Demonstration of programmable light intensity of a micro-LED with a Hf-based ferroelectric ITZO TFT for Mura-free displays.

We demonstrate the programmable light intensity of a micro-LED by compensating threshold voltage variability of thin-film transistors (TFTs) by introducing a non-volatile programmable ferroelectric material, HfZrO2 (HZO) into the gate stack of the TFT. We fabricated an amorphous ITZO TFT, ferroelectric TFTs (FeTFTs), and micro-LEDs and verified the feasibility of our proposed current-driving active matrix circuit. Importantly, we successfully present the programmed multi-level lighting of the micro-LED, utilizing partial polarization switching in the a-ITZO FeTFT. We expect that this approach will be highly promising for the next-generation display technology, replacing complicated threshold voltage compensation circuits with a simple a-ITZO FeTFT.

Ultra-low-current driven InGaN blue micro light-emitting diodes for electrically efficient and self-heating relaxed microdisplay.

InGaN-based micro-light-emitting diodes have a strong potential as a crucial building block for next-generation displays. However, small-size pixels suffer from efficiency degradations, which increase the power consumption of the display. We demonstrate strategies for epitaxial structure engineering carefully considering the quantum barrier layer and electron blocking layer to alleviate efficiency degradations in low current injection regime by reducing the lateral diffusion of injected carriers via reducing the tunneling rate of electrons through the barrier layer and balanced carrier injection. As a result, the fabricated micro-light-emitting diodes show a high external quantum efficiency of 3.00% at 0.1 A/cm2 for the pixel size of 10 × 10 µm2 and a negligible Jmax EQE shift during size reduction, which is challenging due to the non-radiative recombination at the sidewall. Furthermore, we verify that our epitaxy strategies can result in the relaxation of self-heating of the micro-light-emitting diodes, where the average pixel temperature was effectively reduced.

Understanding the Sidewall Passivation Effects in AlGaInP/GaInP Micro-LED.

The passivation effects of sulfur treatment and Al2O3 passivation for AlGaInP/GaInP red micro-light-emitting-diodes (LEDs) were investigated in terms of the external quantum efficiency (EQE) and the current density showing the peak EQE (JEQE, peak). We systematically compared the electrical and optical characteristics of the micro-LEDs with and without passivation according to various sizes. Interestingly, our investigation indicated that simple electrical characteristics such as current density-voltage property are difficult to precisely reflect the minor change in electrical properties due to passivation when the device has the inherently low leakage current. Whereas the EQE was enhanced by 20% and JEQE, peak was largely shifted to a lower current density region at the LED with a size of 15 × 15 µm2. To examine the passivation effects, we carefully analyzed the EQE and JEQE, peak with the ABC recombination model, and established the methodology to investigate the influence of a sidewall in micro-LEDs. As a result, we extracted the surface recombination velocity regarding the surface passivation, showing a nearly 14% reduction with the passivation.

Epitope-preserving magnified analysis of proteome (eMAP).

Synthetic tissue-hydrogel methods have enabled superresolution investigation of biological systems using diffraction-limited microscopy. However, chemical modification by fixatives can cause loss of antigenicity, limiting molecular interrogation of the tissue gel. Here, we present epitope-preserving magnified analysis of proteome (eMAP) that uses purely physical tissue-gel hybridization to minimize the loss of antigenicity while allowing permanent anchoring of biomolecules. We achieved success rates of 96% and 94% with synaptic antibodies for mouse and marmoset brains, respectively. Maximal preservation of antigenicity allows imaging of nanoscopic architectures in 1000-fold expanded tissues without additional signal amplification. eMAP-processed tissue gel can endure repeated staining and destaining without epitope loss or structural damage, enabling highly multiplexed proteomic analysis. We demonstrated the utility of eMAP as a nanoscopic proteomic interrogation tool by investigating molecular heterogeneity in inhibitory synapses in the mouse brain neocortex and characterizing the spatial distributions of synaptic proteins within synapses in mouse and marmoset brains.

Hydrodynamic Metamaterial Cloak for Drag-Free Flow.

Metamaterials engineered based on transformation optics have facilitated inaccessible manipulation of various physical phenomena. However, such metamaterials have not been introduced for flowing viscous matter. Here we propose a hydrodynamic metamaterial cloak that can conceal an object in two-dimensional creeping flow by guiding viscous forces. Coordinate transformation of fluidic space is implemented to calculate a tensoric viscosity based on a form invariance of Navier-Stokes equations. The hydrodynamic cloak with the viscosity tensor is numerically simulated to verify a fictitious fluidic empty space created in it. The corresponding metamaterial microstructure is systemically designed and fabricated in a microfluidic device. The experimental results reveal that a solid object amid the flow can be hydrodynamically hidden without entailing a disturbance in flow fields and experiencing a drag.

Chemical profiles and antioxidant properties of roasted rice hull extracts in bulk oil and oil-in-water emulsion.

We conducted in vitro assays to investigate the antioxidant properties of aqueous or ethanolic extracts of roasted rice hulls. Phenolic compound contents were analyzed via HPLC, and comprehensive chemical profiles were obtained via 1H NMR and 1H-H COSY NMR. Rice hulls were roasted at 150, 180, and 230 °C for 20 min, after which the aqueous and 70% ethanol extracts were obtained. In vitro assays showed that rice hulls roasted at 230 °C possessed very strong antioxidant properties (p < 0.05). Comprehensive chemical profiles determined via NMR showed that roasting increased the contents of specific amino acids and monosaccharides and reduced the organic acid contents. p-Coumaric, vanillic, and ferulic acids were the most dominant phenolic compounds present in the sample. Added roasted rice hull extracts enhanced the oxidative stability of bulk oil and in O/W emulsions at 60 °C. However, the extracts accelerated lipid oxidation rates of oils heated at 180 °C.

Programmable microfluidic logic device fabricated with a shape memory polymer.

Manipulation of particles in a microfluidic system is an important research subject in biomedical engineering. However, most conventional passive techniques for particle control have difficulties in integrating other functions into microfluidic channels. A unique microfluidic valve was proposed in this study for switchable particle control by employing a shape memory polymer (SMP). A microfluidic logic device can be programmed based on deformation of the SMP microchannel constructed on a poly(dimethylsiloxane) (PDMS) film. Particles in a viscoelastic flow were focused at preferred equilibrium locations by the competition between inertia and elastic forces. The channel shape played an important role in determining those forces in the channel. Hydrodynamic behavior and shape recovery behavior of the SMP microchannel were modeled theoretically. It was confirmed that the particle valve prepared with the SMP implemented a programmable binary logic operation in the microfluidic channel.

Carbon Nanotube Embedded Nanostructure for Biometrics.

Low electric energy loss is a very important problem to minimize the decay of transferred energy intensity due to impedance mismatch. This issue has been dealt with by adding an impedance matching layer at the interface between two media. A strategy was proposed to improve the charge transfer from the human body to a biometric device by using an impedance matching nanostructure. Nanocomposite pattern arrays were fabricated with shape memory polymer and carbon nanotubes. The shape recovery ability of the nanopatterns enhanced durability and sustainability of the structure. It was found that the composite nanopatterns improved the current transfer by two times compared with the nonpatterned composite sample. The underlying mechanism of the enhanced charge transport was understood by carrying out a numerical simulation. We anticipate that this study can provide a new pathway for developing advanced biometric devices with high sensitivity to biological information.