Shape-Dependent Locomotion of DNA-Linked Magnetic Nanoparticle Films.

The shape-dependent aero- and hydro-dynamics found in nature have been adopted in a wide range of areas spanning from daily transportation to forefront biomedical research. Here, we report DNA-linked nanoparticle films exhibiting shape-dependent magnetic locomotion, controlled by DNA sequences. Fabricated through a DNA-directed layer-by-layer assembly of iron oxide and gold nanoparticles, the multifunctional films exhibit rotational and translational motions under magnetic fields, along with reversible shape morphing via DNA strand exchange reactions.

Self-Mixed Biphasic Liquid Metal Composite with Ultra-High Stretchability and Strain-Insensitivity for Neuromorphic Circuits.

Neuromorphic circuits that can function under extreme deformations are important for various data-driven wearable and robotic applications. Herein, biphasic liquid metal particle (BMP) with unprecedented stretchability and strain-insensitivity (ΔR/R = 1.4@ 1200% strain) is developed to realize a stretchable neuromorphic circuit that mimics a spike-based biologic sensory system.

Plasmonic metasurfaces of cellulose nanocrystal matrices with quadrants of aligned gold nanorods for photothermal anti-icing.

Cellulose nanocrystals (CNCs) are intriguing as a matrix for plasmonic metasurfaces made of gold nanorods (GNRs) because of their distinctive properties, including renewability, biodegradability, non-toxicity, and low cost. Nevertheless, it is very difficult to precisely regulate the positioning and orientation of CNCs on the substrate in a consistent pattern. In this study, CNCs and GNRs, which exhibit tunable optical and anti-icing capabilities, are employed to manufacture a uniform plasmonic metasurface using a drop-casting technique.

Simple and Multiplexed Detection of Nucleic Acid Targets Based on Fluorescent Ring Patterns and Deep Learning Analysis.

Simple diagnostic tests for nucleic acid targets can provide great advantages for applications such as rapid pathogen detection. Here, we developed a membrane assay for multiplexed detection of nucleic acid targets based on the visualization of two-dimensional fluorescent ring patterns. A droplet of the assay solution is applied to a cellulose nitrate membrane, and upon radial chromatographic flow and evaporation of the solvent, fluorescent patterns appear under UV irradiation.

Anomalous crystalline ordering of particles in a viscoelastic fluid under high shear.

Addition of particles to a viscoelastic suspension dramatically alters the properties of the mixture, particularly when it is sheared or otherwise processed. Shear-induced stretching of the polymers results in elastic stress that causes a substantial increase in measured viscosity with increasing shear, and an attractive interaction between particles, leading to their chaining. At even higher shear rates, the flow becomes unstable, even in the absence of particles.

Vapor distribution changes evaporative flux profiles of a sessile droplet.

Hypothesis: We propose that during the evaporation of sessile droplets, the evaporative flux profile is primarily influenced by droplet geometry and composition under diffusion-limited conditions. Most studies have focused solely on the evaporation feature from the liquid to the gas phase, neglecting the extent to which the evaporated vapors affect the evaporation process. We hypothesize that if the molecular weight of the evaporated vapors is significantly high or low compared to the ambient gas, it could alter the evaporative flux.

Autonomous Interfacial Assembly of Polymer Nanofilms via Surfactant-Regulated Marangoni Instability.

Interfacial polymerization (IP) provides a versatile platform for fabricating defect-free functional nanofilms for various applications, including molecular separation, energy, electronics, and biomedical materials. Unfortunately, coupled with complex natural instability phenomena, the IP mechanism and key parameters underlying the structural evolution of nanofilms, especially in the presence of surfactants as an interface regulator, remain puzzling. Here, we interfacially assembled polymer nanofilm membranes at the free water-oil interface in the presence of differently charged surfactants and comprehensively characterized their structure and properties.

Liquid Metal Micro- and Nanodroplets: Characteristics, Fabrication Techniques, and Applications.

Gallium-based liquid metal micro- and nanodroplets are being extensively explored in innumerable emerging technologies. Although many of these systems involve the interfaces of liquid metal with a continuous phase liquid ( microfluidic channels and emulsions), the static or dynamic phenomena at the interface have been scarcely discussed. In this study, we begin by introducing the interfacial phenomena and characteristics observed at the interface between a liquid metal and continuous-phase liquids.

Multiplexed electrospraying of water in cone-jet mode using a UV-embossed pyramidal micronozzle film.

The electrospraying of water in the cone-jet mode is difficult in practical applications owing to its low throughput and the electrical discharge caused by the high surface tension of water. A film with multiple dielectric micronozzles is essential for multiplexed electrospraying of water in cone-jet mode without electrical discharge. Thus, a pyramidal micronozzle film with five nozzles was fabricated using the UV-embossing process.

Controlled nucleation in evaporative crystallization using a confined-vapor driven solutal Marangoni effect.

In droplet evaporation, the onset of evaporative crystallization near a contact line is inevitable if there is a coffee-ring effect increasing the local concentration of suspended particles at the edge. In this study, we present a novel idea to control the nucleation location of surfactant crystallization by using the vapor-driven solutal Marangoni effects of a binary mixture drop in a confined chamber. Here, the evaporated volatile vapors near the droplet surface can change the local surface tension and generate a radially inward flow that suppresses the conventional coffee-ring flow (, evaporatively-driven capillary flow).

Real-Time Visualization of Scent Accumulation Reveals the Frequency of Floral Scent Emissions.

Flowers emit a bouquet of volatiles to attract pollinators or to protect flowers from pathogen and herbivore attacks. Most floral volatiles are synthesized in the cytoplasm of petals and released into the headspace at a specific time of day. Various floral scent sampling methods coupled with gas chromatography-mass spectrometry have been used to measure the quality and quantity of floral volatiles.

Interfacial properties of liquid metal immersed in various liquids.

Hypothesis: When gallium-based liquid metal (LM) droplets are injected through different solvent media, the oxygen solubility of the environment influences the droplet eccentricity. The formation of an oxide membrane in solvents can determine whether a bulk-scale droplet behaves in a liquidlike or solidlike manner. In the case of LM emulsions, the solvent's oxygen solubility leads to varying degrees of organic solvent adsorption.

Vapor Absorption and Marangoni Flows in Evaporating Drops.

We experimentally and analytically studied vapor-driven solutal Marangoni flow by varying volatile liquid sources on top of the water droplet. We checked and compared the effects of solubility and vapor pressures of volatile liquids on the internal flow pattern using particle image velocimetry (PIV) and the droplet shape using shadowgraphy experiments. To explain the internal flow, we explored the absorption and evaporation mechanism of the vapors and we found that Henry's constant of the volatile liquid is the primary factor.

Self-Induced Solutal Marangoni Flows Realize Coffee-Ring-Less Quantum Dot Microarrays with Extensive Geometric Tunability and Scalability.

Currently, quantum dot light-emitting diodes (QD-LEDs) are receiving extensive attention. To maximize their luminous performance, the uniformity of the QD-LEDs is crucial. Although the spontaneously self-induced solutal Marangoni flow of an evaporating binary mixture droplet has been widely investigated and used to suppress coffee-ring patterns in ink-jet printing technology, unfortunately, ring shapes are still present at the edges, and the Marangoni flow generated by the selective evaporation of volatile liquid components cannot be controlled due to its nonlinear instabilities.

Population Pharmacokinetics of Meropenem in Critically Ill Korean Patients and Effects of Extracorporeal Membrane Oxygenation.

Limited studies have investigated population pharmacokinetic (PK) models and optimal dosage regimens of meropenem for critically ill adult patients using the probability of target attainment, including patients receiving extracorporeal membrane oxygenation (ECMO). A population PK analysis was conducted using non-linear mixed-effect modeling. Monte Carlo simulation was used to determine for how long the free drug concentration was above the minimum inhibitory concentration (MIC) at steady state conditions in patients with various degrees of renal function.

Crystal capillary origami capsule with self-assembled nanostructures.

The self-assembling mechanism of elasto-capillaries opens new applications in micro and nanotechnology by providing 3D assembly structures with 2D planar unit cells, so-called capillary origami. To date, the final structure has been designed based on the predetermined shape and size of the unit cell. Here, we show that plate-like salt crystallites grow and cover the emulsion interface, which is driven by Laplace pressure.

Evaporation and deposition of inclined colloidal droplets.

Colloidal droplets on flat solid substrates commonly leave symmetric ring-like deposits due to coffee-ring flows during evaporation. On inclined substrates, droplet shapes may become asymmetric by gravity. On this basis, it is not clear how their evaporation dynamics and final deposits are changed depending on inclination.

Fabrication of Chiral M13 Bacteriophage Film by Evaporation-Induced Self-Assembly.

Biomacromolecules are likely to undergo self-assembly and show specific collective behavior concentrated in the medium. Although the assembly procedures have been studied for unraveling their mysteries, there are few cases to directly demonstrate the collective behavior and phase transition process in dynamic systems. In the contribution, the drying process of M13 droplet is investigated, and can be successfully simulated by a doctor blade coating method.

Controlling uniform patterns by evaporation of multi-component liquid droplets in a confined geometry.

Surface-coating technologies are important for a variety of applications, e.g. ink-jet printing, micro-electronic engineering and biological arrays.

Orientation Control of Semiconducting Polymers Using Microchannel Molds.

The molecular orientation of organic semiconductors (OSCs) is of fundamental importance to anisotropic electrical behavior as well as superior properties in practical applications. Here, a simple and effective method is demonstrated to fabricate highly oriented semiconducting polymers, poly(3-hexylthiophene) (P3HT) and poly{[,'-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]--5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)), by mass transfer effect under microchannel molds by diffusion and convection. Furthermore, parallel or perpendicular molecular arrangements relative to the channel direction were achieved by varying the widths of the microchannels, which are directly observed using polarized optical microscopy and two-dimensional grazing-incidence X-ray diffraction experiments.

Phase synchronization of fluid-fluid interfaces as hydrodynamically coupled oscillators.

Hydrodynamic interactions play a role in synchronized motions of coupled oscillators in fluids, and understanding the mechanism will facilitate development of applications in fluid mechanics. For example, synchronization phenomenon in two-phase flow will benefit the design of future microfluidic devices, allowing spatiotemporal control of microdroplet generation without additional integration of control elements. In this work, utilizing a characteristic oscillation of adjacent interfaces between two immiscible fluids in a microfluidic platform, we discover that the system can act as a coupled oscillator, notably showing spontaneous in-phase synchronization of droplet breakup.

Highly efficient oxygen evolution reaction via facile bubble transport realized by three-dimensionally stack-printed catalysts.

Despite highly promising characteristics of three-dimensionally (3D) nanostructured catalysts for the oxygen evolution reaction (OER) in polymer electrolyte membrane water electrolyzers (PEMWEs), universal design rules for maximizing their performance have not been explored. Here we show that woodpile (WP)-structured Ir, consisting of 3D-printed, highly-ordered Ir nanowire building blocks, improve OER mass activity markedly. The WP structure secures the electrochemically active surface area (ECSA) through enhanced utilization efficiency of the extended surface area of 3D WP catalysts.

Fluid-Matrix Interface Triggers a Heterogeneous Activation of Macrophages.

Spontaneous activation of macrophages in response to inflammation is a key part of innate immunity and host defense. Macrophages represent a heterogeneous population of cells with different phenotypic profiles performing distinct functions in host defense. Although a spectrum of macrophage activation stages exists in an inflamed region, the effect of local physical conditions on the heterotypic activation of macrophages is unknown.

Control of solutal Marangoni-driven vortical flows and enhancement of mixing efficiency.

Hypothesis: In droplet microfluidics applications, flow control and mixing in a small volume without any active external devices is a challenge. Vapor-mediated solutal Marangoni flows can be effectively generated by applying the vapor of a volatile liquid, which can be possibly controlled, and can eventually be used in a mixing enhancement device.

Experiments: We investigated and controlled vapor-mediated solutal Marangoni flows by varying the local surface tension.