Photonic crystal slabs integrated into organic light-emitting diodes (OLEDs) allow for the extraction of waveguide modes and thus an increase in OLED efficiency. We fabricated linear Bragg gratings with a 460-nm period on flexible polycarbonate substrates using UV nanoimprint lithography. A hybrid organic-inorganic nanoimprint resist is used that serves also as a high refractive index layer. OLEDs composed of a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer anode, an organic emission layer [poly(p-phenylene vinylene) (PPV)-derivative "Super Yellow"], and a metal cathode (LiF/Al) are deposited onto the flexible grating substrates. The effects of photonic crystal slab deformation in a flexible OLED are studied in theory and experiment. The substrate deformation is modeled using the finite-element method. The influence of the change in the grating period and the waveguide thickness under bending are investigated. The change in the grating period is found to be the dominant effect. At an emission angle of 20°a change in the resonance wavelength of 1.2% is predicted for a strain of 1.3% perpendicular to the grating grooves. This value is verified experimentally by analyzing electroluminescence and photoluminescence properties of the fabricated grating OLEDs.
Rapid advances in information technology rely on novel patterning techniques. The authors present a simple UV capillary force lithography process, which allows one to imprint a multiscale system, consisting of 250 nm wide nanobridges and a 8–20 μm wide wiring in one lithography step. An additional annealing step for 5 min at 75 °C improved the capillary rise.
The extraction of guided modes from a 100 nm organic emission layer by compound binary gratings with multiple superimposed periods at different ratios is investigated. We measure angle-dependent photoluminescence from samples with double-period (350 and 450 nm), triple-period (350, 400, and 450 nm), and multiperiod (350, 400, 450, and 500 nm) gratings and show that each period component produces two outcoupling features due to first-order Bragg scattering of the TE(0) guided mode. The averaged angular color change is reduced by up to a factor of 11 compared to a single-period grating structuring.
We present a low-cost and simple method to fabricate a novel lock-and-key mixer microfluidics using an economic stereolithography (SLA) three-dimensional (3D) printer, which costs less than USD 400 for the investment. The proposed study is promising for a high throughput fabrication module, typically limited by conventional microfluidics fabrications, such as photolithography and polymer-casting methods. We demonstrate the novel modular lock-and-key mixer for the connector and its chamber modules with optimized parameters, such as exposure condition and printing orientation. In addition, the optimization of post-processing was performed to investigate the reliability of the fabricated hollow structures, which are fundamental to creating a fluidic channel or chamber. We found out that by using an inexpensive 3D printer, the fabricated resolution can be pushed down to 850 µm and 550 µm size for squared- and circled-shapes, respectively, by the gradual hollow structure, applying vertical printing orientation. These strategies opened up the possibility of developing straightforward microfluidics platforms that could replace conventional microfluidics mold fabrication methods, such as photolithography and milling, which are costly and time consuming. Considerably cheap commercial resin and its tiny volume employed for a single printing procedure significantly cut down the estimated fabrication cost to less than 50 cents USD/module. The simulation study unravels the prominent properties of the fabricated devices for biological fluid mixers, such as PBS, urine and plasma blood. This study is eminently prospective toward microfluidics application in clinical biosensing, where disposable, low-cost, high-throughput, and reproducible chips are highly required.
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