Printable Functional Chips Based on Nanoparticle Assembly

Structural and dynamical equilibrium properties of hard board-like particles in parallel confinement

We performed Monte Carlo and dynamic Monte Carlo simulations to model the diffusion of monodispersed suspensions composed of impenetrable cuboidal particles, specifically hard board-like particles (HBPs), in the presence of parallel hard walls. The impact of the walls was investigated by adjusting the size of the simulation box while maintaining constant packing fractions, fixed at η = 0.150, for systems consisting of HBPs with prolate, dual-shaped, and oblate geometries. We observed that increasing the distance between the walls led to the recovery of an isotropic bulk phase, while local particle organization near the walls remained stable. Due to their shape, oblate HBPs exhibit more efficient anchoring at wall surfaces compared to prolate shapes. The formation of nematic-like particle assemblies near the walls, confirmed by theoretical calculations based on density functional theory, significantly influenced local particle dynamics. This effect was particularly pronounced to the extent that a modest portion of cuboids near the walls tended to diffuse exclusively in planes parallel to the confinement, even more efficiently than observed in the bulk regions.

Nanoparticle Assembly: From Self-Organization to Controlled Micropatterning for Enhanced Functionalities

Nanoparticles form long-range micropatterns via self-assembly or directed self-assembly with superior mechanical, electrical, optical, magnetic, chemical, and other functional properties for broad applications, such as structural supports, thermal exchangers, optoelectronics, microelectronics, and robotics. The precisely defined particle assembly at the nanoscale with simultaneously scalable patterning at the microscale is indispensable for enabling functionality and improving the performance of devices. This article provides a comprehensive review of nanoparticle assembly formed primarily via the balance of forces at the nanoscale (e.g., van der Waals, colloidal, capillary, convection, and chemical forces) and nanoparticle-template interactions (e.g., physical confinement, chemical functionalization, additive layer-upon-layer). The review commences with a general overview of nanoparticle self-assembly, with the state-of-the-art literature review and motivation. It subsequently reviews the recent progress in nanoparticle assembly without the presence of surface templates. Manufacturing techniques for surface template fabrication and their influence on nanoparticle assembly efficiency and effectiveness are then explored. The primary focus is the spatial organization and orientational preference of nanoparticles on non-templated and pre-templated surfaces in a controlled manner. Moreover, the article discusses broad applications of micropatterned surfaces, encompassing various fields. Finally, the review concludes with a summary of manufacturing methods, their limitations, and future trends in nanoparticle assembly.

Rapid Fabrication of High-Resolution Flexible Electronics via Nanoparticle Self-Assembly and Transfer Printing

Printed electronic technology serves as a key component in flexible electronics and wearable devices, yet achieving compatibility with both high resolution and high efficiency remains a significant challenge. Here, we propose a rapid fabrication method of high-resolution nanoparticle microelectronics via self-assembly and transfer printing. The tension gradient-electrostatic attraction composite-induced nanoparticle self-assembly strategy is constructed, which can significantly enhance the self-assembly efficiency, stability, and coverage by leveraging the meniscus Marangoni effect and the electric double-layer effect. The close-packed nanoparticle self-assembly layer can be rapidly formed on microstructure surfaces over a large area. Inspired by ink printing, a transfer printing strategy is further proposed to transform the self-assembly layer into conformal micropatterns. Large-area, high-resolution (2 μm), and ultrathin (1 μm) nanoparticle microelectronics can be stably fabricated, yielding a significant improvement over fluid printing methods. The unique deformability, recoverability, and scalability of nanoparticle microelectronics are revealed, providing promising opportunities for various academic and real applications.

Patterning of Hydrophilic and Hydrophobic Gold and Magnetite Nanoparticles by Dip Pen Nanolithography

Nanoparticles offer unique physical and chemical properties. Dip pen nanolithography of nanoparticles enables versatile patterning and nanofabrication with potential application in electronics and sensing, but is not well studied yet. Herein, the patterned deposition of various nanoparticles onto unmodified silicon substrates is presented. It is shown that aqueous solutions of hydrophilic citrate and cyclodextrin functionalized gold nanoparticles as well as poly(acrylic) acid decorated magnetite nanoparticles are feasible for writing nanostructures. Both smaller and larger nanoparticles can be patterned. Hydrophobic oleylamine or n-dodecylamine capped gold nanoparticles and oleic acid decorated magnetite nanoparticles are deposited from toluene. Tip loading is carried out by dip-coating, and writing succeeds fast within 0.1 s. Also, coating with longer tip dwell times, at different relative humidity and varying frequency are studied for deposition of nanoparticle clusters. The resulting feature size is between 300 and 1780 nm as determined by scanning electron microscopy. Atomic force microscopy confirms that the heights of the deposited structures correspond to a single or double layer of nanoparticles. Higher writing speeds lead to smaller line thicknesses, offering possibilities to more complex structures. Dip pen nanolithography can hence be used to pattern nanoparticles on silicon substrates independent of the surface chemistry.

Surfactant-Tunable Nanoparticle Assembly via a Template-Directed Strategy

Nanoparticle (NP) self-assembly from suspension evaporation has been a topic of interest in recent times to fabricate a solid-state structure with diverse functions. We present a simple and facile evaporation-induced strategy for the formation of NP arrays on a flat substrate utilizing a template-directed sandwich system. The lithographic features assist the assembly of the typical nanoparticles (NPs), including SiO₂, QDs@PS FMs, and QDs, on the top into circle, stripe, triangle, or square geometries with a fixed width of 2 μm. Additionally, an anionic surfactant, sodium dodecyl sulfonate (SDS), is incorporated into a negatively charged, hydrophilic SiO₂ dispersion to govern the aggregation and self-assembly of NPs, fine tuning the morphologies of the residual structures on the substrate. SDS is attributed to modify the nature of SiO₂ NPs to be hydrophobic, increase the hydrophobic attraction, dominating particle-particle and particle-interface interactions, and strengthen the particle-particle repulsive electrostatic force that results in the reduction of SiO₂ NPs trapped in the separated colloidal suspension drop. Thus, using the SDS surfactant with the concentration ranging from 0 to 1 wt %, the obtained well-ordered SiO₂ NP pattern packing on the substrate varies from six layers to one layer.

In Situ Self-Assembly of Nanoscale Particles into Macroscale Ordered Monolayers with Enhanced Memory Performance

In situ fabrication of macroscale ordered monolayers of nanoparticles (NPs) on targeted substrates is highly desirable for precision electronic and optical devices, while it remains a great challenge. In this study, a solution is provided to address this challenge by developing a colloidal ink formulation and employing the direct-ink-writing (DIW) technique, where on-demand delivery of ink at a targeted location and directional evaporation with controllable rate are leveraged to precisely guide the deposition of polystyrene-grafted gold NPs (Au@PS NPs) into a macroscale monolayer with an ordered Au NP array embedded in a PS thin film. A 2D steady-state diffusion-controlled evaporation model, which explains the parameter dependence of the experimental results and gives semiquantitative agreement with the experimental evaporation kinetics is proposed. The ordered monolayer is used as both nanocrystal floating gates and the tunneling layer for nonvolatile memory devices. It shows significantly enhanced performance compared with a disordered NP film prepared by spin coating. This approach allows for fine control of NP self-assembly to print macroscaleordered monolayers directly onto substrates, which has great promise for application in broad fields, including microelectronic and photoelectronic devices, sensors, and functional coatings.

Recent Advances in Printable Flexible Optical Devices: From Printing Technology and Optimization Strategies to Perspectives

Recently, flexible optical devices have triggered booming developments in various research fields, including display equipment, sensors, energy conversion, and so on, due to their high compatibility, portability, and wearability. With the advantages of strong design ability, high precision, and high integration, printing technologies have been recognized as promising methods to realize flexible optical devices. In this Perspective, recent progress on printing strategies for fabricating flexible optical devices are introduced systematically. First, through adjusting the composition of inks, selecting flexible substrates, and controlling external stimulation, fabrication of flexible optical devices based on inkjet printing is illustrated. Then, flexible optical devices fabricated by template-induced printing, 3D printing, slot-die printing, and screen printing are summarized. Finally, prospects and future development directions based on printing technology for flexible optical devices are proposed.

Fabrication of modern lithium ion batteries by 3D inkjet printing: opportunities and challenges

Inkjet printing (IJP) is a prospective additive manufacturing technology that enables the rapid and precise deposition of thin films or patterns. It offers numerous advantages over other thin-film manufacturing processes, including cost-effectiveness, ease of use, reduced waste material, and scalability. The key advantage of this technique is the ability of the fabrication of complex patterns with very high precision. The IJP gives the possibility of building three-dimensional (3D) structures on the microscale, which is beneficial for modern Li-Ion batteries (LIBs) and All-Solid-State Li-Ion Batteries (ASSLIBs). In contrast to typical laminated composite electrodes manufactured by tape casting and calendaring, 3D electrode design allows the electrolyte to penetrate through the electrode volume, increasing the surface-to-volume ratio and reducing ion diffusion paths. Thus, 3D electrodes/electrolyte structures are one of the most promising strategies for producing next-generation lithium-ion batteries with enhanced electrochemical performance. Although in the literature review, the IJP is frequently reported as a future perspective for the fabrication of 3D electrodes/electrolytes structures for LIBs, only a few works focus on this subject. In this review, we summarize the previous studies devoted to the topic and discuss different bottlenecks and challenges limiting further development.

Combining printing and nanoparticle assembly: Methodology and application of nanoparticle patterning

Functional nanoparticles (NPs) with unique photoelectric, mechanical, magnetic, and chemical properties have attracted considerable attention. Aggregated NPs rather than individual NPs are generally required for sensing, electronics, and catalysis. However, the transformation of functional NP aggregates into scalable, controllable, and affordable functional devices remains challenging. Printing is a promising additive manufacturing technology for fabricating devices from NP building blocks because of its capabilities for rapid prototyping and versatile multifunctional manufacturing. This paper reviews recent advances in NP patterning based on the combination of self-assembly and printing technologies (including two-, three-, and four-dimensional printing), introduces the basic characteristics of these methods, and discusses various fields of NP patterning applications.

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Nanoparticles (NPs) printing assembly is a good solution for patterned devices

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NPs assembly can be combined with 2D, 3D, and 4D printing technologies

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A variety of ink-dispersed NPs are available for printing assembly

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NPs printing assembly technology is applied for nanosensing, energy storage, photodetector

3D Printing-Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications

3D printing (additive manufacturing (AM)) has enormous potential for rapid tooling and mass production due to its design flexibility and significant reduction of the timeline from design to manufacturing. The current state-of-the-art in 3D printing focuses on material manufacturability and engineering applications. However, there still exists the bottleneck of low printing resolution and processing rates, especially when nanomaterials need tailorable orders at different scales. An interesting phenomenon is the preferential alignment of nanoparticles that enhance material properties. Therefore, this review emphasizes the landscape of nanoparticle alignment in the context of 3D printing. Herein, a brief overview of 3D printing is provided, followed by a comprehensive summary of the 3D printing-enabled nanoparticle alignment in well-established and in-house customized 3D printing mechanisms that can lead to selective deposition and preferential orientation of nanoparticles. Subsequently, it is listed that typical applications that utilized the properties of ordered nanoparticles (e.g., structural composites, heat conductors, chemo-resistive sensors, engineered surfaces, tissue scaffolds, and actuators based on structural and functional property improvement). This review's emphasis is on the particle alignment methodology and the performance of composites incorporating aligned nanoparticles. In the end, significant limitations of current 3D printing techniques are identified together with future perspectives.

From colloidal particles to photonic crystals: advances in self-assembly and their emerging applications

Over the last three decades, photonic crystals (PhCs) have attracted intense interests thanks to their broad potential applications in optics and photonics. Generally, these structures can be fabricated via either "top-down" lithographic or "bottom-up" self-assembly approaches. The self-assembly approaches have attracted particular attention due to their low cost, simple fabrication processes, relative convenience of scaling up, and the ease of creating complex structures with nanometer precision. The self-assembled colloidal crystals (CCs), which are good candidates for PhCs, have offered unprecedented opportunities for photonics, optics, optoelectronics, sensing, energy harvesting, environmental remediation, pigments, and many other applications. The creation of high-quality CCs and their mass fabrication over large areas are the critical limiting factors for real-world applications. This paper reviews the state-of-the-art techniques in the self-assembly of colloidal particles for the fabrication of large-area high-quality CCs and CCs with unique symmetries. The first part of this review summarizes the types of defects commonly encountered in the fabrication process and their effects on the optical properties of the resultant CCs. Next, the mechanisms of the formation of cracks/defects are discussed, and a range of versatile fabrication methods to create large-area crack/defect-free two-dimensional and three-dimensional CCs are described. Meanwhile, we also shed light on both the advantages and limitations of these advanced approaches developed to fabricate high-quality CCs. The self-assembly routes and achievements in the fabrication of CCs with the ability to open a complete photonic bandgap, such as cubic diamond and pyrochlore structure CCs, are discussed as well. Then emerging applications of large-area high-quality CCs and unique photonic structures enabled by the advanced self-assembly methods are illustrated. At the end of this review, we outlook the future approaches in the fabrication of perfect CCs and highlight their novel real-world applications.

Non-close-packed arrangement of soft elastomer microspheres on solid substrates

Unlike rigid microparticles, soft and deformable elastomer (rubber) microspheres were found to exhibit a non-close-packed arrangement on solid substrates after the evaporation of water from their dispersions. The microscopic observation revealed that individual microspheres are ordered in regular intervals at the air/water interface of a sessile droplet and remain fixed on the substrate without being affected by the capillary forces during evaporation due to their deformability. Moreover, using the Langmuir-Blodgett method, thin films of non-close-packed structures could be successfully generated over large areas. Our findings may potentially help to control the arranged structures of elastomer microspheres, which can be expected to improve the nano-science and technology for the precise control for e.g. surface patterning.

A Diverse Micromorphology of Photonic Crystal Chips for Multianalyte Sensing

The diversity by nano/microstructural material or device constructing can provide the exciting opportunity for sensitivity and selectivity to achieve facile and efficient multianalyte recognition for clinical diagnosis, environment monitoring, etc., in complex system analysis. Colloidal poly(styrene-methyl methacrylate-acrylic acid) (poly(St-MMA-AA)) nanoparticle-assembled photonic crystals (PCs) can achieve manipulative 3D structural colors and approach PC sensor chip for high-efficient multianalysis utilizing simple dye. Focusing on the morphology effects of structural color, a PC microchip is designed and constructed with various geometrical micromorphologies. Based on the angle dependence of colloidal-crystal structural color, the stopband distribution is explored on various morphological PC pixels. Selective fluorescent enhancement is realized for stopband-matched PCs, which approach the successful discrimination of metal ions and complex multianalysis of groundwater. Meanwhile, printed droplet-shaping manipulation can achieve a large-scale structural-color sensor array of chips with designable nano/microstructures via colloidal assembly. It will be the critical puzzle piece between macromorphology and microstructure for the structural-color researches.

Controlled diffusion of nanoparticles by viscosity gradient for photonic crystal with dual photonic band gaps

Coalescence of droplets containing nanoparticles has been paid much attention regarding fabrication of functional photonic crystal (PC) patterns. However, most studies focus on the coalescence of droplets containing the same nanoparticles. Currently, an active challenge comes from the coalescence of droplets containing different nanoparticles due to the spontaneous mutual diffusion of different nanoparticles between coalescing miscible droplets driven by the released Gibbs free energy. Such diffusion breaks the self-assembly of nanoparticles into promising PCs with dual photonic band gaps (PBGs). In this work, a viscosity gradient was induced in coalescing droplets containing different nanoparticles to control the diffusion of nanoparticles and impede the diffusion across the coalescing interface. Nanoparticles diffused along the viscosity gradient to droplet surfaces and self-assembled into a period structure which enhanced the interaction of nanoparticles and contributed to impeding the random diffusion between droplets. At the same time, the high viscosity at the coalescing interface slowed down the horizontal movement of nanoparticles further and consequently the diffusion of nanoparticles across the interface was impeded. By use of such controlled diffusion of nanoparticles in the viscosity gradient, PCs with PBGs were achieved. These results demonstrate the controlled diffusion of nanoparticles during the coalescence of miscible droplets to facilely fabricate PCs with PBGs in the absence of an existing external field.

Molecular and functional extracellular vesicle analysis using nanopatterned microchips monitors tumor progression and metastasis

Longitudinal cancer monitoring is crucial to clinical implementation of precision medicine. There is growing evidence indicating important functions of extracellular vesicles (EVs) in tumor progression and metastasis, including matrix remodeling via transporting matrix metalloproteases (MMPs). However, the clinical relevance of EVs remains largely undetermined, partially owing to challenges in EV analysis. Distinct from existing technologies mostly focused on characterizing molecular constituents of EVs, here we report a nanoengineered lab-on-a-chip system that enables integrative functional and molecular phenotyping of tumor-associated EVs. A generalized, high-resolution colloidal inkjet printing method was developed to allow robust and scalable manufacturing of three-dimensional (3D) nanopatterned devices. With this nanochip platform, we demonstrated integrative analysis of the expression and proteolytic activity of MMP14 on EVs to detect in vitro cell invasiveness and monitor in vivo tumor metastasis, using cancer cell lines and mouse models. Analysis of clinical plasma specimen showed that our technology could be used for cancer detection including accurate classification of age-matched controls and patients with ductal carcinoma in situ, invasive ductal carcinoma, or locally metastatic breast cancer in a training cohort (n = 30, 96.7% accuracy) and an independent validation cohort (n = 70, 92.9% accuracy). With clinical validation, our technology could provide a useful liquid biopsy tool to improve cancer diagnostics and real-time surveillance of tumor evolution in patients to inform personalized therapy.

Fabrication of Single-Nanocrystal Arrays

To realize the full potential of nanocrystals in nanotechnology, it is necessary to integrate single nanocrystals into addressable structures; for example, arrays and periodic lattices. The current methods for achieving this are reviewed. It is shown that a combination of top-down lithography techniques with directed assembly offers a platform for attaining this goal. The most promising of these directed assembly methods are reviewed: capillary force assembly, electrostatic assembly, optical printing, DNA-based assembly, and electrophoretic deposition. The last of these appears to offer a generic approach to fabrication of single-nanocrystal arrays.

Design and tailoring of inks for inkjet patterning of metal oxides

Inkjet printing has become a promising, efficient, inexpensive, scalable technique for materials deposition, mask-less and digital patterning in many device applications. Meanwhile, the ink preparation remains a challenge especially for printing functional oxide materials. Based on the principles of inkjet printing (especially relevant for piezoelectric drop-on-demand inkjet printer) and the process of the conversion of liquid ink into solid thin films of oxide materials, we present two approaches to the design and tailoring of inks: (i) oxide particle suspensions (e.g. SiO2, TiO2, Fe3O4) and (ii) metal-acetates precursor solutions for directly printing oxide thin films (e.g. ZnO, MgO, ITO and so forth). The solution inks are stable and produce tunable oxide films with high density and smooth surface. For some of the inks containing multi-type acetates with possible phase separation even before calcinations, we have developed a chelating procedure in order to tailor the films into single-phase homogeneity. The work lays a foundation for inkjet printing of oxides films for functional applications in electronic, photonic and energy devices.

Hollow Colloid Assembled Photonic Crystal Clusters as Suspension Barcodes for Multiplex Bioassays

Barcode particles have a demonstrated value for multiplexed high-throughput bioassays. Here, a novel photonic crystal (PhC) barcode is presented that consists of hollow colloidal nanospheres assembled through microfluidic droplet templates. Due to their gas-filled core, the resultant barcode particles not only show increased refractive index contrast, but also remain in suspension by adjusting the overall density of the PhC to match that of a detection solution. In addition, magnetic nanoparticles can be integrated to give the barcodes a magnetically controllable motion ability. The encoding ability of the barcodes is demonstrated in microRNA detection with high specificity and sensitivity, and the excellent features of the barcodes make them potentially very useful for biomedical applications.

Bioinspired Photonic Barcodes with Graphene Oxide Encapsulation for Multiplexed MicroRNA Quantification

Multiplexed microRNA (miRNA) quantification has a demonstrated value in clinical diagnosis. In this paper, novel mussel-inspired photonic crystal (PhC) barcodes with graphene oxide (GO) encapsulation for multiplexed miRNA detection are presented. Using the excellent adhesion capability of polydopamine, the dispersed GO particles can be immobilized on the surfaces of the PhC barcodes to form an additional functional layer. The GO-decorated PhC barcodes have constant characteristic reflection peaks because the GO immobilization process not only maintains their periodic microstructure but also enhances their stability and anti-incoherent light-scattering capability. The immobilized GO particles are shown to enable high-sensitivity miRNA screening on the surface of the PhC barcodes by integration with a hybridization chain reaction amplification strategy. Because the PhC barcodes have stable encoding reflection peaks, multiplexed low-abundance miRNA quantification can also be achieved rapidly, accurately, and reproducibly by employing different GO-decorated PhC barcodes. These features should make GO-encapsulated PhC barcodes ideal for many practical applications.

Viscoelastic Particle-Laden Interface Inhibits Coffee-Ring Formation

We investigate the evaporation-driven pattern formation in drying drops containing mixtures of polystyrene and soft microgel particles. The well-known coffee-rings that form when drops containing polystyrene particles are dried can be completely undone in the presence of a small quantity of soft colloids. The addition of soft colloids facilitates the adsorption of polystyrene particles to the water-vapor interface leading to a steep increase in their concentration and also imparts viscoelasticity to the interface. Time-resolved video microscopy is used to conclusively show the formation of a gel-like particle-laden interface. The mean square displacement of the polystyrene particles adsorbed to the interface confirms their immobile nature at the interface. This viscoelastic interface almost prevents the bulk flow-assisted migration of polystyrene particles toward the drop edge, leading to the suppression of coffee-ring effect and the formation of uniform particulate deposits.

Fabrication and characterization of a scalable surface textured with pico-liter oil drops for mechanistic studies of bacteria-oil interactions

Texturing a large surface with oily micro-drops with controlled size, shape and volume provides an unprecedented capability in investigating complex interactions of bacteria, cells and interfaces. It has particular implications in understanding key microbial processes involved in remediation of environmental disasters, such as Deepwater Horizon oil spill. This work presents a development of scalable micro-transfer molding to functionalize a substrate with oily drop array to generate a microcosm mimicking bacteria encountering a rising droplet cloud. The volume of each drop within a large “printed” surface can be tuned by varying base geometry and area with characteristic scales from 5 to 50 μm. Contrary to macroscopic counterparts, drops with non-Laplacian shapes, i.e. sharp corners, that appears to violate Young-Laplacian relationship locally, are produced. Although the drop relaxes into a spherical cap with constant mean curvature, the contact line with sharp corners remains pinned. Relaxation times from initial to asymptotic shape require extraordinarily long time (>7 days). We demonstrate that non-Laplacian drops are the direct results of self-pinning of contact line by nanoparticles in the oil. This technique has been applied to study biofilm formation at the oil-water interface and can be readily extended to other colloidal fluids.

Printing 1D Assembly Array of Single Particle Resolution for Magnetosensing

Magnetosensing is a ubiquitous ability for many organism species in nature. 1D assembly, especially that arranged in single-particle-resolution regulation, is able to sense the direction of magnetic field depending on the enhanced dipolar interaction in the linear orientation. Inspired by the magnetosome structure in magnetotactic bacteria, a 1D assembly array of single particle resolution with controlled length and well-behaved configuration is prepared via inkjet printing method assisted with magnetic guiding. In the fabrication process, chains in a "tip-to-tip" regulation with the desired number of particles are prepared in a confined tiny inkjet-printed droplet. By adjusting the receding angle of the substrate, the assembled 1D morphology is kept/deteriorated depending on the pinning/depinning behavior during ink evaporation, which leads to the formation of well-behaved 1D assembly/aggregated dot assembly. Owing to the high-aspect-ratio characteristic of the assembled structure, the as-prepared 1D arrays can be used for magnetic field sensing with anisotropic magnetization M_// /M_⊥ up to 6.03.

Laser Nanopatterning of Colored Ink Thin Films for Photonic Devices

Nanofabrication through conventional methods such as electron beam writing and photolithography is time-consuming, high cost, complex, and limited in terms of the materials which can be processed. Here, we present the development of a nanosecond Nd:YAG laser (532 nm, 220 mJ) in holographic Denisyuk reflection mode method for creating ablative nanopatterns from thin films of four ink colors (black, red, blue, and brown). We establish the use of ink as a recording medium in different colors and absorption ranges to rapidly produce optical nanostructures in 1D geometries. The gratings produced with four different types of ink had the same periodicity (840 nm); however, they produce distant wavelength dependent diffraction responses to monochromatic and broadband light. The nanostructures of gratings consisting of blue and red inks displayed high diffraction efficiency of certain wavelengths while the black and brown ink based gratings diffracted broadband light. These gratings have high potential to be used as low-cost photonic structures in wavelength-dependent optical filters. We anticipate that the rapid production of gratings based on different ink formulations can enable optics applications such as holographic displays in data storage, light trapping, security systems, and sensors.

Bridging the Gap: Rewritable Electronics Using Real-Time Light-Induced Dielectrophoresis on Lithium Niobate

In the context of micro-electronics, the real-time manipulation and placement of components using optics alone promises a route towards increasingly dynamic systems, where the geometry and function of the device is not fixed at the point of fabrication. Here, we demonstrate physically reconfigurable circuitry through light-induced dielectrophoresis on lithium niobate. Using virtual electrodes, patterned by light, to trap, move, and chain individual micro-solder-beads in real-time via dielectrophoresis, we demonstrate rewritable electrical contacts which can make electrical connections between surface-bound components. The completed micro-solder-bead bridges were found to have relatively low resistances that were not solely dominated by the number of interfaces, or the number of discrete beads, in the connection. Significantly, these connections are formed without any melting/fusing of the beads, a key feature of this technique that enables reconfigurability. Requiring only a low-power (~3.5 mW) laser source to activate, and without the need for external power supply or signal generation, the all-optical simplicity of virtual-electrodes may prove significant for the future development of reconfigurable electronic systems.

Three-Dimensional Printing of Highly Conductive Carbon Nanotube Microarchitectures with Fluid Ink

Moving printed electronics to three dimensions essentially requires advanced additive manufacturing techniques yielding multifunctionality materials and high spatial resolution. Here, we report the meniscus-guided 3D printing of highly conductive multiwall carbon nanotube (MWNT) microarchitectures that exploit rapid solidification of a fluid ink meniscus formed by pulling a micronozzle. To achieve high-quality printing with continuous ink flow through a confined nozzle geometry, that is, without agglomeration and nozzle clogging, we design a polyvinylpyrrolidone-wrapped MWNT ink with uniform dispersion and appropriate rheological properties. The developed technique can produce various desired 3D microstructures, with a high MWNT concentration of up to 75 wt % being obtained via post-thermal treatment. Successful demonstrations of electronic components such as sensing transducers, emitters, and radio frequency inductors are also described herein. We expect that the technique presented in this study will facilitate selection of diverse materials in 3D printing and enhance the freedom of integration for advanced conceptual devices.