Direct Laser Writing Research Articles

Two-Photon Direct Laser Writing of Capillary-Coupled Nanosprayer Arrays for ESI-MS.

Electrospray is a widely recognized physical process and has various applications, such as in electrospinning, space propulsion, and mass spectrometry (MS). Particularly, electrospray emitters are integral to the exceptional performance of electrospray ionization mass spectrometry (ESI-MS). This study introduced a novel method for fabricating electrospray emitters using two-photon direct laser writing, resulting in the printing of nanosprayer arrays directly onto capillary tips. Utilizing a novel acrylic polyhedral oligomeric silsesquioxane photoresist, a multinozzle sprayer with micrometer scale channels was designed and printed on a capillary that is compatible with both frontend liquid chromatography and typical MS inlets. The 3D-printed sprayers demonstrated exceptional resistance to organic corrosion and high temperatures. For the nanosprayer arrays, an increase in the total electrospray current was achieved by augmenting the number of electrosprays, while maintaining a constant liquid flow rate and voltage. Notably, the eight-nozzle sprayers exhibited a 2.7-fold enhancement in sensitivity as compared with single-nozzle sprayers. This approach offers a versatile and high-sensitivity nanoelectrospray solution for ESI-MS.

Laser Cleaning‐Assisted Femtosecond Laser Direct Writing of Diamond Antireflective Microstructures with Superhigh Transmittance of 94.5% at 10.6 μm

Diamond‐based subwavelength antireflective microstructures are corrosion resistant, impact resistant, and possess high transmittance, thereby presenting broad application prospects in special optical windows. Nevertheless, fabricating uniform and highly transmissive subwavelength antireflective microstructures on diamond surfaces poses a significant challenge. The hard and brittle properties of diamond result in a large number of chips and particles, adhering to the surfaces during processing, which subsequently impacts the subsequent processing. Herein, a laser cleaning‐assisted femtosecond laser direct‐write processing technology is reported for fabricating subwavelength antireflective microstructures on diamond. To effectively avert the effects of chip accumulation, an elliptical laser spot is employed to clear the chips and polish the microstructure surface. The resulting highquality midinfrared antireflective microstructures are fabricated on diamond, and high transmittance (94.5%, with a 24.4% increase at 10 μm) within a broadband range (10–12 μm) is obtained, which represents the best results without antireflective coatings to the best of knowledge. Moreover, the antireflective structure possesses no significant angular dependence and maintains good working efficiency even at high temperature.

Graphene Oxide Foam-Based Floating Actuators Manipulated via Dual-Marangoni-Effect Propulsion and Magnetic-Field-Guided Navigation.

Intelligent stimuli-responsive actuators that can convert environmental energies into mechanical works have garnered significant research interests. Among different actuation principles, Marangoni effect is distinguished due to simplicity, high efficiency, remote manipulation, and water environment adaptability. Nevertheless, both chemical and physical Marangoni actuators face their own challenges with respect to limited chemical loading, precise light illumination, and relatively poor motion controllability. In this study, floating actuators based on graphene oxide foam (GOF), manipulable via dual Marangoni effects and magnetic field, are fabricated by Direct Laser Writing (DLW). This is the first work to realize dual-Marangoni-effect actuators. Specifically, it is observed that the actuator driven by the chemical Marangoni effect can attain an average speed of 0.57rads-1. Meanwhile, the actuator driven by the photothermal Marangoni effect is capable of reaching an average speed of 0.17rads-1, and the average speed is 1.34cms-1 under the manipulation of magnetic field. Multi-field coupling and dual Marangoni effects make actuators more flexible and intelligent, with promising potential for intelligent control and biomedical engineering.

Patterning Fine Pitch L/S on Photosensitive PBO Using Laser Direct Imaging for High-Density Interconnect Applications

With the miniaturization and enhanced functionality of devices, integrating various components into sophisticated, high-level packaging has become the new direction, moving beyond the limitations of Moore’s law for transistors. The “More than Moore” approach integrates different functional dies within a single package, relying on dense, high-performance interconnects as its framework. Fan-out wafer-level packaging (FOWLP) has become notable for its ability to connect different chiplets and components, with continued increase in input/output density to improve both electrical and thermal performance, while also being cost-effective and flexible in design. Such packaging necessitates advanced redistribution layers (RDL) for optimized performance. For high-density interconnect applications, various polymers are explored, including polybenzoxazoles (PBO), which is standing out due to its excellent mechanical and thermal properties, along with strong adhesion to various substrates. Meanwhile, for dense and intricate routing, more adaptable lithography methods are needed over traditional hard mask photolithography. Direct laser lithography emerges as a more flexible and economical option. This study delves into the finest line-space resolution achievable through direct laser lithography using a maskless aligner from Heidelberg Instruments, targeting sub-3um L/S ratio with photodefinable PBO. It also evaluates how different processing conditions such as substrate type, photoresist material, thickness, exposure dose, and defocus affect resolution limits.

Direct laser writing of planar and stretchable supercapacitors based on a graphene oxide and manganese dioxide nanoparticle composite on a paper substrate

Paper-based supercapacitors (P-SCs) exhibit superior electrochemical performance owing to the flexibility and unique surface properties of paper substrates. Currently, most P-SCs adopt a sandwich structure that is limited by electrode fabrication methods. However, the development of planar paper-based devices is crucial to satisfy the tremendous demand for wearable electronics. Herein, based on the mechanism of interaction between the laser and material, we used direct laser writing (DLW) techniques to fabricate in-plane P-SCs based on graphene oxide (GO) and manganese dioxide (MnO2) composite-covered paper substrates. Owing to the in-plane device structure and pseudocapacitive MnO2, the acquired rGO-MnO2-based planar P-SCs possessed a much higher specific capacitance value (17.7 mF/cm2) than that based on sandwich-structured reduced GO (rGO) (1.71 mF/cm2). In addition, three in-series integrated devices can be easily achieved via the DLW fabrication method, which shows potential for practical applications such as powering a light emitting diode. In addition, by carefully designing the paper substrate structure, the paper-based device exhibited excellent stretching stability. A specific capacitance retention of 86.8% remained after 5000 stretch cycles. Therefore, this study provides valuable insights into the design and fabrication of wearable paper-based electronics.

Multiphoton and Harmonic Imaging of Microarchitected Materials.

Microadditive manufacturing has revolutionized the production of complex, nano- to microscale components across various fields. This work investigates two-photon (2P) and three-photon (3P) fluorescence imaging, as well as third-harmonic generation (THG) microscopy, to examine periodic microarchitected lattice structures fabricated using multiphoton lithography (MPL). By immersing the structures in refractive index matching fluids, we demonstrate high-fidelity 3D reconstructions of both fluorescent structures using 2P and 3P microscopy as well as low-fluorescence structures using THG microscopy. These results show that multiphoton fluorescence (MPF) imaging offers reduced signal decay with respect to depth compared to single-photon techniques in the examined structures. We further demonstrate the ability to nondestructively identify intentional internal modifications of the structure that are not immediately visible with scanning electron microscope (SEM) images and compression-induced fractures, highlighting the potential of these techniques for quality control and defect detection in microadditively manufactured components.

Development of Micro/Nano Pattern Arrays with Grating-Based Periodic Structures using the Direct Laser Lithography System

Introduction: This research delves into utilizing the Direct Laser Lithography System to produce micro/nanopattern arrays with grating-based periodic structures. Initially, refining the variation in periodic structures within these arrays becomes a pivotal pursuit. This demands a deep comprehension of how structural variation aligns with specific applications, particularly in photonics and material science. Methods: Advancements in hardware, software, or process optimization techniques hold potential for reaching this objective. Using an optical beam, this system enables the engraving of moderate periodic and quasi-periodic structures, enhancing pattern formation in a three-dimensional environment. Through cost-effective direct-beam interferometry systems utilizing 405 nm GaN and 290 to 780 nm AlInGaN semiconductor laser diodes, patterns ranging from in period were created, employing 300 nm gratings. Results: The system's cost-efficiency and ability to achieve high-resolution permit the creation of both regular and irregular grating designs. By employing an optical head assembly from a bluray disc recorder, housing a semiconductor laser diode and an objective lens with an NA of 0.85, this system displays promising potential in progressing the fabrication of micro/nanopattern arrays. Conclusion: Assessing their optical, mechanical, and electrical properties and exploring potential applications across varied fields like optoelectronics, photovoltaics, sensors, and biomedical devices represent critical strides for further exploration and advancement.

Nonlinear Refraction and Absorption in Polymers Used for Femtosecond Direct Laser Writing.

Direct laser writing (DLW) has been recognized as a unique technique for three-dimensional (3D) prototyping with resolution beyond the diffraction limit. One trend in DLW technologies is the use of polymers, given their favorable mechanical properties and optical quality, rendering them promising for the next generation of nonlinear photonic devices. However, absorptive properties that facilitate DLW processes may also hinder the performance of polymers as all-optical devices. Furthermore, the increasing use of ultrashort pulse lasers makes refractive index dispersion a factor of fundamental importance in studying candidate materials for broadband applications. Here, we study the suitability of resins commonly used in DLW for all-optical broadband applications. We provide linear and nonlinear refractive and absorptive spectra of acrylate-based resins with different compositions, and IP-S and IP-Dip from Nanoscribe. We found nonlinear refractive indices four times higher than reported values for fused silica, one of the most widely used photonic materials, and we evaluate the potential of these materials using group velocity dispersion and figures of merits as comparative metrics.

Laser‐Direct‐Writing Reversible Aligned Wrinkling on Arbitrary Films Assisted by a Detachable Assembly Strategy

AbstractDynamic oriented wrinkling especially on arbitrary film materials is highly desirable yet remains a great challenge. Here, fabrication of programmable aligned wrinkling patterns on different film/substrate systems via a laser‐direct‐writing (LDW) method is reported, regardless of photofunctionality and transparence of the target films. The key is related to smart introduction of photothermal materials (PTMs) into compliant substrates and even as an independent attachable/detachable layer assembled underneath the film/substrate systems. Experiments and theoretical modeling reveal that with the help of the photothermal effect of PTMs, in situ LDW‐induced localized dynamic anisotropic stress field is responsible for the intriguing LDW path‐parallel aligned wrinkling. Furthermore, dimensional analysis is carried out and explicit solutions quantifying the connection of wrinkling morphology parameters with the LDW conditions are derived for the first time, which enables theoretical pattern designing. It is highlighted that the attachable/detachable assembly strategy for the independent PTMs layer endows arbitrary film/substrate systems with on‐demand photosensitivity when needed, which has been inaccessible previously. As demonstrated, these dynamic oriented wrinkling systems have found broad applications especially in smart soft photonics, e.g., information storage, anticounterfeiting, and responsive optical devices.

In Situ Laser Direct Writing of Graphene-Based Layered Hybrid Materials with Superhydrophilicity.

Laser-induced graphene (LIG) has attracted extensive attention as an electrode material. However, it usually exhibits limited electrochemical performance in many applications due to the limited electrical conductivity and charge storage properties. Herein, we proposed a simple and environmentally friendly strategy for in situ preparation of flexible Au/LIG/PI layered hybrid materials using laser direct writing. The transformation from hydrophobic to superhydrophilic of hybrid materials was successfully achieved. At a laser power of 6.0 W during laser reirradiation, the contact angle of the prepared Au/LIG/PI layered hybrid material was 0°. Characterizations confirmed a formed continuous Au layer covered on the porous LIG skeleton with a uniform distribution. The superhydrophilicity resulting from this unique microstructure greatly enhanced the electrochemical performance of the microsupercapacitors (MSCs) designed and fabricated based on Au/LIG/PI hybrid materials. Meanwhile, this MSC demonstrated excellent flexibility due to the PI substrate. The in situ preparation of superhydrophilic Au/LIG/PI layered hybrid materials provides a strategy for improving the performance of LIG-based MSCs, thereby enhancing their application potential.

A Gym for Cells—Direct Laser Writing of Magnetic Multilayered Micro Actuators for Mechanical Stimulation of Cells

A Gym for Cells—Direct Laser Writing of Magnetic Multilayered Micro Actuators for Mechanical Stimulation of Cells

Bio‐Inspired Hybrid Laser Direct Writing of Interfacial Adhesion for Universal Functional Coatings (Adv. Funct. Mater. 49/2024)

Bio‐Inspired Hybrid Laser Direct Writing of Interfacial Adhesion for Universal Functional Coatings (Adv. Funct. Mater. 49/2024)

Nanoscale thermal effects induce the evolution of electric transport of Nb bridges

Abstract We report the evolution of electric transport of Nb bridges based on nanoscale thermal effects created by nanolaser direct writing (NLDW) on Nb films. The laser–Nb-film interaction was investigated experimentally and by simulation. We demonstrate laser parameters such as irradiation power and interaction time to manipulate the electric transport of Nb bridges, such as the critical current and transition temperature, via simulation, which align with the electron probe microanalyzer results. Based on the optimized laser parameters, we realize the continual changes in current–voltage characteristics via increasing irradiation power. Furthermore, Nb bridges after laser irradiation show the oscillations of the critical current when we apply the coil current under a magnetic field that is perpendicular to the Nb bridges, which is similar to the Fraunhofer pattern in a Josephson junction under a magnetic field. In this case, NLDW shows the potential to manipulate electrical performances, which could be used to trim tri-layer junctions, tune shunt resistors, adjust critical currents or even induce a Josephson junction in situ by further shrinking of the laser spot.

Flexible Strain Sensor Based on Metallized Polyurethane Conductive Sponge Using Laser Direct Writing Process

Flexible Strain Sensor Based on Metallized Polyurethane Conductive Sponge Using Laser Direct Writing Process

Development of highly sensitive and stable patterned PDMS flexible strain sensors for motion monitoring via laser direct writing

Flexible strain sensors have received widespread attention for their potential applications in wearables, human–computer interaction, and healthcare. However, achieving a good balance between sensitivity, stretchability, and stability remains challenging. Here, we report a cost-effective and scalable fabrication strategy that combines laser direct writing (LDW) with 3D printing (3DP) to prepare various patterned Polydimethylsiloxane (P-PDMS) flexible strain sensors. By varying the laser parameters and processing paths, different microstructured patterns can be obtained, which significantly influence the sensor’s performance. By introducing patterned composite microstructures, the sensitivity of the strain sensor was increased by 339 % compared to the sensor without surface structures. Additionally, the strain sensors exhibit high stability and durability, a fast response time (140 ms), low hysteresis (0.009), and an ultra-low detection limit (0.0125 % strain). Besides, the sensors demonstrate excellent electrical performance and thermal stability. Based on their superior performance, we demonstrated their capability for real-time monitoring of human physiological signals. These findings successfully illustrate the potential of laser processing in fabricating complex microstructures, enabling the development of high-sensitivity flexible strain sensors for applications such as wearable health monitoring and human–computer interaction.

Intrinsically Thermally Degradable Microstructures Fabricated by Photodimerization in Rapid 3D Laser Printing

AbstractClassical photoresists utilized in direct laser writing (DLW) rely on photoinitiators and radical polymerization mechanisms to induce the cross‐linking process. Herein, a simple initiator‐free photoresist is introduced that enables the rapid fabrication of intrinsically thermally degradable 3D microstructures via DLW. The reported photoresist exploits the [2 + 2] photo‐dimerization reaction of a multifunctional monosubstituted thiomaleimide compound while harvesting on‐demand microstructure degradation through the intrinsic thermally reversible nature of the photocrosslinks. The photoresist exceeds attainable DLW printing speeds for non‐chain growth resins, readily attaining 1500 µm s−1 and up to 5000 µm s−1, making it a promising system to compete with traditional photo‐initiator containing resists while introducing on‐demand post‐printing degradability.

3-D Direct Laser Writing of Capacitive Ultrasonic Transceivers

3-D Direct Laser Writing of Capacitive Ultrasonic Transceivers

Ultracompact 3D Splitter for Single‐Core to Multi‐Core Optical Fiber Connections Fabricated Through Direct Laser Writing in Polymer (Laser Photonics Rev. 18(11)/2024)

Ultracompact 3D Splitter for Single‐Core to Multi‐Core Optical Fiber Connections Fabricated Through Direct Laser Writing in Polymer (Laser Photonics Rev. 18(11)/2024)

Ultra-high precision nano additive manufacturing of metal oxide semiconductors via multi-photon lithography

As a basic component of the versatile semiconductor devices, metal oxides play a critical role in modern electronic information industry. However, ultra-high precision nanopatterning of metal oxides often involves multi-step lithography and transfer process, which is time-consuming and costly. Here, we report a strategy, using metal-organic compounds as solid precursor photoresist for multi-photon lithography and post-sintering, to realize ultra-high precision additive manufacturing of metal oxides. As a result, we gain metal oxides including ZnO, CuO and ZrO2 with a critical dimension of 35 nm, which sets a benchmark for additive manufacturing of metal oxides. Besides, atomic doping can be easily accomplished by including the target element in precursor photoresist, and heterogeneous structures can also be created by multiple multi-photon lithography, allowing this strategy to accommodate the requirements of various semiconductor devices. For instance, we fabricate an ZnO photodetector by the proposed strategy.

3D Printing of Hierarchical Structures Made of Inorganic Silicon-Rich Glass Featuring Self-Forming Nanogratings.

Hierarchical structures are abundant in nature, such as in the superhydrophobic surfaces of lotus leaves and the structural coloration of butterfly wings. They consist of ordered features across multiple size scales, and their advantageous properties have attracted enormous interest in wide-ranging fields including energy storage, nanofluidics, and nanophotonics. Femtosecond lasers, which are capable of inducing various material modifications, have shown promise for manufacturing tailored hierarchical structures. However, existing methods, such as multiphoton lithography and three-dimensional (3D) printing using nanoparticle-filled inks, typically involve polymers and suffer from high process complexity. Here, we demonstrate the 3D printing of hierarchical structures in inorganic silicon-rich glass featuring self-forming nanogratings. This approach takes advantage of our finding that femtosecond laser pulses can induce simultaneous multiphoton cross-linking and self-formation of nanogratings in hydrogen silsesquioxane. The 3D printing process combines the 3D patterning capability of multiphoton lithography and the efficient generation of periodic structures by the self-formation of nanogratings. We 3D-printed micro-supercapacitors with large surface areas and a high areal capacitance of 1 mF/cm2 at an ultrahigh scan rate of 50 V/s, thereby demonstrating the utility of our 3D printing approach for device applications in emerging fields such as energy storage.