Advanced Materials

On page 5486, Yongmei Zheng, Lei Jiang, and co-workers report that geometrically engineering thin fibers by introducing hump structures, similar to wetted spider capture silk, greatly improves the adhesion of the fibers to drops. An unusual three-phase contact line extends axially along the fibers to achieve stability of the contact line through a combination of “slope” and “curvature” effects. This creates sufficient capillary adhesion to pin the larger hanging drops to the fibers.

Randall D. Kamien, Shu Yang, and co-workers demonstrate an epitaxial approach to tailor the size and symmetry of toric focal conic domain (TFCD) arrays over large areas by exploiting 3D confinement and directed growth of Smectic-A liquid crystals using SU-8 pillar arrays with variable dimensions (size, height, and spacing) and sym-metries. As reported on page 5519, a new variety of TFCD arrays (e.g., square lattices) are obtained beyond the close-packed hexagonal arrangement formed spontaneously on a flat surface.

Pump-probe spectroscopy has provided in the recent years relevant information concerning elementary process in organic-based optoelectronic devices. In this review we describe some of these techniques (from conventional pump-probe to state-of-the-art confocal pump-probe microscopy) and the type of information they provide. Their combination offers unique insights into fundamental processes underneath device operation.

Geometrically engineered thin fibers that feature introduced hump structures similar to wetted spider capture silk greatly improve the adhesive ability to drops than uniform ones, which is attributed to an unusual three-phase contact line that extends axially along the fibers. The hump structures improve the stability of the contact line through a combination of “slope” and “curvature” effects, which creates sufficient capillary adhesion to pin drops.

Inkjet-printable aqueous suspensions of conjugated polymer precursorsare developed for fabrication of patterned color images on paper substrates. Printing of a diacetylene (DA)-surfactant composite ink on unmodified paper and photopaper, as well as on a banknote, enables generation of latent images that are transformed to blue-colored polydiacetylene (PDA) structures by UV irradiation. Both irreversible and reversible thermochromism with the PDA printed images are demonstrated and applied to flexible and disposable sensors and to displays.

Continuous tuning of lasing wavelength is achieved in cholesteric liquid crystal lasers by embedding a network of nanopores with an average size of 10 nm filled with liquid crystals inside a polymerized matrix with helical order. The device possesses both high transparency and a fast response time because the tuning is driven by local reorientation of the liquid crystal molecules in the nanopores.

2D mica crystals (with thickness < 100 nm) obtained by mechanical exfoliation are incorporated for the first time into the design of organic thin film field-effect transistor arrays and organic single crystal transistors as a gate insulator. The size of mica crystals could be up to the dimensions of an A4 piece of paper. All devices so fabricated exhibited high mobility and low operating voltage, indicating the high quality of the crystals and the great potential of mica crystals as a flexible, low-cost, transparent insulator for organic electronics.

Spiral vessels extracted from plant tissues can be utilized as abiotemplate for the production of left-handed metal microcoils with approximately 50-μm coil diameter. The silver microcoil functions as a solenoid with small self-inductance ranging to the picohenry level. As reported by Kaori Kamata and co-workers, this method provides an environmentally conscious and cheap route to develop electromagnetic-responsive materials such as microantenna targeting the high-frequency region.

Silver microcoil is fabricated through a biotemplating process combined with electroless plating. Spiral vessels in Lotus root are employed as a biotemplate because of their left-handed coil structure. The silver microcoil exhibits a solenoidal microcoil showing self-inductance in the level of picohenry, which could be applied for electromagnetic-responsive materials in the high-frequency region such as millimeter waves or terahertz waves.

An exploratory study on novel silylethynylated N-heteropentacenes, which have their N atoms on the terminal rings of the pentacene backbone, is reported. This study leads to both p- and n-channel organic thin-film transistors with high field-effect mobility and also reveals that the position of the N atoms plays an important role in tuning the structures and properties of organic semiconductors based on N-heteropentacenes.

SU-8 pillar-assisted epitaxial assembly of toric focal conic domains (TFCDs) arrays of smectic-A liquid crystals is studied. The 3D nature of the pillar array is crucial to confine and direct the formation of TFCDs on the top of each pillar and between neighboring pillars, leading to highly ordered square and hexagonal array TFCDs. Excellent agreement between the experimentally obtained critical pillar diameter and elasticity calculation is found.

A novel solution-stamping process for the preparation of a highly conductive aluminum thin film on both rigid and flexible substrates is proposed. The superior electrical properties of Al thin films fabricated by the solution-stamping process compared to silver and gold films fabricated from colloidal nanoparticles are experimentally demonstrated, and their applications in electronic circuits on rigid and flexible substrates and to organic light-emitting diodes (OLEDs) are investigated.

A conducting diblock copolymer of PS-b-P3HT was added to serve as a compatibilizer in a P3HT/PCBM blend, which improved the power-conversion efficiency from 3.3% to 4.1% due to the enhanced crystallinity, morphology, interface interaction, and depth profile of PCBM.

We demonstrate InGaAs mid-infrared quantum well infrared photodetectors (MIR PV-QWIPs) that enable cost-effective mature GaAs-based detection and imaging technologies, with exceptional material uniformity, reproducibility, and yield, over a large area, with high spectral selectivity, innate polarization sensitivity, radiation hardness, high detectivity, and high speed operation at TEC temperatures without bias.

Periodic nanostructuring can enhance the optical nonlinearity of plasmonic metals by several orders of magnitude. By patterning a gold film, the largest sub-100 femtosecond nonlinearity is achieved, which is suitable for terahertz rate all-optical data processing as well as ultrafast optical limiters and saturable absorbers.

A TEMPO-substituted ionic liquid was selectively incorporated into well-defined, self-assembled block copolymer templates, which served as an active layer for organic nonvolatile memory. Phase structures (sphere, cylinder, and lamellae) and their orientation modulated the resistive switching behavior, which demonstrated the unprecedented, morphology-driven charge transport in the organic electronic devices.

Nanopatternable polydimethylsiloxane (PDMS) oligomer layers are utilized as an interfacial nanoadhesive for the intrinsic trans-ferability and universal adhesiveness. As reported by Tingrui Pan and co-workers, the PDMS oligomer adhesive can be controllably printed onto arbitrary hydrophilic substrates with a nanometer resolution for highly localized irreversible bonding.

A nanopatternable polydimethylsiloxane (PDMS) oligomer layer is demonstrated as an interfacial adhesive for its intrinsic transferability and universal adhesiveness. Utilizing the well-established surface modification and bonding techniques of PDMS surfaces, irreversible bonding is formed (up to 400 kPa) between a wide range of substrate pairs, representing ones within and across different materials categories, including metals, ceramics, thermoset, and thermoplastic polymers.

High-resolution transmission electron microscopy (HRTEM) is used to observe a TiO2/ITO-coated composite nanostructure grown onto single-walled carbon nanotubes (SWCNTs). The SWCNTs, indium tin oxide (ITO), and TiO2 mixtures of anatase (A) and rutile (R) are clearly distinguished in the HRTEM images. The thickness of the SWCNT was about 3 nm, and the TiO2 shell included different polycrystalline structures.

Blue, green, and red electrophosphorescent polymer light-emitting diodes have been fabricated on silver nanowire-polymer composite electrode. The devices are 20%-50% more efficient than control devices on ITO/glass and exhibit small efficiency roll-off at high luminances. The blue PLEDs were repeatedly bent to 1.5 mm radius concave or convex with calculated strain in the emissive layer approximately 5% (tensile or compressive).

Domain wall movement assisted transport of particles: Exchange-biased samples with designed stripe-domains show strong stray fields and an asymmetric magnetization reversal. Using these characteristics superparamagnetic particles can be trapped and transported directly on the sample over large-scale areas. High particle velocities, small external fields, and automatically reduced particle clustering allow broad applicability of this transport method.

2D sandwich-like sheets of iron oxide grown on graphene as high energy anode material for supercapacitors are prepared from the direct growth of FeOOH nanorods on the surface of graphene and the subsequent electrochemical transformation of FeOOH to Fe₃O₄. The Fe₃O₄@RGO nanocomposites exhibit superior capacitance (326 F g⁻¹), high energy density (85 Wh kg⁻¹), large power, and good cycling performance in 1 mol L⁻¹ LiOH solution.