RESUMEN
We discuss invisibility cloaking of metal grid electrodes on Lambertian light emitters by using dielectric free-form surfaces. We show that cloaking can be ideal in geometrical optics for all viewing directions if reflections at the dielectric-air interface are negligible. We also present corresponding white-light proof-of-principle experiments that demonstrate close-to-ideal cloaking for a wide range of viewing angles. Remaining imperfections are analyzed by ray-tracing calculations. The concept can potentially be used to enhance the luminance homogeneity of large-area organic light-emitting diodes.
RESUMEN
Surface-enhanced Raman spectroscopy (SERS) combines the high speciï¬city of Raman scattering with high sensitivity due to an enhancement of the electromagnetic ï¬eld by metallic nanostructures. However, the tyical fabrication methods of SERS substrates suffer from low throughput and therefore high costs. Furthermore, point-of-care applications require the investigation of liquid solutions and thus the integration of the SERS substrate in a microfluidic chip. We present a roll-to-roll fabrication approach for microfluidics with integrated, highly efficient, surface-enhanced Raman scattering structures. Microfluidic channels are formed using roll-to-roll hot embossing in polystyrene foil. Aerosol jet printing of a gold nanoparticle ink is utilized to manufacture highly efficient, homogeneous, and reproducible SERS structures. The modified channels are sealed with a solvent-free, roll-to-roll, thermal bonding process. In continuous flow measurements, these chips overcome time-consuming incubation protocols and the poor reproducibility of SERS experiments often caused by inhomogeneous drying of the analyte. In the present study, we explore the influence of the printing process on the homogeneity and the enhancement of the SERS structures. The feasibility of aerosol-jet-modified microfluidic channels for highly sensitive SERS detection is demonstrated by using solutions with different concentrations of Rhodamine 6G and adenosine. The printed areas provide homogeneous enhancement factors of ~4 × 106. Our work shows a way towards the low-cost production of tailor-made, SERS-enabled, label-free, lab-on- chip systems for bioanalysis.
RESUMEN
The integration of periodic nanodisk arrays into the channel of a light-emitting field-effect transistor leads to enhanced and directional electroluminescence from thin films of purified semiconducting single-walled carbon nanotubes. The maximum enhancement wavelength is tunable across the near-infrared and is directly linked to the periodicity of the arrays. Numerical calculations confirm the role of increased local electric fields in the observed emission modification. Large current densities are easily achieved due to the high charge carrier mobilities of carbon nanotubes and will facilitate new electrically driven plasmonic devices.
RESUMEN
One of the primary challenges in explosive detection using fluorescence quenching is the identification and quantification of detected targets. In this work, we explore the reliability of aerosol jet printed sensor arrays for the discrimination of nitroaromatic traces using linear discriminant analysis (LDA). We varied the amount of the deposited material by controlling the printer's shutter to investigate the impact on the detection reliability. For a twofold variation of the amount of the deposited material, we report excellent classification rates between 81 and 96% for the discrimination of nitrobenzene, 1,3-dinitrobenzene, and 2,4-dinitrotoluene at 1, 3, and 10 parts per billion in air, respectively. Our results close to the detection limits indicate a remarkable identification and quantification of explosive trace vapors because of high control of the printing process. This work demonstrates the high potential of digitally printed fluorescence quenching sensor arrays and the excellent capabilities of LDA as a simple supervised statistical learning technique.
RESUMEN
Self-organization of functional materials induced by low surface-energetic direct printed structures is presented. This study investigates fundamental fluid and substrate interactions and fabricates all-printed small area organic photodetectors with On-Off ratios of ≈10(5) and dark current densities of ≈10(-4) mA cm(-2) , as well as ring oscillators based on n-type organic field-effect transistors showing working frequencies up to 400 Hz.
RESUMEN
Hybrid photonic-plasmonic modes in periodic arrays of metallic nanostructures offer a promising trade-off between high-quality cavities and subdiffraction mode confinement. However, their application in electrically driven light-emitting devices is hindered by their sensitivity to the surrounding environment and to charge injecting metallic electrodes in particular. Here, we demonstrate that the planar structure of light-emitting field-effect transistor (LEFET) ensures undisturbed operation of the characteristic modes. We incorporate a square array of gold nanodisks into the charge transporting and emissive layer of a polymer LEFET in order to tailor directionality and emission efficiency via the Purcell effect and variation of the fractional local density of states in particular. Angle- and polarization-resolved spectra confirm that the enhanced electroluminescence correlates with the dispersion curves of the surface lattice resonances supported by these structures. These LEFETs reach current densities on the order of 10 kA/cm2, which may pave the way toward practical optoelectronic devices with tailored emission patterns and potentially electrically pumped plasmonic lasers.
RESUMEN
Light-emitting electrochemical cells (LECs) are fabricated by gravure printing. The compromise between device performance and printing quality is correlated to the ink formulation and the printing process. It is shown that the rheological properties of the ink formulations of LECs can be tailored without changing the chemical composition of the material blend.
