Cell density-dependent differential proliferation of neural stem cells on omnidirectional nanopore-arrayed surface

112Ysciescopu

Roll-to-flat texturing system with infrared preheating for manufacturing a microfluidic device

In the present study, a roll-to-flat (R2F) texturing system with infrared preheating was developed and characterized for the purpose of massively producing thermoplastic microfluidic devices with the height of 100 pm-scale. A thermoplastic substrate preheated up to its glass transition temperature (T-g) by a halogen lamp was textured between a roll mold and a plane actuator. After texturing, the substrate could be immediately cooled down as the roll mold screened the substrate from the infrared heat source. In order to characterize the transcription performance of the developed R2F texturing system for 100 gm features, a parametric study was carried out based on the Taguchi method with four kinds of thermoplastic materials, cyclic olefin copolymer (COC), polycarbonate (PC), polymethylmethacrylate (PMMA), and polystyrene (PS), which are the most commonly used in manufacturing microfluidic devices. As an application example of the developed system, a microfluidic device having a serpentine microchannel was fabricated via R2F texturing and subsequent thermal bonding. (C) 2013 Elsevier B.V. All rights reserved.X1134sciescopu

Development of contaminant-free and effective micro-mixing methods based on non-contact dispensing system

This paper presents the development and characterization of two different types of effective micro-mixing methods with small volumes of liquids, both of which are based on simple non-contact dispensing systems to avoid the contamination between mixing-target liquids, thereby preventing undesirable crosstalk in biochemical assays. The principle of micro-mixing methods is to control the trajectory and volume of dispensing droplets. The first micro-mixing method induces mixing by smashing two different droplets in the air by dispensing the droplets simultaneously (called, a simultaneous micro-mixing method, SMM). The second method is to dispense two different droplets into a well in a controlled alternating manner (namely, an alternating micro-mixing method, AMM). In the dispensing system developed in this study for the micro-mixing, pressurized air transfers a liquid from a reservoir to a nozzle via a high-speed-solenoid valve, thus injecting liquid droplets with volume ranging from several ten nanoliters to several microliters, depending on the viscosity of the liquid. The droplet volumes of mixing-target liquids dispensed from the dispensing system were measured under various dispensing conditions by changing operating pressure and opening time of high-speed-solenoid valve. Sodium hydroxide (NaOH) ethanol solution and phenolphthalein ethanol solution added with glycerol were used as the mixing-target liquids to quantitatively characterize the mixing performances. The mixing performances were evaluated according to the different volumes of dispensing droplets and micro-mixing methods. The SMM exhibited a higher mixing performance compared to the AMM. However, both micro-mixing methods achieved the improved mixing performances compared with conventional mixing methods, such as micro-stirrer and micro-well shaking. The present methods could be useful in the automated micro-mixing system for clinical applications. (C) 2013 Elsevier B.V. All rights reserved.X111sciescopu

A Study on Mechanical Characteristics of Phosphor Film Containing Methyl Silicone Resin Based on Crosslinking Reaction Analysis

This study reveals a methodological research for predicting mechanical properties of phosphor films through the chemical crosslinking reaction of methyl silicone resin during fabrication of the phosphor films. Crosslinking point according to the type of methyl silicone resins was verified through the magnitude of the absorption peak of the functional group and the curing reaction heat. Then, we measured mechanical properties of the fabricated phosphor films. As a result, it was figured out that the number of the crosslinking point was directly proportional to the total curing reaction heat, and also affected the mechanical properties of the phosphor films. Based on the correlation of curing reaction heat and crosslinking point of the methyl silicone resins and mechanical properties of the fabricated phosphor films, we proposed a methodology that can understand and control the phosphor films in advance of finishing the fabrication of the final phosphor products

Design and numerical simulation of complex flow generation in a microchannel by magnetohydrodynamic (MHD) actuation

In this paper we present a design methodology for the generation of magnetohydrodynamic (MHD) complex flows in a simple straight microchannel inside which electrodes are patterned on the two side walls and the bottom wall. The Lorentz force, a driving force for the MHD flow, can be variously induced in the microchannel by changing the applied voltages at the patterned electrodes and the magnetic field The design methodology for determining the required condition for the applied voltage at each electrode is discussed for generating axial, transverse, sinusoidal, and multi-vortical flows under a given magnetic field Three-dimensional CFD (computational fluid dynamics) simulations demonstrate the successful generation of the designed complex flows in a microchannel. The mixing performances of axial, sinusoidal, and multi-vortical flows were evaluated as an application example of the present MHD complex flows. The present design methodology may be also applied for the precise control of the fluid flow inside a microchannel, not to mention the micromixing.X111211sciescopuskc

Injection Molded Plastic Lens for Relay Lens System and Optical Imaging Probe

In this study, we designed, fabricated and characterized a plastic lens which can be used as an optical compartment of a relay lens system for a disposable endoscope or an imaging probe for optical-resolution photoacoustic microscopy (OR-PAM). Cost-effective injection molding using polycarbonate (PC) as a material was conducted for the mass production of the PC lens. The effects of important processing parameters, i.e. mold temperature, injection speed, packing pressure and packing time, on the transcription quality of the PC lenses were investigated quantitatively using the design of experiments based on the Taguchi method. Optical performances, i.e., focal length and birefringence, were evaluated to determine the optimal injection molding condition for the replication. The PC lenses facilitated the feasibility of developing a disposable length-adjustable endoscope comprising a relay lens system. The PC lens was also applied to an optical imaging probe in an OR-PAM for in vivo observation of mouse micro-vasculatures.X113sciescopuskc

Facile Tailoring of Contact Layer Characteristics of the Triboelectric Nanogenerator Based on Portable Imprinting Device

Renewable energy harvesting technologies have been actively studied in recent years for replacing rapidly depleting energies, such as coal and oil energy. Among these technologies, the triboelectric nanogenerator (TENG), which is operated by contact-electrification, is attracting close attention due to its high accessibility, light weight, high shape adaptability, and broad applications. The characteristics of the contact layer, where contact electrification phenomenon occurs, should be tailored to enhance the electrical output performance of TENG. In this study, a portable imprinting device is developed to fabricate TENG in one step by easily tailoring the characteristics of the polydimethylsiloxane (PDMS) contact layer, such as thickness and morphology of the surface structure. These characteristics are critical to determine the electrical output performance. All parts of the proposed device are 3D printed with high-strength polylactic acid. Thus, it has lightweight and easy customizable characteristics, which make the designed system portable. Furthermore, the finger tapping-driven TENG of tailored PDMS contact layer with microstructures is fabricated and easily generates 350 V of output voltage and 30 μA of output current with a simple finger tapping motion-related biomechanical energy

Development of the Triboelectric Nanogenerator Using a Metal-to-Metal Imprinting Process for Improved Electrical Output

Triboelectric nanogenerators (TENG), which utilize contact electrification of two different material surfaces accompanied by electrical induction has been proposed and is considered as a promising energy harvester. Researchers have attempted to form desired structures on TENG surfaces and successfully demonstrated the advantageous effect of surface topography on its electrical output performance. In this study, we first propose the structured Al (SA)-assisted TENG (SA-TENG), where one of the contact layers of the TENG is composed of a structured metal surface formed by a metal-to-metal (M2M) imprinting process. The fabricated SA-TENG generates more than 200 V of open-circuit voltage and 60 µA of short-circuit current through a simple finger tapping motion. Given that the utilization of the M2M imprinting process allows for the rapid, versatile and easily accessible structuring of various metal surfaces, which can be directly used as a contact layer of the TENG to substantially enhance its electrical output performance, the present study may considerably broaden the applicability of the TENG in terms of its fabrication standpoint

Spontaneous occurrence of liquid-solid contact electrification in nature: Toward a robust triboelectric nanogenerator inspired by the natural lotus leaf

The successive process of contact and detachment of aqueous liquid from the solid surface with its resultant net electrical charge generation is termed as "discrete liquid-solid contact electrification", which is unobtrusively ubiquitous in our daily life. So far, the natural occurrence of discrete liquid-solid contact electrification on surfaces in nature has not been investigated and reported despite the beneficial characteristics of such surfaces. This study firstly reveals the existence of the discrete liquid-solid contact electrification phenomenon and concomitant net electrical charge generation on the natural lotus leaf surface. To advantageously utilize the generated net electrical charges, for the first time, the naturally occurring surface is directly employed to fabricate the natural lotus leaf-TENG, called the LL-TENG. The further investigation about the electricity generation is continued by altering contact material of the LL-TENG to fluoropolymer while maintaining the lotus leaf's superior surface characteristics, in a simple and cost-effective manner via thermal nanoimprinting. The artificially modified TENG not only significantly increases the amount of the generated electricity, but also shows sustained electrical output performance even after 1 month of exposure in the external dusty environment with the help of the outstanding "lotus effect".1185sciescopu