Mosquito Eye Research Articles

Enhancing durability of superhydrophobic surfaces via nanoparticle-induced bipolar interface effects and micro-nano composite structures: A femtosecond laser and chemical modification approach

Superhydrophobic coatings are vital in energy, aerospace, and chemical engineering, while their complex preparation and limited durability hinder widespread application. Therefore, inspired by the unique structures of hydrophobic cotton surfaces and mosquito eyes in nature, a durable aluminum alloy superhydrophobic surface is developed using a combination of femtosecond laser and chemical modification methods. Initially, porous microneedle micro-nanostructures are ablated on the surface of the aluminum alloy via femtosecond laser technology. Then, epoxy resin modified with γ-aminopropyl triethoxysilane (KH550) forms a covalently bonded intermediate layer. Finally, biphasic silicon dioxide (BP-SiO2) nanoparticles modified by hexadecyltrimethoxysilane (HDTMS) are used to construct the top hydrophobic layer. The covalent interface interactions between the aluminum alloy substrate and the intermediate layer, as well as between the intermediate layer and the top layer, significantly enhance the durability of the superhydrophobic surface. The prepared F-M@KH-EP/BP-SiO2 coating exhibits outstanding superhydrophobic properties, with a water contact angle (CA) as high as 168.56° and a sliding angle (SA) as low as 1.52° More encouragingly, the composite coating maintains its excellent water resistance even when subjected to harsh mechanical durability damage, including sandpaper wear, tape stripping tests, water drop and sand impact tests. Moreover, the prepared coatings maintain distinguished non-wettability in harsh operating conditions such as corrosive liquid environments, ultraviolet radiation, ultrasonic vibration, etc. Additionally, the coating demonstrates remarkable self-cleaning properties. Superhydrophobic surface durability is significantly enhanced by combining nanoparticle-induced bipolar interface effect and micro-nano structures. These findings provide theoretical reference for the design and application of durable superhydrophobic coatings.

Bioinspired Graphene Oxide-Magnetite Nanocomposite Coatings as Protective Superhydrophobic Antifouling Surfaces.

Antifouling (AF) nanocoatings made of polydimethylsiloxane (PDMS) are more cost-efficient and eco-friendly substitutes for the already outlawed tributyltin-based coatings. Here, a catalytic hydrosilation approach was used to construct a design inspired by composite mosquito eyes from non-toxic PDMS nanocomposites filled with graphene oxide (GO) nanosheets decorated with magnetite nanospheres (GO-Fe3O4 nanospheres). Various GO-Fe3O4 hybrid nanofillers were dispersed into the PDMS resin through a solution casting method to evaluate the structure-property relationship. A simple coprecipitation procedure was used to fabricate magnetite nanospheres with an average diameter of 30-50 nm, a single crystal structure, and a predominant (311) lattice plane. The uniform bioinspired superhydrophobic PDMS/GO-Fe3O4 nanocomposite surface produced had a micro-/nano-roughness, low surface-free energy (SFE), and high fouling release (FR) efficiency. It exhibited several advantages including simplicity, ease of large-area fabrication, and a simultaneous offering of dual micro-/nano-scale structures simply via a one-step solution casting process for a wide variety of materials. The superhydrophobicity, SFE, and rough topology have been studied as surface properties of the unfilled silicone and the bioinspired PDMS/GO-Fe3O4 nanocomposites. The coatings' physical, mechanical, and anticorrosive features were also taken into account. Several microorganisms were employed to examine the fouling resistance of the coated specimens for 1 month. Good dispersion of GO-Fe3O4 hybrid fillers in the PDMS coating until 1 wt % achieved the highest water contact angle (158° ± 2°), the lowest SFE (12.06 mN/m), micro-/nano-roughness, and improved bulk mechanical and anticorrosion properties. The well-distributed PDMS/GO-Fe3O4 (1 wt % nanofillers) bioinspired nanocoating showed the least biodegradability against all the tested microorganisms [Kocuria rhizophila (2.047%), Pseudomonas aeruginosa (1.961%), and Candida albicans (1.924%)]. We successfully developed non-toxic, low-cost, and economical nanostructured superhydrophobic FR composite coatings for long-term ship hull coatings. This study may expand the applications of bio-inspired functional materials because for multiple AF, durability and hydrophobicity are both important features in several industrial applications.

Mosquito's eyes inspired, hydrophobic and multifunctional coating on flexible polyurethane (PU) foam: highly efficient oil spills remediation and exceptional flame-retardant performance

Inspired by the structure of mosquito's compound eyes, a hydrophobic flexible polyurethane (PU) foam composite (named as PU@SiO2/ADP) with good flame-retardant property was fabricated by coating aluminum diethylhypophosphite (ADP) and in situ-formed SiO2 nanoparticles. Owning to considerable surface roughness of stacked SiO2 nanoparticles and intrinsic hydrophobicity of ADP, the water contact angle (WCA) of modified PU foam increased from 113° to 133°. The absorption capacity of modified foam to oils and organic solvents was also evaluated. The results showed that the absorption ratios of the modified PU to dichloromethane reached 69 g/g. The oil-water separation results proved that PU@SiO2/ADP foam could rapidly and selectively absorb oils or organic solvents from the water surface even under turbulent flow conditions. Fabricated hydrophobic PU maintained excellent oil absorption properties after 10 absorption-squeezing cycles, demonstrating good recyclability. The modified PU foam also showed high flame retardancy. The surface treatment method applied in this research not only provides an effective strategy for fabricating a promising absorbent PU foam for oil spill treatment, but also brings a promising prospect for enhancing the flame-retardant performance of these absorbent polymer composites. This work provides support and reference for the improvement of similar materials in future works.

Biting Innovations of Mosquito-Based Biomaterials and Medical Devices.

Mosquitoes are commonly viewed as pests and deadly predators by humans. Despite this perception, investigations of their survival-based behaviors, select anatomical features, and biological composition have led to the creation of several beneficial technologies for medical applications. In this review, we briefly explore these mosquito-based innovations by discussing how unique characteristics and behaviors of mosquitoes drive the development of select biomaterials and medical devices. Mosquito-inspired microneedles have been fabricated from a variety of materials, including biocompatible metals and polymers, to mimic of the mouthparts that some mosquitoes use to bite a host with minimal injury during blood collection. The salivary components that these mosquitoes use to reduce the clotting of blood extracted during the biting process provide a rich source of anticoagulants that could potentially be integrated into blood-contacting biomaterials or administered in therapeutics to reduce the risk of thrombosis. Mosquito movement, vision, and olfaction are other behaviors that also have the potential for inspiring the development of medically relevant technologies. For instance, viscoelastic proteins that facilitate mosquito movement are being investigated for use in tissue engineering and drug delivery applications. Even the non-wetting nanostructure of a mosquito eye has inspired the creation of a robust superhydrophobic surface coating that shows promise for biomaterial and drug delivery applications. Additionally, biosensors incorporating mosquito olfactory receptors have been built to detect disease-specific volatile organic compounds. Advanced technologies derived from mosquitoes, and insects in general, form a research area that is ripe for exploration and can uncover potential in further dissecting mosquito features for the continued development of novel medical innovations.

Multifunctional Liquid Marble Compound Lenses.

Mosquito compound eyes are elaborate multifunctional hierarchical structures. The presence of ordered curved features spanning length scales of nanometers to millimeters provides the mosquito eye with a wide field of view, an infinite depth of field, and antifogging properties. Developing bio-inspired compound lenses is challenging because of the need to mimic all characteristic curvatures along with their functionalities. Herein, we show how the curvature inherent to nanoparticles, emulsion droplets, and liquid marbles can be employed to mimic the hierarchical structure and functionality of mosquito compound eyes. At the nanometer to micrometer length scale we employ nanoparticle-stabilized emulsion droplets of photocurable oil to form microlenses with nanoscale surface features. After polymerization, the microlenses form a monolayer on an oil droplet to create an optically clear, millimeter scale, liquid marble that functions as a compound lens. We characterize the optical and surface properties of the compound lenses and find that they reproduce the functionality of the mosquito eye. Additionally, we exploit the mobility and reconfigurability of liquid marbles to create arrays (centimeter scale) of compound lenses and other types of functional lenses such as the Janus lens that magnifies the image acquired by the compound lens. Simple and scalable methods to create compound lenses could aid in the development of miniaturized advanced vision systems.

Mosquito eyes inspired surfaces with robust antireflectivity and superhydrophobicity

Inspired by the compound eyes of the mosquito, the uniform hierarchical structures with antireflectivity and superhydrophobicity has been designed and prepared by spinning technology. Microscale silica spheres and nanoscale colloidal particles were assembled on glass substrate to produce binary structures. To enhance the hydrophobicity, particles were modified by N-(β-aminoethyl)-γ-aminopropylmethylbimethoxy silane (KH-602) before deposition. And annealing process was used to strengthen the mechanical robustness. The resultant structures exhibited low reflections of less than 0.5%, and high static water contact angle (WCA) of larger than 160°. Furthermore, tape adhesion test and washing test showed that the artificial nano-/micro- structures had excellent mechanical robustness. Meanwhile the superhydrophobic surface owned the capacities of self-cleaning ability and chemical stability. We anticipate that these advantages could potentially enhance the performance of optoelectronic devices and help them to survive in terrible environment. Moreover, this self-assembly method is facile, cost effective, and suitable for high-throughput fabrication of binary colloidal arrays.

Antifogging abilities of model nanotextures.

Nanometre-scale features with special shapes impart a broad spectrum of unique properties to the surface of insects. These properties are essential for the animal's survival, and include the low light reflectance of moth eyes, the oil repellency of springtail carapaces and the ultra-adhesive nature of palmtree bugs. Antireflective mosquito eyes and cicada wings are also known to exhibit some antifogging and self-cleaning properties. In all cases, the combination of small feature size and optimal shape provides exceptional surface properties. In this work, we investigate the underlying antifogging mechanism in model materials designed to mimic natural systems, and explain the importance of the texture's feature size and shape. While exposure to fog strongly compromises the water-repellency of hydrophobic structures, this failure can be minimized by scaling the texture down to nanosize. This undesired effect even becomes non-measurable if the hydrophobic surface consists of nanocones, which generate antifogging efficiency close to unity and water departure of droplets smaller than 2 μm.

Optomotor Reactions Reveal Polarization Sensitvity in the Zika Virus Transmitting Yellow Fever Mosquito Aedes (Stegomyia) aegypti (Diptera; Nematocera).

In polarization-sensitive insect species an orthogonal arrangement of photoreceptive microvilli is a characteristic feature. However, mosquito eyes had not revealed this feature, and polarization sensitivity (PS) was considered to be non-existent in them. Recently, however, gravid Aedes (Stegomyia) aegypti females were found to possess PS, sequels of which could be demonstrated only in the absence of chemicals emitted by conspecifics. Therefore, PS in Ae. aegypti, unlike that of other aquatic insects, apparently does not play a dominant role in locating water bodies, and is difficult to demonstrate in situations free of chemical cues. Here, we present behavioral evidence with Ae. aegypti females, exposed to large-field optomotor stimuli based solely on polarization contrast. Under conditions with stripes of alternating orthogonal directions of polarization, clear optomotor responses were elicited, no different from those in response to a rotating drum with vertical black and white stripes. Thus, Ae. aegypti is indeed polarization-sensitive; it reacts to vertically-striped contrast patterns with low spatial frequency on the basis of both intensity and polarization differences between the stripes.

One-step fabricated bionic PVDF ultrafiltration membranes exhibiting innovative antifouling ability to the cake fouling

In view of the excellent application properties of the bionic materials, a novel polyvinylidene fluoride (PVDF) ultrafiltration membrane with regular nanoscale papillae on the membrane surface imitating the mosquito eye structures was fabricated by one-step molding method. The amphiphilic wetting agent (EW-326) was used in the membrane preparation process for the generation of numerous papillae with the diameter of 200–300nm by adjusting the phase separation process during the membrane formation. The test results of filtration fouling showed that the bionic PVDF membrane exhibited different fouling resistances between the adhesive pollutants (e.g. bovine serum albumin, BSA) and the cake layer pollutants (e.g. sodium alginate, SA) due to the different fouling layers formed on top of the papillae structure. The water flux recovery ratio (FRR) value of bionic PVDF membrane was still higher than 90% even after three fouling cycles with the SA pollutant solution. Meanwhile, this novel modified PVDF membrane also exhibited expected antifouling performance to the sewage. The novel preparation method of bionic membrane exhibits a significant effect for enhancing the antifouling performance of ultrafiltration process with cake layer formed, and can provide new insight into the formation of separation membranes with regulated surface structure.

Nano/Micro-Manufacturing of Bioinspired Materials: a Review of Methods to Mimic Natural Structures.

Through billions of years of evolution and natural selection, biological systems have developed strategies to achieve advantageous unification between structure and bulk properties. The discovery of these fascinating properties and phenomena has triggered increasing interest in identifying characteristics of biological materials, through modern characterization and modeling techniques. In an effort to produce better engineered materials, scientists and engineers have developed new methods and approaches to construct artificial advanced materials that resemble natural architecture and function. A brief review of typical naturally occurring materials is presented here, with a focus on chemical composition, nano-structure, and architecture. The critical mechanisms underlying their properties are summarized, with a particular emphasis on the role of material architecture. A review of recent progress on the nano/micro-manufacturing of bio-inspired hybrid materials is then presented in detail. In this case, the focus is on nacre and bone-inspired structural materials, petals and gecko foot-inspired adhesive films, lotus and mosquito eye inspired superhydrophobic materials, brittlestar and Morpho butterfly-inspired photonic structured coatings. Finally, some applications, current challenges and future directions with regard to manufacturing bio-inspired hybrid materials are provided.

Design of bioinspired, smart, multiscale interfacial materials with superwettability

Abstract

Biomimetic Antireflective Hierarchical Arrays

We report a simple method for the fabrication of biomimetic antireflective hierarchical arrays based on the combination of self-assembled polymer spheres and nanoimprint lithography (NIL). The hierarchical structures are fabricated by creating nanopillars on the microscale round protrusion arrays, which are similar to natural mosquito eyes consisting of combined micro- and nanostructures. The hierarchical arrays dramatically suppress the surface reflection from visible to near-infrared regions with an angle of incidence of up to 70°.

Recent developments in bio-inspired special wettability

Nature is a school for scientists and engineers. After four and a half billion years of stringent evolution, some creatures in nature exhibit fascinating surface wettability. Biomimetics, mimicking nature for engineering solutions, provides a model for the development of functional surfaces with special wettability. Recently, bio-inspired special wetting surfaces have attracted wide scientific attention for both fundamental research and practical applications, which has become an increasingly hot research topic. This Critical Review summarizes the recent work in bio-inspired special wettability, with a focus on lotus leaf inspired self-cleaning surfaces, plants and insects inspired anisotropic superhydrophobic surfaces, mosquito eyes inspired superhydrophobic antifogging coatings, insects inspired superhydrophobic antireflection coatings, rose petals and gecko feet inspired high adhesive superhydrophobic surfaces, bio-inspired water collecting surfaces, and superlyophobic surfaces, with particular focus on the last two years. The research prospects and directions of this rapidly developing field are also briefly addressed (159 references).

A transgenic sensor strain for monitoring the RNAi pathway in the yellow fever mosquito, Aedes aegypti

The RNA interference pathway functions as an antiviral defense in invertebrates. In order to generate a phenotypic marker which “senses” the status of the RNAi pathway in Aedes aegypti, transgenic strains were developed to express EGFP and DsRED marker genes in the eye, as well as double-stranded RNA homologous to a portion of the EGFP gene. Transgenic “sensor” mosquitoes exhibited robust eye-specific DsRED expression with little EGFP, indicating RNAi-based silencing. Cloning and high-throughput sequencing of small RNAs confirmed that the inverted-repeat transgene was successfully processed into short-interfering RNAs by the mosquito RNAi pathway. When the A. aegypti homologues of the genes DCR-2 or AGO-2 were knocked down, a clear increase in EGFP fluorescence was observed in the mosquito eyes. Knockdown of DCR-2 was also associated with an increase in EGFP mRNA levels, as determined by Northern blot and real-time PCR. Knockdown of AGO-3, a gene involved in the germline-specific piRNA pathway, did not restore EGFP expression at either the mRNA or protein level. This transgenic sensor strain can now be used to identify other components of the mosquito RNAi pathway and has the potential to be used in the identification of arboviral suppressors of RNAi.

Fog free

Making anti-fogging surfaces by mimicking the structures that are found in the mosquito eye still remains a challenge

Fundamental differences in the optical structure of the eyes of nocturnal and diurnal mosquitoes

We have studied the anatomy and optics of the eyes of a range of mosquito species from the wholly dark-active blood-feeding Anopheles gambiae to the diurnal plant-feeder Toxorhynchites brevipalpis. Consistent with studies by Sato in the 1950s, we find that dark-active and crepuscular species have short fused rhabdoms with a conical construction. This maximises the amount of light the rhabdoms receive from the almost hemispherical wide-aperture lenses. Toxorhynchites, on the other hand, has long narrow rhabdomeres that are separated from each other over their entire length, and so resemble the open rhabdoms of advanced flies (Brachycera and Cyclorrhapha). These findings are confirmed by studies of the pseudopupil, whose form indicates the layout of the rhabdomere tips in the focal plane of each ommatidial lens. In anopheline species the pseudopupil is a single undivided ellipse, indicating a fused rhabdom structure, whereas in Toxorhynchites there is a ring of six outer elements surrounding a central one. This means that each rhabdomere views a separate direction in space, and our measurements indicate that, as in higher Diptera, adjacent rhabdomeres share their fields of view with one of the rhabdomeres in the immediately adjacent ommatidia. This in turn means that in the diurnal type of mosquito eye there is a basis for neural superposition, but the fused construction of anopheline rhabdoms precludes this. The Aedes species studied were similar to Anopheles but with lenses of less extreme aperture, and Sabethes cyaneus, a diurnal blood-feeder, was intermediate in structure, with fused conical rhabdoms in the centre of the eye and unfused rhabdomeres around the periphery.

Mosquito eye design: conical rhabdoms are matched to wide aperture lenses

Night-active mosquitoes have photopigment-containing rhabdoms that take the form of a wide hollow cone, with the distal apex at the focus of the ommatidial lens. It is shown geometrically, and with the aid of a gelatin model, that such a structure can trap light over an angle of up to 60 deg, roughly equal to the width of the cone of light provided by the lens. This gives a gain in light-gathering power of up to nine times that of the more usual cylinder-shaped rhabdom with an acceptance angle of less than 25 deg.

Vitamin A deficiency: effect on mosquito eye ultrastructure.

Mosquitoes (Aedes aegypti) were reared aseptically for one generation on an artificial diet containing neither vitamin A nor its usual precursor in animals, betacarotene. Function (electrical response to light) in the compound eyes of these animals was severely impaired. Ultrastructure of the photoreceptor cells was abnormal in two respects: multivesicular bodies were absent, and masses of smooth membrane lamellae were present near the nucleus. The organization of the photoreceptor organelle, the rhabdomere, was normal. The eyes of control mosquitoes, to whose diet beta-carotene was added, were functionally and structurally normal. Multivesicular bodies were normally abundant and the perinuclear membrane masses were not present.

The effect of light and light deprivation upon the ultrastructure of the larval mosquito eye. 3. Multivesicular bodies and protein uptake.

AbstractThe formation of multivesicular and lamellar bodies, organelles characteristic of arthropod photoreceptor cells, is shown in the mosquito eye to be dependent upon light. The organelles are nearly absent from light deprived eyes; they form in large numbers when such eyes are first illuminated. Multivesicular bodies form adjacent to the rhabdomere, then move proximally into the body of the cell, ultimately being transformed into lamellar and probably dense bodies. Experiments in which ferritin was injected into the hemolymph of the head confirmed the hypothesis that the coated vesicles of the rhabdomere are pinocytotic vesicles. Ferritin taken into the cell by rhabdomeric vesicles is sequestered in multivesicular bodies.

The effect of light and light deprivation upon the ultrastructure of the larval mosquito eye. II. The rhabdom

AbstractThe surface area of the rhabdom membrane is two to three times greater in mosquito larvae grown in darkness than it is in larvae grown in light. Moreover, light adapted rhabdom microvilli are covered with a surface coat and produce coated vesicles, while the light deprived rhabdom has no coat and does not form coated vesicles. The light adapted microvilli are held together by septate desmosomes; the light deprived microvilli appear to be packed loosely together.When a light deprived rhabdom is first exposed to light, the membranes of adjacent microvilli rapidly fuse so that the intervillous space is lost. During the next several hours the rhabdom reorganizes to the light adapted state. The intervillous space reopens. The area of the rhabdom membrane diminishes. The coat forms, and coated vesicles are produced in large numbers. This light induced transformation is of interest because of the presumed photoreceptive function of the rhabdom.