Nanofabricated Concentric Ring Structures by Templated Self-Assembly of a Diblock Copolymer

The formation of well-controlled circular patterns on the nanoscale is important for the fabrication of a range of devices such as sensors, memories, lasers, transistors, and quantum devices. Concentric, smooth ring patterns with tunable dimensions have been formed from a cylinder-forming poly(styrene-b-dimethylsiloxane) (PS-PDMS) diblock copolymer under confinement in shallow circular trenches. The high etch selectivity between PS and PDMS facilitates pattern transfer, illustrated by the fabrication of arrays of ferromagnetic cobalt rings with a density of 1.1 × 109/cm2. The effects of confinement diameter and commensurability on the diameter and period of the concentric rings are analyzed using a free energy model that includes interfacial, strain, and bending energies. This work provides a simple process for the fabrication of nanoscale circular patterns with very narrow line width using a much coarser-scale template, and may facilitate the miniaturization of a variety of microelectronic devices

Polychromatic Quantum Dot Array to Compose a Community Signal Ensemble for Multiplexed miRNA Detection

We herein describe a polychromatic quantum dot array (PQDA) to compose a community signal ensemble enabling accurate and precise quantification of miRNAs in a multiplexed manner. Advanced multicomponent ultrahigh-resolution patterning technique achieved by capsulation-assisted transfer printing following self-assembly-based poly­(methyl methacrylate) (PMMA) patterning is utilized to manufacture the PQDA, which is designed to discharge a target miRNAs-specific set of fluorescent quantum dots (QDs) through the activity of duplex-specific nuclease (DSN). On the basis of the community signal ensemble produced by the discharged QD profiles, target miRNAs are very specifically identified down to a femtomolar level (1.27 fM) in a multiplexed manner over a wide dynamic range of up to 6 orders of magnitude. The practical diagnostic capability of this strategy is also demonstrated by reliably identifying breast cancer-specific miRNAs from heterogeneous cancer cell lysates

High-Capacity Ti₃C₂T_<i>x</i> MXene Electrodes Achieved by Eliminating Intercalated Water Molecules Using a Co-solvent System

Synthesizing layered transition-metal carbides, MXenes, with a mesoporous structure remains challenging but is highly useful because it converts the laminated two-dimensional structures into versatile porous materials. Hydrogen bonds between intercalated H2O molecules and oxygen terminal groups on the surface are formed in aqueous solution processes, and this is a determining factor of surface area. We developed an extraction method to remove intercalated water molecules based on a simple intermolecular force attraction strategy in a co-solvent system using a combination of polar-protic/-aprotic and non-polar solvents. As a result, self-aggregated mesoporous Ti3C2Tx was realized without any additives. The dipole–dipole interaction between H2O and CHCl3 molecules under non-polar solvent conditions assists the extraction of intercalated H2O from the MXene suspension, which can form a self-aggregated morphology (not re-stacked horizontally). The process yields Ti3C2Tx with a layered structure of embedded mesopores and a specific surface area that is 13-fold higher than that of standard MXene. Electrodes made with the resulting MXene exhibited a larger specific capacitance of 224 F/g (1 A/g), with an improved cyclic retention of 96.4%@10,000 cycles. This intermolecular attraction-induced approach, involving the manipulation of morphology, is simple to mass-produce and can be used for MXene-based electrochemical applications

Deep-Nanoscale Pattern Engineering by Immersion-Induced Self-Assembly

The directed self-assembly (DSA) of block copolymers (BCPs) is expected to complement conventional optical lithography due to its excellent pattern resolution and cost-effectiveness. Recent studies have shown that BCPs with a large Flory–Huggins interaction parameter (χ) are critical for a reduction of the thermodynamic defect density as well as an increase in pattern density. However, due to their slower self-assembly kinetics, high-χ BCPs typically necessitate solvent vapor annealing, which requires complex facilities and procedures compared to simple thermal annealing. Here, we introduce an immersion-triggered directed self-assembly (iDSA) process and demonstrate the combined advantages of excellent simplicity, productivity, large-area capability, and tunability. We show that the vapor-free, simple immersion of high-χ BCPs in a composition-optimized mixture of nonswelling and swelling solvents can induce the ultrafast (≤5 min) formation of nanoscale patterns with a pattern size ranging from 8–18 nm. Moreover, iDSA enables the reversible formation of seven different nanostructures from one sphere-forming BCP, demonstrating the outstanding controllability of this self-assembly route

Fabrication of Diverse Metallic Nanowire Arrays Based on Block Copolymer Self-Assembly

Metallic nanowires are useful for fabricating highly integrated nanoscale electrical, magnetic, and photonic devices. However, conventional methods based on bottom-up growth techniques are subject to concerns such as broad distributions in their dimension as well and difficulties in precise placement of the nanowires. These issues can be solved by the guided self-assembly of block copolymer thin films that can produce periodic arrays of monodisperse nanoscale features with excellent positional accuracy. Here, we report transfer of high-quality linear block copolymer patterns into various metals, Ti, W, Pt, Co, Ni, Ta, Au, and Al, to fabricate highly ordered nanowire arrays with widths down to 9 nm. This novel patterning process does not require specific film deposition techniques or etch-chemistries. We also describe their structural, magnetic, and electrical properties

A Path to Ultranarrow Patterns Using Self-Assembled Lithography

The templated self-assembly of block copolymer (BCP) thin films can generate regular arrays of 10−50 nm scale features with good positional and orientational accuracy, but the ordering, registration and pattern transfer of sub-10-nm feature sizes is not well established. Here, we report solvent-annealing and templating methods that enable the formation of highly ordered grating patterns with a line width of 8 nm and period 17 nm from a self-assembled poly(styrene-b-dimethylsiloxane) (PS-PDMS) diblock copolymer. The BCP patterns can be registered hierarchically on a larger-period BCP pattern, which can potentially diversify the available pattern geometries and enables precise pattern registration at small feature sizes. Sub-10-nm-wide tungsten nanowires with excellent order and uniformity were fabricated from the self-assembled patterns using a reactive ion etching process

Direct Fabrication of Micro/Nano-Patterned Surfaces by Vertical-Directional Photofluidization of Azobenzene Materials

Anisotropic movement of azobenzene materials (i.e., azobenzene molecules incorporated in polymer, glass, or supramolecules) has provided significant opportunities for the fabrication of micro/nanoarchitectures. The examples include circular holes, line gaps, ellipsoidal holes, and nanofunnels. However, all of the previous studies have only focused on the lateral directional movement for the structural shaping of azobenzene materials. Herein, we propose structural shaping based on a vertical directional movement of azobenzene materials. To do this, light with oblique incidence, containing normal direction light polarization, was illuminated onto azobenzene materials film contact with patterned elastomeric molds (i.e., PDMS) so that the resulting vertical directional movement of azobenzene materials fills in the cavities of the molds and results in pattern formation. As a result, a range of patterns with sizes of features from micro- to sub-100 nm scale was successfully fabricated in a large area (few cm2), and the structural height was deterministically controlled by simply adjusting irradiation time. In addition to the notable capability of fabricating the single-scale structures, the technique provides a facile way to fabricate complex hierarchical multiscale structures, ensuring its versatility and wide applicability to various applications. As a selected exemplary application of the multiscale structures, a superhydrophobic surface has been successfully demonstrated

Controlling the Morphology of Side Chain Liquid Crystalline Block Copolymer Thin Films through Variations in Liquid Crystalline Content

In this paper, we describe methods for manipulating the morphology of side-chain liquid crystalline block copolymers through variations in the liquid crystalline content. By systematically controlling the covalent attachment of side chain liquid crystals to a block copolymer (BCP) backbone, the morphology of both the liquid crystalline (LC) mesophase and the phase-segregated BCP microstructures can be precisely manipulated. Increases in LC functionalization lead to stronger preferences for the anchoring of the LC mesophase relative to the substrate and the intermaterial dividing surface. By manipulating the strength of these interactions, the arrangement and ordering of the ultrathin film block copolymer nanostructures can be controlled, yielding a range of morphologies that includes perpendicular and parallel cylinders, as well as both perpendicular and parallel lamellae. Additionally, we demonstrate the utilization of selective etching to create a nanoporous liquid crystalline polymer thin film. The unique control over the orientation and order of the self-assembled morphologies with respect to the substrate will allow for the custom design of thin films for specific nanopatterning applications without manipulation of the surface chemistry or the application of external fields

Direct Fabrication of Micro/Nano-Patterned Surfaces by Vertical-Directional Photofluidization of Azobenzene Materials

Anisotropic movement of azobenzene materials (i.e., azobenzene molecules incorporated in polymer, glass, or supramolecules) has provided significant opportunities for the fabrication of micro/nanoarchitectures. The examples include circular holes, line gaps, ellipsoidal holes, and nanofunnels. However, all of the previous studies have only focused on the lateral directional movement for the structural shaping of azobenzene materials. Herein, we propose structural shaping based on a vertical directional movement of azobenzene materials. To do this, light with oblique incidence, containing normal direction light polarization, was illuminated onto azobenzene materials film contact with patterned elastomeric molds (i.e., PDMS) so that the resulting vertical directional movement of azobenzene materials fills in the cavities of the molds and results in pattern formation. As a result, a range of patterns with sizes of features from micro- to sub-100 nm scale was successfully fabricated in a large area (few cm2), and the structural height was deterministically controlled by simply adjusting irradiation time. In addition to the notable capability of fabricating the single-scale structures, the technique provides a facile way to fabricate complex hierarchical multiscale structures, ensuring its versatility and wide applicability to various applications. As a selected exemplary application of the multiscale structures, a superhydrophobic surface has been successfully demonstrated