Laser Wet Etching Research Articles

Femtosecond laser constructed anti-pollution silica glass surfaces with high-viscosity-oil adhesion prevention

Transparent surfaces with anti-pollution and anti-adhesive properties show promise for optical windows. However, there is currently no effective way to create glass surfaces that are impervious to highly viscous and sticky oils, like crude oil. In this research, an electrical-heating silica glass with resistance to high viscosity oil was prepared using a femtosecond laser process. An inner micro-channel system was fabricated by the femtosecond laser wet etching method, and the surface was treated to be superhydrophilic/underwater superoleophobic through femtosecond laser irradiation. The prepared sample could be electrically heated by its internal heating unit, which could reduce the viscosity of the crude oil. Thus, the prepared sample is resistant not only to typically low-viscosity oils, but also prevents the adhesion of crude oil, which would be widely applied in anti-pollution optical windows.

Mammalian Cornea Inspired Anti‐Fogging Silica Glass Surface Achieved by Femtosecond Laser

AbstractFog 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 mechanism of the mammalian cornea) on silica glass by using femtosecond lasers is proposed to achieve durable and environment‐friendly optical devices that can achieve anti‐fogging in real time. The femtosecond laser wet etching method is used to fabricate the inside cabin of glass. The cabin filled with graphene spontaneously heats the sample under sunlight to prevent fog formation. In addition to exhibiting excellent anti‐fogging characteristics, the prepared sample achieves high optical transmittance, high durability, and excellent self‐repair capability. Thus, the proposed method exhibits considerable potential for application in numerous domains.

Chalcogenide Glass IR Artificial Compound Eyes Based on Femtosecond Laser Microfabrication

AbstractThe compact and lightweight infrared (IR) optics devices are highly demanded in booming applications. However, fabrication of IR optics devices with high efficiency is still technically challenging, especially artificial compound eyes (ACE) with low aberration imaging and large field of view. In this work, a method of femtosecond laser wet etching combining with the “two‐step” precision glass molding based on chalcogenide glass is proposed to fabricate glass IR ACE. The as‐prepared consists of 6000 ommatidia (diameter of 88 µm and the sag height of 11 µm) arranged in a hexagonal manner with perfect parabolic morphology and high uniformity. The chalcogenide glass IR ACE exhibits excellent optical performance both in IR active imaging and IR passive imaging with high transmittance (60–70%) ranging from 2.5 to 15 µm. The ommatidia have a high resolution up to 20.16 lp mm−1, and imaging with large field of view up to 60° and low aberration can be achieved. Furthermore, the proposed technology shows advantages to fabricate glass IR ACE with low cost and high efficiency, and glass IR ACE shows great potential in IR imaging, robot vision, IR 3D motion tracking, and so on.

Highly Stable and Transparent Slippery Surface on Silica Glass Fabricated by Femtosecond Laser

Underwater optical window plays an important role in ocean detection. Studies show that marine biofouling is one of the biggest challenges that affect the performance of the optical window. Recently, nepenthes‐inspired lubrication‐infused slippery surfaces (SLIPS) with excellent anti‐biological adsorption features have been widely used to resolve this problem. However, low mechanical resistance and the easy loss of infused lubricants affect the slippery capability of this method. In the present study, a novel 3D bionic slippery surface was fabricated using a femtosecond laser wet etching on silica glass. In this method, the lubricant of the compartment structure SLIPS is stored in the inner compartment and is transported to the surface under the effect of the capillary forth. The unique structure of the proposed scheme dramatically improved the surface durability compared with the normal SLIPS, and does not affect the intrinsic transparency of the substrate material. The performed analyses revealed that the proposed scheme has excellent optical transmittance and durability, and is expected to have wide applications in the ocean detection field.

Bioinspired Anti‐Fogging and Anti‐Fouling Artificial Compound Eyes

AbstractCurved 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 multi‐functional 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 oil in the cross‐linked PDMS endows the as‐fabricated ACE with excellent water repellence and anti‐fogging, anti‐fouling, and self‐cleaning abilities. In addition, the ACE shows high optical performance and the ommatidia have a spatial resolution of 50.8 lp mm−1. The imaging and focusing experiments demonstrate its high optical properties and uniformity. It is anticipated that this research may provide useful guidelines for the fabrication of anti‐fogging and anti‐fouling optical devices, and such device enables potential applications in autonomous vehicles, medical, or vision systems under harsh environmental conditions.

Microlens arrays enable variable-focus imaging

Microlens array (MLA) is a key part of optical element for biomedical inspection, lab-on-a-chip device, and light-field cameras. However, conventional MLAs always have only one focal plane, which makes them difficult to capture targets at different positions. To solve this problem, a planar multi-focus MLA (MF-MLA) was prepared on a polydimethylsiloxane (PDMS) substrate by a combination of femtosecond laser wet etching (FLWE) and soft lithography techniques. The modulation transfer function (MTF) values of the microlenses all exceeded 0.2 when the spatial frequency was less than 200 lp/mm, indicating the high imaging ability of the lenses. The reported MF-MLA had three different focal lengths, so that targets at different positions could be easily imaged on a single image sensor. In addition, MLAs with more focal points could be fabricated by selecting appropriate processing parameters. It is anticipated that the as-fabricated MF-MLA will become a promising device to improve the performance of the optical system, especially in optical remote sensing, biomedical imaging, and machine vision.

Fabrication of Three-Dimensional Microvalves of Internal Nested Structures Inside Fused Silica.

Nested structures inside the hard material play a pivotal role in the microfluidics systems, such as the microvalve and the micropump. In this article, we demonstrate a novel and facile method of fabricating nested structures inside the fused silica with a two-step process femtosecond laser wet etching (FLWE) process. Inside fused silica, a spherical structure was made with a diameter of nearly 80 µm in a square chamber. In addition, we designed a simple microvalve with this sphere controlling the current’s flow. The novel microvalve structure can be easily integrated into the functional microfluidics systems and will be widely applied in the Lab-on-chip (LOC) system.

Femtosecond laser hybrid fabrication of a 3D microfluidic chip for PCR application.

Microfluidic chips have gradually become a focus of scientific research. However, the fabrication of key functional components in microfluidic chips is always limited by the existing processing methods. The microfluidic chip is difficult to be three-dimensional (3D) and integrated. In response to the key problems of 3D integrated microfluidic chip fabrication, this paper presents a hybrid method for fabricating a microfluidic chip integrated 3D microchannels and metal microstructures by femtosecond laser wet etch technology and liquid metal injection. The integrated microfluidic chip fabricated by this method is expected to be applied to the core reaction unit of integrated PCR devices.

3D integrated coreless microtransformer processed by femtosecond laser micro/nano fabrication

Electronic and information hardware is developing in the direction of lightweight products, miniaturization, and integration. The transformer is still the most effective solution for signal isolation and power transfer. In response to the key problems of microtransformer fabrication, this paper presents a hybrid method for fabricating micro/nano structures via femtosecond laser wet etch technology and liquid metal microinjection. This research aims to develop a new method of creating an integrated microtransformer, offering an effective solution for the fabrication of widely applicable 3D integrated complex structures. The embedded 3D microtransformer can be easily integrated with other microelectrical, mechanical, and optical systems, with potential applications in MEMS, sensors and lab-on-chips.

飞秒激光辐照结合湿法腐蚀在晶体材料微结构制备中的应用

飞秒激光辐照结合湿法腐蚀在晶体材料微结构制备中的应用

Underwater superoleophobic and anti-oil microlens array prepared by combing femtosecond laser wet etching and direct writing techniques.

As an important micro-optical device, microlens array (MLA) also has broad applications in aqueous environment apart from atmosphere, such as bioscience research, ocean exploration, and microfluidic systems. However, the surface of the normal MLA is easily polluted by oil contaminations when the MLA is practically applied in a water medium, leading to the loss of its optical imaging ability. Herein, we fabricated a functional MLA with underwater anti-oil and self-cleaning abilities by combining the femtosecond laser wet etching (FLWE) and the femtosecond laser direct writing (FLDW) techniques. The as-prepared close-packed MLA is composed of 10000 single microlenses with the aperture diameter of 50 µm. The surface of each microlens is further textured with micro/nanoparticles. Clear and uniform images could be captured by using the resultant MLA in water, demonstrating great underwater imaging ability. The modulation transfer function value is larger than 0.6 at 55 lp/mm. In addition, the micro/nanostructures endow the as-fabricated MLA surface with underwater superoleophobicity and oil-repellent performance. Various oils can be repelled by the resultant MLA in water. Underwater 1,2-dichloroethane oil droplet on the textured MLA has a contact angle of 158.0 ± 0.5° and a sliding angle of 2.0 ± 0.2°. The underwater superoleophobic MLA also has good mechanical durability. The anti-oil and self-cleaning functions will broaden the applications of the MLA in ocean exploration, bioscience research, microfluidic system, and many underwater MLA-based systems.

Integration of Great Water Repellence and Imaging Performance on a Superhydrophobic PDMS Microlens Array by Femtosecond Laser Microfabrication

Microlens arrays (MLAs), as the important optical devices, are easily polluted by the water droplets or power‐like‐contaminates in the air. Endowing the artificial MLAs with anti‐water and self‐cleaning abilities remains great challenge. In this paper, the authors report a novel method for fabricating superhydrophobic polydimethylsiloxane (PDMS) MLAs by the combination of femtosecond laser wet etching and femtosecond laser direct writing methods. The resultant surface is composed of a convex MLA and the surrounding rough micro/nanoscale hierarchical structures. Water droplet on the surface of the as‐prepared MLA shows a contact angle of 162° and can easily roll away when the substrate is slightly tilted 0.5°. In addition to their excellent imaging performance, such ultralow adhesive and ultrahigh superhydrophobicity also endows the as‐prepared MLA with excellent anti‐water ability as well as the self‐cleaning function relative to the normal MLA. The authors believe that the anti‐water and self‐cleaning MLAs will potentially have many important applications in solar cells, medical endoscopes, and other optical systems that are often used in the humid environment or outdoors.

Fabrication of high integrated microlens arrays on a glass substrate for 3D micro-optical systems

Microlens array have been developed as an essential element in integrated micro-optical systems. However, rapidly fabrication of high integration, high fill factor and multi-layer microlens arrays on a hard material is still a challenge. Here, facilely designed high integrated double-sided concave microlens arrays were proposed. These concave microlens arrays possess nearly 5000 close-packed microlenses on a double sides glass substrate, which were created by femtosecond laser wet etch process. The optical properties of integrated microlens arrays were investigated, which exhibit novel diverse imaging patterns, such as coaxial nested rectangular-shaped, coaxial nested hexagonal-shaped, non-coaxial nested hexagonal-shaped imaging patterns, etc. Moreover, diverse imaging patterns can be simply realized by controlling the shape, the size of the microlenses and the arrangement of the microlens arrays on the double-sided glass chips.

3D Multi-Microchannel Helical Mixer Fabricated by Femtosecond Laser inside Fused Silica.

Three-dimensional (3D) multi-microchannel mixers can meet the requirements of different combinations according to actual needs. Rapid and simple creation of 3D multi-microchannel mixers in a “lab-on-a-chip” platform is a significant challenge in micromachining. In order to realize the complex mixing functions of microfluidic chips, we fabricated two kinds of complex structure micromixers for multiple substance mixes simultaneously, separately, and in proper order. The 3D multi-microchannel mixers are fabricated by femtosecond laser wet etch technology inside fused silica. The 3D multi-microchannel helical mixers have desirable uniformity and consistency, which will greatly expand their utility and scope of application.

Laser Assisted Patterning of a-Si:H: Detailed Investigation of Laser Damage

A detailed investigation of the laser damage to amorphous silicon (a-Si:H) layers patterned by laser ablation (LA) and wet chemical etching is presented. This approach can be applied to pattern the rear side of silicon heterojunction interdigitated back-contact solar cells. Only the top sacrificial a-Si:H laser-absorbing layer of an a-Si:H/SiOx/a-Si:H/c-Si stack is ablated. Laser damage in the bottom a-Si:H layer and a-Si:H/c-Si interface is analyzed by both scanning electron microscopy and transmission electron microscopy. We show that the a-Si:H/c-Si passivation is degraded by laser damage and that this degradation can be diminished by increasing laser processing speed. This is attributed to a decrease of laser-irradiated area, and particularly smaller overlapping zones of adjacent laser pulses. The re-passivation quality after LA and wet etching is similar to that of as-passivated samples. This indicates that laser damage is not present in the bulk c-Si substrate but only in the a-Si:H passivation layer, which is removed during subsequent wet etching, thus allowing high quality repassivation.

Miniaturized 3-D Solenoid-Type Micro-Heaters in Coordination With 3-D Microfluidics

We fabricate and characterize a prototype on-chip 3-D micro-heater inside a fused silica chip, which is coordinated with a microfluidic channel. By means of enhanced femtosecond laser wet etching followed by a micro-mold injection process of a liquid metal, the solenoid-type metallic micro-heater, with a size of π × 100 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> × 1120 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , was fabricated twining outward a linear microfluidic channel. The micro-heater exhibits excellent performances, such as precisely current-temperature controllability (temperature range from 0°C to 130°C), rapid heating/cooling process (up to 16 °C/s at the beginning of the heating process and 15.8 °C/s at the beginning of cooling process), and uniform temperature distribution. This work not only provides a high-quality micro-heater for biological or chemical applications, which requires rigid temperature control capabilities, but also proposes a practical route to the fabrication of comprehensive truly-3-D lab-on-a-chip devices and microelectromechanical systems.

A miniaturized Rogowski current transducer with wide bandwidth and fast response

The miniaturization of the 3D Rogowski current transducer down to the micro-scale is essential for device integration and expansion of its application scope, particularly for ‘lab-on-a-chip’ systems. However, fabrication of 3D miniaturized Rogowski coils remains challenging as most relative methods still rely on the 2D micromachining process. In this paper, a miniaturized Rogowski coil current transducer was fabricated using an improved femtosecond laser wet etching technology and a metal microsolidification process, in which a metal alloy with a relatively high melting point was used and a robust but simple packaging structure based on a conical electrode was developed. The results show that the miniaturized Rogowski coil current transducer reveals a response time of less than 1 ns, high sensitivity and good detection capability for high-frequency electrical signals. The miniaturized Rogowski coil can easily be integrated into functional microsystems and will be widely applicable for high-frequency electric signal detection and circuit protection.

Compound Eyes: Dragonfly‐Eye‐Inspired Artificial Compound Eyes with Sophisticated Imaging (Adv. Funct. Mater. 12/2016)

On page 1995, F. Chen, Q. Yang, and co-workers present truly structural compound eyes inspired by dragonfly with 30 000 lenses per eye, fabricated by a high-efficiency strategy that combines single-pulse femtosecond laser wet etching with thermal embossing. These newly artificial compound eyes open the door for seeing the world with insects' eyes.

Dragonfly‐Eye‐Inspired Artificial Compound Eyes with Sophisticated Imaging

The natural compound eye is a striking imaging device with a wealth of fascinating optical features such as a wide field of view (FOV), low aberration, and high sensitivity. Dragonflies in particular possess large, sophisticated compound eyes that exhibit high resolving power and information‐processing capacity. Here, a large‐scale artificial compound eye inspired by the unique designs of natural counterparts is presented. The artificial compound eye is created by a high‐efficiency strategy that combines single‐pulse femtosecond laser wet etching with thermal embossing. These eyes have a macrobase diameter of 5 mm and ≈30 000 close‐packed ommatidia with an average diameter of 24.5 μm. Moreover, the optical properties of the artificial compound eyes are investigated; the results confirm that the eye demonstrates advanced imaging quality, an exceptionally wide FOV of up to 140°, and low aberration.

Lens-on-lens microstructures.

Microlenses with multiple focal lengths play an important role in three-dimensional imaging and the real-time detection of unconfined or fluctuating targets. In this Letter, we present a novel method of fabricating lens-on-lens microstructures (LLMs) using a two-step femtosecond laser wet etching process. A 3×3 LLM array was made with a diameter of 129.0 μm. The fabricated LLM has two focal lengths, 80.4 and 188.7 μm, showing excellent two-level focusing and imaging abilities. Its size and focal length can be controlled by adjusting laser power and etching time. Its surface roughness remains about 61 nm. This simple and efficient method for large-scale production of LLMs has potential applications in diverse optical systems.