The Janus‐SAM Approach for the Flexible Functionalization of Gold and Titanium Oxide Surfaces

A novel approach is developed to address the requirement of multiple stamps and inks for microcontact printing (µCP) onto different substrate surfaces. This approach relies on µCP one divalent molecule, which is able to form Janus self‐assembled monolayers (JSAMs) with a labile cleavable centre, thus providing a facile method for the chemical derivatization of different substrate surfaces. This study presents an answer to the challenges presented within a highly versatile application, µCP. N‐(3‐diethylphosphatoxy)propyl‐11‐mercaptoundecanamide is used for the first time as an ink for µCP onto both gold and titanium oxide surfaces, utilizing the same polydimethylsiloxane stamp. Following printing, the JSAMs are enzymatically treated on these two different substrates to reveal different functional groups. The newly formed surfaces are subjected to additional surface reactions and used for the chemisorption of bovine serum albumin. At each stage, these JSAMs are characterized by X‐ray photoelectron spectroscopy and dynamic water‐contact‐angle measurements. Confocal laser scanning microscopy is used for the characterization of the adsorbed proteins.     

Microcontact Printing onto Oxide‐Free Silicon via Highly Reactive Acid Fluoride‐Functionalized Monolayers

This work describes a new route for patterning organic monolayers on oxide‐free silicon by microcontact printing (µCP) on a preformed, reactive, acid‐fluoride‐terminated monolayer. This indirect printing approach is fast and easily preserves the oxide‐free and well‐defined monolayer–silicon interface, which is the most important property for potential applications in biosensing and molecular electronics. Water‐contact‐angle measurements, ellipsometry, attenuated total reflection infrared spectroscopy, and X‐ray photoelectron spectroscopy (XPS) demonstrate the formation of the initial acid‐fluoride‐terminated monolayers without upside‐down attachment. Subsequent printing for twenty seconds with an N‐hexadecylamine‐inked poly(dimethylsiloxane) stamp results in well‐defined 5‐µm N‐hexadecylamide dots, as evidenced by atomic force microscopy and scanning electron microscopy. Printing with a flat stamp allows investigation of the efficiency of amide formation by µCP and water‐contact‐angle measurements, ellipsometry, and XPS reveal the quantitative conversion of the acid fluoride groups to the corresponding amide within twenty seconds. The absence of silicon oxide, even after immersion in water for 16 h, demonstrates that the oxide‐free monolayer–silicon interface is easily preserved by this patterning route. Finally, it is shown by fluorescence microscopy that complex biomolecules, like functionalized oligo‐DNA, can also be immobilized on the oxide‐free silicon surface via µCP.     

Edge transfer lithography using alkanethiol inks

Edge lithographic patterning techniques are based on the utilization of the edges of micrometer-sized template features for the reproduction of submicrometer structures. Edge transfer lithography (ETL) permits local surface modification in a single step by depositing self-assembled monolayers onto a metal substrate selectively along the feature edges of an elastomeric stamp. In this report two stamp designs are described that now allow for the use of alkanethiol inks in ETL and their use as etch resists to reproduce submicrometer structures in gold. Anisotropically modified stamps are shown to combine the potential for very high-resolution patterning with the versatility and simplicity of microcontact printing.     

印章特性和印刷压力对微接触印刷工艺的影响

微接触印刷（μCP）是一种能在微纳米尺度上完成表面图案化的技术,主要特点是高效和低成本．研究了μCP过程中印章机械特性和印刷压力对形成的微图案质量的影响．为了进一步分析聚二甲基硅氧烷（PDMS）制作的印章特性,浇注了5种配比的PDMS试样,并进行了单轴拉伸和压缩试验,获得了其应力应变关系．制作了3种配比的表面线型图案印章,实施微接触印刷使其印刷压强在1kPa～1MPa．通过图形化分析对最终的微接触印刷质量进行评估．实验结果表明：最优的压强区间为20～200kPa．较小的压力将会产生印章与基底的间隙,而较大的压力将会导致印章的严重变形．由于质量比为20：1的PDMS印章的弹性模量最小,其在中等压力下的微接触印刷质量最好,而较硬的印章可有效地抵抗印刷中产生的变形．     

Microcontact Printing with Laser Direct Writing Carbonization for Facile Fabrication of Carbon‐Based Ultrathin Disk Arrays and Ordered Holey Films

A nanometer‐thick carbon film with a highly ordered pattern structure is very useful in a variety of applications. However, its large‐scale, high‐throughput, and low‐cost fabrication is still a great challenge. Herein, microcontact printing (µCP) and direct laser writing carbonization (DLWc) are combined to develop a novel method that enables ease of fabrication of nanometer‐thick and regularly patterned carbon disk arrays (CDAs) and holey carbon films (HCFs) from a pyromellitic dianhydride‐oxydianiline‐based polyamic acid (PAA) solution. The effect of PAA concentration and pillar lattice structure of the polydimethyl siloxane stamp are systematically studied for their influence on the geometrical parameter, surface morphology, and chemical structure of the finally achieved CDAs and HCFs. Within the PAA concentration being investigated, the averaged thickness of CDAs and HCFs can be tailored in a range from a few tens to a few hundred of nanometers. The µCP+DLWc‐enabled electrically conductive CDAs and HCFs possess the characteristics of ease‐of‐fabrication, nanometer‐thickness, highly regular and controlled patterns and structures, and the ability to form on both hard and soft substrates, which imparts usefulness in electronics, photonics, energy storage, catalysis, tissue engineering, as well as physical, chemical, and bio‐sensing applications.     

Shaping Metallic Nanolattices: Design by Microcontact Printing from Wrinkled Stamps

A method for the fabrication of well‐defined metallic nanostructures is presented here in a simple and straightforward fashion. As an alternative to lithographic techniques, this routine employs microcontact printing utilizing wrinkled stamps, which are prepared from polydimethylsiloxane (PDMS), and includes the formation of hydrophobic stripe patterns on a substrate via the transfer of oligomeric PDMS. Subsequent backfilling of the interspaces between these stripes with a hydroxyl‐functional poly(2‐vinyl pyridine) then provides the basic pattern for the deposition of citrate‐stabilized gold nanoparticles promoted by electrostatic interaction. The resulting metallic nanostripes can be further customized by peeling off particles in a second microcontact printing step, which employs poly(ethylene imine) surface‐decorated wrinkled stamps, to form nanolattices. Due to the independent adjustability of the period dimensions of the wrinkled stamps and stamp orientation with respect to the substrate, particle arrays on the (sub)micro‐scale with various kinds of geometries are accessible in a straightforward fashion. This work provides an alternative, cost‐effective, and scalable surface‐patterning technique to fabricate nanolattice structures applicable to multiple types of functional nanoparticles. Being a top‐down method, this process could be readily implemented into, e.g., the fabrication of optical and sensing devices on a large scale.     

Highly loaded alumina inks for use in a piezoelectric print head

Ink jet printing techniques are used for an increasing number of materials and applications. Properties of the used inks have great influence on process stability and accuracy as well as the resulting part properties. Inks containing ceramic particles have been applied in various studies and applications. The criteria identifying suitable inks vary depending on the applied printing technology. In this study, inks for application in a piezoelectric print head were investigated. Alumina inks with solid loadings up to 21 vol.‐% were prepared and characterized. The Influence of different solid loadings, dispersant concentrations and binding agents was examined. The prepared inks show sufficient stability and fit literature recommendations for successful drop ejection. Considering rheological aspects, two inks with light shear‐thinning behaviour and viscosities of 18 mPas and 23 mPas at high shear rates were recommended for upcoming printing tests. The Re/We^1/2 ratio can be used for predetermination of print ability but the influence of the surface tension is not sufficiently taken into account using the presented calculations. So further printing experiments are essential for clarification of the calculations and obtained print ability values.     

3D Printing of Living Responsive Materials and Devices

3D printing has been intensively explored to fabricate customized structures of responsive materials including hydrogels, liquid‐crystal elastomers, shape‐memory polymers, and aqueous droplets. Herein, a new method and material system capable of 3D‐printing hydrogel inks with programed bacterial cells as responsive components into large‐scale (3 cm), high‐resolution (30 μm) living materials, where the cells can communicate and process signals in a programmable manner, are reported. The design of 3D‐printed living materials is guided by quantitative models that account for the responses of programed cells in printed microstructures of hydrogels. Novel living devices are further demonstrated, enabled by 3D printing of programed cells, including logic gates, spatiotemporally responsive patterning, and wearable devices.     

Axisymmetric thermo-mechanical analysis of laser-driven non-contact transfer printing

An axisymmetric thermo-mechanical model is developed for laser-driven non-contact transfer printing, which involves laser-induced impulsive heating to initiate separation at the interface between a soft, elastomeric stamp and hard micro/nanomaterials (i.e., inks) on its surface, due to a large mismatch in coefficients of thermal expansion. The result is the active ejection of the inks from the stamp, to a spatially separated receiving substrate, thereby representing the printing step. The model gives analytically the temperature field, and also a scaling law for the energy release rate for delamination at the interface between the stamp and an ink in the form of a rigid plate. The normalized critical laser pulse time for interfacial delamination depends only on the normalized absorbed laser power and width of the ink structure, and has been verified by experiments.     

Inside Front Cover: Direct Printing of 3D and Curvilinear Micrometer‐Sized Architectures into Solid Substrates with Sub‐micrometer Resolution (Adv. Mater. 15/2006)

The inside cover shows a hexagonal array of convex microlenses etched directly into glass using a reaction‐diffusion process initiated from a hydrogel stamp. The technique, reported by Grzybowski and co‐workers on p. 2004, allows for direct printing of complex microarchitectures into a variety of materials with sub‐micrometer resolution. The images were generated by longtime exposure of slowly rotating patterns. Cover design by Christopher J. Campbell.     

A 3D Self‐Shaping Strategy for Nanoresolution Multicomponent Architectures

3D printing or fabrication pursues the essential surface behavior manipulation of droplets or a liquid for rapidly and precisely constructing 3D multimaterial architectures. Further development of 3D fabrication desires a self‐shaping strategy that can heterogeneously integrate functional materials with disparate electrical or optical properties. Here, a 3D liquid self‐shaping strategy is reported for rapidly patterning materials over a series of compositions and accurately achieving micro‐ and nanoscale structures. The predesigned template selectively pins the droplet, and the surface energy minimization drives the self‐shaping processing. The as‐prepared 3D circuits assembled by silver nanoparticles carry a current of 208–448 µA at 0.01 V impressed voltage, while the 3D architectures achieved by two different quantum dots show noninterfering optical properties with feature resolution below 3 µm. This strategy can facilely fabricate micro‐nanogeometric patterns without a modeling program, which will be of great significance for the development of 3D functional devices.     

High‐Speed 3D Printing of Millimeter‐Size Customized Aspheric Imaging Lenses with Sub 7 nm Surface Roughness

Advancements in three‐dimensional (3D) printing technology have the potential to transform the manufacture of customized optical elements, which today relies heavily on time‐consuming and costly polishing and grinding processes. However the inherent speed‐accuracy trade‐off seriously constrains the practical applications of 3D‐printing technology in the optical realm. In addressing this issue, here, a new method featuring a significantly faster fabrication speed, at 24.54 mm³ h^?1, without compromising the fabrication accuracy required to 3D‐print customized optical components is reported. A high‐speed 3D‐printing process with subvoxel‐scale precision (sub 5 µm) and deep subwavelength (sub 7 nm) surface roughness by employing the projection micro‐stereolithography process and the synergistic effects from grayscale photopolymerization and the meniscus equilibrium post‐curing methods is demonstrated. Fabricating a customized aspheric lens 5 mm in height and 3 mm in diameter is accomplished in four hours. The 3D‐printed singlet aspheric lens demonstrates a maximal imaging resolution of 373.2 lp mm^?1 with low field distortion less than 0.13% across a 2 mm field of view. This lens is attached onto a cell phone camera and the colorful fine details of a sunset moth's wing and the spot on a weevil's elytra are captured. This work demonstrates the potential of this method to rapidly prototype optical components or systems based on 3D printing.     

Wafer scale synthesis of dense aligned arrays of single-walled carbon nanotubes

Here we present an easy one-step approach to pattern uniform catalyst lines for the growth of dense, aligned parallel arrays of single-walled carbon nanotubes (SWNTs) on quartz wafers by using photolithography or polydimethylsiloxane (PDMS) stamp microcontact printing (μCP). By directly doping an FeCl₃/methanol solution into Shipley 1827 photoresist or polyvinylpyrrolidone (PVP), various catalyst lines can be well-patterned on a wafer scale. In addition, during the chemical vapor deposition (CVD) growth of SWNTs the polymer layers play a very important role in the formation of mono-dispersed nanoparticles. This universal and efficient method for the patterning growth of SWNTs arrays on a surface is compatible with the microelectronics industry, thus enabling of the fabrication highly integrated circuits of SWNTs.     

Hydrothermal Coating of Patterned Carbon Nanotube Forest for Structured Lithium‐Ion Battery Electrodes

Controlling the arrangement and interface of nanoparticles is essential to achieve good transfer of charge, heat, or mechanical load. This is particularly challenging in systems requiring hybrid nanoparticle mixtures such as combinations of organic and inorganic materials. This work presents a process to coat vertically aligned carbon nanotube (CNT) forests with metal oxide nanoparticles using microwave‐assisted hydrothermal synthesis. Hydrothermal processes normally damage delicate CNT forests, which is addressed here by a combination of lithographic patterning, transfer printing, and reduction of the synthesis time. This process is applied for the fabrication of structured Li‐ion battery (LIB) electrodes where the aligned CNTs provide a straight electron transport path through the electrode and the hydrothermal coating process is used to coat the CNTs with conversion anode materials for LIBs. These nanoparticles are anchored on the surface of the CNTs and batteries fabricated following this process show a fourfold longer cyclability. Finally, this process is used to create thick electrodes (350 µm) with a gravimetric capacity of over 900 mAh g^?1.     

Patterning Hydrophobic Surfaces by Negative Microcontact Printing and Its Applications

Here, a negative microcontact printing method is developed to form hydrophilic polydopamine (PDA) patterns with micrometer resolution on hydrophobic including perfluorinated surfaces. In the process of the negative microcontact printing, a uniform PDA thin film is first formed on the hydrophobic surface. An activated polydimethylsiloxane (PDMS) stamp is then placed in contact with the PDA‐coated hydrophobic surface. Taking advantage of the difference in the surface energy between the hydrophobic surface and the stamp, PDA is removed from the contact area after the stamp release. As a result, a PDA pattern complementary to the stamp is obtained on the hydrophobic surface. By using the negative microcontact printing, arrays of liquid droplets and single cells are reliably formed on perfluorinated surfaces. Microlens array with tunable focal length for imaging studies is further created based on the droplet array. The negative microcontact printing method is expected to be widely applicable in high‐throughput chemical and biological screening and analysis.     

Microscale Electro‐Hydrodynamic Cell Printing with High Viability

Cell printing has gained extensive attentions for the controlled fabrication of living cellular constructs in vitro. Various cell printing techniques are now being explored and developed for improved cell viability and printing resolution. Here an electro‐hydrodynamic cell printing strategy is developed with microscale resolution (<100 µm) and high cellular viability (>95%). Unlike the existing electro‐hydrodynamic cell jetting or printing explorations, insulating substrate is used to replace conventional semiconductive substrate as the collecting surface which significantly reduces the electrical current in the electro‐hydrodynamic printing process from milliamperes (>0.5 mA) to microamperes (<10 µA). Additionally, the nozzle‐to‐collector distance is fixed as small as 100 µm for better control over filament deposition. These features ensure high cellular viability and normal postproliferative capability of the electro‐hydrodynamically printed cells. The smallest width of the electro‐hydrodynamically printed hydrogel filament is 82.4 ± 14.3 µm by optimizing process parameters. Multiple hydrogels or multilayer cell‐laden constructs can be flexibly printed under cell‐friendly conditions. The printed cells in multilayer hydrogels kept alive and gradually spread during 7‐days culture in vitro. This exploration offers a novel and promising cell printing strategy which might benefit future biomedical innovations such as microscale tissue engineering, organ‐on‐a‐chip systems, and nanomedicine.     

Patterning of Nanoparticle‐Based Aerogels and Xerogels by Inkjet Printing

Nanoparticle‐based voluminous 3D networks with low densities are a unique class of materials and are commonly known as aerogels. Due to the high surface‐to‐volume ratio, aerogels and xerogels might be suitable materials for applications in different fields, e.g. photocatalysis, catalysis, or sensing. One major difficulty in the handling of nanoparticle‐based aerogels and xerogels is the defined patterning of these structures on different substrates and surfaces. The automated manufacturing of nanoparticle‐based aerogel‐ or xerogel‐coated electrodes can easily be realized via inkjet printing. The main focus of this work is the implementation of the standard nanoparticle‐based gelation process in a commercial inkjet printing system. By simultaneously printing semiconductor nanoparticles and a destabilization agent, a 3D network on a conducting and transparent surface is obtained. First spectro‐electrochemical measurements are recorded to investigate the charge–carrier mobility within these 3D semiconductor‐based xerogel networks.     

Fabrication of Transistors on Flexible Substrates: from Mass‐Printing to High‐Resolution Alternative Lithography Strategies

In this report, the development of conventional, mass‐printing strategies into high‐resolution, alternative patterning techniques is reviewed with the focus on large‐area patterning of flexible thin‐film transistors (TFTs) for display applications. In the first part, conventional and digital printing techniques are introduced and categorized as far as their development is relevant for this application area. The limitations of conventional printing guides the reader to the second part of the progress report: alternative‐lithographic patterning on low‐cost flexible foils for the fabrication of flexible TFTs. Soft and nanoimprint lithography‐based patterning techniques and their limitations are surveyed with respect to patterning on low‐cost flexible foils. These show a shift from fabricating simple microlense structures to more complicated, high‐resolution electronic devices. The development of alternative, low‐temperature processable materials and the introduction of high‐resolution patterning strategies will lead to the low‐cost, self‐aligned fabrication of flexible displays and solar cells from cheaper but better performing organic materials.     

Laser‐Induced Molybdenum Carbide–Graphene Composites for 3D Foldable Paper Electronics

Versatile and low‐cost manufacturing processes/materials are essential for the development of paper electronics. Here, a direct‐write laser patterning process is developed to make conductive molybdenum carbide–graphene (MCG) composites directly on paper substrates. The hierarchically porous MCG structures are converted from fibrous paper soaked with the gelatin‐mediated inks containing molybdenum ions. The resulting Mo₃C₂ and graphene composites are mechanically stable and electrochemically active for various potential applications, such as electrochemical ion detectors and gas sensors, energy harvesters, and supercapacitors. Experimentally, the electrical conductivity of the composite is resilient to mechanical deformation with less than 5% degradation after 750 cycles of 180° repeated folding tests. As such, the direct laser conversion of MCGs on papers can be applicable for paper‐based electronics, including the 3D origami folding structures.