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Micromachines, Volume 4, Issue 2 (June 2013), Pages 128-285

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Research

Jump to: Review

Open AccessArticle Photomechanical Bending of Azobenzene-Based Photochromic Molecular Fibers
Micromachines 2013, 4(2), 128-137; doi:10.3390/mi4020128
Received: 31 December 2012 / Revised: 28 January 2013 / Accepted: 1 March 2013 / Published: 27 March 2013
Cited by 3 | PDF Full-text (2331 KB) | HTML Full-text | XML Full-text
Abstract
Microfibers composed of azobenzene-based photochromic amorphous molecular materials, namely low molecular-mass photochromic materials with a glass-forming property, could be fabricated. These fibers were found to exhibit mechanical bending motion upon irradiation with a laser beam. In addition, the bending direction could be controlled
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Microfibers composed of azobenzene-based photochromic amorphous molecular materials, namely low molecular-mass photochromic materials with a glass-forming property, could be fabricated. These fibers were found to exhibit mechanical bending motion upon irradiation with a laser beam. In addition, the bending direction could be controlled by altering the polarization direction of the irradiated light without changing the position of the light source or the wavelength of the light. In-situ fluorescence observation of mass transport induced at the surface of the fiber doped with CdSe quantum dots suggested that the bending motions were related with the photoinduced mass transport taking place near the irradiated surface of the fiber. Full article
(This article belongs to the Special Issue Glass Micromachining and Applications of Glass)
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Open AccessArticle Pushing the Limits of Electrical Detection of Ultralow Flows in Nanofluidic Channels
Micromachines 2013, 4(2), 138-148; doi:10.3390/mi4020138
Received: 11 December 2012 / Revised: 30 January 2013 / Accepted: 20 March 2013 / Published: 2 April 2013
Cited by 12 | PDF Full-text (1223 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents improvements in flow detection by electrical cross-correlation spectroscopy. This new technique detects molecular number fluctuations of electrochemically active analyte molecules as they are transported by liquid flow through a nanochannel. The fluctuations are used as a marker of liquid flow
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This paper presents improvements in flow detection by electrical cross-correlation spectroscopy. This new technique detects molecular number fluctuations of electrochemically active analyte molecules as they are transported by liquid flow through a nanochannel. The fluctuations are used as a marker of liquid flow as their time of flight in between two consecutive transducers is determined, thereby allowing for the measurement of liquid flow rates in the picoliter-per-minute regime. Here we show an enhanced record-low sensitivity below 1 pL/min by capitalizing on improved electrical instrumentation, an optimized sensor geometry and a smaller channel cross section. We further discuss the impact of sensor geometry on the cross-correlation functions. Full article
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Open AccessArticle Freeform Fabrication of Magnetophotonic Crystals with Diamond Lattices of Oxide and Metallic Glasses for Terahertz Wave Control by Micro Patterning Stereolithography and Low Temperature Sintering
Micromachines 2013, 4(2), 149-156; doi:10.3390/mi4020149
Received: 25 January 2013 / Revised: 26 March 2013 / Accepted: 26 March 2013 / Published: 2 April 2013
Cited by 1 | PDF Full-text (1395 KB) | HTML Full-text | XML Full-text
Abstract
Micrometer order magnetophotonic crystals with periodic arranged metallic glass and oxide glass composite materials were fabricated by stereolithographic method to reflect electromagnetic waves in terahertz frequency ranges through Bragg diffraction. In the fabrication process, the photo sensitive acrylic resin paste mixed with micrometer
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Micrometer order magnetophotonic crystals with periodic arranged metallic glass and oxide glass composite materials were fabricated by stereolithographic method to reflect electromagnetic waves in terahertz frequency ranges through Bragg diffraction. In the fabrication process, the photo sensitive acrylic resin paste mixed with micrometer sized metallic glass of Fe72B14.4Si9.6Nb4 and oxide glass of B2O3·Bi2O3 particles was spread on a metal substrate, and cross sectional images of ultra violet ray were exposed. Through the layer by layer stacking, micro lattice structures with a diamond type periodic arrangement were successfully formed. The composite structures could be obtained through the dewaxing and sintering process with the lower temperature under the transition point of metallic glass. Transmission spectra of the terahertz waves through the magnetophotonic crystals were measured by using a terahertz time domain spectroscopy. Full article
(This article belongs to the Special Issue Glass Micromachining and Applications of Glass)
Open AccessArticle Fabrication of a Polymer High-Aspect-Ratio Pillar Array Using UV Imprinting
Micromachines 2013, 4(2), 157-167; doi:10.3390/mi4020157
Received: 30 January 2013 / Revised: 3 March 2013 / Accepted: 7 April 2013 / Published: 17 April 2013
Cited by 4 | PDF Full-text (714 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents UV imprinting methods for fabricating a high-aspect-ratio pillar array. A polydimethylsiloxane (PDMS) mold was selected as the UV imprinting mold. The pillar pattern was formed on a 50 × 50 mm2 area on a polyethylene terephthalate (PET) film without
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This paper presents UV imprinting methods for fabricating a high-aspect-ratio pillar array. A polydimethylsiloxane (PDMS) mold was selected as the UV imprinting mold. The pillar pattern was formed on a 50 × 50 mm2 area on a polyethylene terephthalate (PET) film without remarkable deformation. The aspect ratios of the pillar and space were about four and ten, respectively. The mold was placed into contact with a UV-curable resin under a reduced pressure, and the resin was cured by UV light irradiation after exposure to atmospheric pressure. The PDMS mold showed good mold releasability and high flexibility. By moderately pressing the mold before UV-curing, the thickness of the residual layer of the imprinted resin was reduced and the pattern was precisely imprinted. Both batch pressing and roll pressing are available. Full article
(This article belongs to the Special Issue Micromachined Tools for Nanoscale Science and Technology)
Open AccessArticle Review on Electrodynamic Energy Harvesters—A Classification Approach
Micromachines 2013, 4(2), 168-196; doi:10.3390/mi4020168
Received: 29 December 2012 / Revised: 20 January 2013 / Accepted: 22 January 2013 / Published: 29 April 2013
Cited by 13 | PDF Full-text (11999 KB) | HTML Full-text | XML Full-text
Abstract
Beginning with a short historical sketch, electrodynamic energy harvesters with focus on vibration generators and volumes below 1dm3 are reviewed. The current challenges to generate up to several milliwatts of power from practically relevant flows and vibrations are addressed, and the variety of
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Beginning with a short historical sketch, electrodynamic energy harvesters with focus on vibration generators and volumes below 1dm3 are reviewed. The current challenges to generate up to several milliwatts of power from practically relevant flows and vibrations are addressed, and the variety of available solutions is sketched. Sixty-seven different harvester concepts from more than 130 publications are classified with respect to excitation, additional boundary conditions, design and fabrication. A chronological list of the harvester concepts with corresponding references provides an impression about the developments. Besides resonant harvester concepts, the review includes broadband approaches and mechanisms to harvest from flow. Finally, a short overview of harvesters in applications and first market ready concepts is given. Full article
Open AccessArticle Active and Precise Control of Microdroplet Division Using Horizontal Pneumatic Valves in Bifurcating Microchannel
Micromachines 2013, 4(2), 197-205; doi:10.3390/mi4020197
Received: 2 February 2013 / Revised: 21 April 2013 / Accepted: 2 May 2013 / Published: 7 May 2013
Cited by 4 | PDF Full-text (1636 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a microfluidic system for the active and precise control of microdroplet division in a micro device. Using two horizontal pneumatic valves formed at downstream of bifurcating microchannel, flow resistances of downstream channels were variably controlled. With the resistance control, volumetric
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This paper presents a microfluidic system for the active and precise control of microdroplet division in a micro device. Using two horizontal pneumatic valves formed at downstream of bifurcating microchannel, flow resistances of downstream channels were variably controlled. With the resistance control, volumetric ratio of downstream flows was changed and water-in-oil microdroplets were divided into two daughter droplets of different volume corresponding to the ratio. The microfluidic channels and pneumatic valves were fabricated by single-step soft lithography process of PDMS (polydimethylsiloxane) using SU-8 mold. A wide range control of the daughter droplets’ volume ratio was achieved by the simple channel structure. Volumetric ratio between large and small daughter droplets are ranged from 1 to 70, and the smallest droplet volume of 14 pL was obtained. The proposed microfluidic device is applicable for precise and high throughput droplet based digital synthesis. Full article
Open AccessArticle Photomasks Fabrication Based on Optical Reduction for Microfluidic Applications
Micromachines 2013, 4(2), 206-214; doi:10.3390/mi4020206
Received: 16 March 2013 / Revised: 22 April 2013 / Accepted: 10 May 2013 / Published: 28 May 2013
Cited by 3 | PDF Full-text (1234 KB) | HTML Full-text | XML Full-text
Abstract
A procedure for fabrication of photomasks on photographic films with minimum feature achievable of about 20 μm, which are particularly suitable for the fast prototyping of microfluidic devices, has been improved. We used a commercial photographic enlarger in reverse mode obtaining 10:1 reduction
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A procedure for fabrication of photomasks on photographic films with minimum feature achievable of about 20 μm, which are particularly suitable for the fast prototyping of microfluidic devices, has been improved. We used a commercial photographic enlarger in reverse mode obtaining 10:1 reduction factor with error less than 1%. Masks have been characterized by optical transmission measurement and contact profilometry: the exposed region completely absorbs light in the wavelength region explored, while the non-exposed region is transparent from 350 nm on; the average film thickness is of 410 nm and its roughness is about 120 nm. A PDMS microfluidic device has been realized and tested in order to prove the effectiveness of designed photomasks used with the common UV light box. Full article
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Open AccessArticle Fabrication of Nanopillar Micropatterns by Hybrid Mask Lithography for Surface-Directed Liquid Flow
Micromachines 2013, 4(2), 232-242; doi:10.3390/mi4020232
Received: 19 March 2013 / Revised: 12 May 2013 / Accepted: 23 May 2013 / Published: 5 June 2013
PDF Full-text (1176 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel method for fabricating nanopillar micropatterns for surface-directed liquid flows. It employs hybrid mask lithography, which uses a mask consisting of a combination of a photoresist and nanoparticles in the photolithography process. The nanopillar density is controlled by varying
[...] Read more.
This paper presents a novel method for fabricating nanopillar micropatterns for surface-directed liquid flows. It employs hybrid mask lithography, which uses a mask consisting of a combination of a photoresist and nanoparticles in the photolithography process. The nanopillar density is controlled by varying the weight ratio of nanoparticles in the composite mask. Hybrid mask lithography was used to fabricate a surface-directed liquid flow. The effect of the surface-directed liquid flow, which was formed by the air-liquid interface due to nanopillar micropatterns, was evaluated, and the results show that the oscillation of microparticles, when the micro-tool was actuated, was dramatically reduced by using a surface-directed liquid flow. Moreover, the target particle was manipulated individually without non-oscillating ambient particles. Full article
Open AccessArticle Analysis of Electric Fields inside Microchannels and Single Cell Electrical Lysis with a Microfluidic Device
Micromachines 2013, 4(2), 243-256; doi:10.3390/mi4020243
Received: 16 March 2013 / Revised: 13 May 2013 / Accepted: 28 May 2013 / Published: 7 June 2013
Cited by 3 | PDF Full-text (3124 KB) | HTML Full-text | XML Full-text
Abstract
Analysis of electric fields generated inside the microchannels of a microfluidic device for electrical lysis of biological cells along with experimental verification are presented. Electrical lysis is the complete disintegration of cell membranes, due to a critical level of electric fields applied for
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Analysis of electric fields generated inside the microchannels of a microfluidic device for electrical lysis of biological cells along with experimental verification are presented. Electrical lysis is the complete disintegration of cell membranes, due to a critical level of electric fields applied for a critical duration on a biological cell. Generating an electric field inside a microchannel of a microfluidic device has many advantages, including the efficient utilization of energy and low-current requirement. An ideal microchannel model was compared with a practical microchannel model using a finite element analysis tool that suggests that the overestimation error can be over 10%, from 2.5 mm or smaller, in the length of a microchannel. Two analytical forms are proposed to reduce this overestimation error. Experimental results showed that the high electric field is confined only inside the microchannel that is in agreement with the simulation results. Single cell electrical lysis was conducted with a fabricated microfluidic device. An average of 800 V for seven seconds across an 8 mm-long microchannel with the dimension of 100 μm × 20 μm was required for lysis, with electric fields exceeding 100 kV/m and consuming 300 mW. Full article
Open AccessArticle Microfluidic Platform for Enzyme-Linked and Magnetic Particle-Based Immunoassay
Micromachines 2013, 4(2), 257-271; doi:10.3390/mi4020257
Received: 12 March 2013 / Revised: 4 June 2013 / Accepted: 4 June 2013 / Published: 18 June 2013
Cited by 5 | PDF Full-text (1411 KB) | HTML Full-text | XML Full-text
Abstract
This article presents design and testing of a microfluidic platform for immunoassay. The method is based on sandwiched ELISA, whereby the primary antibody is immobilized on nitrocelluose and, subsequently, magnetic beads are used as a label to detect the analyte. The chip takes
[...] Read more.
This article presents design and testing of a microfluidic platform for immunoassay. The method is based on sandwiched ELISA, whereby the primary antibody is immobilized on nitrocelluose and, subsequently, magnetic beads are used as a label to detect the analyte. The chip takes approximately 2 h and 15 min to complete the assay. A Hall Effect sensor using 0.35-μm BioMEMS TSMC technology (Taiwan Semiconductor Manufacturing Company Bio-Micro-Electro-Mechanical Systems) was fabricated to sense the magnetic field from the beads. Furthermore, florescence detection and absorbance measurements from the chip demonstrate successful immunoassay on the chip. In addition, investigation also covers the Hall Effect simulations, mechanical modeling of the bead–protein complex, testing of the microfluidic platform with magnetic beads averaging 10 nm, and measurements with an inductor-based system. Full article
(This article belongs to the Special Issue Bioinspired Microsensors and Micromachines)
Open AccessArticle On-Chip Enucleation of Bovine Oocytes using Microrobot-Assisted Flow-Speed Control
Micromachines 2013, 4(2), 272-285; doi:10.3390/mi4020272
Received: 1 April 2013 / Revised: 1 June 2013 / Accepted: 6 June 2013 / Published: 21 June 2013
Cited by 12 | PDF Full-text (921 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we developed a microfluidic chip with a magnetically driven microrobot for oocyte enucleation. A microfluidic system was specially designed for enucleation, and the microrobot actively controls the local flow-speed distribution in the microfluidic chip. The microrobot can adjust fluid resistances
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In this study, we developed a microfluidic chip with a magnetically driven microrobot for oocyte enucleation. A microfluidic system was specially designed for enucleation, and the microrobot actively controls the local flow-speed distribution in the microfluidic chip. The microrobot can adjust fluid resistances in a channel and can open or close the channel to control the flow distribution. Analytical modeling was conducted to control the fluid speed distribution using the microrobot, and the model was experimentally validated. The novelties of the developed microfluidic system are as follows: (1) the cutting speed improved significantly owing to the local fluid flow control; (2) the cutting volume of the oocyte can be adjusted so that the oocyte undergoes less damage; and (3) the nucleus can be removed properly using the combination of a microrobot and hydrodynamic forces. Using this device, we achieved a minimally invasive enucleation process. The average enucleation time was 2.5 s and the average removal volume ratio was 20%. The proposed new system has the advantages of better operation speed, greater cutting precision, and potential for repeatable enucleation. Full article

Review

Jump to: Research

Open AccessReview Automated Ultrafiltration Device for Environmental Nanoparticle Research and Implications: A Review
Micromachines 2013, 4(2), 215-231; doi:10.3390/mi4020215
Received: 28 February 2013 / Revised: 16 May 2013 / Accepted: 17 May 2013 / Published: 3 June 2013
PDF Full-text (2296 KB) | HTML Full-text | XML Full-text
Abstract
Nanoparticle research and development have brought significant breakthroughs in many areas of basic and applied sciences. However, efficiently collecting nanoparticles in large quantities in pure and natural systems is a major challenge in nanoscience. This review article has focused on experimental investigation and
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Nanoparticle research and development have brought significant breakthroughs in many areas of basic and applied sciences. However, efficiently collecting nanoparticles in large quantities in pure and natural systems is a major challenge in nanoscience. This review article has focused on experimental investigation and implications of nanoparticles in soil, clay, geological and environmental sciences. An automated ultrafiltration device (AUD) apparatus was used to demonstrate efficient collection and separation of nanoparticles in highly weathering red soils, black soils, and gouge of earthquake fault, as well as zeolite. The kaolinite, illite, goethite, and hematite were identified in highly weathering red soils. Transmission electron microscopic (TEM) images showed the presence of hematite nanoparticles on the surface coating of kaolinite nanoparticles and aggregated hematite nanoparticles overlapping the edge of a kaolinite flake in a size range from 4 to 7 nm. The maximum crystal violet (CV) and methylene blue (MB) adsorption amount of smectite nanoparticles (<100 nm) separated by black soils were about two to three times higher than those of bulk sample (<2000 nm). The smectite nanoparticles adsorb both CV and MB dyes efficiently and could be employed as a low-cost alternative to remove cationic dyes in wastewater treatment. Quartz grain of <50 nm was found in the gouge of fault by X-ray diffraction (XRD) analysis and TEM observation. Separated quartz could be used as the index mineral associated with earthquake fracture and the finest grain size was around 25 nm. Comparing the various particle-size fractions of zeolite showed significant differences in surface area, Si to Al molar ratio, morphology, crystallinity, framework structure, and surface atomic structure of nanoparticles from those of the bulk sample prior to particle-size fractionations. The AUD apparatus has the characteristics of automation, easy operation, and high efficiency in the separation of nanoparticles and would, thus, facilitate future nanoparticle research and developments in basic and applied sciences. Full article
(This article belongs to the Special Issue Micromachined Tools for Nanoscale Science and Technology)

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