Search

Owing to the relatively high conductivity and unique redox behavior, polyaniline (PANI) has been one of the most technologically promising conducting polymers. Although various methodologies have been developed, fabrication of PANI microfibers has been a challenging task owing to the poor solubility in most organic solvents. By taking advantage of a microfluidic technology and organic soluble acid labile t-Boc-protected PANI (t-Boc-PANI) as the conducting polymer precursor, fabrication of PANI microfibers in a size-controlled manner is possible. Introduction of a THF solution containing t-Boc-PANI, and dodecylbenzenesulfonic acid (DBSA) as a core flow, and water as a sheath flow into a microfluidic channel with a 3D hydrodynamic focusing effect results in crystallization of the polymer fiber. By changing the flow rate, linear PANI microfibers that range from 16.2 to 39.4 μm in diameter are readily obtained., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We examined two-dimensional (2D) optical feedback control of phototaxis flagellate Euglena cells confined in closed-type microfluidic channels (microaquariums), and demonstrated that the 2D optical feedback enables the control of the density and position of Euglena cells in microaquariums externally, flexibly, and dynamically. Using three types of feedback algorithms, the density of Euglena cells in a specified area can be controlled arbitrarily and dynamically, and more than 70% of the cells can be concentrated into a specified area. Separation of photo-sensitive/insensitive Euglena cells was also demonstrated. Moreover, Euglena-based neuro-computing has been achieved, where 16 imaginary neurons were defined as Euglena-activity levels in 16 individual areas in microaquariums. The study proves that 2D optical feedback control of photoreactive flagellate microbes is promising for microbial biology studies as well as applications such as microbe-based particle transportation in microfluidic channels or separation of photo-sensitive/insensitive microbes.

We developed and examined a toxicity sensing microchip, where 200-300 cells of flagellated microbes ( Euglena gracilis ) were placed and their movements were monitored with a video camera. The microchip had two microchannels for test sample and reference flow, and the cells were confined completely in a separated closed-space (micro-aquarium). The two microchannels run aside of the micro-aquarium, and molecules of test sample permeated into the micro-aquarium from the microchannels via diffusion through porous polydimethylsiloxane (PDMS) wall. The toxicity of test sample was evaluated real-time from the spatial distribution of the cells and swimming motion. Highly quantitative toxicity monitoring was achieved, owing to the complete confinement of microbial cells and sensitive chemotaxis of the cells. [ABSTRACT FROM AUTHOR]

Printed electronics have recently attracted extensive attention due to their superior productivity to conventional semiconductor fabrication methods. To develop printing devices optimized for printed electronics, numerical studies on ink flows are often necessary, and, therefore, it is critical to provide accurate ink properties for reliable numerical results. However, it is difficult to find such data in literature since inks for printed electronics contains conductive metallic nanoparticles and they are not only non-Newtonian but expensive. Thus, we propose utilizing a microfluidic chip to investigate rheological properties of conductive inks. By using micro particle image velocimeter along with an immersion oil technique, we examine the flow characteristics of two commercial conductive inks containing Ag nanoparticles on microfluidic chips. We found that the ink flows show a stronger shear-thinning behavior as the Ag content increases. Finally, suitable rheological models applicable to numerical simulations for those inks are suggested after comparing the experimental data to frequently used rheological models. [ABSTRACT FROM AUTHOR]

We examined two-dimensional (2D) optical feedback control of phototaxis flagellate Euglenacells confined in closed-type microfluidic channels (microaquariums), and demonstrated that the 2D optical feedback enables the control of the density and position of Euglenacells in microaquariums externally, flexibly, and dynamically. Using three types of feedback algorithms, the density of Euglenacells in a specified area can be controlled arbitrarily and dynamically, and more than 70% of the cells can be concentrated into a specified area. Separation of photo-sensitive/insensitive Euglenacells was also demonstrated. Moreover, Euglena-based neuro-computing has been achieved, where 16 imaginary neurons were defined as Euglena-activity levels in 16 individual areas in microaquariums. The study proves that 2D optical feedback control of photoreactive flagellate microbes is promising for microbial biology studies as well as applications such as microbe-based particle transportation in microfluidic channels or separation of photo-sensitive/insensitive microbes. [ABSTRACT FROM AUTHOR]

This article discusses the importance of on-chip sample preconcentration for integrated microfluidic analysis. The advances of microfluidic integrated circuits enabled the miniaturization of several biochemical techniques, which results in faster and cheaper analysis using smaller amounts of sample and reagents. Several reasons make sample preconcentration an important process in the development of multifunctional integrated microfluidic devices.

A multifunctional microfluidic cartridge for electrochemical biosensing (µCEB) was developed with a cleanroom-free rapid prototyping technique. A seven-layered µCEB platform including a gold (Au) electrode substrate was fabricated by alternating patterned thin plastic and adhesive films. To provide conformal bonding between layers, pressure sensitive adhesive (PSA) tape was adopted to fabricate a leak-free, porous membranes embedded µCEB platform compatible with relatively high flow rates. In addition, the embedded porous membranes provide multiple functions in the µCEB device, including (1) controlling fluid flow, (2) storing a dried detergent, and (3) trapping liquid waste. To demonstrate the utility of the µCEB, we performed an electrochemical-based immunoassay to detect various concentrations of Creatine Kinase (CK)-Myocardial Band (MB). During the immunoassay, the membranes controlled the flow path to minimize a carryover between the assay steps and released the stored dried-reagent to remove non-specifically bound detection antibodies. With a linear sweep voltammetry (LSV) electrochemical sensing technique, a limit of detection of 0.25 ng mL-1 was achieved. The multilayered prototyping technique enables rapid and low-cost fabrication of multifunctional microfluidic electrochemical devices with single-use sample processing components. [ABSTRACT FROM AUTHOR]

The article focuses on the measurement of the flow temperature in microfluidic devices using the thermoresponsive property of the polydiacetylenes (PDAs) supramolecules. A microfluidic chip, which consists of a glass wafer and PDMS substrate, was fabricated to generate temperature. It was found out that the fluorescence intensities of PDA sensors vary with temperature flow. It concludes that temperature flow in microfluidic devices is measured through the fluorescent intensities of PDA.

• We report an ICP-coupled electrokinetic method for the detection of LMW thiols. • The interaction between the redox regulator and DNA operator sensed LMW thiols. • The protein/DNA complex was rapidly separated by LMW thiols in microfluidics. • This platform is useful for monitoring rapid redox changes in LMW thiols. Despite the diagnostic potential of low-molecular-weight (LMW) thiols in human diseases, their rapid and simple detection is challenging due to their reversible redox changes. Herein, we report a rapid electrokinetic detection of LMW thiols using the interaction between Bacillus subtilis -derived organic hydroperoxide resistance regulatory protein (OhrR BS) and its operator DNA element in ion concentration polarization (ICP)-coupled microfluidic multiple channels. The dimeric OhrR BS was tightly bound to the dye-labeled dsDNA element with high binding affinity (K D ≈ 4 nM) under the reduced conditions. The presence of organic hydroperoxide (OHP) and LMW thiol (X–SH) caused rapid oxidation of the reduced Cys residue (OhrR BS –SH) of the protein into the sulfenic acid form (OhrR BS –SOH) by OHP and subsequently into the disulfide form (OhrR BS –S–S–X) by LMW thiol via S-thiolation, leading to a rapid release of OhrR BS from the fluorescent dsDNA element. Based on this principle, the fluorescence zones of the dsDNA-protein complex in response to LMW thiols were rapidly separated in the microfluidic channels by electrokinetic mobility. Owing to the ability of ICP-coupled microfluidics to concentrate charged samples, this electrokinetic method enabled the rapid determination (<35 min) and improved sensitivity (>2 μM) of LMW thiols, depending on their molecular weights and concentrations. Additionally, this strategy enabled the simultaneous detection of free and total LMW thiols in mouse serum. These results suggest that the ICP-coupled microfluidic platform in combination with the OhrR BS –DNA complex will be useful for monitoring rapid redox changes of LMW thiols in real samples. [ABSTRACT FROM AUTHOR]