High Repellency Research Articles

Hydrophobicity of periodic structure with taper angle under pressure impact

Biomimetic periodic structures have garnered attention due to their excellent water repellency. The normal-taper angle, which is aspects of the cross-sectional structure, is important factor in achieving water repellency and pressure resistance; however, the underlying physical phenomenon has not been fully explained. Moreover, once a surface becomes hydrophobic, it is difficult to measure the apparent contact angle. The purpose of this paper is to clarify the taper angle that provides high water repellency under pressure impact conditions by formulating the relationship between the taper angle and the height of a droplet bouncing, instead of traditional contact angles, using experimental results. We fabricated multiple samples with different taper angles and groove width/tooth width ratios, through micro-processing using a femtosecond-pulsed laser and a control algorithm, and investigated their effects on water repellency. By using height of a droplet bouncing as an evaluation parameter, we were able to effectively differentiate between taper angles in terms of water repellency. Additionally, we suggested that in the bouncing phenomenon, where droplets are given velocity by falling, the sidewall of the periodic structure and the taper angle affect liquid repellency. To explain this phenomenon, we proposed a pressured-taper angle model where a droplet is pressed against the taper angle. Based on both experimental findings and the pressured-taper angle model, a relationship between the equilibrium contact angle, the taper angle, and the lifting force angle was revealed. Moreover, using this pressured-taper angle model, the taper angle of the periodic structure to achieve maximum liquid repellency was estimated from the equilibrium contact angle of the base material.

Toxicity and Repellency of (E/Z)-3-Butylidenephthalide: A Natural Compound Isolated from Ligusticum porteri Root Extract Evaluated Against Imported Fire Ants (Hymenoptera: Formicidae).

Imported fire ants are pests of significant importance, especially in the southern United States. We tested (E/Z)-3-butylidenephthalide, a natural compound that was isolated from the ethanolic extract of Ligusticum porteri roots, as a repellent and toxicant against workers of imported fire ants. A series of serial concentrations, starting from 156 µg/g until failure, were tested using digging bioassays. Workers removed significantly less sand from the vials treated with (E/Z)-3-butylidenephthalide as compared to the ethanol control. Based on sand removal data, (E/Z)-3-butylidenephthalide treatment resulted in a more significant digging suppression against red imported fire ant workers at concentrations ranging between 19.5 and 0.6 µg/g than the solvent control whereas sand removal at 0.3 µg/g was similar with the solvent control. Black imported fire ants showed repellency at serial concentrations ranging between 19.5 and 0.15 µg/g whereas the hybrid imported fire ants showed repellency between 19.5 and 4.9 µg/g. In DEET treatments, red and black imported fire ants showed repellency at dosages of 125 to 62.5 µg/g, whereas the treatment failed at the dose of 15.6 µg/g in hybrid fire ants. (E/Z)-3-butylidenephthalide with LC50 values of 11 and 16.4 µg/g was toxic against red and black imported fire ants, respectively, followed by hybrid imported fire ants (LC50 = 104.7 µg/g). Fipronil with LC50 values of 0.49, 0.33, and 0.53 µg/g against red, black, and hybrid fire ants, respectively, was more toxic than (E/Z)-3-butylidenephthalide. In residual bioassay, toxic activity lasted for 3 weeks at dosages of 250 and 500 μg/g against HIFA. The high repellency and toxicity of (E/Z)-3-butylidenephthalide against imported fire ants makes it a natural compound of interest for further evaluation under natural field conditions.

Toward Water and Oil Repellent Coating: Synthesis of Fluorinated Methacrylate-Glycidyl Methacrylate Copolymers.

The development of durable and eco-friendly coatings with excellent adhesion and remarkable surface properties remains a critical pursuit in various industries. This study introduces an innovative methodology for the synthesis of glycidyl methacrylate-co-fluorinated methacrylate (P(GMA-co-FMA)) random copolymers with variable fluorine contents derived from GMA and FMA monomers. The copolymerization of these constituents yields coatings with enhanced durability and unique surface characteristics. Particularly, the incorporation of FMA introduces novel surface functionalities, leading to high water and oil repellent properties. The copolymer-coated surfaces exhibited impressive water contact angles ranging from 105° to 125° and decane contact angles ranging from 50° to 85°. The wettability of the P(GMA-co-FMA) coatings demonstrated a strong dependence on the fluorine content in the copolymers, with higher fluorine content resulting in superior water and oil repellency. Through a comprehensive characterization, we demonstrate the exceptional adhesion and self-cleaning capabilities of the fabricated films. Notably, the self-cleaning efficacy of P(GMA-co-FMA)-coated surfaces persists even following a prolonged duration of 6 months. Furthermore, our investigation reveals the influence of copolymer composition on surface wettability and contact angle hysteresis, providing valuable insights for tailoring coating properties. Overall, the novelty of this study lies in the synthesis of P(GMA-co-FMA) copolymer coatings with superior adhesion and self-cleaning properties. These advancements present promising applications in various fields, including electronics, textiles, and medical supplies, where such durable and functional coatings can significantly enhance product performance and longevity.

Surface Microfabrication of Lactic Acid–Glycolic Acid Copolymers Using a Gas-Permeable Porous Mold

We attempted to perform surface microfabrication of the bioabsorbable material lactic acid–glycolic acid copolymer (LG-80) using a micro-imprint lithography technique with a gas-permeable porous mold at less than 5 °C. As a result, high-resolution surface micromachining with a height of 1.26 μm and a pitch of 2.97 μm was achieved using a convex sapphire mold with a height of 1.3 μm and a pitch of 3 μm. After processing, the LG-80 exhibited high water repellency, and FT-IR analysis of the surface showed no significant change in its chemical structure, confirming that the surface microfabrication was successful, while retaining the properties of the material. This demonstrated new possibilities for surface microfabrication technology for bioabsorbable materials, which are expected to be applied in the medical and life science fields in products such as surgical implants, tissue regeneration materials, and cell culture scaffold materials. In particular, the use of micro-imprint lithography enables low-cost and high-precision processing, which will be a major step toward the practical application of bioabsorbable materials.

Screening of botanical spatial mosquito repellents from 64 essential oils and their interactions with odorant‐binding protein‐3

AbstractPersonal protection from mosquito bites is essential for preventing mosquito‐borne diseases. Mosquito repellents are effective methods for preventing mosquito bites. Due to their ease of use and indirect skin contact, mosquito‐repellent stickers loaded with essential oils (EOs) have recently become favoured as novel spatial repellents. To discover active EOs with high spatial repellency, 64 commercial EOs were screened using a modified arm‐in‐cage assay. Four EOs, including nutmeg, melissa, eucalyptus and cinnamon, displayed longer complete protection times (CPTs) of about 60 min. Ten main constituents from the four active EOs were identified by gas chromatography–mass spectrometry (GC–MS), and their spatial repellent activities were further evaluated. 1,8‐Cineole, cinnamaldehyde and citral showed potent repellent activity, with average CPTs of 67.5, 63.8 and 60 min respectively. The interactions of 1,8‐cineole and citral with odorant‐binding protein‐3 (OBP‐3) were studied via molecular docking. Both compounds are docked well in the high hydrophobic pocket and interacted with AealOBP3 through Van der Waals interactions with Phe105, Phe112, Leu114, Met48 and Val50. These natural products provide promising lead fragments for the further development of botanical spatial repellents.

Long‐Term Immersion Study for Durability of Interconnected Micropatterned Surfaces with Sustained Water Repellency

AbstractThe sustained water repellency of interconnected micropatterned surfaces is explored over an extended duration, with a focus on their resilience during a 90‐day water‐immersion test. Initially, the microstructure surfaces exhibit high water repellency, a characteristic of the Cassie–Baxter state. However, subsequent detailed temporal analyses reveal varying responses depending on the structural topology. The interconnected micropatterned surfaces exhibit remarkable long‐term resistance to water; this is attributed to the formation of large and stable air pockets enabled by their unique microcavity structures. In comparison, hierarchical microcavity surfaces with micropillars exhibit a notable decrease in water repellency, as evidenced by reduced contact angles, suggesting a transition to a wetting state owing to the emergence of surface hydrophilicity during long‐term water exposure. This study demonstrates the importance of stable air‐pocket effects, particularly in applications where the long‐term stability of liquid repellency is critical, and suggests the role of interconnected structures in maintaining water repellency over time.

Global Performance, Trends, and Challenges for Assessment and Management of Per- and Polyfluoroalkyl Substances (PFASs): A Critical Review

Per- and polyfluoroalkyl substances (PFASs) are a large and complex group of thousands of synthetic chemicals with different properties such as strong acidity, high surface activity at very low concentrations, high chemical stability, and water and oil repellency. Many PFASs have been used in various industrial and consumer applications based on the desired functionality and production capability, and have consequently emerged as pervasive environmental contaminants of major concern. Recognition that several PFASs are transported globally, bioaccumulate, and exert multiple adverse effects on environmental quality and health has led to their regulation and ultimate phase-out. Despite decades of global management and research on PFAS, fundamental obstacles still remain in addressing worldwide contamination by these chemicals and their associated impacts on environmental quality and human health. Here, we reviewed the global issues, major barriers, and challenges that must be addressed to remedy the “PFAS problem” from scientific, technological, and policy perspectives. A comprehensive review of the latest scientific research and recent legislative developments regarding PFAS will improve the assessment and management of the numerous PFAS on the market in the near future.

Holistic approach for fabrication of superhydrophobic MXene-based membrane for enhanced membrane distillation

There is growing interest in membrane distillation (MD) as a means of desalinating seawater with 100 % theoretical salt rejection which has the capacity to address freshwater scarcity. MD has huge potential for commercial applications owing to its low operating temperature and pressure requirements. However, wetting polymeric membranes inhibits water permeance and lowers salt rejection. MXene nanosheet-incorporated polyvinylidene (PVDF) membranes have been constructed for enhanced vapor transport with high water repellence and antiwetting properties. MXene nanosheets in PVDF polymeric matrices are responsible for their high super-hydrophobicity, which can mitigate membrane fouling and wetting during the MD process. As far as experimental outcomes are concerned, the pristine PVDF membrane exhibited severe wetting with salt leakage. Ti3C2Tx MXene nanosheets allow the formation of hierarchical polymeric micro/nanostructures, changing the intrinsic hydrophilicity to super-hydrophobicity. Surface engineering of a PVDF membrane with MXene nanosheets enables efficient saline desalination during the MD process. The surface-engineered MXene/PVDF membrane demonstrated a high-water contact angle of 143° with extremely high self-cleaning characteristics as compared to that of pristine PVDF membrane. As far as the performance of the membrane is concerned, the water flux of the pristine PVDF membrane decreased from 6.5 LMH to 6 LMH after the 14th hour which can be attributed to partial pores wetting during MD operation. Eventually, the pristine PVDF membrane exhibited a continuous salt flux (SF) increase. However, MXene/PVDF membrane showed stable water flux (8 LMH) and negligible SF. The study therefore demonstrates a facile and holistic approach for constructing MXene-based PVDF membranes that exhibit superior antiwetting performance during MD operation.

Repellent efficacy of Cyfluthrin-based drug against dipterans in young cattle

The purpose of the research is to study repellent efficacy of Cyfluthrin-based drug against dipterans in young cattle.Materials and methods. In July to September (the peak of attacks by dipterans), two farm scale trials were conducted on two farms in the Stavropol Territory to study repellent efficacy of Cyfluthrin-based drug against dipterans on young cattle. The examining of the animals at the beginning of the trial found that all of them were attacked by dipterans including horseflies, gadflies, mosquitoes, midges and zoophilous flies with 100% infection prevalence and an abundance index of 23.0–35.5 specimens on one animal. The animals in two study groups received the test drug on dry, intact skin of the back, along the spine from the withers to the rump, once at a dose of 0.2 mL of the drug per 10 kg of animal weight. The drug efficacy was assessed based on a decrease in the number or absence of dipterans in the treated animals as compared to the untreated animals (control groups) before the trial and at day 3, 7, 14, 21, 28 and 35. We used a visual inspection technique and counting of the number of dipterans on an animal for 3 minutes.Results and discussion. The use of the Cyfluthrin-based drug at a dose of 0.2 mL per 10 kg of animal weight showed a 100% repellent effect against dipterans. The repellent index was in the range of 78.6–96.4% for 28 days, which is higher than 70%, which indicates a high repellent effect of the drug against dipterans.

Engineering PVDF omniphobic membranes with flower-like micro-nano structures for robust membrane distillation

Conventional PVDF membranes are easily wetted and contaminated in membrane distillation (MD) process, especially when used in separating high-salinity water and oil-contained saline water. To address these issues, an omniphobic membrane was fabricated in this work. ZnO micro-flowers with a rough structure were successfully deposited onto the PVDF membrane with the assistance of polydopamine assistance. After undergoing a fluorination process, the omniphobic membranes were prepared by the synergistic effect of surface microstructure and free energy. The effects of varying Zn(NO3)2 concentrations and deposition times on morphology, pore size and separation efficiency were comprehensively examined. It was demonstrated that at a Zn(NO3)2 concentration of 50 mM and a deposition time of 0.5 h, the resulting PVDF composite membrane exhibited high liquid repellency towards all the test liquids, such as water, ethanol solution, paraffin oil, and etc. Furthermore, the membrane consistently exhibited impressive salt rejection behavior (99.99%) and maintained an average flux (15.54 kg·m−2·h−1) when exposed to high-salinity solution (up to 20 wt%-NaCl). Meanwhile, during treating an oil-contained saline water emulsion with the oil content of 200 ppm, the membrane also displayed high resistance to wetting and fouling during the continuously 24 h tests. The membrane displayed a rejection rate of 99.99 % with an average vapor flux of 18.60 kg·m−2·h−1. In summary, this omniphobic membranes demonstrated a great potential in MD for practical challenging wastewater treatment.

Analysis of Carbon Nanoparticle Coatings via Wettability

Wettability, typically estimated through the contact angle, is a fundamental property of surfaces with wide-ranging implications in both daily life and industrial processes. Recent scientific interest has been paid to the surfaces exhibiting extreme wettability: superhydrophobic and superhydrophilic surfaces, characterized by high water repellency and exceptional water wetting, respectively. Both chemical composition and morphology play a role in the determination of the wettability “performance” of a surface. To tune surface-wetting properties, we considered coatings of carbon nanoparticles (CNPs) in this study. They are a new class of nanomaterials synthesized in flames whose chemistry, dimension, and shape depend on combustion conditions. For the first time, we systematically studied the wettability of CNP coatings produced in a controlled rich ethylene/air flame stabilized over a McKenna burner. A selected substrate was intermittently inserted in the flame at 15 mm above the burner to form a thin coating thanks to a thermophoretic-driven deposition mechanism. The chemical-physical quality and the deposed quantity of the CNPs were varied by opportunely combing the substrate flame insertion number (from 1 to 256) and the carbon-to-oxygen ratio, C/O (from 0.67 to 0.87). The wettability of the coatings was evaluated by measuring the contact angle, CA, with the sessile drop method. When the C/O = 0.67, the CNPs were nearly spherical, smaller than 8 nm, and always generated hydrophilic coatings (CA < 35°). At higher C/O ratios, the CNPs reached dimensions of 100 nm, and fractal shape aggregates were formed. In this case, either hydrophilic (CA < 76°) or superhydrophobic (CA ~166°) behavior was observed, depending on the number of carbon nanoparticles deposed, i.e., film thickness. It is known that wettability is susceptible to liquid surface tension, and therefore, tests were conducted with different fluids to establish a correlation between the flame conditions and the nanostructure of the film. This method offers a fast and simple approach to determining mesoscale information for coating roughness and topographical homogeneity/inhomogeneity of their surfaces.

Larvicidal and repellent effects of essential oils on the brown dog tick (Rhipicephalus sanguineus Sensu lato) with description of new larval repellent activity test method

The aim of this research was to investigate the larvicidal and repellent effects of essential oils (EOs) obtained from two Lamiaceae plant species, Origanum minutiflorum O. Schwarz & P.H. Davis and Dorystoechas hastata Boiss. & Heldr. ex Bentham, both endemic to Turkey, on Rhipicephalus sanguineus s.l. Latreille (Acari: Ixodidae). The study also introduces a new test method that can be used to assess the repellent effects against ticks. Both plant EOs exhibited the highest larvicidal activity against brown dog tick larvae after 24 h and LC50 and LC90 values were determined as 0.101% and 0.125% for O. minutiflorum essential oil and 0.937% and 2.1% for D. hastata essential oil, respectively. In this study, we have described a detailed protocol for a novel larval repellent activity test (LRAT) for essential oils and extracts, using simple equipment. The advantages and limitations of LRAT, when compared to other tests commonly used to determine repellent effect against ticks, are also included in this study. The LRAT was developed with modifications of the larval immersion test (LIT) and proves to be a highly efficient and easily observable method. It can be used to test any active substance that may be toxic to humans and animals. According to the LRAT, at the end of 3 h, O. minutiflorum essential oil showed a high repellent effect, varying between 84.14% and 100% at 1% concentration. This result was not statistically different from the DEET, the positive control. When comparing the larvicidal and repellent activities, O. minutiflorum essential oil was found to be more effective than D. hastata essential oil.

Polyvinylpyrrolidone-stabilised gold nanoparticle coatings inhibit blood protein adsorption

Abstract In this work, the ability of polyvinylpyrrolidone (PVP)-stabilised gold nanoparticle (AuNP) coatings to inhibit blood protein adsorption was evaluated by studying time-resolved solid–liquid interactions of the coatings with the model blood protein bovine serum albumin (BSA). Inhibiting unspecific blood protein adsorption is of crucial importance for blood-contacting implant devices, e.g. vascular grafts, stents, artificial joints, and others, as a preventive strategy for bacterial biofilm formation. A quartz crystal microbalance was used in this work to coat the AuNPs on piezoelectric sensors and to follow time-resolved solid–liquid interactions with the proteins. The AuNP coatings were evaluated for their wettability by contact angle measurements, their surface morphology by light- and atomic force microscopy, and their chemical composition by energy-dispersive X-ray spectroscopy. Results revealed a homogeneous distribution of AuNPs on the sensor surface with a dry mass coverage of 3.37 ± 1.46 µg/cm2 and a contact angle of 25.2 ± 1.1°. Solid–liquid interaction studies by quartz crystal microbalance showed a high repellence of BSA from the PVP-stabilised AuNP coatings and the importance of the PVP in the mechanism of repellence. Furthermore, the conformation of the polymer on the coatings as well as its viscoelastic properties were revealed. Finally, the activated partial thrombin time test and fibrinogen adsorption studies revealed that the AuNPs do not accelerate blood coagulation and can partially inhibit the adhesion of fibrinogen, which is a crucial factor in the common blood coagulation cascade. Such AuNPs have the potential to be used in blood-contact medical applications.

Amphiphobic PTFE membrane as functional covering membrane to hinder ammonia emission during the composting process

Composting is a process of converting potentially harmful organic matter into harmless organic fertilizer through microbial fermentation. This process enables the rational use of resources and represents an embraced technology marked with sustainable development features. Hindering ammonia emissions during composting is vital, as ammonia is a valuable resource and harmful if emitted excessively. Polytetrafluoroethylene (PTFE) membranes are often used as functional covering membranes to prevent ammonia produced by composting from releasing due to its hydrophobicity. However, they are susceptible to oily aerosols in oily composting, which affects microbial decomposition in aerobic composting. Thus, the development of amphiphobic PTFE membrane is necessary and meaningful. For the amphiphobic PTFE membrane, an important issue is the amphiphobic stability of the membrane, especially in the special alkaline environment of composting. Herein, we suggest the use of the polymer to wrap around nanoparticles and PTFE membrane fibers to prepare stable amphiphobic membranes as functional covering membranes for oil-containing composting. Poly(methyl-3,3,3-trifluoropropylsiloxane) (PTFPMS) and 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFTS) entangled with each other and then wrapped the nanoparticles and membrane fibers to form stable amphiphobic membranes with high roughness and low surface energy. The prepared membrane had high liquid repellency to water (～152.8°), diiodomethane (～127.5°), and n-hexadecane (～127.0°). This membrane also possessed a high anti-oil fouling. Moreover, the membrane amphiphobicity exhibited a high stability. This is attributed to the stable fixation of nanoparticles on PTFE membrane fibers with PFTS/PTFPMS. Therefore, the amphiphobicity of the membrane was not affected by ammonia. As for the ammonia filtration efficiency, the amphiphobic membrane had a filtration efficiency of 77.4 % within 10 min, an increase of 6.8 % compared to the PTFE membrane, demonstrating the potential of the membrane we developed toward hindering ammonia emission. This work provides a new way of developing high-performance membrane for the oily composting process.

A novel montmorillonite clay based bio-nanocomposite as an emerging biocontrol agent against stored grain pulse beetle

Chemical pesticides have been conventionally used to control the stored grain pest infestation, but these are hazardous to humans and the environment. Therefore, the herbal pesticides are gaining more importance in insect pest management. The montmorillonite (MMT) nanoclay, is found to be an effective and underexplored adsorbent for fumigant formulation against stored grain pests. Additionally, essential oils (EOs) and their derivatives offer promising alternatives to conventional insecticides, but their application is constrained by higher volatilization, rapid decomposition, and less persistency. To address the issue, this study focuses on purifying microporous MMT through the sedimentation method and encapsulating cinnamaldehyde from cinnamon essential oil to produce a bio-nanocomposite (CEB) for management of insect pest infestations. Furthermore, the raw MMT, purified MMT, and CEB were characterized by different physiochemical techniques such as X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The SEM-EDX analyses demonstrated shiny irregular sheets and confirmed the presence of C-atom along with Si, O, Al, and Mg. The average crystallite size for CEB is specified to be 9.69 nm. The persistency of the cinnamaldehyde and its effective release from the CEB was confirmed by FT-IR analysis until 30 days. CEB displayed potent fumigant toxicity (LC50 = 0.37 mg/cm3) and high repellency (93.33 %) against Callosobruchus chinensis. Quantitative analysis recorded elevated protein levels (5.47 mg/ml) in treated insects. Similarly, the qualitative analysis revealed up and down-regulation of six and eight protein bands, respectively. Overall, findings show that the formulated bio-nanocomposite can better manage pulse beetle infestations in stored grains.

Design of highly robust super-liquid-repellent surfaces that can resist high-velocity impact of low-surface-tension liquids.

Super-liquid-repellent surfaces capable of preventing wetting with various liquids have tremendous application. However, high liquid repellency relies on surface texturing to minimize the solid-liquid interfacial contact, which generally results in impaired interface robustness and pressure resistance. Consequently, the surface tends to undergo a Cassie-Baxter to Wenzel wetting transition and loses liquid repellency under high-velocity liquid impact, especially for low-surface-tension liquids. Here, surface design through combining the nanoscale effect and doubly reentrant structure is demonstrated to solve the above challenge. By utilizing a facile colloidal lithography process, robust liquid repellent surfaces featuring nanoscale doubly reentrant (NDR) structures are constructed. The nanoscale features ensure sufficient triple contact line density at a low solid-liquid contact fraction to enhance the capillary force for liquid suspension. In conjunction with the doubly reentrant topography that maximizes the upward component of capillary force, such NDR surfaces enable an extremely robust solid-liquid-gas composite interface. As a result, the prepared NDR surface maintain excellent repellency upon high-velocity impact of various liquids, including ethylene glycol drops with a Weber number (We) above 306 and ethanol drops with a We of 57. The above findings can help the development of super-liquid-repellent surfaces applicable to harsh conditions of high-velocity liquid impact or high hydrostatic pressure.

Photo-initiated thiol-ene reaction of multi-functional thiol and olefinic organosilicon compounds leading to porous polymers: Solution polymerization and photolithography

Photo-initiated thiol-ene reaction between multi-functional thiol compounds and unsaturated organosilicon compounds in ethanol/dimethyl sulfoxide mixed solvent successfully yielded porous polymers. The morphology of the porous polymer was formed by connected particles, whose diameters ranged from 1 to 6 μm. An increase in the number of thiol group of multi-functional thiol compounds decreased the particle size and increased the Young's modulus of the porous polymers. Porous polymers absorbed various organic solvents and showed high water repellency. Photolithography based on the thiol-ene reaction led to the patterning by the porous polymers.

Do Commercial Insect Repellents Provide Protection against the Tick Amblyomma sculptum (Acari: Ixodidae)?

Amblyomma sculptum is a species of public health interest because it is associated with the transmission of the bacteria that causes Brazilian Spotted Fever (BSF). The use of repellents on humans is a prophylactic measure widely used to provide protection against a series of arthropod vectors, including mosquitoes and ticks. However, in Brazil, the effectiveness of commercial repellents against A. sculptum is little known. Therefore, it is necessary to carry out specific studies to evaluate the repellency of these commercial products, registered for use against mosquitoes, against the star tick. The main goal of the present work was to evaluate the effectiveness of six commercial repellents against A. sculptum. Unfed nymphs, aged between two and eight weeks, were tested against products based on DEET (OFF!® and Repelex®), Icaridin (Exposis® and SBP®), and IR3535 (Johnsons and Henlau). Three bioassays were conducted to evaluate tick behavior: (i) filter paper, (ii) fingertip, and (iii) field. All bases tested showed high repellent activity, differing significantly (p < 0.05) from the control. It was observed the formulation with DEET resulted in the best results in the filter paper bioassay. In the fingertip bioassay, the DEET base repelled a greater number of ticks compared to Icaridin. In the field bioassay, there was no significant difference between the Icaridin base and DEET, and both formulations differed from the control (p < 0.05). The six formulations tested showed significant percentages of repellency against ticks; however, for the fingertip and field bioassays, the products OFF!®, Repelex®, and Exposis® were tested as they showed better performance in the filter paper test. OFF!® showed the best percentage of repellency (100%), followed by Repelex® (96.8%), and Exposis® (93.1%), considering the two-hour period of the bioassay-field-test. Proving the effectiveness of repellents on the market against A. sculptum presented in this study is crucial, since this is the main ectoparasite of humans that can transmit Rickettsia rickettsii when infected. The effectiveness of commercial insect repellents against other tick species that parasitize humans can also be explored.

Development of a Carbon Nanotube-Enhanced FAS Bilayer Amphiphobic Coating for Biological Fluids.

This study reports the development of a novel amphiphobic coating. The coating is a bilayer arrangement, where carbon nanotubes (CNTs) form the underlayer and fluorinated alkyl-silane (FAS) forms the overlayer, resulting in the development of highly amphiphobic coatings suitable for a wide range of substrates. The effectiveness of these coatings is demonstrated through enhanced contact angles for water and artificial blood plasma fluid on glass, stainless steel, and porous PTFE. The coatings were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and contact angle (CA) measurements. The water contact angles achieved with the bilayer coating were 106 ± 2°, 116 ± 2°, and 141 ± 2° for glass, stainless steel, and PTFE, respectively, confirming the hydrophobic nature of the coating. Additionally, the coating displayed high repellency for blood plasma, exhibiting contact angles of 102 ± 2°, 112 ± 2°, and 134 ± 2° on coated glass, stainless steel, and PTFE surfaces, respectively. The presence of the CNT underlayer improved plasma contact angles by 29%, 21.7%, and 16.5% for the respective surfaces. The presence of the CNT layer improved surface roughness significantly, and the average roughness of the bilayer coating on glass, stainless steel, and PTFE was measured to be 488 nm, 301 nm, and 274 nm, respectively. Mechanistically, the CNT underlayer contributed to the surface roughness, while the FAS layer provided high amphiphobicity. The maximum effect was observed on modified glass, followed by stainless steel and PTFE surfaces. These findings highlight the promising potential of this coating method across diverse applications, particularly in the biomedical industry, where it can help mitigate complications associated with device-fluid interactions.

The essential oil of Kochia scoparia (L.) Schrad. as a potential repellent against stored-product insects.

Chemical composition of the essential oil from Kochia scoparia (L.) Schrad. (syn. Bassia scoparia (L.) A. J. Scott) was analyzed in quality and quantity by GC-MS and GC-FID. Repellent activities of the essential oil from K. scoparia (KSEO) were evaluated against two common species of stored-product insects Tribolium castaneum Herbst and Liposcelis bostrychophila Badonnel. Results indicated that KSEO mainly consisted of eugenol, β-caryophyllene, and α-humulene, accounting for 75.6%, 8.2%, and 1.4% of the total oil, respectively. KSEO and the three major components were repellent to T. castaneum and L. bostrychophila adults. Notably, KSEO exerted significant effects, comparable to the positive control DEET at 2 and 4h post-exposure. Eugenol at 63.17-2.53 nL/cm2 exhibited high percentage repellency ranging from 96 to 70% against L. bostrychophila during 4-h exposure. To gain further insights into the repellent activity, molecular docking simulation was performed with eugenol as the ligand and an odorant binding protein TcOBPC12 (gene: TcOBP10B) from the model insect T. castaneum as the receptor. Docking calculation results revealed that TcOBPC12 had binding affinity to eugenol (△G = - 4.52kcal/mol) along with a hydrogen bond of 0.18nm (1.8Å) long forming between them, which could be an important target protein associated with identifying volatile repellent molecules. This work highlights the promising potential of KSEO as a botanical repellent for controlling stored-product insects.