Pillar Array Mixer for Postcolumn Derivatization Integrated into Liquid Chromatography-Based Microfluidic Device.

The chemical derivatization of target analytes can enhance the sensitivity and selectivity of separation-based methods for metabolite analysis using microfluidic devices. However, the development of chromatography-based microfluidic devices with integrated derivatization units is challenging. In this study, a novel derivatization unit with a pillar array (PA)-based mixing channel was developed for postcolumn derivatization during on-chip liquid chromatography (LC).

Efficient Separation of Methanol Single-Micron Droplets by Tailing Phenomenon Using a PDMS Microfluidic Device.

Microdroplet-based fluidic systems have the advantages of small size, short diffusion time, and no cross-contamination; consequently, droplets often provide a fast and precise reaction environment as well as an analytical environment for individual molecules. In order to handle diverse reactions, we developed a method to create organic single-micron droplets (S-MDs) smaller than 5 μm in diameter dispersed in silicone oil without surfactant. The S-MD generation microflow device consists of a mother droplet (MoD) generator and a tapered separation channel featuring multiple side channels.

Deformability-Based Microfluidic Microdroplet Screening to Obtain Agarolytic Bacterial Cells.

Environmental microorganisms possess enzymes that can digest macromolecules such as agarose into smaller molecules that can be utilized for growth. These enzymes could be valuable for the effective utilization of global resources. However, since most of the microorganisms on Earth remain uncultured, there is significant untapped enzymatic potential in nature.

Efficient Synthesis of a Schiff Base Copper(II) Complex Using a Microfluidic Device.

The efficient synthesis of amino acid Schiff base copper(II) complexes using a microfluidic device was successfully achieved. Schiff bases and their complexes are remarkable compounds due to their high biological activity and catalytic function. Conventionally, products are synthesized under reaction conditions of 40 °C for 4 h using a beaker-based method.

High-Efficiency Single-Cell Containment Microdevices Based on Fluid Control.

In this study, we developed a comb-shaped microfluidic device that can efficiently trap and culture a single cell (bacterium). Conventional culture devices have difficulty in trapping a single bacterium and often use a centrifuge to push the bacterium into the channel. The device developed in this study can store bacteria in almost all growth channels using the flowing fluid.

Dielectrophoresis-Based Selective Droplet Extraction Microfluidic Device for Single-Cell Analysis.

We developed a microfluidic device that enables selective droplet extraction from multiple droplet-trapping pockets based on dielectrophoresis. The device consists of a main microchannel, five droplet-trapping pockets with side channels, and drive electrode pairs appropriately located around the trapping pockets. Agarose droplets capable of encapsulating biological samples were successfully trapped in the trapping pockets due to the difference in flow resistance between the main and side channels.

Controlling Microdroplet Inner Rotation by Parallel Carrier Flow of Sesame and Silicone Oils.

We developed a method for passively controlling microdroplet rotation, including interior rotation, using a parallel flow comprising silicone and sesame oils. This device has a simple 2D structure with a straight channel and T-junctions fabricated from polydimethylsiloxane. A microdroplet that forms upstream moves into the sesame oil.

Efficient Generation of Microdroplets Using Tail Breakup Induced with Multi-Branch Channels.

In recent years, research on the application of microdroplets in the fields of biotechnology and chemistry has made remarkable progress, but the technology for the stable generation of single-micrometer-scale microdroplets has not yet been established. In this paper, we developed an efficient and stable single-micrometer-scale droplet generation device based on the fragmentation of droplet tails, called "tail thread mode", that appears under moderate flow conditions. This method can efficiently encapsulate microbeads that mimic cells and chemical products in passively generated single-micrometer-scale microdroplets.

Development of Microdroplet Generation Method for Organic Solvents Used in Chemical Synthesis.

Recently, chemical operations with microfluidic devices, especially droplet-based operations, have attracted considerable attention because they can provide an isolated small-volume reaction field. However, analysis of these operations has been limited mostly to aqueous-phase reactions in water droplets due to device material restrictions. In this study, we have successfully demonstrated droplet formation of five common organic solvents frequently used in chemical synthesis by using a simple silicon/glass-based microfluidic device.

Microdroplet synthesis of azo compounds with simple microfluidics-based pH control.

Conventional solution-phase synthesis of azo compounds is complicated by the need for precise pH and temperature control, high concentrations of pH control reagents, and by-product removal. In this work, we exploited the advantages of microdroplet chemistry to realize the simple and highly efficient synthesis of an azo compound using microfluidics-based pH control. Owing to the small size of microdroplets, heat exchange between a microdroplet and its environment is extremely fast.

Liquid/solution-based microfluidic quantum dots light-emitting diodes for high-colour-purity light emission.

Organic light-emitting diodes (OLEDs) using a liquid organic semiconductor (LOS) are expected to provide extremely flexible displays. Recently, microfluidic OLEDs were developed to integrate and control a LOS in a device combined with microfluidic technology. However, LOS-based OLEDs show poor-colour-purity light emissions owing to their wide full width at half maximum (FWHM).

Integration of Horizontal and Vertical Microfluidic Modules for Core-Shell Droplet Generation and Chemical Application.

This paper presents a method for utilizing three-dimensional microfluidic channels fully to realize multiple functions in a single device. The final device structure was achieved by combining three independent modules that consisted of horizontal and vertical channels. The device allowed for the one-step generation of water-in-oil-in-water droplets without the need for partial treatment of the polydimethylsiloxane channel surface using separate modules for generating water-in-oil droplets on the horizontal plane and oil-in-water droplets on the vertical plane.

Size-Dependent and Property-Independent Passive Microdroplet Sorting by Droplet Transfer on Dot Rails.

A fully passive microdroplet sorting method is presented in this paper. On the rails with dot patterns, the droplets were sorted in different ways depending on their size. However, the effect of droplet properties on the threshold size of the sorting was eliminated.

Structural Formation of Oil-in-Water (O/W) and Water-in-Oil-in-Water (W/O/W) Droplets in PDMS Device Using Protrusion Channel without Hydrophilic Surface Treatment.

This paper presents a simple method of droplet formation using liquids that easily wet polydimethylsiloxane (PDMS) surfaces without any surface treatment. Using only structural features and uniform flow focusing, Oil-in-Water (O/W) and Water-in-Oil-in-Water (W/O/W) droplets were formed in the full PDMS structure. Extrusion channel and three-dimensional flow focusing resulted in effective fluidic conditions for droplet formation and the droplet size could be precisely controlled by controlling the flow rate of each phase.

Construction of integrated gene logic-chip.

In synthetic biology, the control of gene expression requires a multistep processing of biological signals. The key steps are sensing the environment, computing information and outputting products. To achieve such functions, the laborious, combinational networking of enzymes and substrate-genes is required, and to resolve problems, sophisticated design automation tools have been introduced.

Highly flexible transparent electrodes based on mesh-patterned rigid indium tin oxide.

We developed highly bendable transparent indium tin oxide (ITO) electrodes with a mesh pattern for use in flexible electronic devices. The mesh patterns lowered tensile stress and hindered propagation of cracks. Simulations using the finite element method confirmed that the mesh patterns decreased tensile stress by over 10% because of the escaped strain to the flexible film when the electrodes were bent.

Aptamer-Based Carboxyl-Terminated Nanocrystalline Diamond Sensing Arrays for Adenosine Triphosphate Detection.

Here, we propose simple diamond functionalization by carboxyl termination for adenosine triphosphate (ATP) detection by an aptamer. The high-sensitivity label-free aptamer sensor for ATP detection was fabricated on nanocrystalline diamond (NCD). Carboxyl termination of the NCD surface by vacuum ultraviolet excimer laser and fluorine termination of the background region as a passivated layer were investigated by X-ray photoelectron spectroscopy.

Low-temperature direct heterogeneous bonding of polyether ether ketone and platinum.

Direct heterogeneous bonding between polyether ether ketone (PEEK) and Pt was realized at the temperatures lower than 150°C. In order to create sufficient bondability to diverse materials, the surface was modified by vacuum ultraviolet (VUV) irradiation, which formed hydrate bridges. For comparison, direct bonding between surfaces atomically cleaned via Ar fast atom bombardment (FAB) was conducted in a vacuum.

Liquid Chromatography Chip with Low-Dispersion and Low-Pressure-Drop Turn Structure Utilizing a Distribution-Controlled Pillar Array.

To realize efficient, fast separations on pillar array columns with turns, a novel turn with low-dispersion and low-pressure-drop properties was developed. This "pillar-distribution-controlled" (PDC) turn was designed as a constant-radius turn filled with octagonal pillars that were arranged to control the linear velocity of the mobile phase in the radial direction. After the pillar positions were adjusted by computational fluid dynamics analysis, 27 mm long pillar array columns with two turns were fabricated on a 20 × 20 mm(2) silicon glass plate.

Rapid quantitative method for the detection of phenylalanine and tyrosine in human plasma using pillar array columns and gradient elution.

This study reports a fast and quantitative determination method for phenylalanine (Phe) and tyrosine (Tyr) in human plasma using on-chip pressure-driven liquid chromatography. A pillar array column with low-dispersion turns and a gradient elution system was used. The separation of fluorescent derivatives of Phe, Tyr, and other hydrophobic amino acids was successfully performed within 140 s.

Microfluidic Stamping on Sheath Flow.

A microfluidic stamping method to form functional shapes on a cross section in fiber-shaped flow is proposed. Microfluidic stamping and overstamping allow various cross sectional shapes on the 3D flow. The shapes can be controlled by a change in combination of structures and fluidic conditions which correspond to stamp type and stamping force.

Culture-independent method for identification of microbial enzyme-encoding genes by activity-based single-cell sequencing using a water-in-oil microdroplet platform.

Environmental microbes are a great source of industrially valuable enzymes with potent and unique catalytic activities. Unfortunately, the majority of microbes remain unculturable and thus are not accessible by culture-based methods. Recently, culture-independent metagenomic approaches have been successfully applied, opening access to untapped genetic resources.

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.

Isopentenyl pyrophosphate secreted from Zoledronate-stimulated myeloma cells, activates the chemotaxis of γδT cells.

γδT cell receptor (TCR)-positive T cells, which control the innate immune system, display anti-tumor immunity as well as other non-immune-mediated anti-cancer effects. γδT cells expanded ex vivo by nitrogen-containing bisphosphonate (N-BP) treatment can kill tumor cells. N-BP inhibits farnesyl pyrophosphate synthase in the mevalonate pathway, resulting in the accumulation of isopentenyl pyrophosphate (IPP), which is a stimulatory antigen for γδT cells.

Droplet-based microfluidics for high-throughput screening of a metagenomic library for isolation of microbial enzymes.

This paper proposes a high-throughput, function-based screening approach of a metagenomic library for isolating novel microbial enzymes by droplet-based microfluidics. We used gel microdroplets (GMDs) dispersed in oil as picoliter-volume reaction vessels for lipolytic enzyme by encapsulating cells in individual GMDs. Using this approach, we monitored the growth of individual cells encapsulated in GMDs and assessed the enzyme reaction activities at the level of an individual GMD.