Cicada Wings Research Articles

Durability and Surface Oxidation States of Antiviral Nano-Columnar Copper Thin Films.

Antiviral coatings that inactivate a broad spectrum of viruses are important in combating the evolution and emergence of viruses. In this study, nano-columnar Cu thin films have been proposed, inspired by cicada wings (which exhibit mechano-bactericidal activity). Nano-columnar thin films of Cu and its oxides were fabricated by the sputtering method, and their antiviral activities were evaluated against envelope-type bacteriophage Φ6 and non-envelope-type bacteriophage Qβ. Among all of the fabricated films, Cu thin films showed the highest antiviral activity. The infectious activity of the bacteriophages was reduced by 5 orders of magnitude within 30 min by the Cu thin films, by 3 orders of magnitude by the Cu2O thin films, and by less than 1 order of magnitude by the CuO thin films. After exposure to ambient air for 1 month, the antiviral activity of the Cu2O thin film decreased by 1 order of magnitude; the Cu thin films consistently maintained a higher antiviral activity than the Cu2O thin films. Subsequently, the surface oxidation states of the thin films were analyzed by X-ray photoelectron spectroscopy; Cu thin films exhibited slower oxidation to the CuO than Cu2O thin films. This oxidation resistance could be a characteristic property of nanostructured Cu fabricated by the sputtering method. Finally, the antiviral activity of the nano-columnar Cu thin films against infectious viruses in humans was demonstrated by the binding inhibition of the SARS-CoV-2 spike protein to the angiotensin-converting enzyme 2 receptor within 10 min.

Cicada-Wing-Inspired Highly Sensitive Tactile Sensors Based on Elastic Carbon Foam with Nanotextured Surfaces.

Electronic devices with tactile and pressure-sensing capabilities are becoming increasingly popular in the automatic industry, human motion/health monitoring, and artificial intelligence applications. Inspired by the natural nanotopography of the cicada wing, we propose here a straightforward strategy to fabricate a highly sensitive tactile sensor through nanotexturing of erected polyaniline (PANI) nanoneedles on a conductive and elastic three-dimensional (3D) carbon skeleton. The robust and compressible carbon networks offer a resilient and conducting matrix to catering complex scenarios; the biomimetic PANI nanoneedles firmly and densely anchored on a 3D carbon skeleton provide intimate electrical contact under subtle deformation. As a result, a piezoresistive tactile sensor with ultrahigh sensitivity (33.52 kPa-1), fast response/recovery abilities (97/111 ms), and reproducible sensing performance (2500 cycles) is developed, which is capable of distinguishing motions in a wide pressure range from 4.66 Pa to 60 kPa, detecting spatial pressure distribution, and monitoring various gestures in a wireless manner. These excellent performances demonstrate the great potential of nature-inspired tactile sensors for practical human motion monitoring and artificial intelligence applications.

Preparation and investigation of high-performance 3D Ag/SiO2 nanohole array substrate based on cicada wing

In this paper, SiO2 support with 3D ordered nanohole structure was developed by using the nanopillars naturally created on the surface of the cicada wing as the template through a simple strategy of tetraethyl orthosilicate (TEOS) hydrolysis. Then 3D Ag/SiO2 substrate with a high density of hot spots was subsequently obtained by thermal deposition of Ag onto the SiO2 support. SEM and AFM observation reveal the hole walls of SiO2 were covered densely with large Ag particles whose surface was composed of lots of tiny Ag NPs. Especially at the top of the hole walls, six adjacent large Ag particles surrounded each hole. FDTD simulation demonstrated both the gaps between the tiny Ag NPs and those between large Ag particles were efficient hot spots, which could concentrate the electric field effectively. By using crystal violet (CV) as the probe molecule, the proposed Ag/SiO2 substrate could detect 10−9 M CV easily and the enhancement factor (EF) was calculated to be 1.7 × 107 due to the combined effect of hot spots and the 3D structure. The hexagonally arrayed nanohole structure endowed the proposed Ag/SiO2 substrate with good uniformity and the relative standard deviation (RSD) was estimated to be as low as 5.79%. The great potential of this substrate in practical applications was demonstrated by the successful detection of tricyclazole down to 0.01 ppm which lived up to the EU standard.

Bio-inspired antimicrobial surfaces fabricated by glancing angle deposition

This paper describes the fabrication of cicada-wing-inspired antimicrobial surfaces using Glancing Angle Deposition (GLAD). From the study of an annual cicada (Neotibicen Canicularis, also known as dog-day cicada) in North America, it is found that the cicada wing surfaces are composed of unique three-dimensional (3D) nanofeature arrays, which grant them extraordinary properties including antimicrobial (antifouling) and antireflective. However, the morphology of these 3D nanostructures imposes challenges in artificially synthesizing the structures by utilizing and scaling up the template area from nature. From the perspective of circumventing the difficulties of creating 3D nanofeature arrays with top-down nanofabrication techniques, this paper introduces a nanofabrication process that combines bottom-up steps: self-assembled nanospheres are used as the bases of the features, while sub-100 nm pillars are grown on top of the bases by GLAD. Scanning electron micrographs show the resemblance of the synthesized cicada wing mimicry samples to the actual cicada wings, both quantitatively and qualitatively. The synthetic mimicry samples are hydrophobic with a water contact angle of 125˚. Finally, the antimicrobial properties of the mimicries are validated by showing flat growth curves of Escherichia coli (E. coli) and by direct observation under scanning electron microscopy (SEM). The process is potentially suitable for large-area antimicrobial applications in food and biomedical industries.

Performance evaluation of novel Ag@GO-biomaterial SERS substrates for the ultrasensitive detection of neomycin in foods

Many biomaterials are hydrophobic, making them attractive materials for the fabrication of surface enhanced Raman spectroscopy (SERS) substrates. Herein, we prepared a series of novel SERS substrates by loading graphene oxide (GO) and silver nanoparticles onto four different hydrophobic biomaterials (rose petals, lotus leaves, cicada wings or dragonfly wings). The obtained Ag@GO-biomaterial SERS substrates offered outstanding SERS performance. These substrates utilized both the electromagnetic mechanism and chemical mechanism to boost the SERS signal, as well as the concentrating effect owing to the hydrophobicity of biomaterials. The Ag@GO-rose petal SERS substrate showed the strongest signal enhancement capability, offering an LOD of 4.52 × 10-11 mol L-1 for the detection of the neomycin. Results encourage the wider use of hydrophobic biomaterials in SERS substrate construction and hazard monitoring.

A hybrid and scalable nanofabrication approach for bio-inspired bactericidal silicon nanospike surfaces

Insects and plants exhibit bactericidal properties through surface nanostructures, such as nanospikes, which physically kill bacteria without antibiotics or chemicals. This is a promising new avenue for achieving antibacterial surfaces. However, the existing methods for fabricating nanospikes are incapable of producing uniform nanostructures on a large scale and in a cost-effective manner. In this paper, a scalable nanofabrication method involving the application of nanosphere lithography and reactive ion etching for constructing nanospike surfaces is demonstrated. Low-cost silicon nanospikes with uniform spacing that were sized similarly to biological nanospikes on cicada wings with a 4-inch wafer scale were fabricated. The spacing, tip radius, and base diameter of the silicon nanospikes were controlled precisely by adjusting the nanosphere diameters, etching conditions, and diameter reduction. The bactericidal properties of the silicon nanospikes with 300 nm spacing were measured quantitatively using the standard viability plate count method; they killed E. coli cells with 59 % efficiency within 30 h. The antibacterial ability of the nanospike surface was further indicated by the morphological differences between bacteria observed in the scanning electron microscopic images as well as the live/dead stains of fluorescence signals. The fabrication process combined the advantages of both top-down and bottom-up methods and was a significant step toward affordable bio-inspired antibacterial surfaces.

Polymeric Antibacterial Surfaces with Nano-pillar Arrays Mimicking Cicada Wings

Cicada wings consist of nanopillar arrays with a pitch, diameter, and height of a few hundred nanometers. These arrays show strong antibacterial performance owing to cell membrane damage caused by the physical interaction with the nanopillars. Polymer-based nanopillars are essential for various industrial applications. Herein, we present the fabrication process of polymer-based nanopillars using a facile thermal nanoimprint technique. Moreover, the conformational information of the nanopillars has been provided.

Fabrication of Superhydrophobic Surfaces Using Inverted Glancing Angle Deposition (I-GLAD)

Abstract This paper presents a novel approach for fabricating superhydrophobic surfaces using inverted glancing angle deposition (I-GLAD). GLAD is an advanced physical vapor deposition technique that utilizes substrate tilt and rotation to create three-dimensional nanofeature arrays. Unlike conventional top-down nanofabrication methods, GLAD offers unique advantages in generating various nanofeatures such as pillars, springs, chevrons, ribbons, and nanoporous membranes. Superhydrophobicity, inspired by natural examples like lotus leaves and cicada wings, relies on highly porous micro/nanostructures that reduce surface energy and impart water-repellent properties. GLAD’s capability to produce hierarchical and porous nanostructures makes it an ideal candidate for superhydrophobic surface fabrication. Previous researches have proposed GLAD processes for superhydrophobic surfaces; however, these approaches suffer from flaws such as being time-consuming or requiring challenging template assistance. In this paper, we introduce a new I-GLAD approach for creating superhydrophobic surfaces that eliminates the need for a seeding layer and an additional coating, simplifying the fabrication process. The fabrication process of I-GLAD includes natural seeding, growing, capping, and inverting. The resulting superhydrophobic surfaces exhibit a high water contact angle of over 155 deg. We further explore additional GLAD recipes to create surfaces with different water contact angles, enabling a comprehensive analysis of superhydrophobic properties. Potential applications for superhydrophobic surfaces include anti-icing coatings, self-cleaning surfaces, and antimicrobial surfaces.

MAS-DNP enables NMR studies of insect wings

NMR is a valuable tool for studying insects. Solid-state NMR has been used to obtain the chemical composition and gain insight into the sclerotization process of exoskeletons. There is typically little difficulty in obtaining sufficient sample quantity for exoskeletons. However, obtaining enough sample of other insect components for solid-state NMR experiments can be problematic while isotopically enriching them is near impossible. This is especially the case for insect wing membranes which is of interest to us. Issues with obtaining sufficient sample are the thickness of wing membranes is on the order of microns, each membrane region is surrounded by veins and occupies a small area, and the membranes are separated from the wing by physical dissection. Accordingly, NMR signal enhancement methods are needed. MAS-DNP has a track record of providing significant signal enhancements for a wide variety of materials. Here we demonstrate that MAS-DNP is useful for providing high quality one-dimensional and two-dimensional solid-state NMR spectra on cicada wing membrane at natural isotopic abundance.

Bioinspired antireflective subwavelength nanostructures induced by femtosecond laser for high transparency glass

In nature, the Cicada wing exhibiting a high transparency at wide viewing angles can be bioinspired for the formation of broadband antireflective subwavelength nanostructures (ASS), which can significantly improve the transmittance of optical devices. In this study, a femtosecond laser micro-machining is developed to fabricate a biomimic nanostructure array on optical glass for antireflection. The underlying mechanism for the transmittance enhancement and geometry design of the artificial structure is thoroughly explored by applying a rigorous coupled-wave analysis method both in the visible and the near-infrared band. In addition, the height, diameter, and period of the ASS experimentally induced by the femtosecond laser are adjusted by controlling the laser-processing parameters of pulse energy and scanning velocity. Accordingly, the proposed bioinspired nanostructures featuring a wide-angle omnidirectional antireflection in the visible band, as well as hydrophobicity properties, are anticipated to be widely used in glass displays applications.

Optimization of surface enhanced Raman scattering performance based on Ag nanoparticle-modified vanadium-titanium nanorods with tunable nanogaps.

The combination of new noble metal nanomaterials and surface enhanced Raman scattering (SERS) technology has become a new strategy to solve the problem of low sensitivity in the detection of traditional Chinese medicine. In this work, taking natural cicada wing (C.w.) as a template, by optimizing the magnetron sputtering experimental parameters for the growth of Ag nanoparticles (NPs) on vanadium-titanium (V-Ti) nanorods, the nanogaps between the nanorods were effectively regulated and the Raman signal intensity of the Ag15/V-Ti20/C.w. substrate was improved. The proposed homogeneous nanostructure exhibited high SERS activity through the synergistic effect of the electromagnetic enhancement mechanism at the nanogaps between the Ag NPs modified V-Ti nanorods. The analytical enhancement factor (AEF) value was as high as 1.819 × 108, and the limit of detection (LOD) was 1 × 10-11 M for R6G. The large-scale distribution of regular electromagnetic enhancement "hot spots" ensured the good reproducibility with the relative standard deviation (RSD) value less than 7.31%. More importantly, the active compound of Artemisinin corresponded the pharmacological effect of Artemisia annua was screened out by SERS technology, and achieved a LOD of 0.01 mg/l. This reliable preparation technology was practically applicable to produce SERS-active substrates in detection of pharmacodynamic substance in traditional Chinese medicine.

Self-assembly of hierarchical MXene@SnO2 nanostructure for enhancing the flame retardancy, solar de-icing, and mechanical property of polyurethane resin

Taking into consideration the frigid and thunderstorms, the flame retardancy and de-icing performance are simultaneously desiderated for some open-air key equipment, such as air fuselage and wind turbine blades. Here, inspired by the anti-reflection phenomenon of moth eyes and cicada wings, a multi-functionalized and biomimetic MXene@SnO2 hierarchical nanostructure is prepared to effectively impart flame retardancy and solar de-icing performance to thermoplastic polyurethane (TPU) resin used widely as the finishing coat of protective materials of open-air equipment. Based on the catalytic effect and barrier function, the addition of hierarchical MXene@SnO2 nanostructures also effectively decreases the release of heat and toxic smoke from PU resin, as confirmed by reductions of 50.5% and 33.1% in the peak heat release rate and smoke production rate, respectively. Due to the appropriate refractive index, the light reflection phenomenon is effectively suppressed, thus promoting solar absorption (∼90% at 0.4 mm film) and photo-thermal conversion (∼74.2 °C with simulated solar illumination of 1.0 kW/m2) in TPU-MXene@SnO2 nanocomposites. Within the environment of −20 °C, the surface temperature of TPU-MXene@SnO2 nanocomposites is still up to 32.7 °C and the surface ice pellet begins to melt at ∼40s, much earlier than 600s of pure TPU resin. In addition, the practical application of functionalized TPU nanocomposites is further improved by the higher mechanical properties, attributed to the strong interfacial interaction. Inspired by moth eyes and cicada wings, flame retardancy and solar de-icing performance are first integrated into polymer materials, thus effectively promoting their application in some extreme environments.

Particulate-Droplet Coalescence and Self-Transport on Superhydrophobic Surfaces.

Particulate transport from surfaces governs a variety of phenomena including fungal spore dispersal, bioaerosol transmission, and self-cleaning. Here, we report a previously unidentified mechanism governing passive particulate removal from superhydrophobic surfaces, where a particle coalescing with a water droplet (∼10 to ∼100 μm) spontaneously launches. Compared to previously discovered coalescence-induced binary droplet jumping, the reported mechanism represents a more general capillary-inertial dominated transport mode coupled with particle/droplet properties and is typically mediated by rotation in addition to translation. Through wetting and momentum analyses, we show that transport physics depends on particle/droplet density, size, and wettability. The observed mechanism presents a simple and passive pathway to achieve self-cleaning on both artificial as well as biological materials as confirmed here with experiments conducted on butterfly wings, cicada wings, and clover leaves. Our findings provide insights into particle-droplet interaction and spontaneous particulate transport, which may facilitate the development of functional surfaces for medical, optical, thermal, and energy applications.

Silver Nanopillar Arrayed Thin Films with Highly Surface-Enhanced Raman Scattering for Ultrasensitive Detection.

Surface-enhanced Raman scattering (SERS) technique based on surface plasmon resonance has been considerably investigated in recent years due to its superior sensitivity in the detection of organic or biological molecules at trace levels. However, most research usually focuses on artificial architectures as SERS substrates that always have a complex and expensive micro-nanofabrication process. The high cost of masks for SERS substrates becomes a key obstacle for the widespread commercialization of SERS technology. In this paper, a biomimetic SERS substrate composed of silver-coated nanopillar arrays on the top of a cicada wing was advanced to overcome these challenges as both substrates and masks. Benefiting from the high near-field plasmon resonance coupling at the limited space among neighboring nanopillars, a dramatically increased SERS signal can be achieved using rhodamine 6G (R6G) as a model molecule. Encouragingly, the analytical enhancement factor of the order of more than 108 has been conveniently realized with a reliable detection concentration of R6G of about 100 pM or less. This work provides a promising route for designing cost-effective and highly sensitive SERS substrates and the related mask fabrication using our previously proposed template transfer nanoimprint.

Disordered metasurface-enhanced perovskite composite films with ultra-stable and wide color gamut used for backlit displays

Perovskite nanocrystals (PNCs) are promising to replace the traditional phosphor color conversion layers in backlit displays due to their excellent optical properties, which can enhance the color gamut and saturation of displays. However, poor stability and low luminescence efficiency hinder the development of perovskite-based devices. Here, inspired by the Yunnan cicada wing, a low-cost, easy-to-fabricate, and large-area (> 78 cm2) all-dielectric metasurface based on the Purcell effect is developed to tune and improve the light extraction efficiency of PNCs. All-dielectric metasurfaces composed of weakly disordered TiO2/PS spheres are embedded in the PNCs/PVDF (Poly (vinylidene fluoride)) films prepared by in-situ fabrication strategy, resulting in 3.19-fold photoluminescence (PL) maximum enhancement of these composite films. The stability of PNCs is also markedly improved after PVDF encapsulation. As an application demo, these all-dielectric metasurface-modulated perovskite composite films are applied in LCD backlit, with the color gamut of 157% of commercial LCD and 107% of NTSC, showing tremendous potential in high-end lighting and display. Furthermore, combined with the scalability of large-area fabrication, cost-effective weakly disordered metasurfaces are a potential method to bridge the gap between high-efficient laboratory demonstrations and commercialization in the field of display.

Cicada wing-inspired solar transmittance enhancement and hydrophobicity design for graphene-based solar steam generation: A novel gas phase deposition approach

The severe light reflection phenomenon has become a critical challenge for the sufficient utilization of solar energy. For preventing the predation risk, cicada’s wings are gradually evolved into transparent morphology to preferably blend into the natural environment. The high solar transmittance in cicada wings is due to the presence of surface micro/nanostructures which avoids the large change of refractive index between air and wings. Herein, inspired by the high solar transmittance of cicada’s wings, an extremely-simple gaseous phase deposition with low heating temperature is developed to cover graphene film with methyl-modified silicon dioxide (CH3-SiO2) nanospheres that decelerate the refractive index reduction. The destructive interference effect of CH3-SiO2 nanospheres effectively increases the solar transmittance to promote the absorption and conversion of solar energy into heat by graphene nanosheets. As a result, compared to pure graphene film, CH3-SiO2 nanospheres covered graphene (SiO2-graphene) film presents a temperature increase of ∼6.3 °C with solar illumination of 1.0 kW/m2. After being combined with zwitterion-modified cotton fabric, a novel solar steam generation system mainly composed of SiO2-graphene film is prepared. Due to the hydrophobicity of CH3-SiO2 nanosphere and the hydration effect of zwitterionic polymer, the salt precipitation and oil fouling problems regarded as major challenges in solar desalination are simultaneously solved, thus achieving water evaporation rate near 1.40 kg/m2h at oily seawater environment. Most importantly, the solar transmittance enhancement and anti-reflection design inspired by cicada wings provide a valuable reference to promote the solar absorption capacity of other photo-thermal conversion materials.

Surface Modification of Titanium by Femtosecond Laser in Reducing Bacterial Colonization

In the past few decades, titanium and its alloys have been widely used in the orthopaedic field. However, because titanium is bioinert and lacks antibacterial properties, infection may happen when bacteria attach to implant surfaces and form biofilms. It has been studied that some naturally existing micron-scale topographies can reduce bacterial attachment such as cicada wings and gecko skins. The aim of this in vitro study was to find an implant with good biocompatibility and antimicrobial properties by the modification of micron-scale topographies. In this paper, a femtosecond laser was used to provide microtopography coatings on Ti substrates. The surface morphology of Ti substrates was observed by scanning electron microscopy (SEM). XPS was used to fulfil the chemical compositional analysis. The surface wettability was measured by contact angle measurement system. The effect of microtopography coatings with different surface microstructures on bacterial activities and bone marrow mesenchymal stem cells (BMSC) functions was investigated. The results of in vitro study revealed that microtopography coatings restrain the adhesion of Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis), which are common pathogens of orthopaedic implant infections. In addition, microtopography coatings stimulated BMSC adhesion and proliferation. Our studies suggest that a microtopography-coated sample modified by femtosecond laser showed promising antibacterial properties and favourable biocompatibility. The femtosecond laser technique provides an accurate and valid way to produce microtopography coatings with outstanding biocompatibility and antimicrobial properties, and could be widely used to modify the surface of orthopaedic metal implants with great potential.

Nature-Inspired Antimicrobial Surfaces and Their Potential Applications in Food Industries.

Antimicrobial resistance (AMR) is a growing global concern and has called for the integration of different areas of expertise for designing robust solutions. One such approach is the development of antimicrobial surfaces to combat the emerging resistance in microbes against drugs and disinfectants. This review is a compressive summary of the work done in the field of material science, chemistry, and microbiology in the development of antimicrobial materials and surfaces that are inspired by examples in nature. The focus includes examples of natural antimicrobial surfaces, such as cicada wings or nanopillars, dragonfly wings, shrimp shells, taro leaves, lotus leaves, sharkskin, gecko skin, and butterfly wings, along with their mechanism of action. Techniques, compositions, and combinations that have been developed to synthetically mimic these surfaces against bacterial/viral and fungal growth in food-processing areas have also been discussed. The applications of synthetic mimics of natural antimicrobial surfaces in food-processing environments is still a naïve area of research. However, this review highlights the potential applications of natural antimicrobial surfaces in the food-processing environment as well as outlines the challenges that need mitigations.

Surface-enhanced Raman scattering (SERS) from low-cost silver nanoparticle-decorated cicada wing substrates for rapid detection of difenoconazole in potato

Potato is one of the most important food crops worldwide in terms of human consumption. However, potato farmers employ a variety of pesticides to protect crops from harmful insects and illnesses, and difenoconazole is a commonly used one that has severe effects on human health and the environment. Therefore, detecting difenoconazole quickly and correctly is critical. In this work, we fabricated AgNPs/cicada wing substrates using natural cicada segments, decorated with silver nanoparticles for surface-enhanced Raman scattering (SERS) measurements to detect trace amounts of difenoconazole in potatoes. Results indicated that a linear relationship with the coefficient of detection (R2) of 0.987 and the detection limit (LOD) of 0.016 ppm was observed by targeting a distinctive peak at 808 cm−1 and logarithmic difenoconazole concentrations of 0.1 to 100 ppm. In addition, difenoconazole LODs in potatoes were 63 μg/kg, lower than those specified by the EU (0.1 mg/kg) and Vietnam (4 mg/kg) utilizing this new technique. Therefore, this proposed SERS method could be used to detect difenoconazole in potatoes at trace levels.

Bionic 3D periodic nanostructures by Ag nano-islands deposited on cicada wings for rapid SERS detection

Recently, flexible and wearable sensors are extensively developed in advanced coating materials, especially in label-free and culture-free rapid detection. Surface-enhanced Raman scattering (SERS) detection is the one of the “fingerprinting” and rapid sensing technology, which combined with noble metal nanoparticle arrays and Raman spectroscopy. The bionic 3D regular structures can induce the multiple reflection of the laser in 3D structures to increase SERS intensity. In this study, we used the natural organism wings (cicada wings, CW) as the substrate. Homogenous nano-columnar structures with the size of 69–72 nm were observed on the CW by scanning electron microscope. Ag nano-island arrays were further deposited on the CW by thermal evaporation. The interparticle spacing of the Ag nano-columnar would decrease with increasing the deposited thickness, which could produce a very strong 3D hot-spots effect for enhancing Raman signals. The results show that the optimal SERS signals were found at 100 nm deposited thickness of Ag nano-islands on the CW nanostructure. The limit of detection (LOD) is lower than 10−9 M and the related standard deviation (RSD%) is about 13.7%, showing the high sensitivity and reproducibility of SERS signal for small molecules detection. Particularly, SERS intensity of CW-Ag-100 nm would increase ~1.7 times while bending inner angle achieves 15o, displaying its flexible characterization.