-mode nanogenerator, and solar energy to generate electrical power. The fabricated module has three parts, i.e., the base part operating in triboelectric contact mode, the rotary part employing lateral sliding triboelectricity, and solar cells for harnessing sunlight. The 3D designed module parts have been fabricated using 3D printer and laser cutting machine. Subsequently, the parts were assembled by applying triboelectric (Aluminum and Kapton) material onto them. The triboelectric contact mode generated 0.57 µW of electric power achieving power density achieved 57 µWm−2 at the contact area of 100 cm2. Electric power delivered by triboelectrification of the rotary part was 117 µW, whereas the power density was recorded as 232.6 µWm−2 at the contact area 503.36 cm2, and power delivered by solar cells was 66.64 mW. The designed module successfully delivered power to small electronic devices such as electronic thermometers, digital calculators, digital clocks, and 25 green-coloured LEDs. The implications of these findings suggest that such a hybrid module can significantly extend the operational life and independence of small-scale electronics, making it a promising solution for remote sensing, wearable technology, and IoT devices.

Nanoscale precision welding-enabled quasi-3D conductive carbon blacks for fast-charging and long-lasting secondary batteries

Robust three-dimensional (3D) conductive networks are vital for enhancing the utilization, rate capability, and lifespan of battery electrode materials, which largely relies on the selection and synergy of various conductive additives. As the spatial dimension expands from granular to tubular or lamellar, the conductivity of conductive additives continues to increase, but the cost and dispersion difficulty will sharply rise. This determines that zero-dimensional carbon black (CB) spherical nanoparticles remain the dominant component of current composite conductive additives. Herein, we disclosed a transient high-temperature welding technique that can precisely regulate the “rearrangement-fusion” behavior of carbon atoms at specific temperatures, accurately splicing the CB nanospheres into quasi-3D dendritic aggregates with appropriate spatial extension. This not only enhances the powder conductivity of CBs by 205.1 %, but also improves the processability through reducing the specific surface area. The quasi-3D CBs upgrade their contact mode with active materials from point-to-point to line-to-point, while significantly enhancing the inter-particle connection of active materials. More encouragingly, the modified CBs greatly boost the reaction kinetics, rate and cycling performance of LiFePO4 cathode and SiO@C anode, and derives fast-charging and long-lasting SiO@C//LiFePO4 full battery. Our work provides innovative solutions for upgrading the spatial conductive network within future secondary batteries.

Atomic force microscopy reveals morphological and mechanical properties of schistosoma mansoni tegument

Schistosoma mansoni, an intravascular parasitic worm and the causative agent of schistosomiasis, relies on its tegument (outer layer) for survival and host interaction. This study explored the morphology and mechanical properties of S. mansoni tegument using Atomic Force Microscopy (AFM). Notably, we employed the PeakForce Quantitative Nanomechanical Mapping (PF-QNM) mode in air, enabling simultaneous acquisition of 3D topography and mechanical property contrasts (adhesion, elastic modulus). Additionally, nanoindentation (AFM contact mode) was performed on female worm tegument for elastic modulus measurement. Both techniques revealed an elastic modulus range of fractions or units of GPa for the tegument. Interestingly, mechanical property maps, particularly adhesion contrast, displayed a recurring pattern of light and dark bands. We also measured the depth of annular furrows on the female tegument, finding an average of 128 ± 10 nm. These findings establish AFM, particularly PF-QNM, as a valuable tool to characterize S. mansoni tegument properties, offering insights for future investigations into parasite biology and its response to immunological or pharmacological challenges.

Contact-implicit Model Predictive Control: Controlling diverse quadruped motions without pre-planned contact modes or trajectories

This paper presents a contact-implicit model predictive control (MPC) framework for the real-time discovery of multi-contact motions, without predefined contact mode sequences or foothold positions. This approach utilizes the contact-implicit differential dynamic programming (DDP) framework, merging the hard contact model with a linear complementarity constraint. We propose the analytical gradient of the contact impulse based on relaxed complementarity constraints to further the exploration of a variety of contact modes. By leveraging a hard contact model-based simulation and computation of search direction through a smooth gradient, our methodology identifies dynamically feasible state trajectories, control inputs, and contact forces while simultaneously unveiling new contact mode sequences. However, the broadened scope of contact modes does not always ensure real-world applicability. Recognizing this, we implemented differentiable cost terms to guide foot trajectories and make gait patterns. Furthermore, to address the challenge of unstable initial roll-outs in an MPC setting, we employ the multiple shooting variant of DDP. The efficacy of the proposed framework is validated through simulations and real-world demonstrations using a 45 kg HOUND quadruped robot, performing various tasks in simulation and showcasing actual experiments involving a forward trot and a front-leg rearing motion.

Design and performance analysis of carbon brush collector ring end-face contact for hydro generator

Abstract In hydro generators, the conventional radial contact method often results in unstable contact between carbon brush collector rings due to collector ring deflection. This paper presents a novel end-face contact method designed to enhance stability. The trajectory equations of the brush/ring contact are established when the collector ring swings and the “loss of contact” gaps of the two contact methods are compared. Further comparative analysis is conducted on the current-carrying friction wear of carbon brushes and collector rings in two contact modes. The results show that compared with the radial contact method, the brush/ring in the end-face contact method has a smaller gap and shorter time, the carbon brushes are less susceptible to spark erosion, the increase in friction coefficient and wear rate is small, and the contact resistance is lower and more stable. Scanning electron microscope analysis also shows that the spark erosion on the surface of the carbon brushes in the end contact mode is significantly weaker than that in the radial contact mode.

Investigation on the influence of the slip at the wheel-rail contact patch on the shakedown limit of rail material

Research on factors affecting rolling contact fatigue (RCF) damage of rail materials has become increasingly important since developing effective measures to mitigate RCF damage is crucial. This study focuses on exploring the influence of full slip and partial slip contact modes at the wheel-rail contact patch on the RCF damage behavior and the shakedown limit of the pearlite rail material through wheel-rail RCF rolling-sliding tests. Firstly, based on the wheel-rail adhesion-creep curves in dry, water and oil environments, the creepage required to achieve full slip during the rolling-sliding tests was determined. Then, rolling-sliding tests under full slip contact with different adhesion coefficients were carried out in a dry atmosphere and with the assistance of a third body medium (i.e., oil and water), respectively. Meanwhile, rolling-sliding tests under partial slip contact with the similar contact parameters were performed in a dry atmosphere. The results indicated that RCF damage and wear rates of the rail material under a full slip contact with an adhesion coefficient below the saturation peak on the adhesion-creep curve were significantly less than those under partial slip contact with similar contact parameters. Moreover, under full slip contact with an adhesion coefficient below the saturation peak on the adhesion-creep curve, the pearlite rail materials could exhibit a higher shakedown limit. Furthermore, the influence of full slip and partial slip contact on wheel-rail contact behavior was further analyzed using finite element simulations. Finally, a novel friction modification strategy to mitigate RCF damage and wear of rails was proposed. By applying a specific low-coefficient friction modifier to the wheel-rail interface, the operation of powered wheelsets under controlled creepage conditions that reach the threshold of full slip contact at the wheel-rail contact interface could be employed to achieve the desired adhesion coefficient. Thus, this approach could ensure that the achieved adhesion coefficient met the on-site target adhesion force while reducing RCF damage and wear of rail materials.

Differences in health visiting contacts for children of mothers with and without a history of adversity-related hospital admissions in England (2018/19 to 2019/20): an analysis of novel linked community health and hospital data.

ObjectiveExplore differences in children’s contact with health visiting (HV) services by pre-birth exposure to maternal adversity. ApproachFor the first time, we linked the Community Services Dataset (CSDS), which records HV contacts for children in England from 1 April 2018 to 31 March 2020, to Hospital Episode Statistics (HES) which contains births and mothers’ hospital admissions in the preceding 3 years. We used admissions that included ICD-10 codes related to mental health, substance use and violence to identify children born to mothers with a history of adversity. We compared characteristics of children’s HV contacts (i.e. number, mode, location, duration) stratified by maternal adversity. ResultsOverall, 85.2% of 626,478 children in CSDS linked to a birth record in HES. Among children receiving HV contacts, 11.7% were exposed to maternal adversity: 11.1% mental health, 1.3% substance use, 0.4% violence. Children with maternal adversity had more HV contacts than other children (mean = 3.8 vs 2.7, p<0.001). There were no differences in contact mode (i.e. face-to-face or phone) for children with maternal adversity compared to others, but their contacts were longer (44.5% lasting >30 minutes vs 35.1%, p<0.001) and more likely to be at home (56.3% vs 47.8%, p<0.001). ConclusionsHV services respond in different ways to children with and without pre-birth exposure to serious maternal adversity, reflecting the “proportionate universalism” that underpins HV services in England. ImplicationsThe differential service response for vulnerable children may require additional resources (e.g. staff, training) which should be considered when designing and funding HV services.

Intrauterine Shaping of Fetal Microbiota.

Mechanisms resulting from the physiological immaturity of the digestive system in children delivered before 32 weeks of gestation and, in particular, different interactions between the microbiome and the body have not been fully elucidated yet. Next-generation sequencing methods demonstrated the presence of bacterial DNA in the placenta and amniotic fluid, which may reflect bacterial populations that initiate intestinal colonization in utero. Numerous studies confirmed the hypothesis stating that intestinal bacteria played an important role in the pathogenesis of necrotizing enterocolitis (NEC) early- and late-onset neonatal sepsis (EONS and LONS). The model and scale of disorders within the intestinal microbiome are the subject of active research in premature infants. Neonatal meconium was primarily used as an indicator defining the environment in utero, as it is formed before birth. Metagenomic results and previous data from microbiological bacterial cultures showed a correlation between the time from birth to sample collection and the detection of bacteria in the neonatal meconium. Therefore, it may be determined that the colonization of the newborn's intestines is influenced by numerous factors, which may be divided into prenatal, perinatal, and postnatal, with particular emphasis put on the mode of delivery and contact with the parent immediately after birth. Background: The aim of this review was to collect available data on the intrauterine shaping of the fetal microbiota. Methods: On 13 March 2024, the available literature in the PubMed National Library of Medicine search engine was reviewed using the following selected keywords: "placental microbiome", "intestinal bacteria in newborns and premature infants", and "intrauterine microbiota". Results: After reviewing the available articles and abstracts and an in-depth analysis of their content, over 100 articles were selected for detailed elaboration. We focused on the origin of microorganisms shaping the microbiota of newborns. We also described the types of bacteria that made up the intrauterine microbiota and the intestinal microbiota of newborns. Conclusions: The data presented in the review on the microbiome of both term newborns and those with a body weight below 1200 g indicate a possible intrauterine colonization of the fetus depending on the duration of pregnancy. The colonization occurs both via the vaginal and intestinal route (hematogenous route). However, there are differences in the demonstrated representatives of various types of bacteria, phyla Firmicutes and Actinobacteria in particular, taking account of the distribution in their abundance in the individual groups of pregnancy duration. Simultaneously, the distribution of the phyla Actinobacteria and Proteobacteria is consistent. Considering the duration of pregnancy, it may also be concluded that the bacterial flora of vaginal origin dominates in preterm newborns, while the flora of intestinal origin dominates in term newborns. This might explain the role of bacterial and infectious factors in inducing premature birth with the rupture of fetal membranes.

Comparison of Moses laser and Raykeen laser in patients with impacted upper ureteral stone undergoing flexible ureteroscopic holmium laser lithotripsy

BackgroundTo compare the operative effect and clinical efficacy of the Moses laser mode and the Raykeen holmium laser energy platform powder mode under flexible ureteroscopic lithotripsy in patients with impacted upper ureteral stones.MethodsFrom March 2022 to September 2022, 72 patients were divided into a Moses laser group and a Raykeen laser group according to surgical method, with 36 patients in each group. CT and ureteroscopy confirmed that all patients had isolated impacted upper ureteral stones. The stone volume (mm3), stone density (Hu) and severity of hydronephrosis were measured by CT. Postoperative complications were evaluated using the Clavien–Dindo score.ResultsThere were no complications of ureteral stenosis related to the laser treatment. The operative time and lithotripsy time were lower in the Moses laser group than in the Raykeen laser group (P < 0.05). The stone-free survival rate did not differ significantly between the two groups (P = 0.722). Stone volume was found to be positively correlated with laser energy and lithotripsy time in both groups (P < 0.01). There was no significant correlation between laser energy and lithotripsy time or ureteral stone density (Hu) in the Moses laser group (P > 0.05) or the Raykeen laser group (P > 0.05).ConclusionsThe contact mode of Moses technology and the powder mode of Raykeen laser lithotripsy can be used for the ablation of a single impacted upper ureteral stone. The ablation speed was related to the stone volume and the severity of polyp hyperplasia, not the stone density. We recommend the use of the powdered mode as a therapeutic measure for the treatment of impacted upper ureteral stones in flexible ureteroscopic lithotripsy.

Comparison of pain and healing period after frenectomy using diode laser and Er:YAG laser: a randomized controlled trial.

The frenum is a mucous membrane fold that attaches the lip and the cheek to the alveolar mucosa, the gingiva, and the underlying periosteum. Frenectomy is the surgical removal of the whole frenum, including the area connected to the bones. The purpose of this study was to compare the healing period and postsurgical pain experienced by patients operated with diode and Er:YAG lasers. Twenty referred patients requiring excision of the abnormal upper labial frenum were included in the study. Patients were randomly assigned into two groups: diode group (810 nm, 2W, continuous emission, initiated tip) and Er:YAG group (2,940 nm, 2W, 200 mJ, 10 Hz). Both lasers were applied in contact mode. Postoperative pain was assessed using a numerical rating scale at 3 hours postoperatively and every day during the first postoperative week. The epithelialization process of the wound surface was evaluated using hydrogen peroxide solution applied to the wound on postoperative days 7, 14, 30, 60, and 90. The results showed the mean values of Pain Index after 3 hours (diode group 2.1 ± 2.0, Er:YAG group 2.6 ± 1.4), day 1 (diode group 1.1 ± 1.1, Er:YAG group 1.9 ± 1.4), and day 2 (diode group 0.0 ± 0.0, Er:YAG group 0.9 ± 1.1), with no significant difference after 3 to 7 days (P &#61; 1.00). For the Healing Index there was a significant difference between the diode group and the Er:YAG group (7 days, P &#61; .029; 14 days, P &#61; .001), with no significant difference after 30/60/90 days (P &#61; 1.00). The Er:YAG laser had better clinical results in healing wounds, whereas the diode laser resulted in better decreasing pain levels after frenectomy during the follow-up periods.

Loneliness and Mode of Social Contact in Late Life.

Social contact may alleviate loneliness, but little is known about within-person daily fluctuations in loneliness and social encounters. Older adults who feel lonely may engage in different modes of social contact (in-person, phone, digital). This study asked how different forms of contact are associated with loneliness throughout the day. Participants were 313 community-dwelling older adults (aged 65-90). They completed ecological momentary assessments reporting on their social encounters (e.g., type of social partner, mode of contact) and their loneliness every 3 hr for 5-6 days. We differentiated close social ties from ties not identified as close (i.e., weak ties). We examined within-person effects using multilevel models. Findings revealed that momentary loneliness predicted a greater likelihood of phone contact in the next 3 hr. However, only in-person contact was associated with lower levels of loneliness. Regarding close and weak ties, momentary loneliness was associated with more in-person and phone contact with close ties, yet fewer in-person contacts with weak ties. In-person contact with both close and weak ties predicted lower levels of loneliness. Although older adults engage in both in-person and phone contact when they feel lonely, it appears that only in-person contact may reduce loneliness. Digital contact was not widely adopted as a response to momentary loneliness among these older adults. Findings underscore older adults' willingness to maintain regular contact with close ties. Interventions addressing older adults who are lonely may consider innovative approaches to increase in-person contact.

Investigation of the Effect of Compression Pressure in Contact OCT Imaging on the Measurement of Epidermis Thickness.

Optical coherence tomography (OCT) is a noninvasive 3D imaging technique that offers significant advantages over traditional microscopy and biopsy in measuring epidermal thickness (ET) when assessing skin conditions. However, OCT imagining is often required to be in a contact mode for mitigating the issues of subject movement and uneven skin topology. It is not known whether the contact would affect the ability of ET measurements. In this study, we investigate the relationship between the contact pressure applied and the ET measurements. We observed progressive deformation in the epidermis with the increase of compression forces, where a notable decrease of up to 13% in ET measurement and 70% decrease in capillary vessels was noted when imaging was in contact mode. We also observed 8.1% less deformation properties in scar tissue than in nearby healthy tissue. Our study underscored the importance of controlled pressure in contact imaging mode, which is often neglected.

Analysis and Application of Poly(vinyl alcohol) (PVA) and Polyacrylonitrile (PAN) Nanofiber Membrane-Based Triboelectric Nanogenerators.

The triboelectric property of materials is used to harvest energy from intentional or nonintentional sources of vibration. Contact mode freestanding dielectric based nanogenerators (CFTENGs) have many advantages when compared with other modes of triboelectric nanogenerators. The property of dielectric materials plays an important role in the energy harvesting process. In this work, we aim to fabricate nanofiber membranes of poly(vinyl alcohol) (PVA) and polyacrylonitrile (PAN) and study their properties for CFTENGs. The morphology and porosity of both membranes were tested experimentally. The mechanical property is modeled with a representative volume element (RVE) technique to understand its deflection behavior. In addition, an electromechanical model is developed to predict and analyze the behavior of those membranes in the energy conversion process. Our research reveals that the PAN dielectric layer achieves a maximum open circuit voltage of 192 kV compared to the PVA dielectric layer (2.2 kV) in the CFTENG system. In comparison, the dielectric layer of the PAN nanofiber membrane reflects its flexibility to generate electrical energy in a CFTENG with the effect of contact electrification and electrostatic induction under various sources of unused energies for a wide range of applications. Moreover, the same methodology is applied to various sources of vibration, and their performance is reported. With an appropriate power management circuit, we can design a PAN membrane-based TENG for various applications.

Construction of superhydrophobic composite coating on AZ31B Mg alloy for improved corrosion resistance and anti-wear property

In this study, the EP (epoxy)/L(P) (layered double hydroxides powder)-DTMS (dodecyl-trimethoxy-silane) superhydrophobic composite coating was prepared on AZ31B Magnesium (Mg) alloy surface by spin-coating and self-assembly methods. Mg-Al layered double hydroxides (LDH) powder with ion exchange ability, prepared by hydrothermal coprecipitation, was mixed with EP to construct rough surface and provide good adhesion between the coating and Mg alloy substrate. The introduction of DTMS could reduce the surface energy of coating and improve the compactness of rough surface. Due to the shielding effect of superhydrophobic surface and the ion exchange ability of LDH, it was difficult for corrosive ions (Cl-) to reach the substrate surface in 3.5 wt% NaCl solution. And the corrosion current density was decreased by 4 orders of magnitude. Because of the lubrication of DTMS and the layered structure of L(P), the composite coating had a good wear-reducing effect under the reciprocating point contact mode against with an AISI5200 steel ball. It provided a feasible idea for the construction of multifunctional superhydrophobic coatings on metal surface with self-cleaning, corrosion resistance and wear resistance, which will expand the industrial application fields of superhydrophobic coatings.