Miho Tsuwaki

Microfluidic White Organic Light-Emitting Diode Based on Integrated Patterns of Greenish-Blue and Yellow Solvent-Free Liquid Emitters.

We demonstrated a novel microfluidic white organic light-emitting diode (microfluidic WOLED) based on integrated sub-100-μm-wide microchannels. Single-μm-thick SU-8-based microchannels, which were sandwiched between indium tin oxide (ITO) anode and cathode pairs, were fabricated by photolithography and heterogeneous bonding technologies. 1-Pyrenebutyric acid 2-ethylhexyl ester (PLQ) was used as a solvent-free greenish-blue liquid emitter, while 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb)-doped PLQ was applied as a yellow liquid emitter. In order to form the liquid white light-emitting layer, the greenish-blue and yellow liquid emitters were alternately injected into the integrated microchannels. The fabricated electro-microfluidic device successfully exhibited white electroluminescence (EL) emission via simultaneous greenish-blue and yellow emissions under an applied voltage of 100 V. A white emission with Commission Internationale de l’Declairage (CIE) color coordinates of (0.40, 0.42) was also obtained; the emission corresponds to warm-white light. The proposed device has potential applications in subpixels of liquid-based microdisplays and for lighting.

Microfluidic electrochemiluminescence (ECL) integrated flow cell for portable fluorescence detection

We propose a portable electrochemiluminescence (ECL)-induced fluorescence chip which consists of flow channels for fluorescence sample and multi-color emitting ECL excitation source. A prototype ECL-induced fluorescence chip was fabricated by conventional photolithography and bonding technique. Device performance was evaluated using ECL of rubrene as excitation source and resorufin as fluorescent dye. Fluorescence of 500 μM resorufin (600 nm) was successfully detected using 10 mM rubrene solution (560 nm) under the applied voltage of 4 V. The proposed principle is applicable for portable and on-demand multi fluorescence detection device using its freedom of choice for combination of the ECL light source.

Multi-color microfluidic organic light emitting device using electroluminescence and electrochemiluminescence

We developed a multi-color microfluidic organic light emitting device, which consists of liquid organic light emitting diodes (OLEDs) and electrochemiluminescence (ECL) devices. A 3 × 3 matrix of emitting pixels was fabricated in SU-8 microchannels sandwiched between polyethylene naphthalate (PEN) and glass substrates with indium tin oxide (ITO) anode and cathode pairs. Liquid organic semiconductor and ECL solutions as liquid emitters were injected into the microchannels. The electroluminescence (EL) and ECL were successfully obtained at the emitting pixels in the microchannels. The proposed structure can be applicable for multi-color liquid-based display.

Simple and high-throughput fabrication of large-area and multilayer flexible polymer film structures for microfluidic organic light emitting diode

A simple and high-throughput fabrication of large-area and multilayer polymer film structures was developed and applied for microfluidic organic light emitting diodes (OLED). We employed following three distinguished technologies, a) screen-printing technique for transparent electrodes, b) novel belt-transfer exposure technology for SU-8 microchannels, and c) heterogeneous low temperature bonding technology using self-assembly monolayer. A Liquid organic semiconductor as a liquid emitter was injected to each microchannel and photoluminescence and electroluminescence were obtained not only in a straight state, but also in a bending state. This large-area flexible microfluidic structure for OLED is applicable to nondisposable posters or displays which can be adopted around the curved surfaces of the various structures.