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Micromachines, Volume 3, Issue 1 (March 2012), Pages 1-203

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Research

Open AccessCommunication Displacement Pumping of Liquids Radially Inward on Centrifugal Microfluidic Platforms in Motion
Micromachines 2012, 3(1), 1-9; doi:10.3390/mi3010001
Received: 7 November 2011 / Revised: 12 December 2011 / Accepted: 15 December 2011 / Published: 22 December 2011
Cited by 10 | PDF Full-text (1469 KB) | HTML Full-text | XML Full-text
Abstract
We describe two novel centrifugal microfluidic platform designs that enable passive pumping of liquids radially inward while the platform is in motion. The first design uses an immiscible liquid to displace an aqueous solution back towards the center of the platform, while the
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We describe two novel centrifugal microfluidic platform designs that enable passive pumping of liquids radially inward while the platform is in motion. The first design uses an immiscible liquid to displace an aqueous solution back towards the center of the platform, while the second design uses an arbitrary pumping liquid with a volume of air between it and the solution being pumped. Both designs demonstrated the ability to effectively pump 55% to 60% of the solution radially inward at rotational frequencies as low as 400 rpm (6.7 Hz) to 700 rpm (11.7 Hz). The pumping operations reached completion within 120 s and 400 s respectively. These platform designs for passive pumping of liquids do not require moving parts or complex fabrication techniques. They offer great potential for increasing the number of sequential operations that can be performed on centrifugal microfluidic platforms, thereby reducing a fundamental limitation often associated with these platforms. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Switchable Thermal Interfaces Based on Discrete Liquid Droplets
Micromachines 2012, 3(1), 10-20; doi:10.3390/mi3010010
Received: 5 December 2011 / Revised: 22 December 2011 / Accepted: 22 December 2011 / Published: 6 January 2012
Cited by 8 | PDF Full-text (779 KB) | HTML Full-text | XML Full-text
Abstract
We present a switchable thermal interface based on an array of discrete liquid droplets initially confined on hydrophilic islands on a substrate. The droplets undergo reversible morphological transition into a continuous liquid film when they are mechanically compressed by an opposing substrate to
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We present a switchable thermal interface based on an array of discrete liquid droplets initially confined on hydrophilic islands on a substrate. The droplets undergo reversible morphological transition into a continuous liquid film when they are mechanically compressed by an opposing substrate to create low-thermal resistance heat conduction path. We investigate a criterion for reversible switching in terms of hydrophilic pattern size and liquid volume. The dependence of the liquid morphology and rupture distance on the diameter and areal fraction of hydrophilic islands, liquid volumes, as well as loading pressure is also characterized both theoretically and experimentally. The thermal resistance in the on-state is experimentally characterized for ionic liquids, which are promising for practical applications due to their negligible vapor pressure. A life testing setup is constructed to evaluate the reliability of the interface under continued switching conditions at relatively high switching frequencies. Full article
(This article belongs to the Special Issue Thermal Switches and Control of Heat Transfer in MEMS)
Open AccessArticle Plasmonic Nanostructures Prepared by Soft UV Nanoimprint Lithography and Their Application in Biological Sensing
Micromachines 2012, 3(1), 21-27; doi:10.3390/mi3010021
Received: 2 December 2011 / Revised: 21 December 2011 / Accepted: 28 December 2011 / Published: 6 January 2012
Cited by 11 | PDF Full-text (2668 KB) | HTML Full-text | XML Full-text
Abstract
We prepared high-density plasmonic nanostructures on a glass substrate. By using soft UV nanoimprint lithography, gold nanodisks with a diameter of 65 nm were obtained on an area of 1 mm2. We tested these gold nanosensors in the biotin/streptavidin system to
[...] Read more.
We prepared high-density plasmonic nanostructures on a glass substrate. By using soft UV nanoimprint lithography, gold nanodisks with a diameter of 65 nm were obtained on an area of 1 mm2. We tested these gold nanosensors in the biotin/streptavidin system to study their selectivity and sensitivity of detection. The prepared gold nanodisks could detect streptavidin at 10 pM. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Open AccessArticle A Study on Millimetre-Wave Tunable Bandpass Filter Based on Polymer Cap Deflection
Micromachines 2012, 3(1), 28-35; doi:10.3390/mi3010028
Received: 29 November 2011 / Revised: 28 December 2011 / Accepted: 29 December 2011 / Published: 6 January 2012
PDF Full-text (495 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a new tuning mechanism for millimetre-wave BPF based on deflection of the BCB membrane of BCB packaging cap. A 3-pole parallel-coupled microstrip filter operating at 60 GHz is first implemented on 30 µm-thick BCB polymer substrate and then BCB-capped through
[...] Read more.
This paper presents a new tuning mechanism for millimetre-wave BPF based on deflection of the BCB membrane of BCB packaging cap. A 3-pole parallel-coupled microstrip filter operating at 60 GHz is first implemented on 30 µm-thick BCB polymer substrate and then BCB-capped through our new anti-adhesion layer assisted wafer-level transfer technique. Gold electrodes are fabricated on top of the BCB cap for DC actuation. The implemented BCB capped BPF showed the tuning range of 1.49 GHz from 63.36 GHz to 64.85 GHz with the associated insertion losses of −9.7 dB and −9.4 dB and the return losses better than −11 dB over the tuning range. Full article
Open AccessArticle Design of an Angle Detector for Laser Beams Based on Grating Coupling
Micromachines 2012, 3(1), 36-44; doi:10.3390/mi3010036
Received: 24 December 2011 / Revised: 21 January 2012 / Accepted: 21 January 2012 / Published: 1 February 2012
Cited by 1 | PDF Full-text (412 KB) | HTML Full-text | XML Full-text
Abstract
A novel angle detector for laser beams is designed in this paper. It takes advantage of grating coupling to couple the incident light into a slab waveguide; and, the incident light’s angle can be determined by reading the outputs of light detectors within
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A novel angle detector for laser beams is designed in this paper. It takes advantage of grating coupling to couple the incident light into a slab waveguide; and, the incident light’s angle can be determined by reading the outputs of light detectors within the waveguide. This device offers fast-responding on-chip detection of laser beam’s angle. Compared to techniques based on quadrant photodiodes or lateral effect photodiodes, the device in this paper has far greater detectable range (up to a few degrees, to be specific). Performance of the laser angle detector in this paper is demonstrated by finite-difference-time-domain simulations. Numerical results show that, the detectable angle range can be adjusted by several design parameters and can reach [−4°, 4°]. The laser beam angle detector in this paper is expected to find various applications such as ultra-fast optical interconnects. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
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Open AccessArticle Arbitrary Super Surface Modes Bounded by Multilayered Metametal
Micromachines 2012, 3(1), 45-54; doi:10.3390/mi3010045
Received: 30 December 2011 / Revised: 25 January 2012 / Accepted: 27 January 2012 / Published: 1 February 2012
Cited by 4 | PDF Full-text (619 KB) | HTML Full-text | XML Full-text
Abstract
The dispersion of the fundamental super mode confined along the boundary between a multilayer metal-insulator (MMI) stack and a dielectric coating is theoretically analyzed and compared to the dispersion of surface waves on a single metal-insulator (MI) boundary. Based on the classical Kretschmann
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The dispersion of the fundamental super mode confined along the boundary between a multilayer metal-insulator (MMI) stack and a dielectric coating is theoretically analyzed and compared to the dispersion of surface waves on a single metal-insulator (MI) boundary. Based on the classical Kretschmann setup, the MMI system is experimentally tested as an anisotropic material to exhibit plasmonic behavior and a candidate of “metametal” to engineer the preset surface plasmon frequency of conventional metals for optical sensing applications. The conditions to obtain artificial surface plasmon frequency are thoroughly studied, and the tuning of surface plasmon frequency is verified by electromagnetic modeling and experiments. The design rules drawn in this paper would bring important insights into applications such as optical lithography, nano-sensing and imaging. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Open AccessArticle Surface Plasmon Excitation and Localization by Metal-Coated Axicon Prism
Micromachines 2012, 3(1), 55-61; doi:10.3390/mi3010055
Received: 29 November 2011 / Revised: 1 February 2012 / Accepted: 1 February 2012 / Published: 8 February 2012
Cited by 3 | PDF Full-text (1330 KB) | HTML Full-text | XML Full-text
Abstract
Collimated Gaussian beams are efficiently localized at the apex of a metal-coated axicon prism by surface plasmon excitations. We observed the light scattered at the apex and the light reflected by the prism. Intense scattered light was observed with the radial polarization incidence.
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Collimated Gaussian beams are efficiently localized at the apex of a metal-coated axicon prism by surface plasmon excitations. We observed the light scattered at the apex and the light reflected by the prism. Intense scattered light was observed with the radial polarization incidence. Further, each incidence of the radial, azimuthal, and linear polarizations provided field distributions of bright and dark intensities in the reflected images according to the surface plasmon excitation. We have demonstrated that surface plasmon waves are excited at the sides of the prism in the Kretschmann configuration and that they converge to its apex. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Figures

Open AccessArticle Fabrication and Performance of a Photonic-Microfluidic Integrated Device
Micromachines 2012, 3(1), 62-77; doi:10.3390/mi3010062
Received: 20 December 2011 / Revised: 20 January 2012 / Accepted: 7 February 2012 / Published: 15 February 2012
Cited by 7 | PDF Full-text (410 KB) | HTML Full-text | XML Full-text
Abstract
Fabrication and performance of a functional photonic-microfluidic flow cytometer is demonstrated. The devices are fabricated on a Pyrex substrate by photolithographically patterning the microchannels and optics in a SU-8 layer that is sealed via a poly(dimethylsiloxane) (PDMS) layer through a unique chemical bonding
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Fabrication and performance of a functional photonic-microfluidic flow cytometer is demonstrated. The devices are fabricated on a Pyrex substrate by photolithographically patterning the microchannels and optics in a SU-8 layer that is sealed via a poly(dimethylsiloxane) (PDMS) layer through a unique chemical bonding method. The resulting devices eliminate the free-space excitation optics through integration of microlenses onto the chip to mimic conventional cytometry excitation. Devices with beam waists of 6 μm and 12 μm in fluorescent detection and counting tests using 2.5 and 6 μm beads-show CVs of 9%–13% and 23% for the two devices, respectively. These results are within the expectations for a conventional cytometer (5%–15%) and demonstrate the ability to integrate the photonic components for excitation onto the chip and the ability to maintain the level of reliable detection. Full article
(This article belongs to the Special Issue Polymer MEMS)
Open AccessArticle Prognostics and Health Monitoring of High Power LED
Micromachines 2012, 3(1), 78-100; doi:10.3390/mi3010078
Received: 9 January 2012 / Revised: 10 February 2012 / Accepted: 10 February 2012 / Published: 24 February 2012
Cited by 12 | PDF Full-text (960 KB) | HTML Full-text | XML Full-text
Abstract
Prognostics is seen as a key component of health usage monitoring systems, where prognostics algorithms can both detect anomalies in the behavior/performance of a micro-device/system, and predict its remaining useful life when subjected to monitored operational and environmental conditions. Light Emitting Diodes (LEDs)
[...] Read more.
Prognostics is seen as a key component of health usage monitoring systems, where prognostics algorithms can both detect anomalies in the behavior/performance of a micro-device/system, and predict its remaining useful life when subjected to monitored operational and environmental conditions. Light Emitting Diodes (LEDs) are optoelectronic micro-devices that are now replacing traditional incandescent and fluorescent lighting, as they have many advantages including higher reliability, greater energy efficiency, long life time and faster switching speed. For some LED applications there is a requirement to monitor the health of LED lighting systems and predict when failure is likely to occur. This is very important in the case of safety critical and emergency applications. This paper provides both experimental and theoretical results that demonstrate the use of prognostics and health monitoring techniques for high power LEDs subjected to harsh operating conditions. Full article
(This article belongs to the Special Issue Health and Usage Monitoring Microsystems (HUMMs))
Open AccessArticle Cylindrical Resonator Utilizing a Curved Resonant Grating as a Cavity Wall
Micromachines 2012, 3(1), 101-113; doi:10.3390/mi3010101
Received: 26 December 2011 / Revised: 15 February 2012 / Accepted: 17 February 2012 / Published: 27 February 2012
Cited by 5 | PDF Full-text (1746 KB) | HTML Full-text | XML Full-text
Abstract
A thin-film grating on a curved substrate functions as a highly reflective and wavelength sensitive mirror for a diverging wave that has the same curvature as the substrate. In this paper we propose a cylindrical cavity surrounded by a curved resonant grating wall,
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A thin-film grating on a curved substrate functions as a highly reflective and wavelength sensitive mirror for a diverging wave that has the same curvature as the substrate. In this paper we propose a cylindrical cavity surrounded by a curved resonant grating wall, and describe its resonance characteristics. Through finite-difference time-domain (FDTD) simulation we have clarified that this type of cavity supports two resonance modes: one is confined by Fresnel reflection and the other by resonance reflection of the wall. We have also demonstrated that the latter mode exhibits a Q factor several orders of magnitude higher than that of the former mode. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Open AccessArticle Integrated Biophotonics with CYTOP
Micromachines 2012, 3(1), 114-125; doi:10.3390/mi3010114
Received: 24 January 2012 / Revised: 16 February 2012 / Accepted: 20 February 2012 / Published: 29 February 2012
Cited by 6 | PDF Full-text (513 KB) | HTML Full-text | XML Full-text
Abstract
We describe how the amorphous fluoropolymer CYTOP can be advantageously used as a waveguide cladding material in integrated optical circuits suitable for applications in integrated biophotonics. The unique refractive index of CYTOP (n = 1.34) enables the cladding material to be well index-matched
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We describe how the amorphous fluoropolymer CYTOP can be advantageously used as a waveguide cladding material in integrated optical circuits suitable for applications in integrated biophotonics. The unique refractive index of CYTOP (n = 1.34) enables the cladding material to be well index-matched to an optically probed sample solution. Furthermore, ultra-high index contrast waveguides can be fabricated, using conventional optical polymers as waveguide core materials, offering a route to large-scale integration of optical functions on a single chip. We discuss applications of this platform to evanescent-wave excitation fluorescence microscopy, passive and/or thermo-electrically-controlled on-chip light manipulation, on-chip light generation, and direct integration with microfluidic circuits through low-temperature bonding. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Open AccessArticle Multi-Input Multi-Output Integrated Ionic Polymer-Metal Composite for Energy Controls
Micromachines 2012, 3(1), 126-136; doi:10.3390/mi3010126
Received: 22 December 2011 / Revised: 13 February 2012 / Accepted: 15 February 2012 / Published: 29 February 2012
Cited by 2 | PDF Full-text (483 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an integrated sensor/actuator device with multi-input and multi-output designed on the basis of a standard control representation called a distributed port-Hamiltonian system. The device is made from soft material called an ionic polymer-metal composite (IPMC). The IPMC consists of a
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This paper presents an integrated sensor/actuator device with multi-input and multi-output designed on the basis of a standard control representation called a distributed port-Hamiltonian system. The device is made from soft material called an ionic polymer-metal composite (IPMC). The IPMC consists of a base film of a polyelectrolyte gel and a double layer of plated metal electrodes. The electrodes of the experimental IPMC are sectioned, and it is implemented as a control system with four pairs of inputs/outputs. We stabilize the system, and detect changes in dynamics by using the control representation. Full article
Open AccessArticle A Flexible Capacitive Sensor with Encapsulated Liquids as Dielectrics
Micromachines 2012, 3(1), 137-149; doi:10.3390/mi3010137
Received: 1 February 2012 / Revised: 2 March 2012 / Accepted: 2 March 2012 / Published: 13 March 2012
Cited by 10 | PDF Full-text (3603 KB) | HTML Full-text | XML Full-text
Abstract
Flexible and high-sensitive capacitive sensors are demanded to detect pressure distribution and/or tactile information on a curved surface, hence, wide varieties of polymer-based flexible MEMS sensors have been developed. High-sensitivity may be achieved by increasing the capacitance of the sensor using solid dielectric
[...] Read more.
Flexible and high-sensitive capacitive sensors are demanded to detect pressure distribution and/or tactile information on a curved surface, hence, wide varieties of polymer-based flexible MEMS sensors have been developed. High-sensitivity may be achieved by increasing the capacitance of the sensor using solid dielectric material while it deteriorates the flexibility. Using air as the dielectric, to maintain the flexibility, sacrifices the sensor sensitivity. In this paper, we demonstrate flexible and highly sensitive capacitive sensor arrays that encapsulate highly dielectric liquids as the dielectric. Deionized water and glycerin, which have relative dielectric constants of approximately 80 and 47, respectively, could increase the capacitance of the sensor when used as the dielectric while maintaining flexibility of the sensor with electrodes patterned on flexible polymer substrates. A reservoir of liquids between the electrodes was designed to have a leak path, which allows the sensor to deform despite of the incompressibility of the encapsulated liquids. The proposed sensor was microfabricated and demonstrated successfully to have a five times greater sensitivity than sensors that use air as the dielectric. Full article
(This article belongs to the Special Issue Polymer MEMS)
Open AccessArticle Modeling and Control of Electrowetting Induced Droplet Motion
Micromachines 2012, 3(1), 150-167; doi:10.3390/mi3010150
Received: 1 February 2012 / Revised: 2 March 2012 / Accepted: 12 March 2012 / Published: 14 March 2012
Cited by 6 | PDF Full-text (781 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a general methodology for the dynamic study of electrostatically actuated droplets is presented. A simplified 1D transient model is developed to investigate the transient response of a droplet to an actuation voltage and to study the effect of geometrical and
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In this paper, a general methodology for the dynamic study of electrostatically actuated droplets is presented. A simplified 1D transient model is developed to investigate the transient response of a droplet to an actuation voltage and to study the effect of geometrical and fluid-thermal properties and electrical parameters on this behavior. First, the general approach for the dynamic droplet motion model is described. All forces acting on the droplet are introduced and presented in a simplified algebraic expression. For the retentive force, the empirically extracted correlations are used, and for the electrostatic actuation force, results from electrostatic finite element simulations are used. The dynamic model is applied to electrowetting induced droplet motion between parallel plates in the case of a single actuation electrode and for an array of electrodes. Using this methodology, the influence of the switching frequency and actuation voltage is studied. Furthermore, a linearized equivalent damped mass—spring model is presented to approximate the dynamic droplet motion. It is shown that the optimal switching frequency can be estimated by twice the natural frequency of the linearized damped mass—spring system. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Figures

Open AccessArticle Effective Permittivity for FDTD Calculation of Plasmonic Materials
Micromachines 2012, 3(1), 168-179; doi:10.3390/mi3010168
Received: 9 February 2012 / Revised: 7 March 2012 / Accepted: 7 March 2012 / Published: 14 March 2012
Cited by 4 | PDF Full-text (670 KB)
Abstract
We present a new effective permittivity (EP) model to accurately calculate surface plasmons (SPs) using the finite-difference time-domain (FDTD) method. The computational representation of physical structures with curved interfaces causes inherent errors in FDTD calculations, especially when the numerical grid is coarse. Conventional
[...] Read more.
We present a new effective permittivity (EP) model to accurately calculate surface plasmons (SPs) using the finite-difference time-domain (FDTD) method. The computational representation of physical structures with curved interfaces causes inherent errors in FDTD calculations, especially when the numerical grid is coarse. Conventional EP models improve the errors, but they are not effective for SPs because the SP resonance condition determined by the original permittivity is changed by the interpolated EP values. We perform FDTD simulations using the proposed model for an infinitely-long silver cylinder and gold sphere, and the results are compared with Mie theory. Our model gives better accuracy than the conventional staircase and EP models for SPs. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Open AccessArticle Azimuthally Varying Guided Mode Resonance Filters
Micromachines 2012, 3(1), 180-193; doi:10.3390/mi3010180
Received: 1 February 2012 / Revised: 8 March 2012 / Accepted: 14 March 2012 / Published: 15 March 2012
Cited by 3 | PDF Full-text (965 KB) | HTML Full-text | XML Full-text
Abstract
New and novel sensing schemes require optical functions with unconventional spatial light distributions, as well as complex spectral functionality. Micro-optical elements have shown some flexibility in their ability to spatially encode phase information using surface relief dielectrics. In this paper, we present a
[...] Read more.
New and novel sensing schemes require optical functions with unconventional spatial light distributions, as well as complex spectral functionality. Micro-optical elements have shown some flexibility in their ability to spatially encode phase information using surface relief dielectrics. In this paper, we present a novel optical component that exploits the properties of optically resonant structures to make an azimuthally spatially varying spectral filter. The dispersive properties are quite unique with an angular resonance shift of 28 Deg/nm. This device is fabricated using techniques that are compatible with standard micro-electronic fabrication technologies. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Figures

Open AccessArticle Integrated Thermal and Microcoriolis Flow Sensing System with a Dynamic Flow Range of More Than Five Decades
Micromachines 2012, 3(1), 194-203; doi:10.3390/mi3010194
Received: 6 February 2012 / Revised: 23 February 2012 / Accepted: 13 March 2012 / Published: 15 March 2012
Cited by 4 | PDF Full-text (625 KB) | HTML Full-text | XML Full-text
Abstract
We have realized a micromachined single chip flow sensing system with an ultra-wide dynamic flow range of more than five decades, from 100 nL/h up to more than 10 mL/h. The system comprises both a thermal and a micro Coriolis flow sensor with
[...] Read more.
We have realized a micromachined single chip flow sensing system with an ultra-wide dynamic flow range of more than five decades, from 100 nL/h up to more than 10 mL/h. The system comprises both a thermal and a micro Coriolis flow sensor with partially overlapping flow ranges. Full article
(This article belongs to the Special Issue Micro Flow Controllers)

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