Multifunctional biophotonic nanostructures inspired by the longtail glasswing butterfly for medical devices

Engineering multifunctional surface topography to regulate multiple biological responses

Surface topography or curvature plays a crucial role in regulating cell behavior, influencing processes such as adhesion, proliferation, and gene expression. Recent advancements in nano- and micro-fabrication techniques have enabled the development of biomimetic systems that mimic native extracellular matrix (ECM) structures, providing new insights into cell-adhesion mechanisms, mechanotransduction, and cell-environment interactions. This review examines the diverse applications of engineered topographies across multiple domains, including antibacterial surfaces, immunomodulatory devices, tissue engineering scaffolds, and cancer therapies. It highlights how nanoscale features like nanopillars and nanospikes exhibit bactericidal properties, while many microscale patterns can direct stem cell differentiation and modulate immune cell responses. Furthermore, we discuss the interdisciplinary use of topography for combined applications, such as the simultaneous regulation of immune and tissue cells in 2D and 3D environments. Despite significant advances, key knowledge gaps remain, particularly regarding the effects of topographical cues on multicellular interactions and dynamic 3D contexts. This review summarizes current fabrication methods, explores specific and interdisciplinary applications, and proposes future research directions to enhance the design and utility of topographically patterned biomaterials in clinical and experimental settings.

Enabling Fast AI-Driven Inverse Design of a Multifunctional Nanosurface by Parallel Evolution Strategies

Multifunctional nanosurfaces receive growing attention due to their versatile properties. Capillary force lithography (CFL) has emerged as a simple and economical method for fabricating these surfaces. In recent works, the authors proposed to leverage the evolution strategies (ES) to modify nanosurface characteristics with CFL to achieve specific functionalities such as frictional, optical, and bactericidal properties. For artificial intelligence (AI)-driven inverse design, earlier research integrates basic multiphysics principles such as dynamic viscosity, air diffusivity, surface tension, and electric potential with backward deep learning (DL) on the framework of ES. As a successful alternative to reinforcement learning, ES performed well for the AI-driven inverse design. However, the computational limitations of ES pose a critical technical challenge to achieving fast and efficient design. This paper addresses the challenges by proposing a parallel-computing-based ES (named parallel ES). The parallel ES demonstrated the desired speed and scalability, accelerating the AI-driven inverse design of multifunctional nanopatterned surfaces. Detailed parallel ES algorithms and cost models are presented, showing its potential as a promising tool for advancing AI-driven nanomanufacturing.

Laser-Induced Graphene-Based Sensors in Health Monitoring: Progress, Sensing Mechanisms, and Applications

The rising global population and improved living standards have led to an alarming increase in non-communicable diseases, notably cardiovascular and chronic respiratory diseases, posing a severe threat to human health. Wearable sensing devices, utilizing micro-sensing technology for real-time monitoring, have emerged as promising tools for disease prevention. Among various sensing platforms, graphene-based sensors have shown exceptional performance in the field of micro-sensing. Laser-induced graphene (LIG) technology, a cost-effective and facile method for graphene preparation, has gained particular attention. By converting polymer films directly into patterned graphene materials at ambient temperature and pressure, LIG offers a convenient and environmentally friendly alternative to traditional methods, opening up innovative possibilities for electronic device fabrication. Integrating LIG-based sensors into health monitoring systems holds the potential to revolutionize health management. To commemorate the tenth anniversary of the discovery of LIG, this work provides a comprehensive overview of LIG's evolution and the progress of LIG-based sensors. Delving into the diverse sensing mechanisms of LIG-based sensors, recent research advances in the domain of health monitoring are explored. Furthermore, the opportunities and challenges associated with LIG-based sensors in health monitoring are briefly discussed.

Colorimetric sensing for translational applications: from colorants to mechanisms

Colorimetric sensing offers instant reporting via visible signals. Versus labor-intensive and instrument-dependent detection methods, colorimetric sensors present advantages including short acquisition time, high throughput screening, low cost, portability, and a user-friendly approach. These advantages have driven substantial growth in colorimetric sensors, particularly in point-of-care (POC) diagnostics. Rapid progress in nanotechnology, materials science, microfluidics technology, biomarker discovery, digital technology, and signal pattern analysis has led to a variety of colorimetric reagents and detection mechanisms, which are fundamental to advance colorimetric sensing applications. This review first summarizes the basic components (e.g., color reagents, recognition interactions, and sampling procedures) in the design of a colorimetric sensing system. It then presents the rationale design and typical examples of POC devices, e.g., lateral flow devices, microfluidic paper-based analytical devices, and wearable sensing devices. Two highlighted colorimetric formats are discussed: combinational and activatable systems based on the sensor-array and lock-and-key mechanisms, respectively. Case discussions in colorimetric assays are organized by the analyte identities. Finally, the review presents challenges and perspectives for the design and development of colorimetric detection schemes as well as applications. The goal of this review is to provide a foundational resource for developing colorimetric systems and underscoring the colorants and mechanisms that facilitate the continuing evolution of POC sensors.

Implantable Flexible Sensors for Health Monitoring

Flexible sensors, as a significant component of flexible electronics, have attracted great interest the realms of human-computer interaction and health monitoring due to their high conformability, adjustable sensitivity, and excellent durability. In comparison to wearable sensor-based in vitro health monitoring, the use of implantable flexible sensors (IFSs) for in vivo health monitoring offers more accurate and reliable vital sign information due to their ability to adapt and directly integrate with human tissue. IFSs show tremendous promise in the field of health monitoring, with unique advantages such as robust signal reading capabilities, lightweight design, flexibility, and biocompatibility. Herein, a review of IFSs for vital signs monitoring is detailly provided, highlighting the essential conditions for in vivo applications. As the prerequisites of IFSs, the stretchability and wireless self-powered properties of the sensor are discussed, with a special attention paid to the sensing materials which can maintain prominent biosafety (i.e., biocompatibility, biodegradability, bioresorbability). Furthermore, the applications of IFSs monitoring various parts of the body are described in detail, with a summary in brain monitoring, eye monitoring, and blood monitoring. Finally, the challenges as well as opportunities in the development of next-generation IFSs are presented.

Leafhopper-inspired reversibly switchable antireflection coating with sugar apple-like structure arrays

Optical coatings with reversibly tunable antireflective characteristics hold a tremendous potential for next generation optical energy-related applications. Bioinpsired by the camouflage behavior of small yellow leafhoppers, silica hollow sphere/shape memory polymer composites are self-assembled using a non-lithography-based approach. The average visible transmittance of the as-patterned hierarchical structure array-covered substrate is increased by ca. 6.3% at normal incident, and even improved by more than 20% for an incident angle of 75°. Interestingly, the broadband omnidirectional antireflection performance can be reversibly erased and recovered by applying external stimuli under ambient conditions. To gain a better understanding, its reversibility, mechanical robustness, and the structure-shape effect on the antireflective properties are systematically investigated in this research.

Current Innovations in Intraocular Pressure Monitoring Biosensors for Diagnosis and Treatment of Glaucoma-Novel Strategies and Future Perspectives

Biosensors are devices that quantify biologically significant information required for diverse applications, such as disease diagnosis, food safety, drug discovery and detection of environmental pollutants. Recent advancements in microfluidics, nanotechnology and electronics have led to the development of novel implantable and wearable biosensors for the expedient monitoring of diseases such as diabetes, glaucoma and cancer. Glaucoma is an ocular disease which ranks as the second leading cause for loss of vision. It is characterized by the increase in intraocular pressure (IOP) in human eyes, which results in irreversible blindness. Currently, the reduction of IOP is the only treatment used to manage glaucoma. However, the success rate of medicines used to treat glaucoma is quite minimal due to their curbed bioavailability and reduced therapeutic efficacy. The drugs must pass through various barriers to reach the intraocular space, which in turn serves as a major challenge in glaucoma treatment. Rapid progress has been observed in nano-drug delivery systems for the early diagnosis and prompt therapy of ocular diseases. This review gives a deep insight into the current advancements in the field of nanotechnology for detecting and treating glaucoma, as well as for the continuous monitoring of IOP. Various nanotechnology-based achievements, such as nanoparticle/nanofiber-based contact lenses and biosensors that can efficiently monitor IOP for the efficient detection of glaucoma, are also discussed.

Multi-scale dissection of wing transparency in the clearwing butterfly Phanus vitreus

Optical transparency is rare in terrestrial organisms, and often originates through loss of pigmentation and reduction in scattering. The coloured wings of some butterflies and moths have repeatedly evolved transparency, offering examples of how they function optically and biologically. Because pigments are primarily localized in the scales that cover a colourless wing membrane, transparency has often evolved through the complete loss of scales or radical modification of their shape. Whereas bristle-like scales have been well documented in glasswing butterflies, other scale modifications resulting in transparency remain understudied. The butterfly Phanus vitreus achieves transparency while retaining its scales and exhibiting blue/cyan transparent zones. Here, we investigate the mechanism of wing transparency in P. vitreus by light microscopy, focused ion beam milling, microspectrophotometry and optical modelling. We show that transparency is achieved via loss of pigments and vertical orientation in normal paddle-like scales. These alterations are combined with an anti-reflective nipple array on portions of the wing membrane being more exposed to light. The blueish coloration of the P. vitreus transparent regions is due to the properties of the wing membrane, and local scale nanostructures. We show that scale retention in the transparent patches might be explained by these perpendicular scales having hydrophobic properties.

Glasswing-Butterfly-Inspired Multifunctional Scleral Lens and Smartphone Raman Spectrometer for Point-of-Care Tear Biomarker Analysis

Augmenting contact lenses with sensing capabilities requires incorporating multiple functionalities within a diminutive device. Inspired by multifunctional biophotonic nanostructures of glasswing butterflies, a nanostructured scleral lens with enhanced optical, bactericidal, and sensing capabilities is reported. When used in conjunction with a smartphone-integrated Raman spectrometer, the feasibility of point-of-care applications is demonstrated. The bioinspired nanostructures made on parylene films are mounted on the anterior and posterior side of a scleral lens to create a nanostructured lens. Compared to unstructured parylene, nanostructured parylene minimizes glare by 4.3-fold at large viewing angles up to 80^o . When mounted on a scleral lens, the nanostructures block 2.8-fold more ultraviolet (UVA) light while offering 1.1-fold improved transmission in the visible regime. Furthermore, the nanostructures exhibit potent bactericidal activity against Escherichia coli, killing 89% of tested bacteria within 4 h. The same nanostructures, when gold-coated, are used to perform rapid label-free multiplex detection of lysozyme and lactoferrin, the protein biomarkers of the chronic dry eye disease, in whole human tears using drop-coating deposition Raman spectroscopy. The detection of both proteins in whole human tear samples from different subjects using the nanostructured lens produced excellent correlation with commercial enzyme-based assays while simultaneously displaying a 1.5-fold lower standard deviation.

Ultrasensitive, Fast-Responsive, Directional Airflow Sensing by Bioinspired Suspended Graphene Fibers

The development of high-performance miniaturized and flexible airflow sensors is essential to meet the need of emerging applications. Graphene-based airflow sensors are hampered by the sluggish response and recovery speed and low sensitivity. Here we employ laser-induced graphene (LIG) with poststructural biomimicry for fabricating high-performance, flexible airflow sensors, including cotton-like porous LIG, caterpillar fluff-like vertical LIG fiber, and Lepidoptera scale-like suspended LIG fiber (SLIGF) structures. The structural engineering changes the deformation behavior of LIGs under stress, among which the synchronous propagation of the scale-like structure of SLIGF is the most conducive to airflow sensing. The SLIGF achieves the shortest average response time of 0.5 s, the highest sensitivity of 0.11 s/m, and a record-low detection threshold of 0.0023 m/s, benchmarked against the state-of-the-art airflow sensors. Furthermore, we showcase the SLIGF airflow sensors in weather forecasting, health, and communications applications. Our study will help develop next-generation waterflow, sound, and motion sensors.

Spontaneous phase separation of ternary fluid mixtures

We computationally study the spontaneous phase separation of ternary fluid mixtures using the lattice Boltzmann method both when all the surface tensions are equal and when they have different values. To rationalise the phase diagram of possible phase separation mechanisms, previous theoretical works typically rely on analysing the sign of the eigenvalues resulting from a simple linear stability analysis, but we find this does not explain the observed simulation results. Here, we classify the possible separation pathways into four basic mechanisms, and develop a phenomenological model that captures the composition regimes where each mechanism is prevalent. We further highlight that the dominant mechanism in ternary phase separation involves enrichment and instability of the minor component at the fluid-fluid interface, which is absent in the case of binary fluid mixtures.

Recent Advances of Intraocular Lens Materials and Surface Modification in Cataract Surgery

Advances in cataract surgery have increased the demand for intraocular lens (IOL) materials. At present, the progress of IOL materials mainly contains further improving biocompatibility, providing better visual quality and adjustable ability, reducing surgical incision, as well as dealing with complications such as posterior capsular opacification (PCO) and ophthalmitis. The purpose of this review is to describe the research progress of relevant IOL materials classified according to different clinical purposes. The innovation of IOL materials is often based on the common IOL materials on the market, such as silicon and acrylate. Special properties and functions are obtained by adding extra polymers or surface modification. Most of these studies have not yet been commercialized, which requires a large number of clinical trials. But they provide valuable thoughts for the optimization of the IOL function.

Single-Step Fabrication of Longtail Glasswing Butterfly-Inspired Omnidirectional Antireflective Structures

Most bio-inspired antireflective nanostructures are extremely vulnerable and suffer from complicated lithography-based fabrication procedures. To address the issues, we report a scalable and simple non-lithography-based approach to engineer robust antireflective structures, inspired by the longtail glasswing butterfly, in a single step. The resulting two-dimensional randomly arranged 80/130/180 nm silica colloids, partially embedded in a polymeric matrix, generate a gradual refractive index transition at the air/substrate interface to suppress light reflection. Importantly, the randomly arranged subwavelength silica colloids display even better antireflection performance for large incident angles than that of two-dimensional non-close-packed silica colloidal crystals. The biomimetic coating is of considerable technological importance in numerous practical applications.

Aligned CuO nanowire array for a high performance visible light photodetector

Recently, copper oxide (CuO) has drawn much attention as a promising material in visible light photodetection with its advantages in ease of nanofabrication. CuO allows a variety of nanostructures to be explored to enhance the optoelectrical performance such as photogenerated carriers scattering and bandgap engineering. However, previous researches neglect in-depth analysis of CuO’s light interaction effects, restrictively using random orientation such as randomly arranged nanowires, single nanowires, and dispersed nanoparticles. Here, we demonstrate an ultra-high performance CuO visible light photodetector utilizing perfectly-aligned nanowire array structures. CuO nanowires with 300 nm-width critical dimension suppressed carrier transport in the dark state and enhanced the conversion of photons to carriers; additionally, the aligned arrangement of the nanowires with designed geometry improved the light absorption by means of the constructive interference effect. The proposed nanostructures provide advantages in terms of dark current, photocurrent, and response time, showing unprecedentedly high (state-of-the-art) optoelectronic performance, including high values of sensitivity (S = 172.21%), photo-responsivity (R = 16.03 A/W, λ = 535 nm), photo-detectivity (D^* = 7.78 × 10¹¹ Jones), rise/decay time (τ_r/τ_d = 0.31 s/1.21 s).

Zinc-coordinated polydopamine surface with a nanostructure and superhydrophilicity for antibiofouling and antibacterial applications

A superhydrophilic nanostructured surface of zinc-coordinated polydopamine is formed by the growth and intertwining of the PDA/Zn nanowires via Zn–N and Zn–O bonds, which has potential for preventing biomaterial-associated biofouling and infections.

In vivo visualization of butterfly scale cell morphogenesis in Vanessa cardui

Many organisms exhibit functional micro- and nanoscale materials with structural definition and performance that challenge synthetic fabrication techniques, yet we know little about the processes that enable their formation. Using butterfly scales as a model system for functional biomaterials, we establish a timeline of scale formation and quantify relevant structural parameters for developing painted lady butterflies. We overcome challenges of previous efforts by imaging structure formation directly in living organisms, which allows us to continuously observe the evolving wing tissue and the fine details of individual scale cells. Visualization of scale structure formation in live butterflies forms the basis for modeling the underlying biomechanical processes and opens avenues for their translation into advanced fabrication strategies.

During metamorphosis, the wings of a butterfly sprout hundreds of thousands of scales with intricate microstructures and nano-structures that determine the wings’ optical appearance, wetting characteristics, thermodynamic properties, and aerodynamic behavior. Although the functional characteristics of scales are well known and prove desirable in various applications, the dynamic processes and temporal coordination required to sculpt the scales’ many structural features remain poorly understood. Current knowledge of scale growth is primarily gained from ex vivo studies of fixed scale cells at discrete time points; to fully understand scale formation, it is critical to characterize the time-dependent morphological changes throughout their development. Here, we report the continuous, in vivo, label-free imaging of growing scale cells of Vanessa cardui using speckle-correlation reflection phase microscopy. By capturing time-resolved volumetric tissue data together with nanoscale surface height information, we establish a morphological timeline of wing scale formation and gain quantitative insights into the underlying processes involved in scale cell patterning and growth. We identify early differences in the patterning of cover and ground scales on the young wing and quantify geometrical parameters of growing scale features, which suggest that surface growth is critical to structure formation. Our quantitative, time-resolved in vivo imaging of butterfly scale development provides the foundation for decoding the processes and biomechanical principles involved in the formation of functional structures in biological materials.

Practicable Applications of Aggregation-Induced Emission with Biomedical Perspective

Considerable efforts have been made into developing aggregation-induced emission fluorogens (AIEgens)-containing nano-therapeutic systems due to the excellent properties of AIEgens. Compared to other fluorescent molecules, AIEgens have advantages including low background, high signal-to-noise ratio, good sensitivity, and resistance to photobleaching, in addition to being exempt from concentration quenching or aggregation-caused quenching effects. The present review outlines the major developments in the biomedical applications of AIEgens-containing systems. From a literature survey, the recent AIE works are reviewed and the reasons why AIEgens are chosen in various biomedical applications are highlighted. The research activities on AIEgens-containing systems are increasing rapidly, therefore, the present review is timely.

Antimicrobial properties of nanostructured surfaces - demonstrating the need for a standard testing methodology

Bioinspired nanostructured materials that exhibit antimicrobial properties are being synthesized and tested at increasing rates for use in healthcare, manufacturing processes, and diagnostics. Although progress has been made in improving and understanding their bactericidal activity, arguably, the biggest problem currently in the field is the lack of a standard testing methodology that allows for optimal characterization and better comparison of emerging nanostructures. Here, we examine two forms of nanostructured silicon that vary in their ability to kill certain bacterial species due to different physical mechanisms and derive guidelines for the comparative testing. We perform a comprehensive evaluation of methodologies used extensively in the field (e.g., colony counting and live dead analysis) and the novel application of high-throughput flow cytometry. The data reveal how the techniques are complementary but not always directly equivalent or correlative. Therefore, comparison of results obtained using different methodologies on different materials can be grossly misleading. We report significant variations in bactericidal efficiencies depending on experimental environments (medium type, etc.) and methodologies employed. In addition, we demonstrate how cytometry is yet another powerful complementary tool that can aid the mechanistic understanding of antimicrobial activities of rough surfaces. Besides standardization for comparison, ultimately, evaluation methods need to consider anticipated applications. Then and only then can the true potential (or limitation) of a novel material be determined for its suitability for advancement in a particular field of use.

Bioinspired Multifunctional Glass Surfaces through Regenerative Secondary Mask Lithography

Nature-inspired nanopatterning offers exciting multifunctionality spanning antireflectance and the ability to repel water/fog, oils, and bacteria; strongly dependent upon nanofeature size and morphology. However, such patterning in glass is notoriously difficult, paradoxically, due to the same outstanding chemical and thermal stability that make glass so attractive. Here, regenerative secondary mask lithography is introduced and exploited to enable customized glass nanopillars through dynamic nanoscale tunability of the side-wall profile and aspect ratio (>7). The method is simple and versatile, comprising just two steps. First, sub-wavelength scalable soft etch masks (55-350 nm) are generated through an example of block copolymer micelles or nanoimprinted photoresist. Second, their inherent durability problem is addressed by an innovative cyclic etching, when the original mask becomes embedded within a protective secondary organic mask, which is tuned and regenerated, permitting dynamic nanofeature profiling with etching selectivity >1:32. It is envisioned that such structuring in glass will facilitate fundamental studies and be useful for numerous practical applications-from displays to architectural windows. To showcase the potential, glass features are tailored to achieve excellent broadband omnidirectional antireflectivity, self-cleaning, and unique antibacterial activity toward Staphylococcus aureus.

Surface Design for Antibacterial Materials: From Fundamentals to Advanced Strategies

Healthcare-acquired infections as well as increasing antimicrobial resistance have become an urgent global challenge, thus smart alternative solutions are needed to tackle bacterial infections. Antibacterial materials in biomedical applications and hospital hygiene have attracted great interest, in particular, the emergence of surface design strategies offer an effective alternative to antibiotics, thereby preventing the possible development of bacterial resistance. In this review, recent progress on advanced surface modifications to prevent bacterial infections are addressed comprehensively, starting with the key factors against bacterial adhesion, followed by varying strategies that can inhibit biofilm formation effectively. Furthermore, "super antibacterial systems" through pre-treatment defense and targeted bactericidal system, are proposed with increasing evidence of clinical potential. Finally, the advantages and future challenges of surface strategies to resist healthcare-associated infections are discussed, with promising prospects of developing novel antimicrobial materials.

Developmental, cellular and biochemical basis of transparency in clearwing butterflies

The wings of butterflies and moths (Lepidoptera) are typically covered with thousands of flat, overlapping scales that endow the wings with colorful patterns. Yet, numerous species of Lepidoptera have evolved highly transparent wings, which often possess scales of altered morphology and reduced size, and the presence of membrane surface nanostructures that dramatically reduce reflection. Optical properties and anti-reflective nanostructures have been characterized for several ‘clearwing’ Lepidoptera, but the developmental processes underlying wing transparency are unknown. Here, we applied confocal and electron microscopy to create a developmental time series in the glasswing butterfly, Greta oto, comparing transparent and non-transparent wing regions. We found that during early wing development, scale precursor cell density was reduced in transparent regions, and cytoskeletal organization during scale growth differed between thin, bristle-like scale morphologies within transparent regions and flat, round scale morphologies within opaque regions. We also show that nanostructures on the wing membrane surface are composed of two layers: a lower layer of regularly arranged nipple-like nanostructures, and an upper layer of irregularly arranged wax-based nanopillars composed predominantly of long-chain n-alkanes. By chemically removing wax-based nanopillars, along with optical spectroscopy and analytical simulations, we demonstrate their role in generating anti-reflective properties. These findings provide insight into morphogenesis and composition of naturally organized microstructures and nanostructures, and may provide bioinspiration for new anti-reflective materials.

Summary: Transparency is a fascinating, yet poorly studied, optical property in living organisms. We elucidated the developmental processes underlying scale and nanostructure formation in glasswing butterflies, and their roles in generating anti-reflective properties.

Broader-Band and Flexible Antireflective Films with the Window-like Structures Inspired by the Backside of Butterfly Wing Scales

Antireflective performance is critical for most optical devices, such as the efficient solar energy utilization in photovoltaic cells of an aerospace craft and optical displays of scientific precise equipment. Therein, outstanding broad-band antireflection is one of the most crucial properties for antireflection films (ARFs). Unfortunately, it is still a challenging work to realize perfect "broader-band" antireflection because both the low refractive indices materials and time-consuming nanotexturing technologies are required in the fabricating process. Even in this case, a broader-band and flexible ARF with hierarchical structures is successfully developed, which is inspired by butterfly wing scales. First, the butterfly wings surface is treated with acid and stuck on a clean glass. Now, all the scales on the wings will form a strong adhesion with the glass substrate. Then, the wings are removed and the scales are left on the glass slide. Now the backside of scales is facing outward, the backside structures of the scales are coincidentally used as the template. Finally, the structure is replicated and the ARF with a controllable thickness is successfully fabricated by rotating PDMS on the biological template. In this work, the bionic ARFs realize the transmission of nearly 90% and more than 90% in the visible light and infrared region. It enhanced transmission to 13% under standard illumination compared with flat PDMS films of the same thickness. Furthermore, the ARF is flexible enough that it could bend nearly 180° to meet the special antireflection requirements in some extreme conditions. It is expected that this bioinspired AR film could revolutionize the technologies of broader-band antireflective materials and impact numerous applications from glass displays to optoelectronic devices.

Phase-Separated Nanophotonic Structures by Inkjet Printing

The spontaneous phase separation of two or more polymers is a thermodynamic process that can take place in both biological and synthetic materials and which results in the structuring of the matter from the micro- to the nanoscale. For photonic applications, it allows forming quasi-periodic or disordered assemblies of light scatterers at high throughput and low cost. The wet process methods currently used to fabricate phase-separated nanostructures (PSNs) limit the design possibilities, which in turn hinders the deployment of PSNs in commercialized products. To tackle this shortcoming, we introduce a versatile and industrially scalable deposition method based on the inkjet printing of a polymer blend, leading to PSNs with a feature size that is tuned from a few micrometers down to sub-100 nm. Consequently, PSNs can be rapidly processed into the desired macroscopic design. We demonstrate that these printed PSNs can improve light management in manifold photonic applications, exemplified here by exploiting them as a light extraction layer and a metasurface for light-emitting devices and point-of-care biosensors, respectively.

Butterfly wing architectures inspire sensor and energy applications

Natural biological systems are constantly developing efficient mechanisms to counter adverse effects of increasing human population and depleting energy resources. Their intelligent mechanisms are characterized by the ability to detect changes in the environment, store and evaluate information, and respond to external stimuli. Bio-inspired replication into man-made functional materials guarantees enhancement of characteristics and performance. Specifically, butterfly architectures have inspired the fabrication of sensor and energy materials by replicating their unique micro/nanostructures, light-trapping mechanisms and selective responses to external stimuli. These bio-inspired sensor and energy materials have shown improved performance in harnessing renewable energy, environmental remediation and health monitoring. Therefore, this review highlights recent progress reported on the classification of butterfly wing scale architectures and explores several bio-inspired sensor and energy applications.

Construction of Bi/Bi5O7I anchored on a polymer with boosted interfacial charge transfer for biofouling resistance and photocatalytic H2 evolution

The prepared coatings possess hydrogen production, antifouling performance, self-cleaning properties, this strategy can be a promising candidate to restrict biofouling and photocatalytic hydrogen production for marine coating applications.

Synergistic Antimicrobial Activity of a Nanopillar Surface on a Chitosan Hydrogel

Despite ongoing efforts and technology development, the contamination of medical device surfaces by disease-causing microbes remains problematic. Two approaches to producing antimicrobial surfaces are using antimicrobial materials and applying physical topography such as nanopatterns. In this work, we describe the use of physical topography on a soft hydrogel to control microbial growth. We demonstrate this approach by using chitosan hydrogel films with nanopillars having periodicities ranging from 300 to 500 nm. The flat hydrophilic chitosan films exhibit antimicrobial activity against the pathogenic bacteria Pseudomonas aeruginosa and filamentous fungi Fusarium oxysporum. The addition of nanopillars to the hydrogel surface further reduces the growth of P. aeruginosa and F. oxysporum up to ∼52 and ∼99%, respectively. Multiple modes of antimicrobial action appear to act synergistically to inhibit microbial growth on the nanopillar hydrogels. We verified that the strongly bactericidal and fungicidal nanopillared material retains biocompatibility to human epithelial cells with the MTT assay. The nanopillared material is a promising candidate for applications that require a biocompatible and antimicrobial film. The study demonstrates that taking advantage of multiple modes of antimicrobial action can effectively inhibit pathogenic microbial growth.

From Octahedron Crystals to 2D Silicon Nanosheets: Facet-Selective Cleavage and Biophotonic Applications

2D silicon nanosheets (SiNSs) are promising materials for biomedicine but facile synthesis of SiNSs remains a challenge. Herein, by means of a sulfur-iodine co-assisted chemical vapor transport method, octahedron silicon (oct-Si) crystals with fully exposed {111} planes are prepared as precursors for efficient synthesis of SiNSs by facet-selective exfoliation. The 13 nm thick SiNSs have good biocompatibility and the sharp Raman scattering signal facilitates intracellular Raman imaging upon exposure to a near-infrared (NIR) laser. Furthermore, the SiNSs have excellent NIR photothermal characteristics such as a large extinction coefficient of 11.3 L g^-1 cm^-1 and high photothermal conversion efficiency of 21.4% at 1064 nm. In vitro experiments demonstrate superior NIR-II photothermal therapeutic effects in killing cancer cells. Comparing to conventional methods, the novel facet-selective cleavage strategy is more controllable and environmentally friendly boding well for the fabrication of non-van der Waals 2D materials. The multimodal photonic behavior also suggests large potential of the SiNSs pertaining to integrated multi-NIR biophotonic techniques using single nanomaterials.

Implantable self-aligning fiber-optic optomechanical devices for in vivo intraocular pressure-sensing in artificial cornea

Artificial cornea is an effective treatment of corneal blindness. Yet, intraocular pressure (IOP) measurements for glaucoma monitoring remain an urgent unmet need. Here, we present the integration of a fiber-optic Fabry-Perot pressure sensor with an FDA-approved keratoprosthesis for real-time IOP measurements using a novel strategy based on optical-path self-alignment with micromagnets. Additionally, an alternative noncontact sensor-interrogation approach is demonstrated using a bench-top optical coherence tomography system. We show stable pressure readings with low baseline drift (<2.8 mm Hg) for >4.5 years in vitro and efficacy in IOP interrogation in vivo using fiber-optic self-alignment, with good initial agreement with the actual IOP. Subsequently, IOP drift in vivo was due to retroprosthetic membrane (RPM) formation on the sensor secondary to surgical inflammation (more severe in the current pro-fibrotic rabbit model). This study paves the way for clinical adaptation of optical pressure sensors with ocular implants, highlighting the importance of controlling RPM in clinical adaptation.

Bioinspired Disordered Flexible Metasurfaces for Human Tear Analysis Using Broadband Surface-Enhanced Raman Scattering

Flexible surface-enhanced Raman scattering (SERS) has received attention as a means to move SERS-based broadband biosensing from bench to bedside. However, traditional flexible periodic nano-arrangements with sharp plasmonic resonances or their random counterparts with spatially varying uncontrollable enhancements are not reliable for practical broadband biosensing. Here, we report bioinspired quasi-(dis)ordered nanostructures presenting a broadband yet tunable application-specific SERS enhancement profile. Using simple, scalable biomimetic fabrication, we create a flexible metasurface (flex-MS) of quasi-(dis)ordered metal-insulator-metal (MIM) nanostructures with spectrally variable, yet spatially controlled electromagnetic hotspots. The MIM is designed to simultaneously localize the electromagnetic signal and block background Raman signals from the underlying polymeric substrate-an inherent problem of flexible SERS. We elucidate the effect of quasi-(dis)ordering on broadband tunable SERS enhancement and employ the flex-MS in a practical broadband SERS demonstration to detect human tear uric acid within its physiological concentration range (25-150 μM). The performance of the flex-MS toward noninvasively detecting whole human tear uric acid levels ex vivo is in good agreement with a commercial enzyme-based assay.

Robust Biomimetic Hierarchical Diamond Architecture with a Self-Cleaning, Antibacterial, and Antibiofouling Surface

Biofouling is a worldwide problem from healthcare to marine exploration. Aggressive biofouling, wear, and corrosion lead to severe deterioration in function and durability. Here, micro- and nanostructured hierarchical diamond films mimicking the morphology of plant leaves were developed to simultaneously achieve superhydrophobicity, antibacterial efficacy, and marine antibiofouling, combined with mechanical and chemical robustness. These coatings were designed and successfully constructed on various commercial substrates, such as titanium alloys, silicon, and quartz glass via a chemical vapor deposition process. The unique surface structure of diamond films reduced bacteria attachment by 90-99%. In the marine environment, these biomimetic diamond films significantly reduced more than 95% adhesion of green algae. The structured diamond films retained mechanical robustness, superhydrophobicity, and antibacterial efficacy under high abrasion and corrosive conditions, exhibiting at least 20 times enhanced wear resistance than the bare commercial substrates even after long-term immersion in seawater.

Grayscale Nanopixel Printing at Sub-10-nanometer Vertical Resolution via Light-Controlled Nanocapillarity

Nanotextures play increasingly important roles in nanotechnology. Recent studies revealed that their functionalities can be further enhanced by spatially modulating the height of their nanoscale pixels. Realizing the concept, however, is very challenging as it requires "grayscale" printing of the nanopixels in which their height is controlled within a few nanometers as a micrometric function of position. This work demonstrates such a high vertical and lateral resolution grayscale printing of polymeric nanopixels. We realize the height modulation by exploiting the discovery that the capillary rise of certain photopolymers can be optically controlled to stop at a predetermined height with sub-10-nm accuracy. Microscale spatial patterning of the control light directly extends the height modulation into a two-dimensionally patterned, grayscale nanopixel printing. Its utility is verified through readily reconfigurable, maskless printing of grayscale nanopixel arrays in dielectric and metallo-dielectric forms. This work also reveals the highly nonlinear and unstable nature of the polymeric nanocapillary effect, expanding its understanding and application scope.

Highly Transparent and Sensitive Graphene Sensors for Continuous and Non-invasive Intraocular Pressure Monitoring

Intraocular pressure (IOP) is the prime indicator for the diagnosis and treatment of glaucoma. IOP has circadian rhythm changes and is dependent on body gestures; therefore, a single measurement in the clinic can be misleading for diagnosis. Herein, few-layer graphene is utilized to develop non-invasive sensors with high transparency, sensitivity, linearity, and biocompatibility for 24 h continuous IOP monitoring. The graphene Wheatstone bridge consisting of two strain gauges and two compensating resistors is designed to improve the sensitivity and accuracy of IOP measurement. Testing results on a silicone eyeball indicate that the output voltage of the sensor is proportional to the IOP fluctuation. Under the various ranges and speeds of IOP fluctuation, the sensor exhibits excellent performance of dynamic cycles and step responses with an average sensitivity of 150 μV/mmHg. With the linear relationship, the average relative error between the calibrated IOP and the standard pressure is maintained at about 5%. More than 100 cycles and interval time measurements illustrate that the sensor possesses significant stability, durability, and reliability. Furthermore, a wireless system is designed for the sensor to realize IOP monitoring using a mobile phone. This sensor, with the average transparency of 85% and its ease of fabrication, as well as its portability for continuous IOP monitoring, brings new promise to the diagnosis and treatment of glaucoma.

Bactericidal Characteristics of Bioinspired Nontoxic and Chemically Stable Disordered Silicon Nanopyramids

Controlling bacterial growth using artificial nanostructures inspired from natural species is of immense importance in biomedical applications. In the present work, a low cost, fast processing, and scalable anisotropic wet etching technique is developed to fabricate the densely packed disordered silicon nanopyramids (SiNPs) with nanosized sharp tips. The bactericidal characteristics of SiNPs are assessed against strains implicated in nosocomial and biomaterial-related infections. Compared to the bare silicon with no antibacterial activities, SiNPs of 1.85 ± 0.28 μm height show 55 and 75% inhibition of Escherichia coli (Gram-negative) and Bacillus subtilis (Gram-positive) bacteria, whereas the silicon nanowires (SiNWs) fabricated using a metal-assisted chemical etching method show 50 and 58% inhibition of E. coli and B. subtilis. The mechanistic studies using a scanning electron microscope and live/dead bacterial cell assay reveal cell rupture and predominance of dead cells on contact with SiNPs and SiNWs, which confirms their bactericidal effects. Chemical stability and cell viability studies demonstrate the biocompatible nature of SiNP and SiNW surfaces. Owing to their capability to kill both Gram-negative and positive bacteria and minimal toxicity to murine fibroblast cells, SiNPs can be used as an antibacterial coating on medical devices to prevent nosocomial and biomaterial-related infections.

Scalable Fabrication of Quasi-One-Dimensional Gold Nanoribbons for Plasmonic Sensing

Plasmonic nanostructures have a wide range of applications, including chemical and biological sensing. However, the development of techniques to fabricate submicrometer-sized plasmonic structures over large scales remains challenging. We demonstrate a high-throughput, cost-effective approach to fabricate Au nanoribbons via chemical lift-off lithography (CLL). Commercial HD-DVDs were used as large-area templates for CLL. Transparent glass slides were coated with Au/Ti films and functionalized with self-assembled alkanethiolate monolayers. Monolayers were patterned with lines via CLL. The lifted-off, exposed regions of underlying Au were selectively etched into large-area grating-like patterns (200 nm line width; 400 nm pitch; 60 nm height). After removal of the remaining monolayers, a thin In2O3 layer was deposited and the resulting gratings were used as plasmonic sensors. Distinct features in the extinction spectra varied in their responses to refractive index changes in the solution environment with a maximum bulk sensitivity of ∼510 nm/refractive index unit. Sensitivity to local refractive index changes in the near-field was also achieved, as evidenced by real-time tracking of lipid vesicle or protein adsorption. These findings show how CLL provides a simple and economical means to pattern large-area plasmonic nanostructures for applications in optoelectronics and sensing.

Thermal-Disrupting Interface Mitigates Intercellular Cohesion Loss for Accurate Topical Antibacterial Therapy

Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug-resistant pathogens. Although several strategies such as photothermal therapy and magneto-thermal therapy can suppress bacterial infections, excessive heat often damages host cells and lengthens the healing time. Here, a localized thermal managing strategy, thermal-disrupting interface induced mitigation (TRIM), is reported, to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat-responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimizes the risk of skin damage during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface features plays a critical role in maintaining intercellular cohesion of the epidermis during photothermal therapy. Finally, endowing wound dressing with the TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effects of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy.

Aluminum Metasurface with Hybrid Multipolar Plasmons for 1000-Fold Broadband Visible Fluorescence Enhancement and Multiplexed Biosensing

Aluminum (Al)-based nanoantennae traditionally suffer from weak plasmonic performance in the visible range, necessitating the application of more expensive noble metal substrates for rapidly expanding biosensing opportunities. We introduce a metasurface comprising Al nanoantennae of nanodisks-in-cavities that generate hybrid multipolar lossless plasmonic modes to strongly enhance local electromagnetic fields and increase the coupled emitter's local density of states throughout the visible regime. This results in highly efficient electromagnetic field confinement in visible wavelengths by these nanoantennae, favoring real-world plasmonic applications of Al over other noble metals. Additionally, we demonstrate spontaneous localization and concentration of target molecules at metasurface hotspots, leading to further improved on-chip detection sensitivity and a broadband fluorescence-enhancement factor above 1000 for visible wavelengths with respect to glass chips commonly used in bioassays. Using the metasurface and a multiplexing technique involving three visible wavelengths, we successfully detected three biomarkers, insulin, vascular endothelial growth factor, and thrombin relevant to diabetes, ocular and cardiovascular diseases, respectively, in a single 10 μL droplet containing only 1 fmol of each biomarker.

Conceptual design considerations for a wireless intraocular pressure sensor system for effective glaucoma management

As a leading form of preventable visual impairment, it is imperative to assess glaucoma treatment as a function of intraocular pressure (IOP). IOP can spike throughout the day. This necessitates a device that can (1) monitor IOP outside of clinical visits by providing a memory when IOP exceeds a set threshold indicating the possibility for glaucomatous damage to occur; and (2) accurately assess IOP. Both requirements point ultimately towards the development of an implantable device. The Wireless Intraocular Pressure Sensor System (WIPSS) devised by our team uses optical technologies and may assist an overseeing clinician with assessing glaucoma treatment efficacy and avoiding irreversible glaucomatous visual field loss downstream.

Enhanced broadband fluorescence detection of nucleic acids using multipolar gap-plasmons on biomimetic Au metasurfaces

Recent studies on metal-insulator-metal-based plasmonic antennas have shown that emitters could couple with higher-order gap-plasmon modes in sub-10-nm gaps to overcome quenching. However, these gaps are often physically inaccessible for functionalization and are not scalably manufacturable. Here, using a simple biomimetic batch-fabrication, a plasmonic metasurface is created consisting of closely-coupled nanodisks and nanoholes in a metal-insulator-metal arrangement. The quadrupolar mode of this system exhibits strong broadband resonance in the visible-near-infrared regime with minimal absorptive losses and effectively supresses quenching, making it highly suitable for broadband plasmon-enhanced fluorescence. Functionalizing the accessible insulator nanogap, analytes are selectively immobilized onto the plasmonic hotspot enabling highly-localized detection. Sensing the streptavidin-biotin complex, a 91-, 288-, 403- and 501-fold fluorescence enhancement is observed for Alexa Fluor 555, 647, 750 and 790, respectively. Finally, the detection of single-stranded DNA (gag, CD4 and CCR5) analogues of genes studied in the pathogenesis of HIV-1 between 10 pM-10 μM concentrations and then CD4 mRNA in the lysate of transiently-transfected cells with a 5.4-fold increase in fluorescence intensity relative to an untransfected control is demonstrated. This outcome promises the use of biomimetic Au metasurfaces as platforms for robust detection of low-abundance nucleic acids.

Microbicide surface nano-structures

The prevention of infectious diseases is a global challenge where multidrug-resistant bacteria or "superbugs" pose a serious threat to worldwide public health. Microtopographic surfaces have attracted much attention as they represent a biomimetic and nontoxic surface antibacterial strategy to replace biocides. The antimicrobial effect of such natural and biomimetic surface nanostructures involves a physical approach which eradicates bacteria via the structural features of the surfaces without any release of biocides or chemicals. These recent developments present a significant proof-of-concept and a powerful tool in which cellular adhesion and death caused by a physical approach, can be controlled by the micro/nanotopology of such surfaces. This represents an innovative direction of development of clean, effective and nonresistant antimicrobial surfaces. The minireview will cover novel approaches for the construction of nanostructures on surfaces in order to create antimicrobial surface in an environmentally friendly, nontoxic manner.

Sub-micrometer insights into the cytoskeletal dynamics and ultrastructural diversity of butterfly wing scales

BACKGROUND

The color patterns that adorn lepidopteran wings are ideal for studying cell type diversity using a phenomics approach. Color patterns are made of chitinous scales that are each the product of a single precursor cell, offering a 2D system where phenotypic diversity can be studied cell by cell, both within and between species. Those scales reveal complex ultrastructures in the sub-micrometer range that are often connected to a photonic function, including iridescent blues and greens, highly reflective whites, or light-trapping blacks.

RESULTS

We found that during scale development, Fascin immunostainings reveal punctate distributions consistent with a role in the control of actin patterning. We quantified the cytoskeleton regularity as well as its relationship to chitin deposition sites, and confirmed a role in the patterning of the ultrastructures of the adults scales. Then, in an attempt to characterize the range and variation in lepidopteran scale ultrastructures, we devised a high-throughput method to quickly derive multiple morphological measurements from fluorescence images and scanning electron micrographs. We imaged a multicolor eyespot element from the butterfly Vanessa cardui (V. cardui), taking approximately 200 000 individual measurements from 1161 scales. Principal component analyses revealed that scale structural features cluster by color type, and detected the divergence of non-reflective scales characterized by tighter cross-rib distances and increased orderedness.

CONCLUSION

We developed descriptive methods that advance the potential of butterfly wing scales as a model system for studying how a single cell type can differentiate into a multifaceted spectrum of complex morphologies. Our data suggest that specific color scales undergo a tight regulation of their ultrastructures, and that this involves cytoskeletal dynamics during scale growth.

Fabry-Pérot optical sensor and portable detector for monitoring high-resolution ocular hemodynamics

Our understanding of ocular hemodynamics and its role in ophthalmic disease progression remains unclear due to the shortcomings of precise and on-demand biomedical sensing technologies. Here, we report high-resolution in vivo assessment of ocular hemodynamics using a Fabry-Pérot cavity-based micro-optical sensor and a portable optical detector. The designed optical system is capable of measuring both static intraocular pressure and dynamic ocular pulsation profiles in parallel. Through a dynamic intensity variation analysis method which improves sensing resolution by 3-4 folds, our system is able to extract systolic/diastolic phases from a single ocular pulsation profile. Using a portable detector, we performed in vivo studies on rabbits and verified that ophthalmic parameters obtained from our optical system closely match with traditional techniques such as tonometry, electrocardiography, and photo-plethysmography.