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Micromachines, Volume 8, Issue 12 (December 2017)

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Editorial

Jump to: Research, Review

Open AccessEditorial Multidisciplinary Role of Microfluidics for Biomedical and Diagnostic Applications: Biomedical Microfluidic Devices
Micromachines 2017, 8(12), 343; doi:10.3390/mi8120343
Received: 24 November 2017 / Revised: 24 November 2017 / Accepted: 24 November 2017 / Published: 27 November 2017
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Abstract
Life scientists are closely working with engineers to solve biological and biomedical problems through the application of engineering tools.[...] Full article
(This article belongs to the Special Issue Biomedical Microfluidic Devices)

Research

Jump to: Editorial, Review

Open AccessArticle Analytical Solution of Electro-Osmotic Peristalsis of Fractional Jeffreys Fluid in a Micro-Channel
Micromachines 2017, 8(12), 341; doi:10.3390/mi8120341
Received: 18 September 2017 / Revised: 8 November 2017 / Accepted: 19 November 2017 / Published: 23 November 2017
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Abstract
The electro-osmotic peristaltic flow of a viscoelastic fluid through a cylindrical micro-channel is studied in this paper. The fractional Jeffreys constitutive model, including the relaxation time and retardation time, is utilized to describe the viscoelasticity of the fluid. Under the assumptions of long
[...] Read more.
The electro-osmotic peristaltic flow of a viscoelastic fluid through a cylindrical micro-channel is studied in this paper. The fractional Jeffreys constitutive model, including the relaxation time and retardation time, is utilized to describe the viscoelasticity of the fluid. Under the assumptions of long wavelength, low Reynolds number, and Debye-Hückel linearization, the analytical solutions of pressure gradient, stream function and axial velocity are explored in terms of Mittag-Leffler function by Laplace transform method. The corresponding solutions of fractional Maxwell fluid and generalized second grade fluid are also obtained as special cases. The numerical analysis of the results are depicted graphically, and the effects of electro-osmotic parameter, external electric field, fractional parameters and viscoelastic parameters on the peristaltic flow are discussed. Full article
(This article belongs to the Special Issue Micro/Nano-Chip Electrokinetics, Volume II)
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Open AccessArticle Micromachined Resonant Frequency Tuning Unit for Torsional Resonator
Micromachines 2017, 8(12), 342; doi:10.3390/mi8120342
Received: 22 October 2017 / Revised: 5 November 2017 / Accepted: 22 November 2017 / Published: 25 November 2017
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Abstract
Achieving the desired resonant frequency of resonators has been an important issue, since it determines their performance. This paper presents the design and analysis of two concepts for the resonant frequency tuning of resonators. The proposed methods are based on the stiffness alteration
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Achieving the desired resonant frequency of resonators has been an important issue, since it determines their performance. This paper presents the design and analysis of two concepts for the resonant frequency tuning of resonators. The proposed methods are based on the stiffness alteration of the springs by geometrical modification (shaft-widening) or by mechanical restriction (shaft-holding) using micromachined frequency tuning units. Our designs have advantages in (1) reversible and repetitive tuning; (2) decoupled control over the amplitude of the resonator and the tuning ratio; and (3) a wide range of applications including torsional resonators. The ability to tune the frequency by both methods is predicted by finite element analysis (FEA) and experimentally verified on a torsional resonator driven by an electrostatic actuator. The tuning units and resonators are fabricated on a double silicon-on-insulator (DSOI) wafer to electrically insulate the resonator from the tuning units. The shaft-widening type and shaft-holding type exhibit a maximum tuning ratio of 5.29% and 10.7%, respectively. Full article
(This article belongs to the Special Issue Micro-Resonators: The Quest for Superior Performance)
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Open AccessArticle The Parametric Study of Electroosmotically Driven Flow of Power-Law Fluid in a Cylindrical Microcapillary at High Zeta Potential
Micromachines 2017, 8(12), 344; doi:10.3390/mi8120344
Received: 1 November 2017 / Revised: 21 November 2017 / Accepted: 24 November 2017 / Published: 28 November 2017
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Abstract
Due to the increasingly wide application of electroosmotic flow in micromachines, this paper investigates the electroosmotic flow of the power-law fluid under high zeta potential in a cylindrical microcapillary for different dimensionless parameters. The electric potential distribution inside a cylindrical microcapillary is presented
[...] Read more.
Due to the increasingly wide application of electroosmotic flow in micromachines, this paper investigates the electroosmotic flow of the power-law fluid under high zeta potential in a cylindrical microcapillary for different dimensionless parameters. The electric potential distribution inside a cylindrical microcapillary is presented by the complete Poisson-Boltzmann equation applicable to an arbitrary zeta potential. By solving the Cauchy momentum equation of power-law fluids, the velocity profile, the volumetric flow rate, the average velocity, the shear stress distribution and dynamic viscosity of electroosmotic flow of power-law fluids in a cylindrical microcapillary are studied for different low/high zeta potential, flow behavior index, dimensionless electrokinetic width. The velocity profile gradually changes from parabolic to plug-like shape as the flow behavior index decreases or as the dimensionless electrokinetic width increases. For shear thinning fluids, the viscosity is greater in the center of the microchannel than that near the channel wall, the reverse is true for the shear thickening fluids. Greater volumetric rate and average velocity can be achieved by enhancing the dimensionless electrokinetic width, flow behavior index and zeta potential. It is noted that zeta potential and flow behavior index are important parameters to adjust electroosmotic flow behavior in a cylindrical microcapillary. Full article
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Open AccessArticle Modeling and Simulation of a Machining Process Chain for the Precision Manufacture of Polar Microstructure
Micromachines 2017, 8(12), 345; doi:10.3390/mi8120345
Received: 13 November 2017 / Revised: 21 November 2017 / Accepted: 21 November 2017 / Published: 27 November 2017
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Abstract
This paper presents a functional microstructured surface, named Polar Microstructure. Polar microstructure is a three dimensional (3D) structured surface possessing a pattern of distribution of latitude and longitude micro-topographies with geometrical characteristics, which is similar to that in the Earth’s north or south
[...] Read more.
This paper presents a functional microstructured surface, named Polar Microstructure. Polar microstructure is a three dimensional (3D) structured surface possessing a pattern of distribution of latitude and longitude micro-topographies with geometrical characteristics, which is similar to that in the Earth’s north or south pole. The spacing of its small surface features can achieve form accuracy at the micrometer level. Polar microstructure has great potential for applications in precision measurement of angle displacement based on the characteristics of its surface features. This paper presents the development of a machining process chain system that integrates single point diamond turning (SPDT) and diamond broaching together to fabricate polar microstructure. A framework of a machining process chain system is presented which is composed of input module, design module, simulation module, output module, and metrology module. After that, modeling of the machining process chain composed of SPDT and diamond broaching is built up. The model takes into consideration the initial surface topography of the workpiece. Simulations have been conducted to obtain the optimal machining parameters in each machining process. A series of experiments was conducted for the ultra-precision machining of various types of polar microstructures. The machining results show that the machining process chain system is technically feasible and effective in the precision manufacturing of polar microstructure. The experimental results agree well with the simulated results. Full article
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Open AccessArticle Investigation of CMOS Multiplexer Jet Matrix Addressing and Micro-Droplets within a Printhead Chip
Micromachines 2017, 8(12), 346; doi:10.3390/mi8120346
Received: 14 August 2017 / Revised: 19 November 2017 / Accepted: 22 November 2017 / Published: 29 November 2017
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Abstract
In this study, we demonstrate and investigate a new droplet injection design. We create a thermal inkjet (TIJ) printhead using an application-specific integrated circuit system and bulk micromachining technology (microelectromechanical systems). We design inkjet printhead chips with a new structure and investigate their
[...] Read more.
In this study, we demonstrate and investigate a new droplet injection design. We create a thermal inkjet (TIJ) printhead using an application-specific integrated circuit system and bulk micromachining technology (microelectromechanical systems). We design inkjet printhead chips with a new structure and investigate their properties. For the new structure, the integration of complementary metal-oxide-semiconductors (MOSs) and enhancement-mode devices, as well as power switches and a TIJ heater transducer, enables logic functions to be executed on-chip. This capability is used in the proposed design to address individual jets with even fewer input lines than in matrix addressing. A high number of jets (at least 896) can be addressed with only 11 input lines. E1 (Enable 1) and E2 (Enable 2) are set up dependently, and they have the ability to reverse their signals in relation to each other (i.e., if E1 is disabled, E2 is enabled and vice versa). The E1 and E2 signals each service 448 jets. If one of the MOSs is turned on, then it corresponds to a power line with a similar function. If an addressing gate terminal of the other MOS has a discharge action, then we can control a different heater to generate heating bubbles in the jet inks. The operating frequency for addressing these measurements is 18 kHz in normal mode, 26 kHz in draft mode, and 16 kHz in best mode. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)
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Open AccessArticle Effects of the Manufacturing Process on the Reliability of the Multilayer Structure in MetalMUMPs Actuators: Residual Stresses and Variation of Design Parameters
Micromachines 2017, 8(12), 348; doi:10.3390/mi8120348
Received: 3 November 2017 / Revised: 27 November 2017 / Accepted: 28 November 2017 / Published: 29 November 2017
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Abstract
Potential problems induced by the multilayered manufacturing process pose a serious threat to the long-term reliability of MEMSCAP® actuators under in-service thermal cycling. Damage would initiate and propagate in different material layers because of a large mismatch of their thermal expansions. In
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Potential problems induced by the multilayered manufacturing process pose a serious threat to the long-term reliability of MEMSCAP® actuators under in-service thermal cycling. Damage would initiate and propagate in different material layers because of a large mismatch of their thermal expansions. In this research, residual stresses and variations of design parameters induced by metal multi-user micro electromechanical system processes (MetalMUMPs) were examined to evaluate their effects on the thermal fatigue lifetime of the multilayer structure and, thus, to improve MEMSCAP® design. Since testing in such micro internal structure is difficult to conduct and traditional testing schemes are destructive, a numerical subdomain method based on a finite element technique was employed. Thermomechanical deformation from metal to insulator layers under in-service temperature cycling (obtained from the multiphysics model of the entire actuator, which was validated by experimental and specified analytical solutions) was accurately estimated to define failures with a significant efficiency and feasibility. Simulation results showed that critical failure modes included interface delamination, plastic deformation, micro cracking, and thermal fatigue, similarly to what was concluded in the MEMSCAP® technical report. Full article
(This article belongs to the Special Issue Microsystems for Power, Energy, and Actuation)
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Open AccessArticle Swimming Characteristics of Bioinspired Helical Microswimmers Based on Soft Lotus-Root Fibers
Micromachines 2017, 8(12), 349; doi:10.3390/mi8120349
Received: 27 October 2017 / Revised: 24 November 2017 / Accepted: 28 November 2017 / Published: 30 November 2017
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Abstract
Various kinds of helical swimmers inspired by E. coli bacteria have been developed continually in many types of researches, but most of them are proposed by the rigid bodies. For the targeted drug delivery, the rigid body may hurt soft tissues of the
[...] Read more.
Various kinds of helical swimmers inspired by E. coli bacteria have been developed continually in many types of researches, but most of them are proposed by the rigid bodies. For the targeted drug delivery, the rigid body may hurt soft tissues of the working region with organs. Due to this problem, the biomedical applications of helical swimmers may be restricted. However, the helical microswimmers with the soft and deformable body are appropriate and highly adaptive in a confined environment. Thus, this paper presents a lotus-root-based helical microswimmer, which is fabricated by the fibers of lotus-root coated with magnetic nanoparticles to active under the magnetic fields. The helical microstructures are derived from the intrinsic biological structures of the fibers of the lotus-root. This paper aims to study the swimming characteristic of lotus-root-based microswimmers with deformable helical bodies. In the initial step under the uniform magnetic actuation, the helical microswimmers are bent lightly due to the heterogeneous distribution of the internal stress, and then they undergo a swimming motion which is a spindle-like rotation locomotion. Our experiments report that the microswimmers with soft bodies can locomote faster than those with rigid bodies. Moreover, we also find that the curvature of the shape decreases as a function of actuating field frequency which is related to the deformability of lotus-root fibers. Full article
(This article belongs to the Special Issue Locomotion at Small Scales: From Biology to Artificial Systems)
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Open AccessArticle Pick-and-Place Operation of Single Cell Using Optical and Electrical Measurements for Robust Manipulation
Micromachines 2017, 8(12), 350; doi:10.3390/mi8120350
Received: 22 October 2017 / Revised: 17 November 2017 / Accepted: 28 November 2017 / Published: 30 November 2017
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Abstract
A robust pick and placement operation of a single cell is necessary for efficient sample collection. Detection and manipulation of single cells requires minimum invasiveness. We report a less-invasive method for picking up and placing single cells using optical and electrical observations for
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A robust pick and placement operation of a single cell is necessary for efficient sample collection. Detection and manipulation of single cells requires minimum invasiveness. We report a less-invasive method for picking up and placing single cells using optical and electrical observations for robust cell manipulation. We measured the ionic current through a glass pipette during a cell capture and release operation to detect its capture. Trapping a cell on the pipette tip by suction decreased the current and allowed the detection of cell capture within 1 s. A time-series ionic current was sensitive to the location of a cell and effective at detecting a single cell. A time-series ionic current had a higher signal-to-noise ratio than time-series microscope images. Cell membrane integrity was analyzed at the different capturing and voltage conditions. Serum protein coating shows improvement of a cell release from a pipette tip. Measurement of trajectory and distance of a cell reveals that the movement depends on an ejection flow and the flow in a dish. We achieved a pick-up and placement operation for single cells that was compatible with an open-top microwell while performing observations using optical microscopy and measurements using an electrical current. Full article
(This article belongs to the Special Issue Micro/Nano Robotics, Volume II)
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Open AccessArticle Low-Cost High-Speed In-Plane Stroboscopic Micro-Motion Analyzer
Micromachines 2017, 8(12), 351; doi:10.3390/mi8120351
Received: 13 November 2017 / Revised: 27 November 2017 / Accepted: 30 November 2017 / Published: 30 November 2017
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Abstract
Instrumentation for high-speed imaging and laser vibrometry is essential for the understanding and analysis of microstructure dynamics, but commercial instruments are largely unaffordable for most microelectromechanical systems (MEMS) laboratories. We present the implementation of a very low cost in-plane micro motion stroboscopic analyzer
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Instrumentation for high-speed imaging and laser vibrometry is essential for the understanding and analysis of microstructure dynamics, but commercial instruments are largely unaffordable for most microelectromechanical systems (MEMS) laboratories. We present the implementation of a very low cost in-plane micro motion stroboscopic analyzer that can be directly attached to a conventional probe station. The low-cost analyzer has been used to characterize the harmonic motion of 52.1 kHz resonating comb drive microactuators using ~50 ns pulsed light-emitting diode (LED) stroboscope exposure times, producing sharp and high resolution (~0.5 μm) device images at resonance, which rivals those of several orders of magnitude more expensive systems. This paper details the development of the high-speed stroboscopic imaging system and presents experimental results of motion analysis of example microstructures and a discussion of its operating limits. The system is shown to produce stable stroboscopic LED illumination to freeze device images up to 11 MHz. Full article
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Open AccessArticle Wide Linearity Range and Highly Sensitive MEMS-Based Micro-Fluxgate Sensor with Double-Layer Magnetic Core Made of Fe–Co–B Amorphous Alloy
Micromachines 2017, 8(12), 352; doi:10.3390/mi8120352
Received: 21 October 2017 / Revised: 19 November 2017 / Accepted: 29 November 2017 / Published: 30 November 2017
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Abstract
This paper reports a novel micro-fluxgate sensor based on a double-layer magnetic core of a Fe–Co–B-based amorphous ribbon. The melt-spinning technique was carried out to obtain a Fe–Co–B-based amorphous ribbon composite of Fe58.1Co24.9B16Si1, and the
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This paper reports a novel micro-fluxgate sensor based on a double-layer magnetic core of a Fe–Co–B-based amorphous ribbon. The melt-spinning technique was carried out to obtain a Fe–Co–B-based amorphous ribbon composite of Fe58.1Co24.9B16Si1, and the obtained amorphous ribbon was then annealed at 595 K for 1 h to benefit soft magnetic properties. The prepared ribbon showed excellent soft magnetic behavior with a high saturated magnetic intensity (Bs) of 1.74 T and a coercivity (Hc) of less than 0.2 Oe. Afterward, a micro-fluxgate sensor based on the prepared amorphous ribbon was fabricated via microelectromechanical systems (MEMS) technology combined with chemical wet etching. The resulting sensor exhibited a sensitivity of 1985 V/T, a wide linearity range of ±1.05 mT, and a perming error below 0.4 μT under optimal operating conditions with an excitation current amplitude of 70 mA at 500 kHz frequency. The minimum magnetic field noise was about 36 pT/Hz1/2 at 1 Hz under the same excitation conditions; a superior resolution of 5 nT was also achieved in the fabricated sensor. To the best of our knowledge, a compact micro-fluxgate sensor with such a high-resolution capability has not been reported elsewhere. The microsensor presented here with such improved characteristics may considerably enhance the development of micro-fluxgate sensors. Full article
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Open AccessArticle Electrical Tweezer for Droplet Transportation, Extraction, Merging and DNA Analysis
Micromachines 2017, 8(12), 353; doi:10.3390/mi8120353
Received: 1 November 2017 / Revised: 21 November 2017 / Accepted: 28 November 2017 / Published: 30 November 2017
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Abstract
Droplets of aqueous solutions distributed in an immiscible oil phase are increasingly used and investigated as a means to handle and assay small volumes of samples. The primary attraction of this method is that surface interactions are kept to a minimum, and changes
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Droplets of aqueous solutions distributed in an immiscible oil phase are increasingly used and investigated as a means to handle and assay small volumes of samples. The primary attraction of this method is that surface interactions are kept to a minimum, and changes in sample concentration, especially due to adsorption to the walls, are avoided. Microfluidic methods to generate, transport, merge, split and perform reactions in droplets were developed recently. These methods depend on the continuous flow of the two phases involved inside closed microfluidic channels. Alternatively, an electrowetting phenomenon was also exploited to control the movement of droplets between two solid substrates. However, there are some situations where small volume sample transport and assaying are required in open systems. Here, we demonstrate a simple electromechanical probe (tweezers) that is capable of manipulating a small aqueous droplet in a bi-layer oil phase. The tweezer consists of two needles positioned close to each other and uses polarization of the aqueous droplet in an applied electrical field to confine the droplet between the needles with minimal solid contact. Mechanical motion of the tweezer can be used to transport the droplet to various positions. Operations such as aliquoting, merging and transport are demonstrated. Finally, this method was used to perform a DNA amplification assay where droplets of the sample and the amplification mixture are aliquoted separately, mixed and amplified using an in-situ heater. This electromechanical tweezer is of interest in low-throughput, small-volume biological and chemical assays where the investigator requires direct and open access to the samples. Full article
(This article belongs to the Special Issue Biomedical Microdevices: Design, Fabrication and Application)
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Open AccessArticle Rotating Circular Micro-Platform with Integrated Waveguides and Latching Arm for Reconfigurable Integrated Optics
Micromachines 2017, 8(12), 354; doi:10.3390/mi8120354
Received: 31 October 2017 / Revised: 28 November 2017 / Accepted: 30 November 2017 / Published: 1 December 2017
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Abstract
This work presents a laterally rotating micromachined platform integrated under optical waveguides to control the in-plane propagation direction of light within a die to select one of multiple outputs. The platform is designed to exhibit low constant optical losses throughout the motion range
[...] Read more.
This work presents a laterally rotating micromachined platform integrated under optical waveguides to control the in-plane propagation direction of light within a die to select one of multiple outputs. The platform is designed to exhibit low constant optical losses throughout the motion range and is actuated electrostatically using an optimized circular comb drive. An angular motion of ±9.5° using 180 V is demonstrated. To minimize the optical losses between the moving and fixed parts, a gap-closing mechanism is implemented to reduce the initial air gap to submicron values. A latch structure is implemented to hold the platform in place with a resolution of 0.25° over the entire motion range. The platform was integrated with silicon nitride waveguides to create a crossbar switch and preliminary optical measurements are reported. In the bar state, the loss was measured to be 14.8 dB with the gap closed whereas in the cross state it was 12.2 dB. To the authors’ knowledge, this is the first optical switch based on a rotating microelectromechanical device with integrated silicon nitride waveguides reported to date. Full article
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Open AccessArticle Analysis of Membrane Behavior of a Normally Closed Microvalve Using a Fluid-Structure Interaction Model
Micromachines 2017, 8(12), 355; doi:10.3390/mi8120355
Received: 20 October 2017 / Revised: 28 November 2017 / Accepted: 29 November 2017 / Published: 6 December 2017
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Abstract
In this paper, membrane deflection against fluid flow and opening membrane (threshold) pressure were studied using fluid-structure interaction (FSI) analysis, and compared with experimental data obtained by Jaemin et al. In the current analysis, two different models (I-shaped and V-shaped) were used to
[...] Read more.
In this paper, membrane deflection against fluid flow and opening membrane (threshold) pressure were studied using fluid-structure interaction (FSI) analysis, and compared with experimental data obtained by Jaemin et al. In the current analysis, two different models (I-shaped and V-shaped) were used to perform the FSI simulation. In microvalve modeling, in order to reduce external actuator usage, interconnections are made between two similar microvalves. This typical interconnection creates a pressure distribution in a local environment. Furthermore, to differentiate the volume factor in a microvalve, a length/width (L/W) ratio term was used. Compared with higher- and lower-L/W-ratio models, the higher-L/W model eventually initiates more deflection in a low-pressure regime than the lower-L/W-ratio model. FSI simulations were performed for 4 μL/min, 6 μL/min, 8 μL/min, 10 μL/min, and 12 μL/min flow rates against membrane behavior, and performance evaluations of the microvalves were conducted. It was observed during an FSI simulation that the gate pressure applied to the lower surface deflects the membrane upward, thereby making contact with the wall. Two important parameters (material properties of the structural membrane and the inlet region height) were selected for analysis to evaluate changes in microvalve performance. These results are presented in the current study. Full article
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Open AccessArticle Arrayed Force Sensors Made of Paper, Elastomer, and Hydrogel Particles
Micromachines 2017, 8(12), 356; doi:10.3390/mi8120356
Received: 6 September 2017 / Revised: 2 December 2017 / Accepted: 4 December 2017 / Published: 8 December 2017
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Abstract
This article presents a sensor for detecting the distribution of forces on a surface. The device with nine buttons consisted of an elastomer-based layer as a touch interface resting on a substrate of patterned metallized paper. The elastomer-based layer included a three-by-three array
[...] Read more.
This article presents a sensor for detecting the distribution of forces on a surface. The device with nine buttons consisted of an elastomer-based layer as a touch interface resting on a substrate of patterned metallized paper. The elastomer-based layer included a three-by-three array of deformable, hemispherical elements/reliefs, facing down toward an array of interdigitated capacitive sensing units on patterned metallized paper. Each hemispherical element is 20 mm in diameter and 8 mm in height. When a user applied pressure to the elastomer-based layer, the contact area between the hemispherical elements and the interdigitated capacitive sensing units increased with the deformation of the hemispherical elements. To enhance the sensitivity of the sensors, embedded particles of hydrogel in the elastomer-based layer increased the measured electrical responses. The measured capacitance increased because the effective dielectric permittivity of the hydrogel was greater than that of air. Electromechanical characterization verified that the hydrogel-filled elastomer was more sensitive to force at a low range of loads (23.4 pF/N) than elastomer alone without embedded hydrogel (3.4 pF/N), as the hydrogel reduced the effective elastic modulus of the composite material by a factor of seven. A simple demonstration suggests that the force-sensing array has the potential to contribute to wearable and soft robotic devices. Full article
(This article belongs to the Special Issue Paper-Based Transducers and Electronics)
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Open AccessArticle The Multitasking System of Swarm Robot based on Null-Space-Behavioral Control Combined with Fuzzy Logic
Micromachines 2017, 8(12), 357; doi:10.3390/mi8120357
Received: 26 November 2017 / Revised: 6 December 2017 / Accepted: 7 December 2017 / Published: 9 December 2017
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Abstract
A swarm robot is a collection of large numbers of simple robots used to perform complex tasks that a single robot cannot perform or only perform ineffectively. The swarm robot works successfully only when the cooperation mechanism among individual robots is satisfied. The
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A swarm robot is a collection of large numbers of simple robots used to perform complex tasks that a single robot cannot perform or only perform ineffectively. The swarm robot works successfully only when the cooperation mechanism among individual robots is satisfied. The cooperation mechanism studied in this article ensures the formation and the distance between each pair of individual robots while moving to their destination while avoiding obstacles. The solved problems in this article include; controlling the suction/thrust force between each pair of individual robots in the swarm based on the fuzzy logic structure of the Singer-Input-Singer-Output under Mamdani law; demonstrating the stability of the system based on the Lyapunov theory; and applying control to the multitasking system of the swarm robot based on Null-Space-Behavioral control. Finally, the simulation results make certain that all the individual robots assemble after moving and avoid obstacles. Full article
(This article belongs to the Special Issue Locomotion at Small Scales: From Biology to Artificial Systems)
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Open AccessArticle Numerical Simulation of the Behavior of Toroidal and Spheroidal Multicellular Aggregates in Microfluidic Devices with Microwell and U-Shaped Barrier
Micromachines 2017, 8(12), 358; doi:10.3390/mi8120358
Received: 27 October 2017 / Revised: 2 December 2017 / Accepted: 5 December 2017 / Published: 11 December 2017
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Abstract
A microfluidic system provides an excellent platform for cellular studies. Most importantly, a three-dimensional (3D) cell culture model reconstructs more accurately the in vivo microenvironment of tissue. Accordingly, microfluidic 3D cell culture devices could be ideal candidates for in vitro cell culture platforms.
[...] Read more.
A microfluidic system provides an excellent platform for cellular studies. Most importantly, a three-dimensional (3D) cell culture model reconstructs more accurately the in vivo microenvironment of tissue. Accordingly, microfluidic 3D cell culture devices could be ideal candidates for in vitro cell culture platforms. In this paper, two types of 3D cellular aggregates, i.e., toroid and spheroid, are numerically studied. The studies are carried out for microfluidic systems containing U-shaped barrier as well as microwell structure. For the first time, we obtain oxygen and glucose concentration distributions inside a toroid aggregate as well as the shear stress on its surface and compare its performance with a spheroid aggregate of the same volume. In particular, we obtain the oxygen concentration distributions in three areas, namely, oxygen-permeable layer, multicellular aggregates and culture medium. Further, glucose concentration distributions in two regions of multicellular aggregates and culture medium are investigated. The results show that the levels of oxygen and glucose in the system containing U-shaped barriers are far more than those in the system containing microwells. Therefore, to achieve high levels of oxygen and nutrients, a system with U-shaped barriers is more suited than the conventional traps, but the choice between toroid and spheroid depends on their volume and orientation. The results indicate that higher oxygen and glucose concentrations can be achieved in spheroid with a small volume as well as in horizontal toroid with a large volume. The vertical toroid has the highest levels of oxygen and glucose concentration while the surface shear stress on its surface is also maximum. These findings can be used as guidelines for designing an optimum 3D microfluidic bioreactor based on the desired levels of oxygen, glucose and shear stress distributions. Full article
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Open AccessArticle Nano-Scale Positioning Design with Piezoelectric Materials
Micromachines 2017, 8(12), 360; doi:10.3390/mi8120360
Received: 31 October 2017 / Revised: 3 December 2017 / Accepted: 8 December 2017 / Published: 12 December 2017
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Abstract
Piezoelectric materials naturally possess high potential to deliver nano-scale positioning resolution; hence, they are adopted in a variety of engineering applications widely. Unfortunately, unacceptable positioning errors always appear because of the natural hysteresis effect of the piezoelectric materials. This natural property must be
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Piezoelectric materials naturally possess high potential to deliver nano-scale positioning resolution; hence, they are adopted in a variety of engineering applications widely. Unfortunately, unacceptable positioning errors always appear because of the natural hysteresis effect of the piezoelectric materials. This natural property must be mitigated in practical applications. For solving this drawback, a nonlinear positioning design is proposed in this article. This nonlinear positioning design of piezoelectric materials is realized by the following four steps: 1. The famous Bouc–Wen model is utilized to present the input and output behaviors of piezoelectric materials; 2. System parameters of the Bouc–Wen model that describe the characteristics of piezoelectric materials are simultaneously identified with the particle swam optimization method; 3. Stability verification for the identified Bouc–Wen model; 4. A nonlinear feedback linearization control design is derived for the nano-scale positioning design of the piezoelectric material, mathematically. One important contribution of this investigation is that the positioning error between the output displacement of the controlled piezoelectric materials and the desired trajectory in nano-scale level can be proven to converge to zero asymptotically, under the effect of the hysteresis. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2017)
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Open AccessArticle Laser-Assisted Mist Capillary Self-Alignment
Micromachines 2017, 8(12), 361; doi:10.3390/mi8120361 (registering DOI)
Received: 9 November 2017 / Revised: 6 December 2017 / Accepted: 13 December 2017 / Published: 15 December 2017
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Abstract
This paper reports a method combining laser die transfer and mist capillary self-alignment. The laser die transfer technique is employed to feed selected microchips from a thermal release tape onto a receiving substrate and mist capillary self-alignment is applied to align the microchips
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This paper reports a method combining laser die transfer and mist capillary self-alignment. The laser die transfer technique is employed to feed selected microchips from a thermal release tape onto a receiving substrate and mist capillary self-alignment is applied to align the microchips to the predefined receptor sites on the substrate in high-accuracy. The parameters for a low-power laser die transfer process have been investigated and experimentally optimized. The acting forces during the mist-induced capillary self-alignment process have been analyzed and the critical volume enabling capillary self-alignment has been estimated theoretically and experimentally. We have demonstrated that microchips can be transferred onto receptor sites in 300–400 ms using a low-power laser (100 mW), and chips can self-align to the corresponding receptor sites in parallel with alignment accuracy of 1.4 ± 0.8 μm. The proposed technique has great potential in high-throughput and high-accuracy assembly of micro devices. This paper is extended from an early conference paper (MARSS 2017). Full article
(This article belongs to the Special Issue Microscale Surface Tension and Its Applications)
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Open AccessReview Methods of Micropatterning and Manipulation of Cells for Biomedical Applications
Micromachines 2017, 8(12), 347; doi:10.3390/mi8120347
Received: 7 November 2017 / Revised: 27 November 2017 / Accepted: 28 November 2017 / Published: 29 November 2017
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Abstract
Micropatterning and manipulation of mammalian and bacterial cells are important in biomedical studies to perform in vitro assays and to evaluate biochemical processes accurately, establishing the basis for implementing biomedical microelectromechanical systems (bioMEMS), point-of-care (POC) devices, or organs-on-chips (OOC), which impact on neurological,
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Micropatterning and manipulation of mammalian and bacterial cells are important in biomedical studies to perform in vitro assays and to evaluate biochemical processes accurately, establishing the basis for implementing biomedical microelectromechanical systems (bioMEMS), point-of-care (POC) devices, or organs-on-chips (OOC), which impact on neurological, oncological, dermatologic, or tissue engineering issues as part of personalized medicine. Cell patterning represents a crucial step in fundamental and applied biological studies in vitro, hence today there are a myriad of materials and techniques that allow one to immobilize and manipulate cells, imitating the 3D in vivo milieu. This review focuses on current physical cell patterning, plus chemical and a combination of them both that utilizes different materials and cutting-edge micro-nanofabrication methodologies. Full article
(This article belongs to the Special Issue Medical Microdevices and Micromachines)
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Open AccessReview Extending the Limits of Wireless Power Transfer to Miniaturized Implantable Electronic Devices
Micromachines 2017, 8(12), 359; doi:10.3390/mi8120359
Received: 8 November 2017 / Revised: 2 December 2017 / Accepted: 6 December 2017 / Published: 12 December 2017
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Abstract
Implantable electronic devices have been evolving at an astonishing pace, due to the development of fabrication techniques and consequent miniaturization, and a higher efficiency of sensors, actuators, processors and packaging. Implantable devices, with sensing, communication, actuation, and wireless power are of high demand,
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Implantable electronic devices have been evolving at an astonishing pace, due to the development of fabrication techniques and consequent miniaturization, and a higher efficiency of sensors, actuators, processors and packaging. Implantable devices, with sensing, communication, actuation, and wireless power are of high demand, as they pave the way for new applications and therapies. Long-term and reliable powering of such devices has been a challenge since they were first introduced. This paper presents a review of representative state of the art implantable electronic devices, with wireless power capabilities, ranging from inductive coupling to ultrasounds. The different power transmission mechanisms are compared, to show that, without new methodologies, the power that can be safely transmitted to an implant is reaching its limit. Consequently, a new approach, capable of multiplying the available power inside a brain phantom for the same specific absorption rate (SAR) value, is proposed. In this paper, a setup was implemented to quadruple the power available in the implant, without breaking the SAR limits. A brain phantom was used for concept verification, with both simulation and measurement data. Full article
(This article belongs to the Special Issue Wireless Microdevices and Systems for Biomedical Applications)
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