A Versatile Approach for Direct Patterning of Liquid Metal Using Magnetic Field

Patterning of liquid metal (LM) is usually an integral step toward its practical applications. However, the high surface tension along with surface oxide makes direct patterning of LM very challenging. Existing LM patterning techniques are designed for limited types of planar substrates, which require multiple‐step operation, delicate molds and masks, and expensive equipment. In this work, a simple, versatile, and equipment‐free approach for direct patterning of LM on various substrates using magnetic field is reported. To achieve this, magnetic microparticles are dispersed into LM by stirring. When a moving magnetic field is applied to the LM droplet, the aggregated magnetic microparticles deform the droplet to a continuous line. In addition, this approach is also applicable to supermetallophobic substrates since the applied magnetic field significantly enhances the contact between LM and substrate. Moreover, remote manipulation of the magnetic microparticles allows direct patterning of LM on nonplanar surfaces, even in a narrow and near closed space, which is impossible for the existing techniques. A few applications are also demonstrated using the proposed technique for flexible electronics and wearable sensors.     

Universal Patterning for 2D Van der Waals Materials via Direct Optical Lithography

Advanced patterning techniques are essential to pursue applications of 2D van der Waals (vdW) materials in electrical and optical devices. Here, the direct optical lithography (DOL) of vdW materials by single-pulse irradiation of high-power light through a photomask is reported. The DOL exhibits large-scale patterning with a sub-micrometer resolution and clean surface, which can be applied to various combinations of vdW materials and substrates. In addition, the thermal profile during DOL is investigated using the finite element method, and the ideal conditions of DOL according to the materials and substrates are determined.     

Direct Holographic Patterning of ZnO

Zinc oxide thin films are holographically patterned on submicronic scale by direct photodissolution method. The photodissolution process in solution is highly sensitive in the UV range (355 nm). 1D and 2D nanostructures are successfully obtained by this photoresist‐free process. The kinetic of the reaction is studied by recording the transmitted intensity through the evolution of the ZnO film thickness along the reaction time. Application of an electrical potential strongly increases the dissolution rate (1.5 μm min^?1) and decreases the pattern formation time. As a first demonstration of the potential of all‐in liquid direct ZnO heterostructuring, selective growth of ZnO nanorods is performed by chemical bath deposition using holographically patterned ZnO films as a substrate.     

Direct Laser Patterning of a 2D WSe2 Logic Circuit

Carrier doping is the basis of the modern semiconductor industry. Great efforts are put into the control of carrier doping for 2D semiconductors, especially the layered transition metal dichalcogenides. Here, the direct laser patterning of WSe₂ devices via light-induced hole doping is systematically studied. By changing the laser power, scan speed, and the number of irradiation times, different levels of hole doping can be achieved in the pristine electron-transport-dominated WSe₂, without obvious sample thinning. Scanning transmission electron microscopy characterization reveals that the oxidation of the laser-radiated WSe₂ is the origin of the carrier doping. Photocurrent mapping shows that after the same amount of laser irradiation, with increasing thickness, the laser patterned PN junction changes from the pure lateral to the vertical-lateral hybrid structure, accompanied by the decrease in the open circuit voltage. The vertical-lateral hybrid PN junction can be tuned to a pure lateral one by further irradiation, showing possibilities to construct complex junction profiles. Moreover, a NOR gate circuit is demonstrated by direct patterning of p-doped channels using laser irradiation without introducing passive layers and metal electrodes with different work functions. This method simplifies device fabrication procedures and shows a promising future in large scale logic circuit applications.     

A Universal Scheme for Patterning of Oxides via Thermal Nanoimprint Lithography

Direct patterning of oxides using thermal nanoimprint lithography is performed using either the sol‐gel or methacrylate route. The sol‐gel method results in resists with long shelf‐life, but with high surface energy and a considerable amount of solvent that affects the quality of imprinting. The methacrylate route, which is limited to certain oxides, produces polymerizable resists, leading to low surface energy, but suffers from the shorter shelf‐life of precursors. By combining the benignant elements from both these routes, a universal method of direct thermal nanoimprinting of oxides is demonstrated using precursors produced by reacting an alkoxide with a polymerizable chelating agent such as 2‐(methacryloyloxy)ethyl acetoacetate (MAEAA). MAEAA possesses β‐ketoester, which results in the formation of environmentally stable, chelated alkoxide with long shelf‐life, and methacrylate groups, which provide a reactive monomer pendant for in situ copolymerization with a cross‐linker during imprinting. Polymerization leads to trapping of cations, lowering of surface energy, strengthening of imprints, which enables easy and clean demolding over 1 cm × 2 cm patterned area with ≈100% yield. Heat‐treatment of imprints gives amorphous/crystalline oxide patterns. This alliance between two routes enables the successful imprinting of numerous oxides including Al₂O₃, Ga₂O₃, In₂O₃, Y₂O₃, B₂O₃, TiO₂, SnO₂, ZrO₂, GeO₂, HfO₂, Nb₂O₅, Ta₂O₅, V₂O₅, and WO₃.     

Enhanced Photocurrent Performance of Flexible Micro-Photodetector Based on PN Nanowires Heterojunction using All-Laser Direct Patterning

UV micro-photodetectors (mPDs) have received significant attention owing to the increasing demand for application in wearable healthcare devices. However, mPDs often suffer from tiny signals owing to their small size. Although this problem can be overcome by using low-dimensional nanomaterials with high surface-to-volume ratios, such as nanowires (NWs), selective synthesis of functional NWs on the desired position of the specific substrate is challenging. This study introduces, for the first time, the laser-induced hydrothermal growth (LIHG) process, in which a strongly focused laser beam generates a localized high-temperature field, enabling the localized growth of CuO NWs on the desired position of the specific substrate. Also, an all-laser direct patterning process for the fabrication of a flexible mPD based on a p-CuO NW/n-ZnO NW heterojunction is demonstrated. The PN NWs heterojunction exhibits remarkable photocurrent enhancement compared to a homojunction with a single semiconductor material. Furthermore, the all-laser direct patterning process of the flexible PN NWs heterojunction can be applied for the fabrication of other flexible optoelectronic applications.     

Patterning Colloidal Crystals and Nanostructure Arrays by Soft Lithography

As one of the most robust and versatile routes to fabricate ordered micro‐ and nanostructures, soft lithography has been extensively applied to pattern a variety of molecules, polymers, biomolecules, and nanomaterials. This paper provides an overview on recent developments employing soft lithography methods to pattern colloidal crystals and related nanostructure arrays. Lift‐up soft lithography and modified microcontact printing methods are applied to fabricate patterned and non‐close‐packed colloidal crystals with controllable lattice spacing and lattice structure. Combining selective etching, imprinting, and micromolding methods, these colloidal crystal arrays can be employed as templates for fabrication of nanostructure arrays. Realization of all these processes is favored by the solvent swelling, elasticity, thermodecomposition, and thermoplastic characteristics of polymer materials. Applications of these colloidal crystals and nanostructure arrays have also been explored, such as biomimetic antireflective surfaces, superhydrophobic coatings, surface‐enhanced Raman spectroscopy substrates, and so on.     

激光直接烧结成形金属零件的实验研究

分析了激光熔池的动态快速冷凝及“球化”效应机理，基于此采用激光烧结直接成形工艺对铁粉和Ni45合金粉末进行了一系列的激光烧结实验。结果表明,直接烧结单组元铁粉易出现翘曲变形和“球化效应”，成形质量不高，即使调整工艺参数获得多层烧结件，但致密度较低;而在基体上烧结Ni45合金粉末,在合适的工艺参数下获得了致密组织较好的多层烧结件，内部组织细密均匀，表面光滑平整，且与基体结合牢固。     

Direct Laser Interference Patterning of Zirconia Using Infra-Red Picosecond Pulsed Laser: Effect of Laser Processing Parameters on the Surface Topography and Microstructure

This study investigates the influence of processing parameters when applying direct laser interference patterning (DLIP) on the morphology and microstructure of zirconia surfaces using a 10 ps-pulsed laser source with 1064 nm wavelength. An experimental testing matrix is built with different values of laser fluence (5.7 – 18.2 J cm⁻²) and pulse overlap (66 – 98%). Surface morphology and microstructure are characterized by confocal microscopy and scanning electron microscopy. Homogeneous line-like patterns with periodic spatial repetition of 5.0 µm, with varying depths, widths, and aspect ratio, are fabricated using proper processing parameters (5.7 – 7.6 J cm⁻² and 92 – 96%). Structures with maximum depth of 1.5 µm and sharp edges are obtained (7.6 J cm⁻² and 96% overlap). Ablated regions presented a morphology typical of photophysical ablation mechanism, with signs of molten material at the surface. Sub-micrometric pores and nanodroplets are registered for all conditions, while sub-micrometric cracks developed only for higher fluences. A processing window conducing to homogenous DLIP structures is set based on experimental data. Periodic structures with multiscale topographic features are successfully obtained on zirconia surfaces using DLIP technology in this study. These outcomes open new perspectives for fabrication of multifunctional zirconia surfaces for advanced biomedical and engineering applications.     

Versatile Crystal Structures and (Opto)electronic Applications of the 2D Metal Mono‐, Di‐, and Tri‐Chalcogenide Nanosheets

Emerging 2D metal chalcogenides present excellent performance for electronic and optoelectronic applications. In contrast to graphene and other 2D materials, 2D metal chalcogenides possess intrinsic bandgaps, versatile band structures, and superior atmospheric stability. The many categories of 2D metal chalcogenides ensure that they can be applied to various practical scenarios. 2D metal monochalcogenides, dichalcogenides, and trichalcogenides are the three main categories of these materials. They have distinct crystal structures resulting in different characteristics. Some basic device characteristics, such as the charge carrier characteristics, scattering mechanisms, interfacial contacts, and band alignments of heterojunctions, are vital factors for practical device applications that ensure that the desired properties can be achieved. Various electronic, optoelectronic, and photonic applications based on 2D metal chalcogenides have been extensively investigated. 2D metal chalcogenides are considered as competitive candidates for future electronic and optoelectronic applications.     

Direct UV Patterning of Electronically Active Fullerene Films

We utilize UV light for the attainment of high‐resolution, electronically active patterns in [6,6]‐phenyl C₆₁‐butyric acid methyl ester (PCBM) films. The patterns are created by directly exposing selected parts of a solution‐cast PCBM film to UV light, and thereafter developing the film by immersing it in a tuned developer solution. We demonstrate that it is possible to attain complex, large‐area PCBM structures with a smallest demonstrated‐feature size of 1 μm by this method, and that the patterned PCBM material exhibits a high average electron mobility (1.2 × 10^?2 cm² V^?1 s^?1) in transistor experiments. The employment of UV light for direct patterning of PCBM for electronic applications is attractive, because PCBM exhibits high absorption in the UV range, and no sacrificial photoresist is needed. The patterning is achieved through the transformation by UV light of the soluble PCBM monomers into insoluble dimers with retained attractive electronic properties.     

Direct Surface Patterning from Solutions: Localized Microchemistry Using a Focused Laser

A method for creating microscale‐patterned surfaces by direct‐write lithography is described. A tightly focused, low‐power infrared laser beam is applied to a homogeneous precursor solution containing soluble reagents. When the laser is focused directly at a glass–solution interface, it initiates the local precipitation of a solid product that attaches firmly to the substrate. Operating the laser momentarily forms isolated spots, whereas moving the microscope stage or the laser spot draws continuous lines. The method has been demonstrated for metallic silver and gold, for oxidized copper, and for molybdenum disulfide, suggesting a broad range of suitable materials. Silver patterns were further modified by chemical reactions. Their morphology and physical properties can be altered during deposition by the use of capping agents, which may provide an onset for further functionalization.     

利用激光直写技术在塑料基材上三维金属布线

激光直写技术广泛应用于半导体、PCB等电子制造和电子封装行业[1～3]。文章介绍了利用激光直写技术在立体塑料表面烧蚀出线路图形,然后采用全加成技术金属布线的方法和原理,同时对立体塑料基材表面激光烧蚀区分别进行扫描电子显微镜(SEM)和电子散射能谱(EDS)分析,从后续镀上线路层的剥离强度和可靠性分析数据来看,这种新型的立体塑料基材以其独有的设计和制作优点将会在很多方面取代PCB而发挥更大的作用。     

影响全息光刻图形质量的因素

使用矩阵转换方法,对全息光刻中全息掩模衍射效率进行了数值模拟计算,讨论了记录介质显影前后特性的改变和再现时全息掩模复位精度对光刻图形质量的影响,并找出了影响图形质量的主要因素.在此基础上设计了实验系统,最后得到了分辨率基本上只受初始光掩模分辨率限制的光刻图形.     

Metal Conductive Surface Patterning on Photoactive Polyimide

Current fabrication methods for metal interconnects and contacts are generally based on conventional photoresist fabrication procedures that require expensive equipment and multiple material/time‐consuming steps. In this work, a photopatternable polyimide is synthesized via the copolymerization of a functional diamine monomer with a 1,4‐dihydropyridine side‐chain which can decompose under UV irradiation into a pyridine group—a promising ligand for palladium ions. After the absorption of palladium ions, the electroless copper plating is carried out to form metal patterns of copper. Copper patterns with smooth boundaries are confirmed by scanning electron microscope and atomic force microscope. Robust interfacial bonding between the copper and the polyimide film is evidenced by Scotch tape adhesion tests. The photopatternable polyimide has the advantages of low Pd consumption, easy operation without expansive equipment. The linear thermal expansion coefficient of the photopatternable polyimide remains close to the one of copper wire, demonstrating the adaptability of the photopatternable polyimide for integrated circuit application. This work presents the approach of (i) the synthesis of a novel photopatternable polyimide and (ii) its application for making flexible conductive metal structures and patterned metal interconnects, which can be expected to have tremendous potential in the field of flexible electronics.     

Direct Writing of Metal Nanoparticles by Localized Plasma Electrochemical Reduction of Metal Cations in Polymer Films

A non‐lithographic, dry approach to patterning metal nanoparticles is presented. Solutions of metal salt and polymer are spin‐coated onto a substrate, dried, and exposed to a rastered microscale plasma operated at atmospheric pressure and room temperature. Interaction of the electrons in the plasma with the film results in electrochemical reduction of the metal cations to crystalline metal nanoparticles. The process is highly localized, making it possible to obtain microscale patterns of metal nanoparticles with line widths as small as ～30 μm. We have applied this technique to a wide range of metals such as Ag, Au, Pt, Ir, and Ru, in various polymeric systems such as polyvinyl alcohol (PVA) and poly(methyl methacrylate) (PMMA). Overall, the approach allows the fabrication of transparent, flexible, patterned films of metal nanoparticles at low cost and high throughput for applications ranging from plasmonics to catalysis.     

Large‐Area Nanoscale Patterning of Functional Materials by Nanomolding in Capillaries

Within the past years there has been much effort in developing and improving new techniques for the nanoscale patterning of functional materials used in promising applications like nano(opto)electronics. Here a high‐resolution soft lithography technique—nanomolding in capillaries (NAMIC)—is demonstrated. Composite PDMS stamps with sub‐100 nm features are fabricated by nanoimprint lithography to yield nanomolds for NAMIC. NAMIC is used to pattern different functional materials such as fluorescent dyes, proteins, nanoparticles, thermoplastic polymers, and conductive polymers at the nanometer scale over large areas. These results show that NAMIC is a simple, versatile, low‐cost, and high‐throughput nanopatterning tool.     

Combinatorial Particle Patterning

The unique properties of solid particles make them a promising element of micro‐ and nanostructure technologies. Solid particles can be used as building blocks for micro and nanostructures, carriers of monomers, or catalysts. The possibility of patterning different kinds of particles on the same substrate opens the pathway for novel combinatorial designs and novel technologies. One of the examples of such technologies is the synthesis of peptide arrays with amino acid particles. This review examines the known methods of combinatorial particle patterning via static electrical and magnetic fields, laser radiation, patterning by synthesis, and particle patterning via chemically modified or microstructured surfaces.