Light propagation in conjugated polymer nanowires decoupled from a substrate

Visualization of Microcapillary Tips Using Waveguided Light

The microcapillary, a glass tube with a nano/micrometer scale aperture, is used for manipulating small objects across diverse disciplines. A primary concern in using the microcapillary involves tip breakage upon contact. Here, we report a method for visualizing the microcapillary tip, enabling precise and instant determination of its contact with other objects. Illumination directed to the back aperture of the microcapillary induces waveguiding through the glass wall, enabling the visualization of the tip through scattering. We demonstrate that the tip scattering is sensitive to contact with an adjacent object owing to the near-field interaction of the waveguided light, providing a clear distinction between the contact and noncontact states. The key advantage of our method encompasses its minimal influence, irrespective of conductivity, and applicability to nanoscale systems. The versatility of our method is shown by the application to a wide range of tip diameters, various substrate and in-filling materials.

Derivatives of diphenylamine and benzothiadiazole in optoelectronic applications: a review

Light-emitting conjugated organic compounds have found special interest among researchers. Because of their adjustable optoelectronic properties they can be applied in e.g. field-effect transistors, sensors, light-emitting diodes or photovoltaic cells. In order to develop high-performance systems, it is important to understand the relationship between the structure and the photophysical properties of the material used. One of the employed strategies is to decrease the band gap of conjugated compounds, often achieved through a “donor–acceptor” approach. One of the popular groups applied as an electron-accepting unit are benzothiadiazoles, while diphenylamine exhibits good electron-donating ability. The functional groups can affect the energy levels of materials, influencing the color of the light emitted. This work presents a review of research focused on the structure-properties relationship of diphenylamine and benzothiadiazole derivatives with optoelectronic applications.

Direct optical wire bonding through open-to-air polymerization for silicon photonic chips

We developed an inter-chip optical link using direct optical wire (DOW) bonding by open-to-air polymerization. An arch-shaped wire was drawn from a tip in a similar way to a metal wire, but the wire was formed from a polymer solution that solidified in the air during wiring. The DOW bonding was examined for silicon photonic chips where grating couplers are integrated for input/output coupling. Cone-shaped studs were formed at the ends of the wire, and their geometry was optimized using finite-difference time-domain simulation to give a mode conversion function. Although the polymer wire had a multimode scale of 7 µm, the wire bonding between the grating couplers showed a relatively low insertion loss of 5.8 dB at a wavelength of 1590 nm compared to a conventional connection using single-mode fiber blocks. It also showed a larger wavelength tolerance within the range of ∼1520-1590 nm. DOW bonding between a grating coupler and a single-mode fiber were also examined to verify the feasibility of out-of-plane connection with edge-coupling devices. The grating-to-fiber wire link also exhibited a large wavelength tolerance.

Direct writing of 3D conjugated polymer micro/nanostructures for organic electronics and bioelectronics

3D direct writing and meniscus-guided pen writing methods, which are capable of fabricating 3D micro/nanostructures from soluble π-conjugated polymers (CPs) and CP precursors, and recent advances in these techniques are addressed in this review.

CdTe microwires as mid-infrared optical waveguides

Cadmium telluride (CdTe) has been proven to be an attractive mid-infrared (MIR) material with a large refractive index (~2.68 at 4.5 μm) and broadband transparency (~1 to 25 μm). CdTe microwires (MWs) with diameters from a few to about ten micrometers were fabricated by a thermal evaporation process. MIR light was coupled into and guided through individual MWs. Excellent optical waveguiding properties of these MWs are experimentally obtained within MIR spectral range (up to 8.6 μm), with waveguiding losses from 1.3 to 13 dB/cm. Our results show that CdTe MWs can be used as wavelength or subwavelength-width waveguides for MIR microphotonics or circuits.

Progression in the Fountain Pen Approach: From 2D Writing to 3D Free-Form Micro/Nanofabrication

The fountain pen approach, as a means for transferring materials to substrates, has shown numerous incarnations in recent years for creating 2D micro/nanopatterns and even generating 3D free-form nanostructures using a variety of material "inks". While the idea of filled reservoirs used to deliver material to a substrate via a capillary remains unchanged since antiquity, the advent of precise micromanipulation systems and functional material "inks" allows the extension of this mechanism to more high-tech applications. Herein, the recent growth in meniscus guided fountain pen approaches for benchtop micro/nanofabrication, which has occurred in the last decade, is discussed. Particular attention is given to the theory, equipment, and experimentation encompassing this unique direct writing approach. A detailed exploration of the diverse ink systems and functional device applications borne from this strategy is put forth to reveal its rapid expansion to a broad range of scientific and engineering disciplines. As such, this informative review is provided for researchers considering adoption of this recent advancement of a familiar technology.

Quantitative Probing of Cu(2+) Ions Naturally Present in Single Living Cells

Quantitative probing of Cu(2+) ions naturally present in single living cells is realized by developing a quantum-dot-embedded nanowire-waveguide probe. The intracellular Cu(2+) ion concentration is quantified by direct monitoring of photoluminescence quenching during the insertion of the nanowire in a living neuron. The measured intracellular Cu(2+) ion concentration is 3.34 ± 1.04 × 10(-6) m (mean ± s.e.m.) in single hippocampal neurons.

A light-driven supramolecular nanowire actuator

A single photomechanical supramolecular nanowire actuator with an azobenzene-containing 1,3,5-tricarboxamide derivative is developed by employing a direct writing method. Single nanowires display photoinduced reversible bending and the bending behavior follows first-order kinetics associated with azobenzene photoisomerization. A wireless photomechanical nanowire tweezers that remotely manipulates a single micro-particle is also demonstrated.