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Micromachines, Volume 3, Issue 2 (June 2012), Pages 204-541

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Research

Jump to: Review

Open AccessCommunication High-Throughput Micro-Debubblers for Bubble Removal with Sub-Microliter Dead Volume
Micromachines 2012, 3(2), 218-224; doi:10.3390/mi3020218
Received: 13 February 2012 / Revised: 12 March 2012 / Accepted: 22 March 2012 / Published: 23 March 2012
PDF Full-text (610 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We present the fabrication and evaluation of microdebubblers that are able to remove large bubbles while keeping a very low dead volume. The devices use a polytetrafluoroethylene membrane that is permeable to air in order to filter air bubbles out of an aqueous
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We present the fabrication and evaluation of microdebubblers that are able to remove large bubbles while keeping a very low dead volume. The devices use a polytetrafluoroethylene membrane that is permeable to air in order to filter air bubbles out of an aqueous sample. The dead volume of the devices is less than one microliter, but bubbles as large as 60 microliters can be removed. This simple solution can be very useful for microfluidic devices for chemical or biological analysis that suffer from channel clogging due to the presence of bubbles in their sample. One embodiment is particularly suited for buffer solutions with living cells. Full article
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Open AccessArticle Microreactortechnology: Real-Time Flow Measurements in Organic Synthesis
Micromachines 2012, 3(2), 244-254; doi:10.3390/mi3020244
Received: 15 February 2012 / Revised: 15 March 2012 / Accepted: 23 March 2012 / Published: 27 March 2012
Cited by 7 | PDF Full-text (1500 KB) | HTML Full-text | XML Full-text
Abstract
With the commercial availability of integrated microreactor systems, the numbers of chemical processes that are performed nowadays in a continuous flow is growing rapidly. The control over mixing efficiency and homogeneous heating in these reactors allows industrial scale production that was often hampered
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With the commercial availability of integrated microreactor systems, the numbers of chemical processes that are performed nowadays in a continuous flow is growing rapidly. The control over mixing efficiency and homogeneous heating in these reactors allows industrial scale production that was often hampered by the use of large amounts of hazardous chemicals. Accurate actuation and in line measurements of the flows, to have a better control over the chemical reaction, is of added value for increasing reproducibility and a safe production. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Mechanical Vibrations of Thermally Actuated Silicon Membranes
Micromachines 2012, 3(2), 255-269; doi:10.3390/mi3020255
Received: 14 February 2012 / Revised: 14 March 2012 / Accepted: 26 March 2012 / Published: 28 March 2012
Cited by 1 | PDF Full-text (2243 KB) | HTML Full-text | XML Full-text
Abstract
A thermally-actuated micro-electro-mechanical (MEMS) device based on a vibrating silicon membrane has been proposed as a viscosity sensor by the authors. In this paper we analyze the vibration mode of the sensor as it vibrates freely at its natural frequency. Analytical examination is
[...] Read more.
A thermally-actuated micro-electro-mechanical (MEMS) device based on a vibrating silicon membrane has been proposed as a viscosity sensor by the authors. In this paper we analyze the vibration mode of the sensor as it vibrates freely at its natural frequency. Analytical examination is compared to finite element analysis, electrical measurements and the results obtained through real-time dynamic optical surface profilometry. The vertical movement of the membrane due to the applied heat is characterized statically and dynamically. The natural vibration mode is determined to be the (1,1) mode and good correlation is found between the analytical predictions, the simulation analysis, the observed mechanical displacement and the electrical measurements. Full article
(This article belongs to the Special Issue Thermal Switches and Control of Heat Transfer in MEMS)
Open AccessArticle Capacitive Tactile Sensor Based on Dielectric Oil Displacement out of a Parylene Dome into Surrounding Channels
Micromachines 2012, 3(2), 270-278; doi:10.3390/mi3020270
Received: 15 February 2012 / Revised: 14 March 2012 / Accepted: 16 March 2012 / Published: 28 March 2012
Cited by 6 | PDF Full-text (2905 KB) | HTML Full-text | XML Full-text
Abstract
We propose a concept of a flexible sensor array using a novel capacitive force sensor not having a vulnerable electrode on the force applied site. It has a polymer domed structure inside which silicone oil is contained. When the force is applied, the
[...] Read more.
We propose a concept of a flexible sensor array using a novel capacitive force sensor not having a vulnerable electrode on the force applied site. It has a polymer domed structure inside which silicone oil is contained. When the force is applied, the oil is pushed into the surrounding thin channels, where the change in capacitance due to the inflowing dielectric oil is measured between two electrodes on the top and bottom surfaces of the channel. Since the channel does not have a directly applied external force to it, the electrodes do not suffer from damage problems. The change in capacitance was simulated using a simplified flow model. The first trial device of the sensing element has been fabricated. A sensitivity of 0.05 pF/gf was achieved. Full article
(This article belongs to the Special Issue Polymer MEMS)
Open AccessArticle A Digitally Controllable Polymer-Based Microfluidic Mixing Module Array
Micromachines 2012, 3(2), 279-294; doi:10.3390/mi3020279
Received: 11 February 2012 / Revised: 15 March 2012 / Accepted: 27 March 2012 / Published: 29 March 2012
Cited by 1 | PDF Full-text (2069 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an integrated digitally controllable microfluidic system for continuous solution supply with a real-time concentration control. This system contains multiple independently operating mixing modules, each integrated with two vortex micropumps, two Tesla valves and a micromixer. The interior surface of the
[...] Read more.
This paper presents an integrated digitally controllable microfluidic system for continuous solution supply with a real-time concentration control. This system contains multiple independently operating mixing modules, each integrated with two vortex micropumps, two Tesla valves and a micromixer. The interior surface of the system is made of biocompatible materials using a polymer micro-fabrication process and thus its operation can be applied to chemicals and bio-reagents. In each module, pumping of fluid is achieved by the vortex micropump working with the rotation of a micro-impeller. The downstream fluid mixing is based on mechanical vibrations driven by a lead zirconate titanate ceramic diaphragm actuator located below the mixing chamber. We have conducted experiments to prove that the addition of the micro-pillar structures to the mixing chamber further improves the mixing performance. We also developed a computer-controlled automated driver system to control the real-time fluid mixing and concentration regulation with the mixing module array. This research demonstrates the integration of digitally controllable polymer-based microfluidic modules as a fully functional system, which has great potential in the automation of many bio-fluid handling processes in bio-related applications. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Design Issues for Low Power Integrated Thermal Flow Sensors with Ultra-Wide Dynamic Range and Low Insertion Loss
Micromachines 2012, 3(2), 295-314; doi:10.3390/mi3020295
Received: 27 February 2012 / Revised: 27 March 2012 / Accepted: 5 April 2012 / Published: 10 April 2012
Cited by 6 | PDF Full-text (636 KB) | HTML Full-text | XML Full-text
Abstract
Flow sensors are the key elements in most systems for monitoring and controlling fluid flows. With the introduction of MEMS thermal flow sensors, unprecedented performances, such as ultra wide measurement ranges, low power consumptions and extreme miniaturization, have been achieved, although several critical
[...] Read more.
Flow sensors are the key elements in most systems for monitoring and controlling fluid flows. With the introduction of MEMS thermal flow sensors, unprecedented performances, such as ultra wide measurement ranges, low power consumptions and extreme miniaturization, have been achieved, although several critical issues have still to be solved. In this work, a systematic approach to the design of integrated thermal flow sensors, with specification of resolution, dynamic range, power consumption and pressure insertion loss is proposed. All the critical components of the sensors, namely thermal microstructure, package and read-out interface are examined, showing their impact on the sensor performance and indicating effective optimization strategies. The proposed design procedures are supported by experiments performed using a recently developed test chip,including several different sensing structures and a flexible electronic interface. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
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Open AccessArticle Flexible Tactile Sensor Using Polyurethane Thin Film
Micromachines 2012, 3(2), 315-324; doi:10.3390/mi3020315
Received: 11 February 2012 / Revised: 5 March 2012 / Accepted: 13 March 2012 / Published: 10 April 2012
Cited by 3 | PDF Full-text (588 KB) | HTML Full-text | XML Full-text
Abstract
A novel capacitive tactile sensor using a polyurethane thin film is proposed in this paper. In previous studies, capacitive tactile sensors generally had an air gap between two electrodes in order to enhance the sensitivity. In this study, there is only polyurethane thin
[...] Read more.
A novel capacitive tactile sensor using a polyurethane thin film is proposed in this paper. In previous studies, capacitive tactile sensors generally had an air gap between two electrodes in order to enhance the sensitivity. In this study, there is only polyurethane thin film and no air gap between the electrodes. The sensitivity of this sensor is higher than the previous capacitive tactile sensors because the polyurethane is a fairly flexible elastomer and the film is very thin (about 1 µm). The polyurethane film is formed by spin-coating and etched back from 6 µm to 1 µm using 48% sulfuric acid. As a result of evaluation, the sensitivity of the developed sensor (diameter is 1 mm) is 1.3 pF/Pa (800 pF/N considering the sensing area). Young’s modulus of the thin polyurethane film was estimated to be 20 kPa. Full article
(This article belongs to the Special Issue Polymer MEMS)
Open AccessArticle Time of Flight Sensor with a Flow Parallel Wire
Micromachines 2012, 3(2), 325-330; doi:10.3390/mi3020325
Received: 5 March 2012 / Revised: 5 April 2012 / Accepted: 18 April 2012 / Published: 26 April 2012
PDF Full-text (306 KB) | HTML Full-text | XML Full-text
Abstract
A time of flight sensor has been equipped with a sensing wire parallel to the flow direction (flow parallel wire, FPW). A heat pulse is generated with a coil in the flow channel. The FPW has a center tap allowing its upstream and
[...] Read more.
A time of flight sensor has been equipped with a sensing wire parallel to the flow direction (flow parallel wire, FPW). A heat pulse is generated with a coil in the flow channel. The FPW has a center tap allowing its upstream and downstream parts to join in a half bridge. When a heat pulse passes the FPW, a large output peak is generated. The time between heat pulse generation and recording the peak maximum is only marginally affected by the properties of the fluid. With a combination of two FPWs, a measuring range of approximately 0.01–0.5 m/s can be achieved. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle MEMS-Based Boiler Operation from Low Temperature Heat Transfer and Thermal Scavenging
Micromachines 2012, 3(2), 331-344; doi:10.3390/mi3020331
Received: 16 March 2012 / Revised: 31 March 2012 / Accepted: 18 April 2012 / Published: 26 April 2012
Cited by 8 | PDF Full-text (1332 KB) | HTML Full-text | XML Full-text
Abstract
Increasing world-wide energy use and growing population growth presents a critical need for enhanced energy efficiency and sustainability. One method to address this issue is via waste heat scavenging. In this approach, thermal energy that is normally expelled to the environment is transferred
[...] Read more.
Increasing world-wide energy use and growing population growth presents a critical need for enhanced energy efficiency and sustainability. One method to address this issue is via waste heat scavenging. In this approach, thermal energy that is normally expelled to the environment is transferred to a secondary device to produce useful power output. This paper investigates a novel MEMS-based boiler designed to operate as part of a small-scale energy scavenging system. For the first time, fabrication and operation of the boiler is presented. Boiler operation is based on capillary action that drives working fluid from surrounding reservoirs across a heated surface. Pressure is generated as working fluid transitions from liquid to vapor in an integrated steamdome. In a full system application, the steam can be made available to other MEMS-based devices to drive final power output. Capillary channels are formed from silicon substrates with 100 µm widths. Varying depths are studied that range from 57 to 170 µm. Operation of the boiler shows increasing flow-rates with increasing capillary channel depths. Maximum fluid mass transfer rates are 12.26 mg/s from 170 µm channels, an increase of 28% over 57 µm channel devices. Maximum pressures achieved during operation are 229 Pa. Full article
(This article belongs to the Special Issue Thermal Switches and Control of Heat Transfer in MEMS)
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Open AccessArticle Strong Electro-Absorption in GeSi Epitaxy on Silicon-on-Insulator (SOI)
Micromachines 2012, 3(2), 345-363; doi:10.3390/mi3020345
Received: 15 March 2012 / Revised: 6 April 2012 / Accepted: 18 April 2012 / Published: 26 April 2012
Cited by 10 | PDF Full-text (359 KB) | HTML Full-text | XML Full-text
Abstract
We have investigated the selective epitaxial growth of GeSi bulk material on silicon-on-insulator substrates by reduced pressure chemical vapor deposition. We employed AFM, SIMS, and Hall measurements, to characterize the GeSi heteroepitaxy quality. Optimal growth conditions have been identified to achieve low defect
[...] Read more.
We have investigated the selective epitaxial growth of GeSi bulk material on silicon-on-insulator substrates by reduced pressure chemical vapor deposition. We employed AFM, SIMS, and Hall measurements, to characterize the GeSi heteroepitaxy quality. Optimal growth conditions have been identified to achieve low defect density, low RMS roughness with high selectivity and precise control of silicon content. Fabricated vertical p-i-n diodes exhibit very low dark current density of 5 mA/cm2 at −1 V bias. Under a 7.5 V/µm E-field, GeSi alloys with 0.6% Si content demonstrate very strong electro-absorption with an estimated effective ∆α/α around 3.5 at 1,590 nm. We compared measured ∆α/α performance to that of bulk Ge. Optical modulation up to 40 GHz is observed in waveguide devices while small signal analysis indicates bandwidth is limited by device parasitics. Full article
(This article belongs to the Special Issue Nano-photonic Devices)
Open AccessArticle Micro-Ramps for Hypersonic Flow Control
Micromachines 2012, 3(2), 364-378; doi:10.3390/mi3020364
Received: 3 March 2012 / Revised: 27 March 2012 / Accepted: 19 April 2012 / Published: 26 April 2012
Cited by 19 | PDF Full-text (5789 KB) | HTML Full-text | XML Full-text
Abstract
Shock/boundary layer interaction (SBLI) is an undesirable phenomenon, occurring in high-speed propulsion systems. The conventional method to manipulate and control SBLI is using a bleed system that involves the removal of a certain amount of mass of the inlet flow to control boundary
[...] Read more.
Shock/boundary layer interaction (SBLI) is an undesirable phenomenon, occurring in high-speed propulsion systems. The conventional method to manipulate and control SBLI is using a bleed system that involves the removal of a certain amount of mass of the inlet flow to control boundary layer separation. However, the system requires a larger nacelle to compensate the mass loss, larger nacelles contribute to additional weight and drag and reduce the overall performance. This study investigates a novel type of flow control device called micro-ramps, a part of the micro vortex generators (VGs) family that intends to replace the bleed technique. Micro-ramps produce pairs of counter-rotating streamwise vortices, which help to suppress SBLI and reduce the chances of flow separation. Experiments were done at Mach 5 with two micro-ramp models of different sizes. Schlieren photography, surface flow visualization and infrared thermography were used in this investigation. The results revealed the detailed flow characteristics of the micro-ramp, such as the primary and secondary vortices. This helps us to understand the overall flow physics of micro-ramps in hypersonic flow and their application for SBLI control. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
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Open AccessArticle A Hybrid Thermopneumatic and Electrostatic Microvalve with Integrated Position Sensing
Micromachines 2012, 3(2), 379-395; doi:10.3390/mi3020379
Received: 20 March 2012 / Revised: 17 April 2012 / Accepted: 24 April 2012 / Published: 27 April 2012
Cited by 4 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a low-power hybrid thermopneumatic microvalve with an electrostatic hold and integrated valve plate position sensing. This combination of actuators in a single structure enables a high throw and force actuator with low energy consumption, a combination that is difficult to
[...] Read more.
This paper presents a low-power hybrid thermopneumatic microvalve with an electrostatic hold and integrated valve plate position sensing. This combination of actuators in a single structure enables a high throw and force actuator with low energy consumption, a combination that is difficult to otherwise achieve. The completed 7.5 mm × 10.3 mm × 1.5 mm valve has an open flow rate of 8 sccm at 600 Pa, a leak rate of 2.2 × 10−3 sccm at 115 kPa, a open-to-closed fluidic conductance ratio of nearly one million, an actuation time of 430 ms at 250 mW, and a required power of 90 mW while closed. It additionally requires no power to open, and has a built-in capacitive position sensor with a sensitivity of 9.8 fF/kPa. The paper additionally presents analytical models of the valve components, design tradeoffs, and guidelines for achieving an optimized device. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Design Considerations for a Micromachined Proportional Control Valve
Micromachines 2012, 3(2), 396-412; doi:10.3390/mi3020396
Received: 6 February 2012 / Revised: 6 April 2012 / Accepted: 24 April 2012 / Published: 27 April 2012
Cited by 6 | PDF Full-text (354 KB) | HTML Full-text | XML Full-text
Abstract
Precise mass flow control is an essential requirement for novel, small-scale fluidic systems. However, a small-volume, low-leakage proportional control valve for minute fluid flows has not yet been designed or manufactured. A survey is therefore made of the primary design considerations of a
[...] Read more.
Precise mass flow control is an essential requirement for novel, small-scale fluidic systems. However, a small-volume, low-leakage proportional control valve for minute fluid flows has not yet been designed or manufactured. A survey is therefore made of the primary design considerations of a micromachined, proportional control valve. Performance requirements are identified based on various applications. Valve operating principles and actuation schemes presented in the literature are evaluated with respect to functionality and technological feasibility. Proceeding from these analyses, we identify the design concepts and actuation schemes that we think are best suited for the fabrication of the intended microvalve. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessArticle Temperature Frequency Characteristics of Hexamethyldisiloxane (HMDSO) Polymer Coated Rayleigh Surface Acoustic Wave (SAW) Resonators for Gas-Phase Sensor Applications
Micromachines 2012, 3(2), 413-426; doi:10.3390/mi3020413
Received: 29 March 2012 / Revised: 18 April 2012 / Accepted: 27 April 2012 / Published: 2 May 2012
Cited by 5 | PDF Full-text (575 KB) | HTML Full-text | XML Full-text
Abstract
Temperature induced frequency shifts may compromise the sensor response of polymer coated acoustic wave gas-phase sensors operating in environments of variable temperature. To correct the sensor data with the temperature response of the sensor the latter must be known. This study presents and
[...] Read more.
Temperature induced frequency shifts may compromise the sensor response of polymer coated acoustic wave gas-phase sensors operating in environments of variable temperature. To correct the sensor data with the temperature response of the sensor the latter must be known. This study presents and discusses temperature frequency characteristics (TFCs) of solid hexamethyldisiloxane (HMDSO) polymer coated sensor resonators using the Rayleigh surface acoustic wave (RSAW) mode on ST-cut quartz. Using a RF-plasma polymerization process, RSAW sensor resonators optimized for maximum gas sensitivity have been coated with chemosensitive HMDSO films at 4 different thicknesses: 50, 100, 150 and 250 nm. Their TFCs have been measured over a (−100 to +110) °C temperature range and compared to the TFC of an uncoated device. An exponential 2,500 ppm downshift of the resonant frequency and a 40 K downshift of the sensor’s turn-over temperature (TOT) are observed when the HMDSO thickness increases from 0 to 250 nm. A partial temperature compensation effect caused by the film is also observed. A third order polynomial fit provides excellent agreement with the experimental TFC curve. The frequency downshift due to mass loading by the film, the TOT and the temperature coefficients are unambiguously related to each other. Full article
(This article belongs to the Special Issue Micromachined High Frequency Acoustic Wave Resonators and Filters)
Open AccessArticle Quantitative Studies on PDMS-PDMS Interface Bonding with Piranha Solution and its Swelling Effect
Micromachines 2012, 3(2), 427-441; doi:10.3390/mi3020427
Received: 10 March 2012 / Revised: 26 April 2012 / Accepted: 26 April 2012 / Published: 4 May 2012
Cited by 19 | PDF Full-text (954 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a low-cost yet effective method of irreversible bonding between two elastomeric polydimethylsiloxane (PDMS) interfaces using Piranha solution is investigated. Piranha solutions at a weight ratio of 3:1 using different acids and hydrogen peroxide were attempted. The average tensile strengths of
[...] Read more.
In this paper, a low-cost yet effective method of irreversible bonding between two elastomeric polydimethylsiloxane (PDMS) interfaces using Piranha solution is investigated. Piranha solutions at a weight ratio of 3:1 using different acids and hydrogen peroxide were attempted. The average tensile strengths of the device bonded with concentrated sulfuric acid-based piranha solution and nitric acid-based piranha solution were found to be 200 ± 20 kPa and 100 ± 15 kPa respectively. A PDMS surface treated with Piranha Solution demonstrated an increase in hydrophilicity. In addition, relatively straightforward swelling studies of PDMS using a weight loss method with common organic solvents were also investigated. Experimental results show that hexane, toluene, ethyl acetate, n-propyl alcohol and acetone swell PDMS significantly over a duration of up to 1 h and above; PDMS samples reached a steady state of swelling only after 5 min of immersion in other solvents. This will enable researchers to develop devices for the future according to the interaction between the material and the solvents in contact. Full article
(This article belongs to the Special Issue Polymer MEMS)
Open AccessArticle Highly Sensitive and Miniaturized Fluorescence Detection System with an Autonomous Capillary Fluid Manipulation Chip
Micromachines 2012, 3(2), 462-479; doi:10.3390/mi3020462
Received: 10 April 2012 / Revised: 27 April 2012 / Accepted: 9 May 2012 / Published: 10 May 2012
Cited by 7 | PDF Full-text (748 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel, highly sensitive and ultra-small fluorescent detection system, including an autonomous capillary fluid manipulation chip. The optical detector integrates a LED light source, all necessary optical components, and a photodiode with preamplifier into one package of about 2 cm
[...] Read more.
This paper presents a novel, highly sensitive and ultra-small fluorescent detection system, including an autonomous capillary fluid manipulation chip. The optical detector integrates a LED light source, all necessary optical components, and a photodiode with preamplifier into one package of about 2 cm × 2 cm × 2 cm. Also, the low-cost and simple pumpless microfluidic device works well in sample preparation and manipulation. This chip consists of capillary stop valves and trigger valves which are fabricated by lithography and then bonded with a polydimethylsiloxane-ethylene oxide polymer polydimethylsiloxane (PEO-PDMS) cover. The contact angle of the PEO-PDMS can be adjusted by changing the concentration of the PEO. Hence, the fluidic chip can achieve functionalities such as timing features and basic logical functions. The prototype has been tested by fluorescence dye 5-Carboxyfluorescein (5-FAM) dissolved into the solvent DMSO (Dimethyl Sulfoxide). The results prove a remarkable sensitivity at a pico-scale molar, around 1.08 pM. The low-cost and miniaturized optical detection system, with a self-control capillary-driven microfluidic chip developed in this work, can be used as the crucial parts in portable biochemical detection applications and point of care testing. Full article
Open AccessArticle Flexible Helicoids, Atomic Force Microscopy (AFM) Cantilevers in High Mode Vibration, and Concave Notch Hinges in Precision Measurements and Research
Micromachines 2012, 3(2), 480-491; doi:10.3390/mi3020480
Received: 27 March 2012 / Revised: 30 April 2012 / Accepted: 11 May 2012 / Published: 16 May 2012
Cited by 3 | PDF Full-text (747 KB) | HTML Full-text | XML Full-text
Abstract
Flexible structures are the main components in many precision measuring and research systems. They provide miniaturization, repeatability, minimal damping, low measuring forces, and very high resolution. This article focuses on the modeling, development, and comparison of three typical flexible micro- nano-structures: flexible helicoids,
[...] Read more.
Flexible structures are the main components in many precision measuring and research systems. They provide miniaturization, repeatability, minimal damping, low measuring forces, and very high resolution. This article focuses on the modeling, development, and comparison of three typical flexible micro- nano-structures: flexible helicoids, atomic force microscopy (AFM) cantilevers, and concave notch hinges. Our theory yields results which allow us to increase the accuracy and functionality of these structures in new fields of application such as the modeling of helicoidal DNA molecules’ mechanics, the definition of instantaneous center of rotation in concave flexure notch hinges, and the estimation of the increase of spring constants and resolution at higher mode vibration in AFM cantilevers with an additional concentrated and end extended mass. We developed the original kinetostatic, reverse conformal mapping of approximating contours, and non-linear thermomechanical fluctuation methods for calculation, comparison, and research of the micromechanical structures. These methods simplify complicated solutions in micro elasticity but provide them with necessary accuracy. All our calculation results in this article and in all corresponding referenced author’s publications are in a good agreement with experimental and finite element modeling data within 10% or less. Full article
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Open AccessArticle Optical Spectrum and Electric Field Waveform Dependent Optically-Induced Dielectrophoretic (ODEP) Micro-Manipulation
Micromachines 2012, 3(2), 492-508; doi:10.3390/mi3020492
Received: 30 March 2012 / Revised: 1 May 2012 / Accepted: 2 May 2012 / Published: 16 May 2012
Cited by 16 | PDF Full-text (2962 KB) | HTML Full-text | XML Full-text
Abstract
In the last seven years, optoelectronic tweezers using optically-induced dielectrophoretic (ODEP) force have been explored experimentally with much success in manipulating micro/nano objects. However, not much has been done in terms of in-depth understanding of the ODEP-based manipulation process or optimizing the input
[...] Read more.
In the last seven years, optoelectronic tweezers using optically-induced dielectrophoretic (ODEP) force have been explored experimentally with much success in manipulating micro/nano objects. However, not much has been done in terms of in-depth understanding of the ODEP-based manipulation process or optimizing the input physical parameters to maximize ODEP force. We present our work on analyzing two significant influencing factors in generating ODEP force on a-Si:H based ODEP chips: (1) the waveforms of the AC electric potential across the fluidic medium in an ODEP chip based microfluidic platform; and (2) optical spectrum of the light image projected onto the ODEP chip. Theoretical and simulation results indicate that when square waves are used as the AC electric potential instead of sine waves, ODEP force can double. Moreover, numerical results show that ODEP force increases with increasing optical frequency of the projected light on an ODEP chip following the Fermi-Dirac function, validating that the optically-induced dielectrophoresis force depends strongly on the electron-hole carrier generation phenomena in optoelectronic materials. Qualitative experimental results that validate the numerical results are also presented in this paper. Full article
Open AccessArticle High-Q MEMS Resonators for Laser Beam Scanning Displays
Micromachines 2012, 3(2), 509-528; doi:10.3390/mi3020509
Received: 13 April 2012 / Revised: 5 May 2012 / Accepted: 31 May 2012 / Published: 6 June 2012
Cited by 33 | PDF Full-text (3380 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports on design, fabrication and characterization of high-Q MEMS resonators to be used in optical applications like laser displays and LIDAR range sensors. Stacked vertical comb drives for electrostatic actuation of single-axis scanners and biaxial MEMS mirrors were realized in a
[...] Read more.
This paper reports on design, fabrication and characterization of high-Q MEMS resonators to be used in optical applications like laser displays and LIDAR range sensors. Stacked vertical comb drives for electrostatic actuation of single-axis scanners and biaxial MEMS mirrors were realized in a dual layer polysilicon SOI process. High Q-factors up to 145,000 have been achieved applying wafer level vacuum packaging technology including deposition of titanium thin film getters. The effective reduction of gas damping allows the MEMS actuator to achieve large amplitudes at high oscillation frequencies while driving voltage and power consumption can be minimized. Exemplarily shown is a micro scanner that achieves a total optical scan angle of 86 degrees at a resonant frequency of 30.8 kHz, which fulfills the requirements for HD720 resolution. Furthermore, results of a new wafer based glass-forming technology for fabrication of three dimensionally shaped glass lids with tilted optical windows are presented. Full article
(This article belongs to the Special Issue Micromachined High Frequency Acoustic Wave Resonators and Filters)
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Open AccessArticle Simulation and Experimental Characterization of Microscopically Accessible Hydrodynamic Microvortices
Micromachines 2012, 3(2), 529-541; doi:10.3390/mi3020529
Received: 26 April 2012 / Revised: 22 May 2012 / Accepted: 8 June 2012 / Published: 15 June 2012
Cited by 4 | PDF Full-text (1091 KB) | HTML Full-text | XML Full-text
Abstract
Single-cell studies of phenotypic heterogeneity reveal more information about pathogenic processes than conventional bulk-cell analysis methods. By enabling high-resolution structural and functional imaging, a single-cell three-dimensional (3D) imaging system can be used to study basic biological processes and to diagnose diseases such as
[...] Read more.
Single-cell studies of phenotypic heterogeneity reveal more information about pathogenic processes than conventional bulk-cell analysis methods. By enabling high-resolution structural and functional imaging, a single-cell three-dimensional (3D) imaging system can be used to study basic biological processes and to diagnose diseases such as cancer at an early stage. One mechanism that such systems apply to accomplish 3D imaging is rotation of a single cell about a fixed axis. However, many cell rotation mechanisms require intricate and tedious microfabrication, or fail to provide a suitable environment for living cells. To address these and related challenges, we applied numerical simulation methods to design new microfluidic chambers capable of generating fluidic microvortices to rotate suspended cells. We then compared several microfluidic chip designs experimentally in terms of: (1) their ability to rotate biological cells in a stable and precise manner; and (2) their suitability, from a geometric standpoint, for microscopic cell imaging. We selected a design that incorporates a trapezoidal side chamber connected to a main flow channel because it provided well-controlled circulation and met imaging requirements. Micro particle-image velocimetry (micro-PIV) was used to provide a detailed characterization of flows in the new design. Simulated and experimental results demonstrate that a trapezoidal side chamber represents a viable option for accomplishing controlled single cell rotation. Further, agreement between experimental and simulated results confirms that numerical simulation is an effective method for chamber design. Full article
(This article belongs to the Special Issue Micro Flow Controllers)

Review

Jump to: Research

Open AccessReview Efficient Design of Coupled Microcavities at Optical Frequencies
Micromachines 2012, 3(2), 204-217; doi:10.3390/mi3020204
Received: 1 February 2012 / Revised: 2 March 2012 / Accepted: 20 March 2012 / Published: 23 March 2012
PDF Full-text (263 KB) | HTML Full-text | XML Full-text
Abstract
Simple and efficient approaches for filter design at optical frequencies using a large number of coupled microcavities are proposed. The design problem is formulated as an optimization problem with a unique global solution. Various efficient filter designs are obtained at both the drop
[...] Read more.
Simple and efficient approaches for filter design at optical frequencies using a large number of coupled microcavities are proposed. The design problem is formulated as an optimization problem with a unique global solution. Various efficient filter designs are obtained at both the drop and through ports. Our approaches are illustrated through a number of examples. Full article
Open AccessReview Micromachined Flow Sensors in Biomedical Applications
Micromachines 2012, 3(2), 225-243; doi:10.3390/mi3020225
Received: 23 February 2012 / Revised: 6 March 2012 / Accepted: 21 March 2012 / Published: 26 March 2012
Cited by 23 | PDF Full-text (955 KB) | HTML Full-text | XML Full-text
Abstract
Application fields of micromachined devices are growing very rapidly due to the continuous improvement of three dimensional technologies of micro-fabrication. In particular, applications of micromachined sensors to monitor gas and liquid flows hold immense potential because of their valuable characteristics (e.g., low energy
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Application fields of micromachined devices are growing very rapidly due to the continuous improvement of three dimensional technologies of micro-fabrication. In particular, applications of micromachined sensors to monitor gas and liquid flows hold immense potential because of their valuable characteristics (e.g., low energy consumption, relatively good accuracy, the ability to measure very small flow, and small size). Moreover, the feedback provided by integrating microflow sensors to micro mass flow controllers is essential to deliver accurately set target small flows. This paper is a review of some application areas in the biomedical field of micromachined flow sensors, such as blood flow, respiratory monitoring, and drug delivery among others. Particular attention is dedicated to the description of the measurement principles utilized in early and current research. Finally, some observations about characteristics and issues of these devices are also reported. Full article
(This article belongs to the Special Issue Micro Flow Controllers)
Open AccessReview Hydrodynamic Flow Confinement Technology in Microfluidic Perfusion Devices
Micromachines 2012, 3(2), 442-461; doi:10.3390/mi3020442
Received: 24 March 2012 / Revised: 18 April 2012 / Accepted: 2 May 2012 / Published: 10 May 2012
Cited by 6 | PDF Full-text (1752 KB) | HTML Full-text | XML Full-text
Abstract
Hydrodynamically confined flow device technology is a young research area with high practical application potential in surface processing, assay development, and in various areas of single cell research. Several variants have been developed, and most recently, theoretical and conceptual studies, as well as
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Hydrodynamically confined flow device technology is a young research area with high practical application potential in surface processing, assay development, and in various areas of single cell research. Several variants have been developed, and most recently, theoretical and conceptual studies, as well as fully developed automated systems, were presented. In this article we review concepts, fabrication strategies, and application areas of hydrodynamically confined flow (HCF) devices. Full article
(This article belongs to the Special Issue Micro Flow Controllers)

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