Dae-Young Chung

Polypyrrole/Agarose-based electronically conductive and reversibly restorable hydrogel.

Conductive hydrogels are a class of composite materials that consist of hydrated and conducting polymers. Due to the mechanical similarity to biointerfaces such as human skin, conductive hydrogels have been primarily utilized as bioelectrodes, specifically neuroprosthetic electrodes, in an attempt to replace metallic electrodes by enhancing the mechanical properties and long-term stability of the electrodes within living organisms. Here, we report a conductive, smart hydrogel, which is thermoplastic and self-healing owing to its unique properties of reversible liquefaction and gelation in response to thermal stimuli. In addition, we demonstrated that our conductive hydrogel could be utilized to fabricate bendable, stretchable, and patternable electrodes directly on human skin. The excellent mechanical and thermal properties of our hydrogel make it potentially useful in a variety of biomedical applications such as electronic skin.

Heterogeneous stacking of nanodot monolayers by dry pick-and-place transfer and its applications in quantum dot light-emitting diodes

Layered assembly structures composed of nanomaterials, such as nanocrystals, have attracted considerable attention as promising candidates for new functional devices whose optical, electromagnetic and electronic behaviours are determined by the spatial arrangement of component elements. However, difficulties in handling each constituent layer in a material-specific manner limit the 3D integration of disparate nanomaterials into the appropriate heterogeneous electronics. Here we report a pick-and-place transfer method that enables the transfer of large-area nanodot assemblies. This solvent-free transfer utilizes a lifting layer and allows for the reliable transfer of a quantum dot (QD) monolayer, enabling layer-by-layer design. With the controlled multistacking of different bandgap QD layers, we are able to probe the interlayer energy transfer among different QD monolayers. By controlling the emission spectrum through such designed monolayer stacking, we have achieved white emission with stable optoelectronic properties, the closest to pure white among the QD light-emitting diodes reported so far.

Nanoscale patterning of colloidal quantum dots on transparent and metallic planar surfaces.

The patterning of colloidal quantum dots with nanometer resolution is essential for their application in photonics and plasmonics. Several patterning approaches, such as the use of polymer composites, molecular lock-and-key methods, inkjet printing and microcontact printing of quantum dots have been recently developed. Herein, we present a simple method of patterning colloidal quantum dots for photonic nanostructures such as straight lines, rings and dot patterns either on transparent or metallic substrates. Sub-10 nm width of the patterned line could be achieved with a well-defined sidewall profile. Using this method, we demonstrate a surface plasmon launcher from a quantum dot cluster in the visible spectrum.

A Re-configurable 0.5V to 1.2V, 10MS/s to 100MS/s, Low-Power 10b 0.13um CMOS Pipeline ADC

This work describes a re-configurable 0.5 V to 1.2 V, 10 MS/s to 100 MS/s, 10 b two-step pipeline ADC. The prototype ADC in a 0.13 um CMOS process demonstrates the measured DNL and INL within 0.35 LSB and 0.49 LSB, respectively. The ADC with an active die area of 0.98 mm2 shows the maximum SNDR and SFDR of 56.0 dB and 69.6 dB, respectively, and a power consumption of 19.2 mW at a nominal condition of 0.8 V and 60 MS/s.

Nanoscale patterning of colloidal quantum dots for surface plasmon generation

The patterning of colloidal quantum dots with nanometer resolution is essential for their application in photonics and plasmonics. Several patterning approaches, such as the use of polymer composites, molecular lock-and-key methods, inkjet printing, and microcontact printing of quantum dots, have limits in fabrication resolution, positioning and the variation of structural shapes. Herein, we present an adaptation of a conventional liftoff method for patterning colloidal quantum dots. This simple method is easy and requires no complicated processes. Using this method, we formed straight lines, rings, and dot patterns of colloidal quantum dots on metallic substrates. Notably, patterned lines approximately 10 nm wide were fabricated. The patterned structures display high resolution, accurate positioning, and well-defined sidewall profiles. To demonstrate the applicability of our method, we present a surface plasmon generator elaborated from quantum dots.

Patterning of colloidal quantum dots for the generation of surface plasmon

Abstract. Patterning of colloidal quantum dot (QD) of a nanometer resolution is important for potential applications in micro- or nanophotonics. Several patterning techniques such as polymer composites, molecular key-lock methods, inkjet printing, and the microcontact printing of QDs have been successfully developed and applied to various plasmonic applications. However, these methods are not easily adapted to conventional complementary metal-oxide semiconductor (CMOS)-compatible processes because of either limits in fabrication resolutions or difficulties in sub-100-nm alignment. Here, we present an adaptation of a conventional lift-off method for the patterning of colloidal QDs. This simple method can be later applied to CMOS processes by changing electron beam lithography to photolithography for building up photon-generation elements in various planar geometries. Various shapes formed by colloidal QD clusters such as straight lines, rings, and dot patterns with sub-100-nm size could be fabricated. The patterned structures show sub-10-nm positioning with good fluorescence properties and well-defined sidewall profiles. To demonstrate the applicability of our method, we present a surface plasmon generator from a QD cluster.