compound eyes with distinguished advantages, such as large field of view (FOV), low aberration, high sensitivity to moving objects, and high temporal resolution. [2] Moreover, the periodically arranged nanoripples make the eyes have superhydrophobicity and anti-fogging property. [3,4] Motivated by these unique features, bionics on the geometrics and optical performance of natural compound eyes have been investigated and have shown great potential in medical endoscopic imaging, digital cameras, and wide-field imaging. [5][6][7][8][9][10] In recent years, various methods have been proposed to fabricate artificial compound eyes (ACEs), such as self-assembly method, inkjet printing and air-assisted deformation, single-pulse femtosecond laser wet etching with thermal embossing, and so on. [11][12][13][14][15] However, in highly humid or low-temperature environments, fog easily forms on the surface of these ACE elements and thus scatters light by the condensed water droplets. Up to now, very few researchers have achieved antifogging surfaces that could be used for optical imaging purposes. Generally speaking, they are working through the following two aspects. The first one is superhydrophobic-induced surfaces that prevent fog from adhering to the micro-lens surface. [16] Another one is superhydrophilic-induced surfaces that can suppress fogging behavior by the rapid spread of condensing water droplets. [17] The disadvantages of these methods are obvious. Superhydrophobic surfaces always require hexagonal nipples or close-packed protuberances of nanoscale on the surface of microstructures, which brings a great challenge to current micro/nano manufacturing processes, and is not conducive to mass production. Furthermore, these superwetting surfaces are unstable when suffering from high pressure, long-term working, or abrasion, which results in the loss of anti-fogging ability. Therefore, it still remains a challenge to develop a more facile process to fabricate bioinspired artificial compound eyes that reproduces the functionality of the natural compound eyes.It is interesting that Nepenthes pitcher plants can prevent insects to stand on their pitcher and, instead make them slide down from the rim to the bottom. [18] This excellent characteristic benefits from a layer of lubricating fluid stored in Curved artificial compound eyes (ACEs) attract enormous research interest owing to their potential applications in medical devices, surveillance imaging, target tracking, and so on. However, fog, dust, or other liquids are likely to condense on the device surface under a humid, low-temperature environment or outdoors, thus affecting the optical performance. In this work, a multifunctional ACE (MF-ACE) is fabricated by a combination of i) femtosecond laser wet etching, ii) soft lithography, and iii) polydimethylsiloxane (PDMS) swelling methods. The fabricated device is close-packed with over 3000 microlenses (≈108 µm diameter and ≈15 µm height) on a spherical macrolens (6.56 cm diameter and 0.87 cm height). The trapped silicone...
The surface of camera‐based medical devices is easily smeared by blood and fog during the surgical procedure, causing visual field loss and bringing great distress to both doctors and patients. In this article, a slippery liquid‐infused porous surface (SLIPS) on a quartz window surface that can repel various liquids, especially blood droplets is reported. A femtosecond laser pulse train was used to create periodic microhole structures on the silica surface. The subsequent low surface energy treatment and lubricant infusion led to the successful preparation of a slippery surface. Such blood‐repellent windows exhibited high transparency, great antifogging, and antibacterial properties. In addition, the slippery ability of the as‐prepared surface exhibited outstanding stability since the surface could withstand harsh treatments/environments, such as repeated pipette scratches and immersion in different pH solutions. The as‐prepared millimeter‐sized quartz samples with SLIPS were attached to the endoscope lens as a protective coating and could maintain high visibility after repeated immersion in blood. We believe that the coating developed in this study will provide inspiration for the design of next‐generation endoscopes or other camera‐guided devices that will resist fouling, keep clear vision, and reduce operation time, thus offering great potential applications in lesion diagnosis and therapy.
In recent years, the demand for optical components such as microlenses has been increasing, and various methods have been developed. However, fabrication of submillimeter microlenses with tunable numerical aperture (NA) on hard and brittle materials remains a great challenge using the current methods. In this work, we fabricated a variable NA microlens array with submillimeter size on a silica substrate, using a femtosecond laser-based linear scanning-assisted wet etching method. At the same time, the influence of various processing parameters on the microlens morphology and NA was studied. The NA of the microlenses could be flexibly adjusted in the range of 0.2 to 0.45 by changing the scanning distance of the laser and assisted wet etching. In addition, the imaging and focusing performance tests demonstrated the good optical performance and controllability of the fabricated microlenses. Finally, the optical performance simulation of the prepared microlens array was carried out. The result was consistent with the actual situation, indicating the potential of the submillimeter-scale microlens array prepared by this method for applications in imaging and detection.
windshields, rearview mirrors, and other equipment can result in catastrophic traffic accidents that can endanger human safety. [5,6] Furthermore, fog formation impairs the light absorption rate and imaging quality of optical components [7,8] and generates microscopic droplets on the surface of optical materials, magnifying the reflection of their surfaces and diminishing their clarity drastically. In chilly and humid conditions, fog can freeze into frost and completely block light from radiating onto the surface. [9][10][11] Such conditions not only cause glare and ghosting, which adversely affects the normal operations of lenses, lasers, displays, and other optical components, but also reduces light flux in the optical system and its transmittance, which can limit imaging clarity and contrast. [12][13][14] Fogging always occurs when the surface temperature of the substrate is lower than the dew point of ambient water vapor. Thus, water vapor condenses into tiny droplets on the surface of the substrate when reaching saturation or supersaturation in air. [15][16][17] Substrate surface fogging can be attributed to the following two factors. The first factor is environmental factors. When the temperature of the solid substrate surface is lower than the dew point of the water vapor under a given humidity, water vapor in air condenses into tiny water droplets, known as fog droplets, because of external water vapor and temperature variations. The second factor is the inherent nature of the material; the surface tension between the gas, liquid, and solid phases can determine vapor formation. [18] The surface tension of the matrix material is primarily determined by the intermolecular force of the surface. The greater the intermolecular force is, the higher the surface tension of the matrix is.The eyes of warm-blooded animals hardly fog even under extreme environments. For example, in human eyes, the cornea is an optical organ that performs observation and imaging activities. Human eyes do not fog even under some extreme circumstances because of two factors. The first cause is that eyes always maintain a steady temperature of ≈37 °C, which renders eyes warmer than the surrounding temperature. Therefore, the temperature difference does not reach atomization, and the condensation of water droplets is inhibited. Furthermore, tears constantly wet the cornea from time to time, which prevents the generation of fog droplets.Fog generation can severely damage optical systems by degrading the light absorption rate and imaging quality of optical components. Furthermore, fog can reduce the light flux and transmittance of the optical system, resulting in poor imaging clarity and contrast. Studies have focused on minimizing fog formation and effects. Drawbacks such as high energy consumption and waste pollution severely limit the application of conventional methods. However, achieving high fog resistance of optical components remains a challenge. A novel method of fabricating anti-fogging slippery surfaces (inspired by the anti-fog ...
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