1,721,517 research outputs found
Gradient shadow pattern reveals refractive index of liquid
Full text linkWe propose a simple method that uses a gradient shadow pattern (GSP) to measure the refractive index n(L) of liquids. A light source generates a "dark-bright-dark" GSP when it is projected through through the back of a transparent, rectangular block with a cylindrical chamber that is filled with a liquid sample. We found that there is a linear relationship between nL and the proportion of the bright region in a GSP, which provides the basic principle of the proposed method. A wide range 1.33 <= n(L) <= 1.46 of liquids was measured in the single measurement setup with error < 0.01. The proposed method is simple but robust to illuminating conditions, and does not require for any expensive or precise optical components, so we expect that it will be useful in many portable measurement systems that use nL to estimate attributes of liquid samples.1110Ysciescopu
A Zeta (zeta)-Pipet Tip to Reduce the Spontaneously Induced Electrical Charge of a Dispensed Aqueous Droplet
Full text linkWe report that the zeta potential of a pipet tip's inner surface is one of the crucial parameters for controlling the electrical charge of the dispensed droplet. Since the charge is unexpected and undesirable for most experiments in various fields of science and, thereby, they can cause unsuspected problems, reducing the charge on a dispensed droplet is important for the results of pipetting-based experiments. We fabricate a graphene-based nanocomposite-coated pipet tip, which we called a zeta-pipet tip, as a proof-of-concept example to reduce the zeta potential of the pipet tip's inner surface. The fabricated zeta-pipet tip can successfully mitigate the undesired droplet separation in the droplet merging experiments in an oil bath, which is one of the unexpected effects caused by the electrification. The findings of this study provide helpful guidelines for researchers in many fields of science and technology, who utilize a pipet tip in their respective experiments.X111112Ysciescopu
A portable pressure pump for microfluidic lab-on-a-chip systems using a porous polydimethylsiloxane (PDMS) sponge
No full textIn this paper, we propose a novel portable and disposable pressure pump using a porous polydimethylsiloxane (PDMS) sponge and demonstrate its application to a microfluidic lab-on-a-chip. The porous PDMS sponge was simply fabricated by a sugar leaching technique based on capillary suction of pre-cured PDMS into lumps of sugar, thereby enabling us to achieve the porous PDMS sponge composed of interconnected micropores. To indicate the characteristics of the porous PDMS sponge and pump, we measured the average porosities of them whose values were 0.64 and 0.34, respectively. A stress-strain relationship of the fabricated portable pressure pump represented a linear behavior in the compressive strain range of 0 to 20%. Within this range, a pumping volume of the pressure pump could be linearly controlled by the compressed strain. Finally, the fabricated porous PDMS pump was successfully demonstrated as a portable pressure pump for a disposable microfluidic lab-on-a-chip for efficient detection of agglutination. The proposed portable pressure pump can be potentially applicable to various disposable microfluidic lab-on-a-chip systems.X112520sciescopu
The Effect of the Aspect Ratio on the Hydrophobicity of Microstructured Polydimethylsiloxane (PDMS) Robust Surfaces
No full textIn this study, we have designed and fabricated robust hydrophobic surfaces that are composed of various micropillar arrays and investigated the effect of the aspect ratio (feature height/feature size) of the micropillar on the wettability of the fabricated surfaces. The robust, micropillar-arrayed surfaces were designed to yield the same Wenzel and Cassie water contact angles (CAs). According to our design rule, one can achieve an enhanced hydrophobic surface by increasing the height of the micropillars. The designed hydrophobic surfaces were fabricated by polydimethylsiloxane (PDMS) replica molding with photolithographically micropatterned SU-8 masters. The hydrophobicity properties of the fabricated PDMS surfaces were fully characterized theoretically and experimentally. From the theoretical and experimental results, it was found that the micropillars of an intrinsically hydrophobic material with a high aspect ratio enhance the hydrophobicity of the surface by increasing the surface roughness (in view of the Wenzel state) and the opportunities for the entrapment of air beneath a water droplet (the Cassie state).X1187sciescopu
Microfluidic synthesis of thermo-responsive poly (N-isopropylacrylamide)–poly(ethylene glycol) diacrylatemicrohydrogels as chemo-embolic microspheres
No full textIn this paper, we have successfully synthesized and characterized poly(N-isopropylacrylamide) (PNIPAAm)-poly(ethylene glycol) diacrylate (PEGDA) microhydrogels. Various combinations of PNIPAAm-PEGDA microhydrogels were fabricated by the generation of monodisperse microdroplets whose sizes were comparable to a blood vessel of 260 and 320 mu m with the help of a hydrodynamic focusing microfluidic device (HFMD), followed by synthesis of the microhydrogels through UV irradiation to the microdroplets. The thermo-responsive behaviors of the various microhydrogels were investigated by changing the PEGDA crosslinker concentration, which was found to be a dominant factor in tuning the shrinkage ratio in response to temperature change. As an in vitro embolization performance evaluation of the microhydrogels as chemo-embolic microspheres, the deliverability of the microhydrogels through a microcatheter was first confirmed and the compact occlusion of a channel was demonstrated based on a tapered microchannel in response to the temperature increase to physiological temperature of 36 degrees C. The controlled release behavior of the fluorescent dye from the microhydrogel was also investigated for chemotherapeutic purposes as a proof of concept study. The PNIPAAm-PEGDA microhydrogels could be used widely in embolization procedures based on the advantages of tunable thermo-responsive and controlled release behaviors.X1167sciescopu
Fabrication and applications of complex-shaped microparticles via microfluidics
No full textComplex-shaped microparticles (MPs) have attracted extensive interest in a myriad of scientific and engineering fields in recent years for their distinct morphology and capability in combining different functions within a single particle. Microfluidic techniques offer an intriguing method for fabricating MPs with excellent monodispersity and complex morphology in parallel while controlling their number and size precisely and independently. To date, there are two notable microfluidics approaches for the synthesis of complex-shaped MPs, namely droplet based, and flow-lithography based microfluidics approaches. It is undoubted that the application of complex-shaped MPs via microfluidic fabrication will hold great promise in a variety of fields including microfabrication, analytical chemistry and biomedicine.111812sciescopu
A Capillary-based Preconcentration Device by using Ion Concentration Polarization through Cation Permselective Membrane Coating
No full textIon Concentration Polarization (ICP), occurring near the ion permselective membrane, is considered to be one of the most intriguing phenomenon in the study of electrokinetics. Both ion enrichment and depletion zones are found to be formed at the anodic side of the microchannel due to the characteristic of the electrical repulsion force which is generated near the ion permselective membrane. Utilizing the ion depletion/enrichment process, ICP phenomenon has been applied in the vast field of inquiries on preconcentration of ionic molecules in the fluid. This study proposes an original capillary-based preconcentration device using Nafion, cation permselective membrane. The sample preconcentration could be easily achieved by utilizing the Nafion coated glass capillary. By applying the DC voltage to the developed preconcentration device, we observed that the charged fluorescent dye was successfully concentrated nearby the ion depletion zone. This observation would provide a platform of new preconcentration device owing to its simplified fabrication procedure compared to the previous devices.1132sciescopuskc
Replication of microlens arrays by injection molding
No full textInjection molding could be used as a mass production technology for microlens arrays. It is of importance, and thus of our concern in the present study, to understand the injection molding processing condition effects on the replicability of microlens array profile. Extensive experiments were performed by varying processing conditions such as flow rate, packing pressure and packing time for three different polymeric materials (PS, PMMA and PC). The nickel mold insert of microlens arrays was made by electroplating a microstructure master fabricated by a modified LIGA process. Effects of processing conditions on the replicability were investigated with the help of the surface profile measurements. Experimental results showed that a packing pressure and a flow rate significantly affects a final surface profile of the injection molded product. Atomic force microscope measurement indicated that the averaged surface roughness value of injection molded microlens arrays is smaller than that of mold insert and is comparable with that of fine optical components in practical use.1183sciescopu
One-step Fabrication of Transparent and Flexible Nanotopographical-Triboelectric Nanogenerators via Thermal Nanoimprinting of Thermoplastic Fluoropolymers
No full textUsing thermal nanoimprinting, a novel transparent and flexible nanotopographical triboelectric nanogenerator (TENG), with simultaneous nanoreplication and integration of the contact layer with the electrode layer, is first demonstrated. It is expected that the present rapid one-step fabrication methodology will give "disposability" to the TENG with extremely reduced manufacturing costs, which may allay commercialization concerns.112611Nsciescopu
OPTIMAL TESTING INPUT SETS FOR REDUCED DIAGNOSIS TIME OF NUCLEAR-POWER-PLANT DIGITAL ELECTRONIC-CIRCUITS
No full textThis paper describes the optimal testing input sets required for the fault diagnosis of the unclear power plant digital electronic circuits. With the complicated systems such as very large scale integration (VLSI), nuclear power plant (NPP), and aircraft, testing is the major factor of the maintenance of the system. Particularly, diagnosis time grows quickly with the complexity of the component In this research, for reduced diagnosis time we derived the optimal testing sets that are the minimal testing sets required for detecting the failure and for locating of the failed component. For reduced diagnosis time, the technique presented by Hayes fits best for our approach to testing sets generation among many conventional methods. However, this method has the following disadvantages; a) it considers only the simple network b) it concerns only whether the system is in failed state or not and does not provide the way to locate the failed component. Therefore we have derived the optimal testing input sets that resolve these problems by Hayes while preserving its advantages. When we applied the optimal testing sets to the automatic fault diagnosis system (AFDS) which incorporates the advanced fault diagnosis method of artificial intelligence technique, we found that the fault diagnosis using the optimal testing sets makes testing the digital electronic circuits much faster than that using exhaustive testing input sets; when we applied them to test the Universal (UV) Card which is a nuclear power plant digital input/output solid state protection system card, we reduced the testing time up to about 100 times
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