Biomimetic apposition compound eye fabricated using microfluidic-assisted 3D printing

Investigating the Influence of Varied Light-Emitting Diode (LED) Wavelengths on Phototactic Behavior and Opsin Genes in Vespinae

The phototactic behavior of insects is commonly used to manage pest populations in practical production. However, this elusive behavior is not yet fully understood. Investigating whether the opsin genes play a crucial role in phototaxis is an intriguing topic. Vespinae (Hymenoptera: Vespidae) are a common group of social wasps that are closely associated with human activities. Efficiently controlling wasp populations while maintaining ecological balance is a pressing global challenge that still has to be resolved. This research aims to explore the phototactic behavior and key opsin genes associated with Vespinae. We found significant differences in the photophilic rates of Vespula germanica and Vespa analis under 14 different light conditions, indicating that their phototactic behavior is rhythmic. The results also showed that the two species exhibited varying photophilic rates under different wavelengths of light, suggesting that light wavelength significantly affects their phototactic behavior. Additionally, the opsin genes of the most aggressive hornet, Vespa basalis, have been sequenced. There are only two opsin genes, one for UV light and the other for blue light, and Vespa basalis lacks long-wavelength visual proteins. However, they exhibit peak phototaxis for long-wavelength light and instead have the lowest phototaxis for UV light. This suggests that the visual protein genes have a complex regulatory mechanism for phototactic behavior in Vespinae. Additionally, visual protein sequences have a high degree of homology among Hymenoptera. Despite the hypotheses put forward by some scholars regarding phototaxis, a clear and complete explanation of insect phototaxis is still lacking to date. Our findings provide a strong theoretical basis for further investigation of visual expression patterns and phototactic mechanisms in Vespinae.

Bioinspired 3D flexible devices and functional systems

Flexible devices and functional systems with elaborated three-dimensional (3D) architectures can endow better mechanical/electrical performances, more design freedom, and unique functionalities, when compared to their two-dimensional (2D) counterparts. Such 3D flexible devices/systems are rapidly evolving in three primary directions, including the miniaturization, the increasingly merged physical/artificial intelligence and the enhanced adaptability and capabilities of heterogeneous integration. Intractable challenges exist in this emerging research area, such as relatively poor controllability in the locomotion of soft robotic systems, mismatch of bioelectronic interfaces, and signal coupling in multi-parameter sensing. By virtue of long-time-optimized materials, structures and processes, natural organisms provide rich sources of inspiration to address these challenges, enabling the design and manufacture of many bioinspired 3D flexible devices/systems. In this Review, we focus on bioinspired 3D flexible devices and functional systems, and summarize their representative design concepts, manufacturing methods, principles of structure-function relationship and broad-ranging applications. Discussions on existing challenges, potential solutions and future opportunities are also provided to usher in further research efforts toward realizing bioinspired 3D flexible devices/systems with precisely programmed shapes, enhanced mechanical/electrical performances, and high-level physical/artificial intelligence.

Nanomaterial-Based Artificial Vision Systems: From Bioinspired Electronic Eyes to In-Sensor Processing Devices

High-performance robotic vision empowers mobile and humanoid robots to detect and identify their surrounding objects efficiently, which enables them to cooperate with humans and assist human activities. For error-free execution of these robots' tasks, efficient imaging and data processing capabilities are essential, even under diverse and complex environments. However, conventional technologies fall short of meeting the high-standard requirements of robotic vision under such circumstances. Here, we discuss recent progress in artificial vision systems with high-performance imaging and data processing capabilities enabled by distinctive electrical, optical, and mechanical characteristics of nanomaterials surpassing the limitations of traditional silicon technologies. In particular, we focus on nanomaterial-based electronic eyes and in-sensor processing devices inspired by biological eyes and animal visual recognition systems, respectively. We provide perspectives on key nanomaterials, device components, and their functionalities, as well as explain the remaining challenges and future prospects of the artificial vision systems.

Microfluidics-based patient-derived disease detection tool for deep learning-assisted precision medicine

Cancer spatial and temporal heterogeneity fuels resistance to therapies. To realize the routine assessment of cancer prognosis and treatment, we demonstrate the development of an Intelligent Disease Detection Tool (IDDT), a microfluidic-based tumor model integrated with deep learning-assisted algorithmic analysis. IDDT was clinically validated with liquid blood biopsy samples (n = 71) from patients with various types of cancers (e.g., breast, gastric, and lung cancer) and healthy donors, requiring low sample volume (∼200 μl) and a high-throughput 3D tumor culturing system (∼300 tumor clusters). To support automated algorithmic analysis, intelligent decision-making, and precise segmentation, we designed and developed an integrative deep neural network, which includes Mask Region-Based Convolutional Neural Network (Mask R-CNN), vision transformer, and Segment Anything Model (SAM). Our approach significantly reduces the manual labeling time by up to 90% with a high mean Intersection Over Union (mIoU) of 0.902 and immediate results (<2 s per image) for clinical cohort classification. The IDDT can accurately stratify healthy donors (n = 12) and cancer patients (n = 55) within their respective treatment cycle and cancer stage, resulting in high precision (∼99.3%) and high sensitivity (∼98%). We envision that our patient-centric IDDT provides an intelligent, label-free, and cost-effective approach to help clinicians make precise medical decisions and tailor treatment strategies for each patient.

Superhydrophobic Multifocal Microlens Array with Depth-of-Field Detection for a Humid Environment

Microlens array (MLA) has been widely applied in augmented reality and optical imaging. When used in a humid environment or medical endoscopy, MLA needs to be both superhydrophobic and multifocal. However, it is not easy to achieve both superhydrophobic and multifocal function by integrating superhydrophobic and multifocal structures on the same surface by means of a simple, efficient, and precise method. In this paper, the superhydrophobic multifocal MLA with superhydrophobic properties and multifocal functions is successfully designed for preparation based on a method of 3D lithography and soft lithography. The 3D lithography can further help the preparation of a multifocal MLA with varying apertures and a multistep superhydrophobic structure with a round dome. The superhydrophobic multifocal MLA with periods 50 and 120 μm has perfect superhydrophobic property. The water droplet can slide and bounce off the surface at a roll angle of less than 12.9° with both multifocal and integrated imaging function, as well as up to 397 μm depth-of-field (DOF) detection range; this greatly exceeds the conventional MLA. The perfect superhydrophobic and optical property can be achieved in an extremely humid environment. The superhydrophobic multifocal MLA proposed in this paper has a promising prospect for actual practices.

Trackable and highly fluorescent nanocellulose-based printable bio-resins for image-guided tissue regeneration

Dynamic tracking of cell migration during tissue regeneration remains challenging owing to imaging techniques that require sophisticated devices, are often lethal to healthy tissues. Herein, we developed a 3D printable non-invasive polymeric hydrogel based on 2,2,6,6-(tetramethylpiperidin-1-yl) oxyl (TEMPO)-oxidized nanocellulose (T-CNCs) and carbon dots (CDs) for the dynamic tracking of cells. The as-prepared T-CNC@CDs were used to fabricate a liquid bio-resin containing gelatin methacryloyl (GelMA) and polyethylene glycol diacrylate (GPCD) for digital light processing (DLP) bioprinting. The shear-thinning properties of the GPCD bio-resin were further improved by the addition of T-CNC@CDs, allowing high-resolution 3D printing and bioprinting of human cells with higher cytocompatibility (viability ∼95 %). The elastic modulus of the printed GPCD hydrogel was found to be ∼13 ± 4.2 kPa, which is ideal for soft tissue engineering. The as-fabricated hydrogel scaffold exhibited tunable structural color property owing to the addition of T-CNC@CDs. Owing to the unique fluorescent property of T-CNC@CDs, the human skin cells could be tracked within the GPCD hydrogel up to 30 days post-printing. Therefore, we anticipate that GPCD bio-resin can be used for 3D bioprinting with high structural stability, dynamic tractability, and tunable mechanical stiffness for image-guided tissue regeneration.

Biomimetic Compound Eyes with Gradient Ommatidium Arrays

Compound eyes are high-performing natural optical perception systems with compact configurations, generating extensive research interest. Existing compound eye systems are often combinations of simple uniform microlens arrays; there are still challenges in making more ommatidia on the compound eye surface to focus to the same plane. Here, a biomimetic gradient compound eye is presented by artificially mimicking dragonflies. The multiple replication process efficiently endows compound eyes with the gradient characteristics of dragonfly compound eyes. Experimental results show that the manufactured compound eye allows multifocus imaging by virtue of the gradient ommatidium array arranged closely in a honeycomb pattern while ensuring excellent optical properties and compact configurations. Thousands of ommatidia showing a gradient trend at the millimeter scale while remaining relatively uniform at the micron scale have gradient focal lengths ranging from 260 to 450 μm. This gradient compound eye allows more ommatidia to focus on the same plane than traditional uniform compound eyes, which have experimentally been shown to capture more than 1100 in-plane clear images simultaneously, promising potential applications in micro-optical devices, optical imaging, and biochemical sensing.

Double-Glued Multi-Focal Bionic Compound Eye Camera

Compound eye cameras are a vital component of bionics. Compound eye lenses are currently used in light field cameras, monitoring imaging, medical endoscopes, and other fields. However, the resolution of the compound eye lens is still low at the moment, which has an impact on the application scene. Photolithography and negative pressure molding were used to create a double-glued multi-focal bionic compound eye camera in this study. The compound eye camera has 83 microlenses, with ommatidium diameters ranging from 400 μm to 660 μm, and a 92.3 degree field-of-view angle. The double-gluing structure significantly improves the optical performance of the compound eye lens, and the spatial resolution of the ommatidium is 57.00 lp mm-1. Additionally, the measurement of speed is investigated. This double-glue compound eye camera has numerous potential applications in the military, machine vision, and other fields.

3D-Printed Micro/Nano-Scaled Mechanical Metamaterials: Fundamentals, Technologies, Progress, Applications, and Challenges

Micro/nano-scaled mechanical metamaterials have attracted extensive attention in various fields attributed to their superior properties benefiting from their rationally designed micro/nano-structures. As one of the most advanced technologies in the 21st century, additive manufacturing (3D printing) opens an easier and faster path for fabricating micro/nano-scaled mechanical metamaterials with complex structures. Here, the size effect of metamaterials at micro/nano scales is introduced first. Then, the additive manufacturing technologies to fabricate mechanical metamaterials at micro/nano scales are introduced. The latest research progress on micro/nano-scaled mechanical metamaterials is also reviewed according to the type of materials. In addition, the structural and functional applications of micro/nano-scaled mechanical metamaterials are further summarized. Finally, the challenges, including advanced 3D printing technologies, novel material development, and innovative structural design, for micro/nano-scaled mechanical metamaterials are discussed, and future perspectives are provided. The review aims to provide insight into the research and development of 3D-printed micro/nano-scaled mechanical metamaterials.

How can machine learning and multiscale modeling benefit ocular drug development?

The eyes possess sophisticated physiological structures, diverse disease targets, limited drug delivery space, distinctive barriers, and complicated biomechanical processes, requiring a more in-depth understanding of the interactions between drug delivery systems and biological systems for ocular formulation development. However, the tiny size of the eyes makes sampling difficult and invasive studies costly and ethically constrained. Developing ocular formulations following conventional trial-and-error formulation and manufacturing process screening procedures is inefficient. Along with the popularity of computational pharmaceutics, non-invasive in silico modeling & simulation offer new opportunities for the paradigm shift of ocular formulation development. The current work first systematically reviews the theoretical underpinnings, advanced applications, and unique advantages of data-driven machine learning and multiscale simulation approaches represented by molecular simulation, mathematical modeling, and pharmacokinetic (PK)/pharmacodynamic (PD) modeling for ocular drug development. Following this, a new computer-driven framework for rational pharmaceutical formulation design is proposed, inspired by the potential of in silico explorations in understanding drug delivery details and facilitating drug formulation design. Lastly, to promote the paradigm shift, integrated in silico methodologies were highlighted, and discussions on data challenges, model practicality, personalized modeling, regulatory science, interdisciplinary collaboration, and talent training were conducted in detail with a view to achieving more efficient objective-oriented pharmaceutical formulation design.

Novel Optofluidic Imaging System Integrated with Tunable Microlens Arrays

Optofluidic tunable microlens arrays (MLAs) can manipulate and control light propagation using fluids. Lately, their applicability to miniature lab-on-a-chip systems is being extensively researched. However, it is difficult to incorporate 3D MLAs directly in a narrow microfluidic channel using common techniques. This has resulted in limited research on variable focal length imaging with optofluidic 3D MLAs. In this paper, we propose a method for fabricating MLAs in polydimethylsiloxane (PDMS)-based microchannels via electrohydrodynamic jet (E-jet) printing to achieve optofluidic tunable MLAs. Using this method, MLAs of diameters 15 to 80 μm can be fabricated in microfluidic channels with widths of 200 and 300 μm. By alternately using solutions with different refractive indices in the microchannel, the optofluidic microlenses exhibit reversible modulation properties while retaining the morphologies and refractive indices of the microlenses. The focal length of the resulting optofluidic chip can have threefold tunability, thereby achieving an imaging depth of approximately 450 μm. This outstanding advantage is useful in observing microspheres and cells flowing in the microfluidic system. Thus, the proposed optofluidic chip exhibits great potential for cell counting and imaging applications.

A Meniscus Multifocusing Compound Eye Camera Based on Negative Pressure Forming Technology

To meet the challenge of preparing a high-resolution compound eye, this paper proposes a multi-focal-length meniscus compound eye based on MEMS negative pressure molding technology. The aperture is increased, a large field of view angle of 101.14° is obtained, and the ommatidia radius of each stage is gradually increased from 250 μm to 440 μm. A meniscus structure is used to improve the imaging quality of the marginal compound eye so that its resolution can reach 36.00 lp/mm. The prepared microlenses have a uniform shape and a smooth surface, and both panoramic image stitching and moving object tracking are achieved. This technology has great potential for application in many fields, including automatic driving, machine vision, and medical endoscopy.

Mosaic-free compound eye camera based on multidirectional photodetectors and single-pixel imaging

Compound-eye wide field-of-view (FOV) imaging generally faces the disadvantages of a complex system, low resolution, and complicated image mosaic. Single-pixel imaging has proven to very beneficial in building a high-resolution and simple wide-FOV camera, but its ability to overcome the problem of image mosaics still needs to be demonstrated. In this Letter, we propose a novel, to the best of our knowledge, kind of artificial compound eye based on multidirectional photodetectors (PDs) and demonstrate theoretically and experimentally that mosaics are unnecessary in multidirectional PD-based single-pixel imaging. In addition, we show experimentally that only nine multidirectional PDs are needed to obtain wide-angle images in a hemisphere to realize wide-FOV mosaic-free imaging. This work greatly simplifies the concept of compound-eye cameras and is very enlightening for detector design in wide-FOV single-pixel imaging, plausibly leading to the development of single-pixel endoscopic imaging.

Realizing the multifunctional metamaterial for fluid flow in a porous medium

Metamaterials are artificial materials that can achieve unusual properties through unique structures. In particular, their "invisibility" property has attracted enormous attention due to its little or negligible disturbance to the background field that avoids detection. This invisibility feature is not only useful for the optical field, but it is also important for any field manipulation that requires minimum disturbance to the background, such as the flow field manipulation inside the human body. There are several conventional invisible metamaterial designs: a cloak can isolate the influence between the internal and external fields, a concentrator can concentrate the external field to form an intensified internal field, and a rotator can rotate the internal field by a specific angle with respect to the external field. However, a multifunctional invisible device that can continuously tune across all these functions has never been realized due to its challenging requirements on material properties. Inside a porous medium flow, however, we overcome these challenges and realize such a multifunctional metamaterial. Our hydrodynamic device can manipulate both the magnitude and the direction of the internal flow and, at the same time, make negligible disturbance to the external flow. Thus, we integrate the functions of the cloak, concentrator, and rotator within one single hydrodynamic metamaterial, and such metamaterials may find potential applications in biomedical areas such as tissue engineering and drug release.

Gradients of Orientation, Composition, and Hydration of Proteins for Efficient Light Collection by the Cornea of the Horseshoe Crab

The lateral eyes of the horseshoe crab, Limulus polyphemus, are the largest compound eyes within recent Arthropoda. The cornea of these eyes contains hundreds of inward projecting elongated cuticular cones and concentrate light onto proximal photoreceptor cells. Although this visual system has been extensively studied before, the precise mechanism allowing vision has remained controversial. Correlating high-resolution quantitative refractive index (RI) mapping and structural analysis, it is demonstrated how gradients of RI in the cornea stem from structural and compositional gradients in the cornea. In particular, these RI variations result from the chitin-protein fibers architecture, heterogeneity in protein composition, and bromine doping, as well as spatial variation in water content resulting from matrix cross-linking on the one hand and cuticle porosity on the other hand. Combining the realistic cornea structure and measured RI gradients with full-wave optical modeling and ray tracing, it is revealed that the light collection mechanism switches from refraction-based graded index (GRIN) optics at normal light incidence to combined GRIN and total internal reflection mechanism at high incident angles. The optical properties of the cornea are governed by different mechanisms at different hierarchical levels, demonstrating the remarkable versatility of arthropod cuticle.

Artificial Hyper Compound Eyes Enable Variable-Focus Imaging on both Curved and Flat Surfaces

The artificial compound eye (ACE) with zoom imaging requires complex power sources. Meanwhile, its curved substrate makes it difficult for the ACE to realize the zoom imaging on flat surfaces. To realize a wide field of view and a zoom function on both curved and flat surfaces simultaneously, a novel ACE is proposed, which is a bionic design inspired by an ancient creature, trilobite. Compared with a dragonfly, photosensitive units of a trilobite's compound eye are composed of ommatidia with different focal lengths. By learning from this concept, an artificial hyper compound eye (AHCE) was fabricated. Its basic components are five microlenses with different curvatures, and they are capable of being treated as five ommatidia with different focal lengths. Five ommatidia form a photosensitive unit to realize a zoom function. AHCE is capable of variable-focus imaging on curved surfaces. With the information share function, we found that the AHCE not only images on curved surfaces but also has a zoom-imaging function on flat surfaces. The results confirm that the AHCE demonstrates an advanced imaging capability, a variable-focus imaging function on both curved and flat surfaces, which may open new opportunities in developing advanced micro-optical devices.

On-demand liquid microlens arrays by non-contact relocation of inhomogeneous fluids in acoustic fields

Microlens arrays (MLAs) are key micro-optical components that possess a high degree of parallelism and ease of integration. However, rapid and low-cost fabrication of MLAs with flexible focusing remains a challenge. Herein, liquid MLAs with dynamic tunability are presented using non-contact acoustic relocation of inhomogeneous fluids. By designing ring-shaped acoustic pressure node (PN) arrays, the denser fluid of miscible liquids is relocated to PNs, and liquid MLAs with ideal morphology are obtained. The experimental results demonstrate that the liquid MLAs possess a powerful reconfigurability with long-term stability and sharp imaging that can conveniently switch between the on and off state and can dynamically magnify by simply adjusting the acoustic amplitude. Moreover, the high biocompatibility inherited from liquids accompanied by the acoustic treatment allows cells to be within working distance of the MLAs without immersion, as would be required for a solid lens. This innovative liquid MLA is inexpensive to manufacture and possesses continuous focus, fast response, and satisfactory bioaffinity, and thus offers promising potential for microfluidic adaptive imaging and biomedical sensing, especially for live cell imaging.

Long-working-distance 3D measurement with a bionic curved compound-eye camera

The bionic curved compound-eye camera is a bionic-inspired multi-aperture camera, which can be designed to have an overlap on the field of view (FOV) in between adjacent ommatidia so that 3D measurement is possible. In this work, we demonstrate the 3D measurement with a working distance of up to 3.2 m by a curved compound-eye camera. In that there are hundreds of ommatidia in the compound-eye camera, traditional calibration boards with a fixed-pitch pattern arrays are not applicable. A batch calibration method based on the CALTag calibration board for the compound-eye camera was designed. Next, the 3D measurement principle was described and a 3D measurement algorithm for the compound-eye camera was developed. Finally, the 3D measurement experiment on objects placed at different distances and directions from the compound-eye camera was performed. The experimental results show that the working range for 3D measurement can cover the whole FOV of 98° and the working distance can be as long as 3.2 m. Moreover, a complete depth map was reconstructed from a raw image captured by the compound-eye camera and demonstrated as well. The 3D measurement capability of the compound-eye camera at long working distance in a large FOV demonstrated in this work has great potential applications in areas such as unmanned aerial vehicle (UAV) obstacle avoidance and robot navigation.

Gradient monolayered porous membrane for liquid manipulation: from fabrication to application

The controlled transport of liquid on a smart material surface has important applications in the fields of microreactors, mass and heat transfer, water collection, microfluidic devices and so on. Porous membranes with special wettability have attracted extensive attention due to their unique unidirectional transport behavior, that is, liquid can easily penetrate in one direction while reverse transport is prevented, which shows great potential in functional textiles, fog collection, oil/water separation, sensors, etc. However, many porous membranes are synthesized from multilayer structural materials with poor mechanical properties and are currently prone to delamination, which limits their stability. While a monolayered porous membrane, especially for gradient structure, is an efficient, stable and durable material owing to its good durability and difficult stratification. Therefore, it is of great significance to fabricate a monolayered porous membrane for controllable liquid manipulation. In this minireview, we briefly introduce the classification and fabrication of typical monolayered porous membranes. And the applications of monolayered porous membranes in unidirectional penetration, selective separation and intelligent response are further emphasized and discussed. Finally, the controllable preparation and potential applications of porous membranes are featured and their prospects discussed on the basis of their current development.

Apposition compound-eye image scanner by glass plate optics

We propose a design approach for a thin image scanner using the concept of an apposition compound eye comprising many imaging units that take only one pixel image. Although light shielding between adjacent imaging units is always one of the main issues for an artificial compound eye, a simple plane structure using three aperture array layers on two glued glass plates prevents such stray light. Our prototyped scanner, with only 6.8-mm thickness as a packaged module, has 632 microlenses with 200-dpi resolution, resulting in a field of view of 80 mm. The evaluated images show no ghost images.

Assembly of complex 3D structures and electronics on curved surfaces

Electronic devices with engineered three-dimensional (3D) architectures are indispensable for frictional-force sensing, wide-field optical imaging, and flow velocity measurement. Recent advances in mechanically guided assembly established deterministic routes to 3D structures in high-performance materials, through controlled rolling/folding/buckling deformations. The resulting 3D structures are, however, mostly formed on planar substrates and cannot be transferred directly onto another curved substrate. Here, we introduce an ordered assembly strategy to allow transformation of 2D thin films into sophisticated 3D structures on diverse curved surfaces. The strategy leverages predefined mechanical loadings that deform curved elastomer substrates into flat/cylindrical configurations, followed by an additional uniaxial/biaxial prestretch to drive buckling-guided assembly. Release of predefined loadings results in an ordered assembly that can be accurately captured by mechanics modeling, as illustrated by dozens of complex 3D structures assembled on curved substrates. Demonstrated applications include tunable dipole antennas, flow sensors inside a tube, and integrated electronic systems capable of conformal integration with the heart.

Bio-inspired spherical compound eye camera for simultaneous wide-band and large field of view imaging

Natural compound eyes have excellent optical characteristics, namely large field of view, small size, no aberration, and sensitive to motion. Some arthropods have more powerful vision. For example, the Morpho butterfly's compound eyes can perceive the near-infrared and ultraviolet light that the human eye cannot see. This wide-band imaging with a large field of view has great potential in wide-area surveillance, all-weather panoramic imaging, and medical imaging. Hence, a wide-band spherical compound eye camera inspired by the Morpho butterfly's eye was proposed. The wide-band spherical compound eye camera which can achieve a large field of view (360° × 171°) imaging over a wide range of wavelengths from 400nm to 1000nm, mainly consists of three parts: a wide-band spherical compound eye with 234 sub-eyes for light collection, a wide-band optical relay system for light transmission, and a wide-band CMOS image sensor for photoelectric conversion. Our experimental results show that the wide-band spherical compound eye camera not only captures a large field of view without anomalous blurring or aberrations but also perceives near-infrared light that is not recognized by the human eye. These features make it possible for distortion-free panoramic vision and panoramic medical diagnosis.

Mid-infrared biomimetic moth-eye-shaped polarization-maintaining and angle-insensitive metalens

Metalenses can potentially reduce the size and complexity of existing cameras, displays, and other optical devices, owing to their capability of flexible manipulation of the polarization, amplitude, and phase of light. However, metalenses capable of maintaining polarization and broadband wavefront shaping under arbitrarily polarized excitation have not been studied. In this study, we present the first demonstration of a biomimetic moth-eye-shaped metalens for polarization-maintaining, broadband and angle-insensitive focusing under an arbitrarily polarized excitation in the mid-infrared waveband (3.1-8.0 µm). Modulation and focusing efficiencies of 92% and 90%, respectively, were achieved. Moreover, a bifocal moth-eye-shaped metalens operating at normal and oblique incidences was realized. Compared to previously reported metalenses, the one proposed in this study exhibited a better focusing under oblique incidence, ensuring light transmission as effectively as a traditional lens. This study paves the way for the development of polarization-maintaining, broadband, and angle-insensitive microscale optical devices and imaging systems.

Bioinspired Compound Eyes for Diffused Light-Harvesting Application

Natural compound eyes endow arthropods with wide-field high-performance light-harvesting capability that enables them to capture prey and avoid natural enemies in dim light. Inspired by natural compound eyes, a curved artificial-compound-eye (cACE) photodetector for diffused light harvesting is proposed and fabricated, and its light-harvesting capability is systematically investigated. The cACE photodetector is fabricated by introducing a cACE as a light-harvesting layer on the surface of a silicon-based photodetector, with the cACE being prepared via planar artificial-compound-eye (pACE) template deformation. The distinctive geometric morphology of the as-prepared cACE effectively reduces its surface reflection and the dependence of the projected area on the incident light direction, thereby significantly improving the light-harvesting ability and output photocurrent of the silicon-based photodetector. Furthermore, the performances of cACE, pACE, and bare polydimethylsiloxane (PDMS)-attached photodetectors as diffused light detectors are investigated under different luminances. The cACE-photodetector output photocurrent is 1.395 and 1.29 times those of the bare PDMS-attached and pACE photodetectors, respectively. Moreover, this photodetector has a desirable geometric shape. Thus, the proposed cACE photodetector will facilitate development of high-performance photodetectors for luminance sensing.