Laser Patterning Method Research Articles

One-step laser-induced Cu-embedded graphene for non-enzymatic glucose sensing in beverages

The detection of glucose in beverages is crucial for dietary management and healthcare. Excessive sugar consumption can lead to severe conditions, such as obesity, diabetes, cardiovascular diseases, and cancer. In this study, Cu-embedded laser-induced graphene (Cu/LIG) materials were fabricated for non-enzymatic glucose detection using a simple, direct, and cost-effective laser-patterning method on a Cu2+/ethyl-cellulose/polyimide membrane. The experimental results showed that the Cu/LIG electrode exhibited lower charge transfer resistance and a distinct diffusion process compared to the LIG electrode. This improvement can be attributed to the optimized graphene formation achieved by employing ethyl-cellulose (EC) and CuCl2 as combustion promoters. Under optimal conditions, Cu/LIG-600 demonstrated excellent electrocatalytic activity for glucose oxidation, with a low response concentration (5 μM), fast response time (2.0 s), and detection ranges of 0.005–0.525 mM (I-t) and 0.5–4.0 mM (CV). Moreover, the sensor exhibited high selectivity, stability (retaining over 90 % activity after 28 days), and satisfactory recovery rates for spiked glucose in Cola, Sprite, Black Tea, and sugarless Soda Water, indicating its potential for non-enzymatic glucose detection in beverages.

Monolithic Integration of Ultraslim Flow Sensor and Medical Guidewire by Laser Filament Scanning Sintering for In Vivo Diagnostics of Cardiovascular Diseases.

In this study, an ultraslim thermal flow sensor system integrated onto a 340 μm diameter medical guidewire was developed using a laser filament scanning sintering method for the early diagnosis of cardiovascular diseases. The proposed system is a calorimetric-based micro thermal flow sensor comprising a microheater and two thermistors. Prior to fabrication, the sensor design was optimized through flow simulation, and the patterned sensor was successfully implemented on a thin and curved surface of the medical guidewire using a laser patterning method with Ag nanoparticles. The performance of the ultraslim thermal flow sensor-on-guidewire system (SoW) was evaluated under pulsatile flow by using an artificial heartbeat simulator with differentially induced fluid flow velocities of up to 60 cm/s. The resulting electrical signals generated by the temperature difference between the two thermistors caused by the fluid flow were measured across different velocity ranges. Based on the obtained data, a calibration curve was derived to establish the relationship between the fluid velocity and the sensor output voltage. Furthermore, the SoW was tested on living animals, whereby the measured blood flow velocities were 60-90 cm/s in the left coronary artery of pigs. This research demonstrates the potential of ultraslim microsensors, such as the developed thermal flow sensor system, for various industries, particularly in the medical field.

Laser patterning of large-scale perovskite single-crystal-based arrays for single-mode laser displays

Lead halide perovskites have attracted considerable attention as potential candidates for high-performance nano/microlasers, owing to their outstanding optical properties. However, the further development of perovskite microlaser arrays (especially based on polycrystalline thin films) produced by the conventional processing techniques is hindered by the chemical instability and surface roughness of the perovskite structures. Herein, we demonstrate a laser patterning of large-scale, highly crystalline perovskite single-crystal films to fabricate reproducible perovskite single-crystal-based microlaser arrays. Perovskite thin films were directly ablated by femtosecond-laser in multiple low-power cycles at a minimum machining line width of approximately 300 nm to realize high-precision, chemically clean, and repeatable fabrication of microdisk arrays. The surface impurities generated during the process can be washed away to avoid external optical loss due to the robustness of the single-crystal film. Moreover, the high-quality, large-sized perovskite single-crystal films can significantly improve the quality of microcavities, thereby realizing a perovskite microdisk laser with narrow linewidth (0.09 nm) and low threshold (5.1 μJ/cm2). Benefiting from the novel laser patterning method and the large-sized perovskite single-crystal films, a high power and high color purity laser display with single-mode microlasers as pixels was successfully fabricated. Thus, this study may offer a potential platform for mass-scale and reproducible fabrication of microlaser arrays, and further facilitate the development of highly integrated applications based on perovskite materials.

Hybrid design and prototyping of metamaterials and metasurfaces

ABSTRACT Metamaterials are engineered materials conceived and designed to achieve very special or even unique physical properties, which depend on the designed micro or nanostructures, more than on the chemical composition of the raw materials employed for their fabrication. Normally metamaterials are made of periodic repetitions of unit cells or Boolean combinations of lattices or porous building blocks. Metasurfaces are the quasi-two-dimensional version of metamaterials and are generally applied to controlling electromagnetic and acoustic waves reaching them. Metamaterials are mainly created through high-precision additive manufacturing technologies, while metasurfaces are normally obtained using micromanufacturing techniques from the electronics industry and laser patterning methods. Consequently, the potential benefits and industrial applications of multi-scale or hierarchical metastructures, which could be obtained by merging metamaterials and metasurfaces, remain unexplored. Through the innovative combination of 3D CAD modelling resources and specific tools for computational mapping of topographical 2D images this study validates the possibility of texturing the building blocks and unit cells of metamaterials, hence reaching designs with interwoven metamaterials and metasurfaces. These microtextured lattices are additively manufactured, using two-photon polymerisation, to demonstrate the feasibility of bridging the gap between metamaterials and metasurfaces and analyse current challenges and potential applications of these digital materials.

3R Electronics: Scalable Fabrication of Resilient, Repairable, and Recyclable Soft-Matter Electronics.

E-waste is rapidly turning into another man-made disaster. It is proposed that a paradigm shift toward a more sustainable future can be made through soft-matter electronics that are resilient, repairable if damaged, and recyclable (3R), provided that they achieve the same level of maturity as industrial electronics. This includes high-resolution patterning, multilayer implementation, microchip integration, and automated fabrication. Herein, a novel architecture of materials and methods for microchip-integrated condensed soft-matter 3R electronics is demonstrated. The 3R function is enabled by a biphasic liquid metal-based composite, a block copolymer with nonpermanent physical crosslinks, and an electrochemical technique for material recycling. In addition, an autonomous laser-patterning method for scalable circuit patterning with an exceptional resolution of <30µm in seconds is developed. The phase-shifting property of the BCPs is utilized for vapor-assisted "soldering" circuit repairing and recycling. The process is performed entirely at room temperature, thereby opening the door for a wide range of heat-sensitive and biodegradable polymers for the next generation of green electronics. The implementation and recycling of sophisticated skin-mounted patches with embedded sensors, electrodes, antennas, and microchips that build a digital fingerprint of the human electrophysiological signals is demonstrated by collecting mechanical, electrical, optical, and thermal data from the epidermis.

Simple and practical methods for utilizing parylene C film based on vertical deposition and laser patterning

We propose two novel methods to effectively utilize parylene C films. First, we demonstrate a vertical deposition method capable of depositing a parylene C film of the same thickness on both sides of a sample. Through this method, we have formed parylene C films with a thickness of 4 μm on both sides of the sample with a thickness deviation of less than 2.5%. Further optical verification indicates that parylene C films formed by this method have a very uniform thickness distribution on each side of the surfaces. Second, we propose a debris-tolerant laser patterning method as a mask-less means to fabricate self-supporting ultrathin parylene C films. This method does not involve any photolithography and entails a simple and rapid process that can be performed using only a few materials with excellent biocompatibility. It is demonstrated that patterned parylene C films exhibit a high degree of surface uniformity and have various geometrical shapes so that they can be used for substrates of highly flexible and/or stretchable devices. Finally, we use both of the proposed methods to fabricate flexible, stretchable, and waterproof-packaged bifacial blue LED modules to illustrate their potential in emerging applications that would benefit from such versatile form factors.

Effects of supra-wavelength periodic structures on the formation of 1D/2D periodic nanostructures by femtosecond lasers

Femtosecond laser-induced periodic surface structure (fs-LIPSS) is a high-throughput parallel laser patterning method to fabricate various surface structures of sub-micrometer scale; the morphology and regularity of the structured surface determine its function. In this paper, single and double femtosecond laser beams are used to fabricate nanostructures on a silicon substrate. In the experiments, it is found that the appearance of supra-wavelength structures with periods longer than the laser wavelength not only deteriorate the regularity of the sub-wavelength periodic ripples but also hinder the fabrication of the deep sub-wavelength ripples when a single femtosecond laser is used. In addition, when double time-delayed femtosecond laser beams are used, 2D nanostructures, such as hexagonally arranged nano-hole array, cannot be fabricated once the supra-wavelength structures appear. The formation mechanism of the supra-wavelength periodic structures, which cannot be explained by the interference between the incident laser and surface plasmon polaritons, may be attributed to the hydrothermal wave on the molten surface layer. These findings provide insights to understand the mechanisms of 1D and 2D nanostructures produced by single and dual femtosecond laser beams, which is critical for fabricating functional surfaces.

Nonthermal laser ablation of high-efficiency semitransparent and aesthetic perovskite solar cells

Abstract Perovskite solar cells (PSC) offer a promising solution for building integrated photovoltaics (BIPVs) due to its high photoelectric conversion efficiency (PCE). However, increasing the transparency of their functional layers dramatically decreases the PCE. Here, a computer controlled laser patterning method was proposed to directly turn PSC modules into semitransparent and with aesthetic artificial pattern, without additional complexities to the conventional PSCs fabrication process. A structured ST-PSC achieving a champion PCE of 17.5% with average visible transparency (AVT) of 18.2%, and a mini-module with 5 × 5 cm2 delivering a PCE of 9.1% with AVT of 37.7% were demonstrated. Rationally designed aesthetic patterns were imprinted on mini-modules, achieving a PCE of 14.4%. These results reveal a new route for low-cost facile fabricating high performance large-area aesthetic BIPV modules, and represent a big step forward toward the fabrication of solar cells with high efficiency and high transparency.

Experimental study on the direct planar metallization on glass by the particle sputtering in laser-induced plasma-assisted ablation

Laser-induced plasma-assisted ablation (LIPAA) is an efficient and low-cost method for processing the metallic pattern on glass. In this study, the metallic sacrificed target was used in the LIPAA process, the feasibility of direct planar metallization on the glass substrate was explored. For this purpose, the morphology and chemical composition of the planar metallization layer on glass substrate, which was fabricated by line-by-line LIPAA, was characterized in detail, and the corresponding metallization regime was clarified. The experimental results indicate that gap distance between the glass specimen and metallic sacrificed substrate has a significant influence on the homogeneity, thickness, compactness, and chemical composition of the metallization layer. In addition, with a small gap distance, the periodic behaviors of generation, accumulation, blockage and spray of the metallic oxide powders between the gap bring about stripes embedded in the metallization layer. Moreover, based on the prepared metallization layer by line-by-line LIPAA, the patterned circuit was fabricated on the glass by laser patterning method and its conductivity was enhanced by successive chemical reduction. The comprehensive performance test for the patterned circuit in terms of morphology, adhesion strength, conductivity demonstrate that the line-by-line LIPAA method presents a great potential for preparing the patterned circuit on glass.

Semitransparent perovskite solar cells with exceptional efficiency and transmittance

A general approach to developing semitransparent perovskite solar cells (ST-PSCs) is to use a transparent metal oxide to replace opaque metal electrodes. However, the performance of such solar cells, unlike that of those using evaporated metal electrodes, deteriorates due to insufficient conductivity of the metal oxide, etc. Herein, a femtosecond laser patterning method is proposed to achieve the efficiency and transparency of ST-PSCs with a typical metal electrode and facilitates the control of transmittance by varying the opening ratio. While providing average visible transmittance > 46%, a certified power conversion efficiency of 8.22% was attained, which outperformed state-of-the-art ST-PSCs reported to date.

Locally controllable laser patterning transfer of thermoplastic polyurethane induced by sustainable bismuth trioxide substrate

In recent years, laser patterning technology has attracted much attention due to its high efficiency and environmental protection. However, the traditional laser patterning method requires the addition of laser-responsive substances to the polymer matrix. This overall filling not only wastes resources, but also affects the excellent performance of the polymer matrix itself. This study reveals the locally controllable laser patterning transfer of thermoplastic polyurethane (TPU) film via a sustainable approach. The laser beam was irradiated on the interface between the laser sensitive bismuth trioxide (Bi2O3) substrate and the transparent TPU film. The Bi2O3 substrate absorbed laser light and partially carbonized the TPU through thermal conduction. The controllable thermal energy generated by laser irradiation made the surface of the TPU film to produce a clear pattern in situ. Repeated experiments had further proved the sustainable use of this Bi2O3 substrate. In addition, laser current and scanning speed were also important parameters for controlling laser-induced carbonization. This research provides a positive reference for efficient, non-destructive, and repeatable laser-induced polymer patterns.

Bioinspired Superhydrophobic Surfaces via Laser-Structuring.

Bioinspired superhydrophobic surfaces are an artificial functional surface that mainly extracts morphological designs from natural organisms. In both laboratory research and industry, there is a need to develop ways of giving large-area surfaces water repellence. Currently, surface modification methods are subject to many challenging requirements such as a need for chemical-free treatment or high surface roughness. Laser micro-nanofabrications are a potential way of addressing these challenges, as they involve non-contact processing and outstanding patterning ability. This review briefly discusses multiple laser patterning methods, which could be used for surface structuring toward creating superhydrophobic surfaces.

Effect of laser patterning on the material behaviour of 22MnB5 steel with induced local strengthening

When using a supporting laser patterning method, it is possible to adaptively tailor the strength variations and formability of a pre-fabricated single panel. This paper focuses on the effect of line and geometrical laser patterning on the strength enhancement and material behaviour of steel sheets. To validate the performance of the laser patterning specimens, a tensile test for evaluating the in-plane deformation behaviour and a 3-point bending test for out-of-plane have been conducted while maintaining the area fraction for the laser-treated area. Close-type laser patterns, e.g., 0°, auxetic, and honeycomb, not only induce a substantial increase in strength but also enhance bending resistance without sacrificing the springback tendency of the initial sheet material.

An Innovative Laser Metasurface Fabrication Technique for Highly Flexible Optoelectronic Devices

Abstract Flexible optoelectronic devices have attracted considerable attention due to their low weight, portability, and ease of integration with other devices. However, major issues still exist: they are subject to repeated stresses, which often leads to damage; and the current fabrication methods such as photolithography and nano-imprint lithography can be very time-consuming or costly. This work aims to develop a novel cost-effective and time-efficient laser metasurface fabrication (LMF) technique for production of flexible optoelectronic devices. The experimental results have shown that the laser patterned flexible surfaces exhibit high visible transmittance, low sheet resistance, and extraordinary mechanical durability under repeated bending cycles. The laser patterned flexible surfaces have also demonstrated the potential to be utilized as heaters, which renders them new de-icing or de-fogging applications. This innovative laser patterning method will provide a new avenue for fabrication of multifunctional optoelectronic devices.

Femtosecond laser patterning based on the control of surface reflectance

In this study, we present a femtosecond laser patterning method based on the control of surface reflectance. This laser patterning method is based on the laser-induced periodic surface structure (LIPSS), and we first studied how the LIPSS pattern evolves and the corresponding surface reflectance changes as process parameters are varied in a large process window. It was found that the reflectance of stainless steel can be changed from 66% to 5%, and by choosing the proper parameters, elegant patterns can be fabricated. Using the method, a multi-faceted ball was successfully fabricated by employing 22 surface reflectance values. The mechanism behind the reflectance change and the effect of the shield gas on the surface morphology and patterning quality were also investigated.

Combined surface hardening and laser patterning approach for functionalising stainless steel surfaces

The paper reports a laser patterning method for producing surfaces with dual scale topographies on ferritic stainless steel plates that are hardened by low temperature plasma surface alloying. Nitrogen and carbon based gasses were used in the alloying process to obtain surface layers with an increased hardness from 172 HV to 1001 HV and 305 HV, respectively. Then, a nanosecond infrared laser was used to pattern the plasma treated surfaces and thus to obtain super-hydrophobicity, by creating cell- or channel-like surface structures. The combined surface hardening and laser patterning approach allowed super-hydrophobic surfaces to be produced on both nitrided and carburised stainless steel plates with effective contact angles higher than 150°. The hardened layers on nitrided samples had cracks and was delaminated after the laser patterning while on plasma carburised samples remained intact. The results showed that by applying the proposed combined approach it is possible to retain the higher hardness of the nitrided stainless steel plates and at the same time to functionalise them to obtain super-hydrophobic properties.

Humidity Sensing Properties of Paper Substrates and Their Passivation with ZnO Nanoparticles for Sensor Applications.

In this paper, we investigated the effect of humidity on paper substrates and propose a simple and low-cost method for their passivation using ZnO nanoparticles. To this end, we built paper-based microdevices based on an interdigitated electrode (IDE) configuration by means of a mask-less laser patterning method on simple commercial printing papers. Initial resistive measurements indicate that a paper substrate with a porous surface can be used as a cost-effective, sensitive and disposable humidity sensor in the 20% to 70% relative humidity (RH) range. Successive spin-coated layers of ZnO nanoparticles then, control the effect of humidity. Using this approach, the sensors become passive to relative humidity changes, paving the way to the development of ZnO-based gas sensors on paper substrates insensitive to humidity.

Highly efficient ITO-free organic light-emitting diodes employing a roughened ultra-thin silver electrode

We investigated an efficient organic light-emitting diodes (OLEDs) using an ultra-thin silver (Ag) anode, whereas Ag was deposited on a roughened glass substrate by laser patterning method. The thin-film property of this roughened silver anode exhibited an optical transmittance of more than 65% in visible light at 532 nm and a low electrical sheet resistance of 3.2 Ω/sq, which is superior to standard indium-tin-oxide (ITO) glass. Therefore, we report an ITO-free, exciplex-forming phosphorescent OLED showing Lambertian emission with a luminance of 128,000 cd/m2 at 8 V, and maximum current efficiency of 92.3 cd/A (external quantum efficiency of ∼24.5%) at 100 cd/m2. We also observed the improvement in hole-injection efficiency at the interface of the Ag anode/di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane due to the modification in the worfunction of roughened Ag anode from 4.6 to 5.4 eV.

CO_2 laser micromachining of nanocrystalline diamond films grown on doped silicon substrates

We demonstrate that nanocrystalline diamond films grown on highly doped silicon substrates can be patterned using a CO2 laser operating at a wavelength of 10.6 μm, where both low doped silicon and diamond exhibit negligible optical absorption. The patterning is initiated by free carrier absorption in the silicon substrate and further enhanced by the thermal runaway effect, which results in surface heating in the silicon substrate and subsequent thermal ablation of the diamond film in an oxygen rich atmosphere. Using this approach, micron-scale grating and dot patterns are patterned in thin film diamond. The localized heating is simulated and analyzed using concurrent optical and thermal finite element modelling. The laser patterning method described here offers a cost effective and rapid solution for micro-structuring diamond films.

Optimized holographic femtosecond laser patterning method towards rapid integration of high-quality functional devices in microchannels.

Rapid integration of high-quality functional devices in microchannels is in highly demand for miniature lab-on-a-chip applications. This paper demonstrates the embellishment of existing microfluidic devices with integrated micropatterns via femtosecond laser MRAF-based holographic patterning (MHP) microfabrication, which proves two-photon polymerization (TPP) based on spatial light modulator (SLM) to be a rapid and powerful technology for chip functionalization. Optimized mixed region amplitude freedom (MRAF) algorithm has been used to generate high-quality shaped focus field. Base on the optimized parameters, a single-exposure approach is developed to fabricate 200 × 200 μm microstructure arrays in less than 240 ms. Moreover, microtraps, QR code and letters are integrated into a microdevice by the advanced method for particles capture and device identification. These results indicate that such a holographic laser embellishment of microfluidic devices is simple, flexible and easy to access, which has great potential in lab-on-a-chip applications of biological culture, chemical analyses and optofluidic devices.