Towards scanning probe lithography-based 4D nanoprinting by advancing surface chemistry, nanopatterning strategies, and characterization protocols

3D Nanolithography by Means of Lipid Ink Spreading Inhibition

While patterning 2D metallic nanostructures are well established through different techniques, 3D printing still constitutes a major bottleneck on the way to device miniaturization. In this work a fluid phase phospholipid ink is used as a building block for structuring with dip-pen nanolithography. Following a bioinspired approach that relies on ink-spreading inhibition, two processes are presented to build 2D and 3D metallic structures. Serum albumin, a widely used protein with an innate capability to bind to lipids, is the key in both processes. Covering the sample surface with it prior to lipid writing, anchors lipids on the substrate, which ultimately allows the creation of highly stable 3D lipid-based scaffolds to build metallic structures.

UV- and Visible-Light Photopatterning of Molecular Gradients Using the Thiol-yne Click Reaction

The rational design of chemical coatings is used to control surface interactions with small molecules, biomolecules, nanoparticles, and liquids as well as optical and other properties. Specifically, micropatterned surface coatings have been used in a wide variety of applications, including biosensing, cell growth assays, multiplexed biomolecule interaction arrays, and responsive surfaces. Here, a maskless photopatterning process is studied, using the photocatalyzed thiol-yne "click" reaction to create both binary and gradient patterns on thiolated surfaces. Nearly defect-free patterns are produced by first coating glass surfaces with mercaptopropylsilatrane, a silanizing agent that forms smoother self-assembled monolayers than the commonly used 3-mercaptopropyltrimethoxysilane. Photopatterning is then performed using UV (365 nm) or visible (405 nm) light to graft molecules onto the surface in tunable concentrations based on the local exposure. The technique is demonstrated for multiple types of molecular grafts, including fluorescent dyes, poly(ethylene glycol), and biotin, the latter allowing subsequent deposition of biomolecules via biotin-avidin binding. Patterning is demonstrated in water and dimethylformamide, and the process is repeated to combine molecules soluble in different phases. The combination of arbitrary gradient formation, broad applicability, a low defect rate, and fast prototyping thanks to the maskless nature of the process creates a particularly powerful technique for molecular surface patterning that could be used for a wide variety of micropatterned applications.

Nanolayer Laser Absorber for Femtoliter Chemistry in Polymer Reactors

Laser-induced forward transfer (LIFT) has the potential to be an alternative approach to atomic force microscopy based scanning probe lithography techniques, which have limitations in high-speed and large-scale patterning. However, traditional donor slides limit the resolution and chemical flexibility of LIFT. Here, a hematite nanolayer absorber for donor slides to achieve high-resolution transfers down to sub-femtoliters is proposed. Being wettable by both aqueous and organic solvents, this new donor significantly increases the chemical scope for the LIFT process. For parallel amino acid coupling reactions, the patterning resolution can now be increased more than five times (>111 000 spots cm^{- 2} for hematite donor vs 20 000 spots cm^{- 2} for standard polyimide donor) with even faster scanning (2 vs 6 ms per spot). Due to the increased chemical flexibility, other types of reactions inside ultrasmall polymer reactors: copper (I) catalyzed click chemistry and laser-driven oxidation of a tetrahydroisoquinoline derivative, suggesting the potential of LIFT for both deposition of chemicals, and laser-driven photochemical synthesis in femtoliters within milliseconds can be explored. Since the hematite shows no damage after typical laser transfer, donors can be regenerated by heat treatment. These findings will transform the LIFT process into an automatable, precise, and highly efficient technology for high-throughput femtoliter chemistry.

Nanofabrication Techniques: Challenges and Future Prospects

Nanofabrication of functional micro/nano-features is becoming increasingly relevant in various electronic, photonic, energy, and biological devices globally. The development of these devices with special characteristics originates from the integration of low-cost and high-quality micro/nano-features into 3D-designs. Great progress has been achieved in recent years for the fabrication of micro/nanostructured based devices by using different imprinting techniques. The key problems are designing techniques/approaches with adequate resolution and consistency with specific materials. By considering optical device fabrication on the large-scale as a context, we discussed the considerations involved in product fabrication processes compatibility, the feature's functionality, and capability of bottom-up and top-down processes. This review summarizes the recent developments in these areas with an emphasis on established techniques for the micro/nano-fabrication of 3-dimensional structured devices on large-scale. Moreover, numerous potential applications and innovative products based on the large-scale are also demonstrated. Finally, prospects, challenges, and future directions for device fabrication are addressed precisely.

Dip-Pen Nanolithography(DPN): from Micro/Nano-patterns to Biosensing

Dip-pen nanolithography is an emerging and attractive surface modification technique that has the capacity to directly and controllably write micro/nano-array patterns on diverse substrates. The superior throughput, resolution, and registration enable DPN an outstanding candidate for biological detection from the molecular level to the cellular level. Herein, we overview the technological evolution of DPN in terms of its advanced derivatives and DPN-enabled versatile sensing patterns featuring multiple compositions and structures for biosensing. Benefitting from uniform, reproducible, and large-area array patterns, DPN-based biosensors have shown high sensitivity, excellent selectivity, and fast response in target analyte detection and specific cellular recognition. We anticipate that DPN-based technologies could offer great potential opportunities to fabricate multiplexed, programmable, and commercial array-based sensing biochips.

Glycopolymer Microarrays with Sub-Femtomolar Avidity for Glycan Binding Proteins Prepared by Grafted-To/Grafted-From Photopolymerizations

We report a novel glycan array architecture that binds the mannose-specific glycan binding protein, concanavalin A (ConA), with sub-femtomolar avidity. A new radical photopolymerization developed specifically for this application combines the grafted-from thiol-(meth)acrylate polymerization with thiol-ene chemistry to graft glycans to the growing polymer brushes. The propagation of the brushes was studied by carrying out this grafted-to/grafted-from radical photopolymerization (GTGFRP) at >400 different conditions using hypersurface photolithography, a printing strategy that substantially accelerates reaction discovery and optimization on surfaces. The effect of brush height and the grafting density of mannosides on the binding of ConA to the brushes was studied systematically, and we found that multivalent and cooperative binding account for the unprecedented sensitivity of the GTGFRP brushes. This study further demonstrates the ease with which new chemistry can be tailored for an application as a result of the advantages of hypersurface photolithography.

Orthogonal Images Concealed Within a Responsive 6-Dimensional Hypersurface

A photochemical printer, equipped with a digital micromirror device (DMD), leads to the rapid elucidation of the kinetics of the surface-initiated atom-transfer radical photopolymerization of N,N-dimethylacrylamide (DMA) and N-isopropylacrylamide (NIPAM) monomers. This effort reveals conditions where polymer brushes of identical heights can be grown from each monomer. With these data, hidden images are created that appear upon heating the substrate above the lower critical solution temperature (LCST) of polyNIPAM. By introducing a third monomer, methacryloxyethyl thiocarbamoyl rhodamine B, a second, orthogonal image appears upon UV-irradiation. With these studies, it is shown how a new photochemical printer accelerates discovery, creates arbitrary patterns, and addresses long-standing problems in brush polymer and surface chemistry. With this technology in hand a new method is demonstrated to encrypt data within hypersurfaces.

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials

There is an astonishing number of optoelectronic, photonic, biological, sensing, or storage media devices, just to name a few, that rely on a variety of extraordinary periodic surface relief miniaturized patterns fabricated on polymer-covered rigid or flexible substrates. Even more extraordinary is that these surface relief patterns can be further filled, in a more or less ordered fashion, with various functional nanomaterials and thus can lead to the realization of more complex structured architectures. These architectures can serve as multifunctional platforms for the design and the development of a multitude of novel, better performing nanotechnological applications. In this work, we aim to provide an extensive overview on how multifunctional structured platforms can be fabricated by outlining not only the main polymer patterning methodologies but also by emphasizing various deposition methods that can guide different structures of functional nanomaterials into periodic surface relief patterns. Our aim is to provide the readers with a toolbox of the most suitable patterning and deposition methodologies that could be easily identified and further combined when the fabrication of novel structured platforms exhibiting interesting properties is targeted.

Evolution and applications of polymer brush hypersurface photolithography

Hypersurface photolithography creates arbitrary polymer brush patterns with independent control over feature diameter, height, and spacing between features, while controlling composition along a polymer chain and between features.

Bio-inspired chiral self-assemblies promoted neuronal differentiation of retinal progenitor cells through activation of metabolic pathway

Retinal degeneration is a main class of ocular diseases. So far, retinal progenitor cell (RPC) transplantation has been the most potential therapy for it, in which promoting RPCs neuronal differentiation remains an unmet challenge. To address this issue, innovatively designed _{L/ d -} phenylalanine based chiral nanofibers (LPG and DPG) are employed and it finds that chirality of fibers can efficiently regulate RPCs differentiation. qPCR, western blot, and immunofluorescence analysis show that right-handed helical DPG nanofibers significantly promote RPCs neuronal differentiation, whereas left-handed LPG nanofibers decrease this effect. These effects are mainly ascribed to the stereoselective interaction between chiral helical nanofibers and retinol-binding protein 4 (RBP4, a key protein in the retinoic acid (RA) metabolic pathway). The findings of chirality-dependent neuronal differentiation provide new strategies for treatment of neurodegenerative diseases via optimizing differentiation of transplanted stem cells on chiral nanofibers.

Recent progress in creating complex and multiplexed surface-grafted macromolecular architectures

Surface-grafted macromolecules, including polymers, DNA, peptides, etc., are versatile modifications to tailor the interfacial functions in a wide range of fields. In this review, we aim to provide an overview of the most recent progress in engineering surface-grafted chains for the creation of complex and multiplexed surface architectures over micro- to macro-scopic areas. A brief introduction to surface grafting is given first. Then the fabrication of complex surface architectures is summarized with a focus on controlled chain conformations, grafting densities and three-dimensional structures. Furthermore, recent advances are highlighted for the generation of multiplexed arrays with designed chemical composition in both horizontal and vertical dimensions. The applications of such complicated macromolecular architectures are then briefly discussed. Finally, some perspective outlooks for future studies and challenges are suggested. We hope that this review will be helpful to those just entering this field and those in the field requiring quick access to useful reference information about the progress in the properties, processing, performance, and applications of functional surface-grafted architectures.

Artificial Biosystems by Printing Biology

The continuous progress of printing technologies over the past 20 years has fueled the development of a plethora of applications in materials sciences, flexible electronics, and biotechnologies. More recently, printing methodologies have started up to explore the world of Artificial Biology, offering new paradigms in the direct assembly of Artificial Biosystems (small condensates, compartments, networks, tissues, and organs) by mimicking the result of the evolution of living systems and also by redesigning natural biological systems, taking inspiration from them. This recent progress is reported in terms of a new field here defined as Printing Biology, resulting from the intersection between the field of printing and the bottom up Synthetic Biology. Printing Biology explores new approaches for the reconfigurable assembly of designed life-like or life-inspired structures. This work presents this emerging field, highlighting its main features, i.e., printing methodologies (from 2D to 3D), molecular ink properties, deposition mechanisms, and finally the applications and future challenges. Printing Biology is expected to show a growing impact on the development of biotechnology and life-inspired fabrication.

Visualization of materials using the confocal laser scanning microscopy technique

The development of materials science always benefits from advanced characterizations. Currently, imaging techniques are of great technological importance in both fundamental and applied research on materials. In comparison to conventional visualization methods, confocal laser scanning microscopy (CLSM) is non-invasive, with macroscale and high-contrast scanning, a simple and fast sample preparation procedure as well as easy operation. In addition, CLSM allows rapid acquisition of longitudinal and cross-sectional images at any position in a material. Therefore, the CLSM-based visualization technique could provide direct and model-independent insight into material characterizations. This review summarizes the recent applications of CLSM in materials science. The current CLSM approaches for the visualization of surface structures, internal structures, spatial structures and reaction processes are discussed in detail. Finally, we provide our thoughts and predictions on the future development of CLSM in materials science. The purpose of this review is to guide researchers to build a suitable CLSM approach for material characterizations, and to open viable opportunities and inspirations for the development of new strategies aiming at the preparation of advanced materials. We hope that this review will be useful for a wide range of research communities of materials science, chemistry, and engineering.

Scanning Probe-Directed Assembly and Rapid Chemical Writing Using Nanoscopic Flow of Phospholipids

Nanofluidic systems offer a huge potential for discovery of new molecular transport and chemical phenomena that can be employed for future technologies. Herein, we report on the transport behavior of surface-reactive compounds in a nanometer-scale flow of phospholipids from a scanning probe. We have investigated microscopic deposit formation on polycrystalline gold by lithographic printing and writing of 1,2-dioleoyl-sn-glycero-3-phosphocholine and eicosanethiol mixtures, with the latter compound being a model case for self-assembled monolayers (SAMs). By analyzing the ink transport rates, we found that the transfer of thiols was fully controlled by the fluid lipid matrix allowing to achieve a certain jetting regime, i.e., transport rates previously not reported in dip-pen nanolithography (DPN) studies on surface-reactive, SAM-forming molecules. Such a transport behavior deviated significantly from the so-called molecular diffusion models, and it was most obvious at the high writing speeds, close to 100 μm s^-1. Moreover, the combined data from imaging ellipsometry, scanning electron microscopy, atomic force microscopy (AFM), and spectroscopy revealed a rapid and efficient ink phase separation occurring in the AFM tip-gold contact zone. The force curve analysis indicated formation of a mixed ink meniscus behaving as a self-organizing liquid. Based on our data, it has to be considered as one of the co-acting mechanisms driving the surface reactions and self-assembly under such highly nonequilibrium, crowded environment conditions. The results of the present study significantly extend the capabilities of DPN using standard AFM instrumentation: in the writing regime, the patterning speed was already comparable to that achievable by using electron beam systems. We demonstrate that lipid flow-controlled chemical patterning process is directly applicable for rapid prototyping of solid-state devices having mesoscopic features as well as for biomolecular architectures.

Graphite and Graphene Fairy Circles: A Bottom-Up Approach for the Formation of Nanocorrals

A convenient covalent functionalization approach and nanopatterning method of graphite and graphene is developed. In contrast to expectations, electrochemically activated dediazotization of a mixture of two aryl diazonium compounds in aqueous media leads to a spatially inhomogeneous functionalization of graphitic surfaces, creating covalently modified surfaces with quasi-uniform spaced islands of pristine graphite or graphene, coined nanocorrals. Cyclic voltammetry and chronoamperometry approaches are compared. The average diameter (45-130 nm) and surface density (20-125 corrals/μm²) of these nanocorrals are tunable. These chemically modified nanostructured graphitic (CMNG) surfaces are characterized by atomic force microscopy, scanning tunneling microscopy, Raman spectroscopy and microscopy, and X-ray photoelectron spectroscopy. Mechanisms leading to the formation of these CMNG surfaces are discussed. The potential of these surfaces to investigate supramolecular self-assembly and on-surface reactions under nanoconfinement conditions is demonstrated.

Development of Dip-Pen Nanolithography (DPN) and Its Derivatives

Dip-pen nanolithography (DPN) is a unique nanofabrication tool that can directly write a variety of molecular patterns on a surface with high resolution and excellent registration. Over the past 20 years, DPN has experienced a tremendous evolution in terms of applicable inks, a remarkable improvement in fabrication throughput, and the development of various derivative technologies. Among these developments, polymer pen lithography (PPL) is the most prominent one that provides a large-scale, high-throughput, low-cost tool for nanofabrication, which significantly extends DPN and beyond. These developments not only expand the scope of the wide field of scanning probe lithography, but also enable DPN and PPL as general approaches for the fabrication or study of nanostructures and nanomaterials. In this review, a focused summary and historical perspective of the technological development of DPN and its derivatives, with a focus on PPL, in one timeline, are provided and future opportunities for technological exploration in this field are proposed.

Nanotribological Printing: A Nanoscale Additive Manufacturing Method

Additive manufacturing methods are transforming the way components and devices are fabricated, which in turn is opening up completely new vistas for conceiving and designing products and engineered systems. Small-scale (submicrometer) additive manufacturing methods are largely in their infancy. While a number of methods exist, a particular challenge lies in finding methods that can produce a range of materials while obtaining sufficiently robust mechanical properties. In this paper, we describe a novel nanoscale additive manufacturing technique deemed "Nanotribological Printing" (NTP), which creates structures through tribomechanical and tribochemical surface interactions at the contact between a substrate and an atomic force microscope probe, where material pattern formation is driven by normal and shear contact stresses. The "ink" consists of nanoparticles or molecules dispersed in a carrier fluid surrounding the atomic force microscope (AFM) probe, which are entrained into the contact during sliding. Being stress-driven, patterning only occurs locally within regions which experience contact and sufficiently high stresses. Thus, imaging and measurement to characterize the morphology and properties of the deposited structures can be conducted in situ during the manufacturing process. Moreover, using local mechanical energy as the kinetic driver activating the solidification process, the method is compact and does not require application of a bias voltage or laser exposure and can be performed at ambient temperatures. We demonstrate (1) control of pattern dimensions with sub-100 nm lateral and sub-5 nm thickness control through variations in contact size and applied stress, (2) creation of amorphous, polycrystalline, and nanocomposite structures including sequential multimaterial deposition, and (3) formation of manufactured structures which exhibit mechanical properties approaching those of bulk counterparts. The ability to create nanoscale patterns using standard AFM cantilever probes and operation modes (contact mode scanning in fluid) with commercial AFM instruments, independent of substrate, establishes NTP as a versatile and easily accessible method for nanoscale additive manufacturing.

Combinatorial Synthesis of Macromolecular Arrays by Microchannel Cantilever Spotting (µCS)

Surface-bound microarrays of multiple oligo- and macromolecules (e.g., peptides, DNA) offer versatile options in biomedical applications like drug screening, DNA analysis, or medical diagnostics. Combinatorial syntheses of these molecules in situ can save significant resources in regard to processing time and material use. Furthermore, high feature densities are needed to enable high-throughput and low sample volumes as generally regarded in combinatorial chemistry. Here, a scanning-probe-lithography-based approach for the combinatorial in situ synthesis of macromolecules is presented in microarray format. Feature sizes below 40 µm allow for the creation of high-density arrays with feature densities of 62 500 features per cm² . To demonstrate feasibility of this approach for biomedical applications, a multiplexed array of functional protein tags (HA- and FLAG-tag) is synthesized, and selective binding of respective epitope recognizing antibodies is shown. This approach uses only small amounts of base chemicals for synthesis and can be further parallelized, therefore, opening up a route to flexible, highly dense, and cost-effective microarrays.

Spatially resolved acyl transfer on surface by organo-catalytic scanning probe nanolithography (o-cSPL)

Local and catalytic acyl transfer for multipatterning of surfaces.

Groundbreaking research done in the area of nanolithography makes it a versatile tool to produce nanopatterns for a broad range of chemical surface functionalization or physical modifications. We report for the first time an organocatalytic scanning probe nanolithography (o-cSPL) approach. Covalent binding of an organocatalyst on the apex of an atomic force microscope (AFM) tip gives way to a system that allows the formation of locally defined acylated-alcohol patterns on self-assembled monolayers (SAMs). With resolutions comparable to those of other cSPL methods, this first example of o-cSPL holds promise for future applications of bottom-up nanolithography set-ups employing this novel technique.

DNA metallization: principles, methods, structures, and applications

This review summarizes the research activities on DNA metallization since the concept was first proposed in 1998, covering the principles, methods, structures, and applications.

Enhanced bioactivity and osteoinductivity of carboxymethyl chitosan/nanohydroxyapatite/graphene oxide nanocomposites

Tissue engineering approaches combine a bioscaffold with stem cells to provide biological substitutes that can repair bone defects and eventually improve tissue functions. The prospective bioscaffold should have good osteoinductivity. Surface chemical and roughness modifications are regarded as valuable strategies for developing bioscaffolds because of their positive effects on enhancing osteogenic differentiation. However, the synergistic combination of the two strategies is currently poorly studied. In this work, a nanoengineered scaffold with surface chemistry (oxygen-containing groups) and roughness (R_q = 74.1 nm) modifications was fabricated by doping nanohydroxyapatite (nHA), chemically crosslinked graphene oxide (GO) and carboxymethyl chitosan (CMC). The biocompatibility and osteoinductivity of the nanoengineered CMC/nHA/GO scaffold was evaluated in vitro and in vivo, and the osteogenic differentiation mechanism of the nanoengineered scaffold was preliminarily investigated. Our data demonstrated that the enhanced osteoinductivity of CMC/nHA/GO may profit from the surface chemistry and roughness, which benefit the β1 integrin interactions with the extracellular matrix and activate the FAK–ERK signaling pathway to upregulate the expression of osteogenic special proteins. This study indicates that the nanocomposite scaffold with surface chemistry and roughness modifications could serve as a novel and promising bone substitute for tissue engineering.

The CMC/nHA/GO scaffold with the surface chemistry and roughness dual effects and the release of phosphate and calcium ions synergistically assist the mineralization and facilitate the bone regeneration.

Solution-Phase Photochemical Nanopatterning Enabled by High-Refractive-Index Beam Pen Arrays

A high-throughput, solution-based, scanning-probe photochemical nanopatterning approach, which does not require the use of probes with subwavelength apertures, is reported. Specifically, pyramid arrays made from high-refractive-index polymeric materials were constructed and studied as patterning tools in a conventional liquid-phase beam pen lithography experiment. Two versions of the arrays were explored with either metal-coated or metal-free tips. Importantly, light can be channeled through both types of tips and the appropriate solution phase (e.g., H₂O or CH₃OH) and focused on subwavelength regions of a substrate to effect a photoreaction in solution that results in localized patterning of a self-assembled monolayer (SAM)-coated Au thin film substrate. Arrays with as many as 4500 pyramid-shaped probes were used to simultaneously initiate thousands of localized free-radical photoreactions (decomposition of a lithium acylphosphinate photoinitiator in an aqueous solution) that result in oxidative removal of the SAM. The technique is attractive since it allows one to rapidly generate features less than 200 nm in diameter, and the metal-free tips afford more than 10-fold higher intensity than the tips with nanoapertures over a micrometer propagation length. In principle, this mask-free method can be utilized as a versatile tool for performing a wide variety of photochemistries across multiple scales that may be important in high-throughput combinatorial screening applications related to chemistry, biology, and materials science.

Recent Advances in Cantilever-Free Scanning Probe Lithography: High-Throughput, Space-Confined Synthesis of Nanostructures and Beyond

Scalability is the major challenge for scanning probe lithography (SPL). Recently developed cantilever-free scanning probe technologies provide a solution to the issue of scalability by incorporating massive arrays of polymer pens, which fundamentally overcome the low-throughput nature of SPL. The further development of cantilever-free SPL brings up a variety of applications in electronics, biology, and chemical synthesis. In this Perspective, we highlight the space-confined synthesis of complex nanostructures enabled by different types of cantilever-free SPL technologies.

Toward 4D Nanoprinting with Tip-Induced Organic Surface Reactions

Future nanomanufacturing tools will prepare organic materials with complex four-dimensional (4D) structure, where the position (x, y, z) and chemical composition within a volume is controlled with sub-1 μm spatial resolution. Such tools could produce substrates that mimic biological interfaces, like the cell surface or the extracellular matrix, whose topology and chemical complexity combine to direct some of the most sophisticated biological events. The control of organic materials at the nanoscale-level of spatial resolution could revolutionize the assembly of next generation optical and electronic devices or substrates for tissue engineering or enable fundamental biological or material science investigations. Organic chemistry provides the requisite control over the orientation and position of matter within a nanoscale reference frame through the formation of new covalent bonds. Several challenges however preclude the integration of organic chemistry with conventional nanomanufacturing approaches, namely most nanolithography platforms would denature or destroy delicate organic and biologically active matter, confirming covalent bond formation at interfaces remains difficult, and finally, only a small handful of the reactions used to transform molecules in solution have been validated on surfaces. Thus, entirely new approaches, where organic transformations and spatial control are considered equally important contributors, are needed to create 4D organic nanoprinting platforms. This Account describes efforts from our group to reconcile nanolithography, and specifically massively parallel scanning probe lithography (SPL), with organic chemistry to further the goal of 4D organic nanoprinting. Massively parallel SPL involves arrays of elastomeric pyramids mounted onto piezoelectric actuators, and creates patterns with feature diameters below 50 nm by using the pyramidal tips for either the direct deposition of ink or the localized delivery of energy to a surface. While other groups have focused on tip and array architetctures, our efforts have been on exploring their use for localizing organic chemistry on surfaces with nanoscale spatial resolution in 3D. Herein we describe the use of massively parallel SPL to create covalently immobilized patterns of organic materials using thermal, catalytic, photochemical, and force-accelerated reactions. In doing so, we have developed a high-throughput protocol for confirming interfacial bond formation. These efforts have resulted in new opportunities for the preparation of glycan arrays, novel approaches for covalently patterning graphene, and a 3D nanoprinter by combining photochemical brush polymerizations with SPL. Achieving true 4D nanoprinting involves advances in surface chemistry and instrumentation development, and to this end 4D micropatterns were produced in a microfluidic photoreactor that can position polymers composed of different monomers within micrometer proximity. A substantial gap remains, however, between these current technologies and the future's 4D nanomanufacturing tools, but the marriage of SPL with organic chemistry is an important step toward this goal. As this field continues to mature we can expect bottom-up 4D nanomanufacturing to begin supplanting conventional top-down strategies for preparing electronics, bioarrays, and functional substrates. In addition, these new printing technologies may enable the preparation of synthetic targets, such as artificial biological interfaces, with a level of organic sophistication that is entirely unachievable using existing technologies.

Performance Characterization of an xy-Stage Applied to Micrometric Laser Direct Writing Lithography

This article concerns the characterization of the stability and performance of a motorized stage used in laser direct writing lithography. The system was built from commercial components and commanded by G-code. Measurements use a pseudo-periodic-pattern (PPP) observed by a camera and image processing is based on Fourier transform and phase measurement methods. The results report that the built system has a stability against vibrations determined by peak-valley deviations of 65 nm and 26 nm in the x and y directions, respectively, with a standard deviation of 10 nm in both directions. When the xy-stage is in movement, it works with a resolution of 0.36 µm, which is an acceptable value for most of research and development (R and D) microtechnology developments in which the typical feature size used is in the micrometer range.

Multi-color polymer pen lithography for oligonucleotide arrays

Multi-color patterning by polymer pen lithography (PPL) was used to fabricate covalently immobilized fluorophore and oligonucleotide arrays with up to five different components. These can easily be translated for presentation of multiple protein types to a single cell.