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Micromachines, Volume 9, Issue 1 (January 2018)

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Cover Story (view full-size image) Bioelectronic medicine has been hailed as a new type of medicine to treat/manage chronic diseases. [...] Read more.
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Open AccessArticle Investigation on the Quality Factor Limit of the (111) Silicon Based Disk Resonator
Micromachines 2018, 9(1), 25; https://doi.org/10.3390/mi9010025
Received: 29 November 2017 / Revised: 4 January 2018 / Accepted: 8 January 2018 / Published: 22 January 2018
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Abstract
Quality factor is one of the most important parameters for a MEMS resonator. Most MEMS resonators are dominated by thermoelastic dissipation (TED). This paper demonstrates that the TED in a disk resonator that is made of (111) single-crystal silicon is surpassed by clamping
[...] Read more.
Quality factor is one of the most important parameters for a MEMS resonator. Most MEMS resonators are dominated by thermoelastic dissipation (TED). This paper demonstrates that the TED in a disk resonator that is made of (111) single-crystal silicon is surpassed by clamping loss. The stiffness-mass decoupling design method, combined with reducing the beam width, was used to engineer high QTED. Experiments show that Q of the (111) disk resonator have an upper boundary that is determined by the clamping loss caused by the unbalanced out-of-plane displacement. The origin of the out-of-plane displacement is explained by theory and simulation. Full article
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Open AccessArticle In Vivo Experimental Study of Noninvasive Insulin Microinjection through Hollow Si Microneedle Array
Micromachines 2018, 9(1), 40; https://doi.org/10.3390/mi9010040
Received: 25 October 2017 / Revised: 2 January 2018 / Accepted: 16 January 2018 / Published: 20 January 2018
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Abstract
An experimental study of in vivo insulin delivery through microinjection by using hollow silicon microneedle array is presented. A case study was carried out on a healthy human subject in vivo to determine the influence of delivery parameters on drug transfer efficiency. As
[...] Read more.
An experimental study of in vivo insulin delivery through microinjection by using hollow silicon microneedle array is presented. A case study was carried out on a healthy human subject in vivo to determine the influence of delivery parameters on drug transfer efficiency. As a microinjection device, a hollow microneedle array (13 × 13 mm2) having 100 microneedles (220 µm high, 130 µm-outer diameter and 50 µm-inner diameter) was designed and fabricated using classical microfabrication techniques. The efficiency of the delivery process was first characterized using methylene blue and a saline solution. Based on these results, the transfer efficiency was found to be predominantly limited by the inability of viable epidermis to absorb and allow higher drug transport toward the capillary-rich region. Two types of fast-acting insulin were used to provide evidence of efficient delivery by hollow MNA to a human subject. By performing blood analyses, infusion of more-concentrated insulin (200 IU/mL, international units (IU)) exhibited similar blood glucose level drop (5–7%) compared to insulin of standard concentration (100 IU/mL), however, significant increase of serum insulin (40–50%) with respect to the preinfusion values was determined. This was additionally confirmed by a distinctive increase of insulin to C-peptide ratio as compared to preinfusion ratio. Moreover, we noticed that this route of administration mimics a multiple dose regimen, able to get a “steady state” for insulin plasma concentration. Full article
(This article belongs to the Special Issue Silicon-based Micro/Nanofabrication for Biomedical Applications)
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Open AccessFeature PaperArticle A Platform for Mechano(-Electrical) Characterization of Free-Standing Micron-Sized Structures and Interconnects
Micromachines 2018, 9(1), 39; https://doi.org/10.3390/mi9010039
Received: 11 December 2017 / Revised: 10 January 2018 / Accepted: 12 January 2018 / Published: 18 January 2018
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Abstract
A device for studying the mechanical and electrical behavior of free-standing micro-fabricated metal structures, subjected to a very large deformation, is presented in this paper. The free-standing structures are intended to serve as interconnects in high-density, highly stretchable electronic circuits. For an easy,
[...] Read more.
A device for studying the mechanical and electrical behavior of free-standing micro-fabricated metal structures, subjected to a very large deformation, is presented in this paper. The free-standing structures are intended to serve as interconnects in high-density, highly stretchable electronic circuits. For an easy, damage-free handling and mounting of these free-standing structures, the device is designed to be fabricated as a single chip/unit that is separated into two independently movable parts after it is fixed in the tensile test stage. Furthermore, the fabrication method allows for test structures of different geometries to be easily fabricated on the same substrate. The utility of the device has been demonstrated by stretching the free-standing interconnect structures in excess of 1000% while simultaneously measuring their electrical resistance. Important design considerations and encountered processing challenges and their solutions are discussed in this paper. Full article
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Open AccessEditorial Editorial for the Special Issue on Ultrafast Laser Fabrication for Lab-on-a-Chip
Micromachines 2018, 9(1), 38; https://doi.org/10.3390/mi9010038
Received: 15 January 2018 / Accepted: 16 January 2018 / Published: 18 January 2018
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Abstract
Ultrafast laser microfabrication is a very powerful method for producing integrated devices in transparent materials [1].[...] Full article
(This article belongs to the Special Issue Ultrafast Laser Fabrication for Lab-on-a-Chip)
Open AccessArticle Chemical Mechanical Planarization and Old Italian Violins
Micromachines 2018, 9(1), 37; https://doi.org/10.3390/mi9010037
Received: 21 December 2017 / Revised: 12 January 2018 / Accepted: 15 January 2018 / Published: 18 January 2018
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Abstract
Previous studies have shown that spectral analysis based on force data can elucidate fundamental physical phenomena during chemical mechanical planarization (CMP). While it has not been literally described elsewhere, such analysis was partly motivated by modern violinmakers and physicists studying Old Italian violins,
[...] Read more.
Previous studies have shown that spectral analysis based on force data can elucidate fundamental physical phenomena during chemical mechanical planarization (CMP). While it has not been literally described elsewhere, such analysis was partly motivated by modern violinmakers and physicists studying Old Italian violins, who were trying to discover spectral relations to sound quality. In this paper, we draw parallels between violins and CMP as far as functionality and spectral characteristics are concerned. Inspired by the de facto standard of violin testing via hammer strikes on the base edge of a violin’s bridge, we introduce for the first time, a mobility plot for the polisher by striking the wafer carrier head of a CMP polisher with a hammer. Results show three independent peaks that can indeed be attributed to the polisher’s natural resonance. Extending our study to an actual CMP process, similar to hammered and bowed violin tests, at lower frequencies the hammered and polished mobility peaks are somewhat aligned. At higher frequencies, peak alignment becomes less obvious and the peaks become more isolated and defined in the case of the polished wafer spectrum. Lastly, we introduce another parameter from violin testing known as directivity, Δ, which in our case, we define as the ratio of shear force variance to normal force variance acquired during CMP. Results shows that under identical polishing conditions, Δ increases with the polishing removal rate. Full article
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Open AccessFeature PaperArticle Hydrogel Fiber Cultivation Method for Forming Bacterial Cellulose Microspheres
Micromachines 2018, 9(1), 36; https://doi.org/10.3390/mi9010036
Received: 8 December 2017 / Revised: 28 December 2017 / Accepted: 15 January 2018 / Published: 17 January 2018
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Abstract
Forming microspheres or microbeads from nanofibrous materials has recently attracted research interest for their applications in various fields, because these structures greatly impact cellular behaviors and functions. However, conventional methods of preparing microspheres or microbeads have limitations, such as limited variety of material.
[...] Read more.
Forming microspheres or microbeads from nanofibrous materials has recently attracted research interest for their applications in various fields, because these structures greatly impact cellular behaviors and functions. However, conventional methods of preparing microspheres or microbeads have limitations, such as limited variety of material. Here, we propose a new fabrication process for forming a nanofibrous microsphere composed of bacterial cellulose (BC), which is synthesized through fermentation by specific bacteria. The process uses a hydrogel fiber containing spherical cavities. The bacteria encapsulated into the cavities produce BC, resulting in the formation of BC microspheres. Because of its simplicity, robustness, and cost-effectiveness, this process is promising for applications, such as in biochemical engineering and cell delivery systems. Full article
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Open AccessArticle Pair Interaction of Catalytical Sphere Dimers in Chemically Active Media
Micromachines 2018, 9(1), 35; https://doi.org/10.3390/mi9010035
Received: 30 December 2017 / Revised: 11 January 2018 / Accepted: 11 January 2018 / Published: 17 January 2018
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Abstract
We study the pair dynamics of two self-propelled sphere dimers in the chemically active medium in which a cubic autocatalytic chemical reaction takes place. Concentration gradient around the dimer, created by reactions occurring on the catalytic sphere surface and responsible for the self-propulsion,
[...] Read more.
We study the pair dynamics of two self-propelled sphere dimers in the chemically active medium in which a cubic autocatalytic chemical reaction takes place. Concentration gradient around the dimer, created by reactions occurring on the catalytic sphere surface and responsible for the self-propulsion, is greatly influenced by the chemical activities of the environment. Consequently, the pair dynamics of two dimers mediated by the concentration field are affected. In the particle-based mesoscopic simulation, we combine molecular dynamics (MD) for potential interactions and reactive multiparticle collision dynamics (RMPC) for solvent flow and bulk reactions. Our results indicate three different configurations between a pair of dimers after the collision, i.e., two possible scenarios of bound dimer pairs and one unbound dimer pair. A phase diagram is sketched as a function of the rate coefficients of the environment reactions. Since the pair interactions are the basic elements of larger scale systems, we believe the results may shed light on the understanding of the collective dynamics. Full article
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Open AccessArticle Static and Dynamic Mechanical Behaviors of Electrostatic MEMS Resonator with Surface Processing Error
Micromachines 2018, 9(1), 34; https://doi.org/10.3390/mi9010034
Received: 30 November 2017 / Revised: 31 December 2017 / Accepted: 12 January 2018 / Published: 17 January 2018
Cited by 1 | Viewed by 804 | PDF Full-text (12017 KB) | HTML Full-text | XML Full-text
Abstract
The micro-electro-mechanical system (MEMS) resonator developed based on surface processing technology usually changes the section shape either due to excessive etching or insufficient etching. In this paper, a section parameter is proposed to describe the microbeam changes in the upper and lower sections.
[...] Read more.
The micro-electro-mechanical system (MEMS) resonator developed based on surface processing technology usually changes the section shape either due to excessive etching or insufficient etching. In this paper, a section parameter is proposed to describe the microbeam changes in the upper and lower sections. The effect of section change on the mechanical properties is studied analytically and verified through numerical and finite element solutions. A doubly-clamped microbeam-based resonator, which is actuated by an electrode on one side, is investigated. The higher-order model is derived without neglecting the effects of neutral plane stretching and electrostatic nonlinearity. Further, the Galerkin method and Newton–Cotes method are used to reduce the complexity and order of the derived model. First of all, the influence of microbeam shape and gap variation on the static pull-in are studied. Then, the dynamic analysis of the system is investigated. The method of multiple scales (MMS) is applied to determine the response of the system for small amplitude vibrations. The relationship between the microbeam shape and the frequency response is discussed. Results show that the change of section and gap distance can make the vibration soften, harden, and so on. Furthermore, when the amplitude of vibration is large, the frequency response softening effect is weakened by the MMS. If the nonlinearity shows hardening-type behavior at the beginning, with the increase of the amplitude, the frequency response will shift from hardening to softening behavior. The large amplitude in-well motions are studied to investigate the transitions between hardening and softening behaviors. Finally, the finite element analysis using COMSOL software (COMSOL Inc., Stockholm, Sweden) is carried out to verify the theoretical results, and the two results are very close to each other in the stable region. Full article
(This article belongs to the Special Issue Micro-Resonators: The Quest for Superior Performance)
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Open AccessEditorial Acknowledgement to Reviewers of Micromachines in 2017
Micromachines 2018, 9(1), 33; https://doi.org/10.3390/mi9010033
Received: 17 January 2018 / Accepted: 17 January 2018 / Published: 17 January 2018
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Abstract
Peer review is an essential part in the publication process, ensuring that Micromachines maintains high quality standards for its published papers.[...] Full article
Open AccessReview Detecting Chemical Hazards in Foods Using Microfluidic Paper-Based Analytical Devices (μPADs): The Real-World Application
Micromachines 2018, 9(1), 32; https://doi.org/10.3390/mi9010032
Received: 2 January 2018 / Revised: 15 January 2018 / Accepted: 16 January 2018 / Published: 17 January 2018
Cited by 4 | Viewed by 1534 | PDF Full-text (864 KB) | HTML Full-text | XML Full-text
Abstract
Food safety remains one of the most important issues in most countries and the detection of food hazards plays a key role in the systematic approach to ensuring food safety. Rapid, easy-to-use and low-cost analytical tools are required to detect chemical hazards in
[...] Read more.
Food safety remains one of the most important issues in most countries and the detection of food hazards plays a key role in the systematic approach to ensuring food safety. Rapid, easy-to-use and low-cost analytical tools are required to detect chemical hazards in foods. As a promising candidate, microfluidic paper-based analytical devices (μPADs) have been rarely applied to real food samples for testing chemical hazards, although numerous papers have been published in this field in the last decade. This review discusses the current status and concerns of the μPAD applications in the detection of chemical hazards in foods from the perspective of food scientists, mainly for an audience with a background in mechanical and chemical engineering who may have interests in exploring the potential of μPAD to address real-world food safety issues. Full article
(This article belongs to the Special Issue Microfluidic Sensors)
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Open AccessArticle Design Considerations for a Sub-mW Wireless Medical Body-Area Network Receiver Front End
Micromachines 2018, 9(1), 31; https://doi.org/10.3390/mi9010031
Received: 31 October 2017 / Revised: 6 January 2018 / Accepted: 12 January 2018 / Published: 17 January 2018
Cited by 1 | Viewed by 824 | PDF Full-text (2380 KB) | HTML Full-text | XML Full-text
Abstract
Wireless medical body-area networks are used to connect sensor nodes that monitor vital parameters. The radio consumes a large portion of the sensor energy budget, and hence its power dissipation should be minimized. The low-noise amplifier (LNA) is an important component of the
[...] Read more.
Wireless medical body-area networks are used to connect sensor nodes that monitor vital parameters. The radio consumes a large portion of the sensor energy budget, and hence its power dissipation should be minimized. The low-noise amplifier (LNA) is an important component of the receiver, and must guarantee low-noise amplification and impedance matching. In this work, an ultra-low-voltage ultra-low-power LNA is proposed that, thanks to the proposed transformer-based gate boosting technique, has a reduced current consumption of only 160 μA and can operate with a supply as low as 0.18 V. The LNA was designed using 40 nm Complementary Metal-Oxide Semiconductor (CMOS) technology and features a voltage gain of 14 dB, 5.2 dB NF and −8.6 dBm IIP3. This performance is comparable to a prior work by the same authors, but with the minimum supply voltage reduced by a factor of 4x. Full article
(This article belongs to the Special Issue Wireless Microdevices and Systems for Biomedical Applications)
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Open AccessArticle 3D Multi-Microchannel Helical Mixer Fabricated by Femtosecond Laser inside Fused Silica
Micromachines 2018, 9(1), 29; https://doi.org/10.3390/mi9010029
Received: 22 November 2017 / Revised: 8 January 2018 / Accepted: 12 January 2018 / Published: 16 January 2018
Cited by 5 | Viewed by 945 | PDF Full-text (2063 KB) | HTML Full-text | XML Full-text
Abstract
Three-dimensional (3D) multi-microchannel mixers can meet the requirements of different combinations according to actual needs. Rapid and simple creation of 3D multi-microchannel mixers in a “lab-on-a-chip” platform is a significant challenge in micromachining. In order to realize the complex mixing functions of microfluidic
[...] Read more.
Three-dimensional (3D) multi-microchannel mixers can meet the requirements of different combinations according to actual needs. Rapid and simple creation of 3D multi-microchannel mixers in a “lab-on-a-chip” platform is a significant challenge in micromachining. In order to realize the complex mixing functions of microfluidic chips, we fabricated two kinds of complex structure micromixers for multiple substance mixes simultaneously, separately, and in proper order. The 3D multi-microchannel mixers are fabricated by femtosecond laser wet etch technology inside fused silica. The 3D multi-microchannel helical mixers have desirable uniformity and consistency, which will greatly expand their utility and scope of application. Full article
(This article belongs to the Special Issue Passive Micromixers) Printed Edition available
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Open AccessArticle The Development of a Triaxial Cutting Force Sensor Based on a MEMS Strain Gauge
Micromachines 2018, 9(1), 30; https://doi.org/10.3390/mi9010030
Received: 17 November 2017 / Revised: 10 January 2018 / Accepted: 11 January 2018 / Published: 15 January 2018
Cited by 1 | Viewed by 1194 | PDF Full-text (7241 KB) | HTML Full-text | XML Full-text
Abstract
Cutting force measurement is a quintessential task for status monitoring during machining. In the past, a number of cutting force sensors have been developed, each featuring a different set of performance advantages. In a pursuit to improve the measuring sensitivity and reduce the
[...] Read more.
Cutting force measurement is a quintessential task for status monitoring during machining. In the past, a number of cutting force sensors have been developed, each featuring a different set of performance advantages. In a pursuit to improve the measuring sensitivity and reduce the cross-interference error, in this paper we propose a triaxial cutting force sensor based on a commercial micro-electro-mechanical system (MEMS) strain gauge. An elastic-sensitive element comprised of two mutual-perpendicular octagonal rings is designed for triaxial cutting force measurement, and a decoupling matrix is derived from static calibration to reduce cross-interference. It can be concluded from static calibration that the sensor’s sensitivity is 0.32 mV/N, 0.32 mV/N, and 0.05 mV/N in triaxial directions, and the proposed decoupling matrix is able to reduce cross-interference error to 0.14%, 0.25%, and 4.42%. Dynamic cutting force measurement shows that the cutting force sensor can reflect the variation of cutting status very well, it is qualified to measure triaxial cutting forces in practical applications. Full article
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Open AccessArticle Fabrication of a Lab-on-Chip Device Using Material Extrusion (3D Printing) and Demonstration via Malaria-Ab ELISA
Micromachines 2018, 9(1), 27; https://doi.org/10.3390/mi9010027
Received: 13 December 2017 / Revised: 7 January 2018 / Accepted: 11 January 2018 / Published: 14 January 2018
Cited by 3 | Viewed by 1620 | PDF Full-text (3862 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Additive manufacturing, such as fused deposition modeling (FDM), has been increasingly employed to produce microfluidic platforms due to ease of use, wide distribution of affordable 3D printers and relatively inexpensive materials for printing. In this work, we discuss fabrication and testing of an
[...] Read more.
Additive manufacturing, such as fused deposition modeling (FDM), has been increasingly employed to produce microfluidic platforms due to ease of use, wide distribution of affordable 3D printers and relatively inexpensive materials for printing. In this work, we discuss fabrication and testing of an FDM-printed fully automated colorimetric enzyme-linked immunosorbent assay (ELISA) designed to detect malaria. The detection platform consists of a disposable 3D-printed fluidic cartridge (with elastomeric silicone domes on top of reagent-storage reservoirs) and a nondisposable frame with servomotors and electronic controls such as an Arduino board and a rechargeable battery. The system is controlled by a novel interface where a music file (so-called “song”) is sent to the Arduino board, where the onboard program converts the set of frequencies into action of individual servomotors to rotate their arms a certain amount, thus depressing specific elastomeric domes atop reagent reservoirs and displacing the specific reagents into the detection wells, where bioassay steps are executed. Another of the distinguished characteristics of the demonstrated system is its ability to aspirate the fluid from the detection wells into the waste reservoir. Therefore, the demonstrated automated platform has the ability to execute even the most complex multi-step assays where dilution and multiple washes are required. Optimization of 3D-printer settings and ways to control leakages typical of FDM-printed fluidic systems are also discussed. Full article
(This article belongs to the Special Issue Additive Manufacturing for Medical Applications)
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Open AccessArticle Design and Near-Infrared Actuation of a Gold Nanorod–Polymer Microelectromechanical Device for On-Demand Drug Delivery
Micromachines 2018, 9(1), 28; https://doi.org/10.3390/mi9010028
Received: 18 December 2017 / Revised: 7 January 2018 / Accepted: 11 January 2018 / Published: 13 January 2018
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Abstract
Polymeric drug delivery systems usually deliver drugs by diffusion with an initial burst of release followed by a slower prolonged release phase. An optimal system would release exact doses of drugs using an on-demand external actuation system. The purpose of this study was
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Polymeric drug delivery systems usually deliver drugs by diffusion with an initial burst of release followed by a slower prolonged release phase. An optimal system would release exact doses of drugs using an on-demand external actuation system. The purpose of this study was to design and characterize a novel drug-delivery device that utilizes near infrared (NIR 800 nm) laser-actuated drug release. The device was constructed from biocompatible polymers comprising a reservoir of drug covered by an elastic perforated diaphragm composed of a bilayer of two polymers with different thermal expansion coefficients (ethylenevinylacetate (EVA) and polydimethylsiloxane (PDMS) containing gold nanoparticles). Upon illumination with a NIR laser, the gold nanoparticles rapidly heated the bilayer resulting in bending and a drug-pumping action through the perforated bilayer, following sequential laser-actuation cycles. Devices filled with the anti-proliferative drug docetaxel were seen to release only small amounts of drug by diffusion but to release large and reproducible amounts of drug over 20 s laser-actuation periods. Because NIR 800 nm is tissue-penetrating without heating tissue, suitable geometry drug-delivery devices might be implanted in the body to be actuated by an externally applied NIR laser to allow for on-demand exact drug dosing in vivo. Full article
(This article belongs to the Special Issue Biomedical Microdevices: Design, Fabrication and Application)
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Open AccessArticle Atomistic and Experimental Investigation of the Effect of Depth of Cut on Diamond Cutting of Cerium
Micromachines 2018, 9(1), 26; https://doi.org/10.3390/mi9010026
Received: 29 November 2017 / Revised: 3 January 2018 / Accepted: 12 January 2018 / Published: 13 January 2018
Cited by 2 | Viewed by 769 | PDF Full-text (8501 KB) | HTML Full-text | XML Full-text
Abstract
The ultra-precision diamond cutting process exhibits strong size effects due to the ultra-small depth of cut that is comparable with the cutting edge radius. In the present work, we elucidate the underlying machining mechanisms of single crystal cerium under diamond cutting by means
[...] Read more.
The ultra-precision diamond cutting process exhibits strong size effects due to the ultra-small depth of cut that is comparable with the cutting edge radius. In the present work, we elucidate the underlying machining mechanisms of single crystal cerium under diamond cutting by means of molecular dynamics simulations, with an emphasis on the evaluation of the effect of depth of cut on the cutting process by using different depths of cut. Diamond cutting experiments of cerium with different depths of cut are also conducted. In particular for the smallest depth of cut of 0.2 nm, shallow cutting simulations varying the sharpness of the cutting edge demonstrate that an atomically sharp cutting edge leads to a smaller machining force and better machined surface quality than a blunt one. Simulation results indicate that dislocation slip is the dominant deformation mechanism of cerium under diamond cutting with each depth of cut. Furthermore, the analysis of the defect zone based on atomic radial distribution functions demonstrates that there are trivial phase transformations from γ-Ce to δ-Ce occurred in both the machined surface and the formed chip. It is found that there is a transition of material removal mode from plowing to cutting with the increase of the depth of cut, which is also consistent with the diamond cutting experiments of cerium with different depths of cut. Full article
(This article belongs to the Special Issue Carbon Based Materials for MEMS/NEMS)
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Open AccessArticle On-Chip Facile Preparation of Monodisperse Resorcinol Formaldehyde (RF) Resin Microspheres
Micromachines 2018, 9(1), 24; https://doi.org/10.3390/mi9010024
Received: 6 December 2017 / Revised: 26 December 2017 / Accepted: 8 January 2018 / Published: 12 January 2018
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Abstract
Monodisperse resorcinol formaldehyde resin (RF) microspheres are an important polymeric material because of their rich surface functional group and uniform structural characteristics and have been increasingly applied as an electrode material, catalyst support, absorbent, and carbon microsphere precursor. The polymerization conditions, such as
[...] Read more.
Monodisperse resorcinol formaldehyde resin (RF) microspheres are an important polymeric material because of their rich surface functional group and uniform structural characteristics and have been increasingly applied as an electrode material, catalyst support, absorbent, and carbon microsphere precursor. The polymerization conditions, such as the gelation/solidification temperature and the residence time, can largely influence the physical properties and the formation of the 3D polymeric network of the RF microspheres as well as the carbon microspheres. However, few studies have reported on the complexity of the gelation and solidification processes of resol. In this work, we developed a new RF microsphere preparation device that contains three units: a droplet generation unit, a curing unit, and a collection unit. In this system, we controlled the gelation and solidification processes of the resol and observed its curing behavior, which helped us to uncover the curing mechanism of resol. Finally, we obtained the optimized polymerization parameters, obtaining uniform RF microspheres with a variation coefficient of 4.94%. The prepared porous RF microspheres presented a high absorption ability, reaching ~90% at 10 min. Thus, our method demonstrated the practicality of on-chip monodisperse microspheres synthesis. The product was useful in drug delivery and adsorbing large poisonous molecules. Full article
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Open AccessFeature PaperArticle Hydrophobic Janus Foam Motors: Self-Propulsion and On-The-Fly Oil Absorption
Micromachines 2018, 9(1), 23; https://doi.org/10.3390/mi9010023
Received: 21 December 2017 / Revised: 7 January 2018 / Accepted: 9 January 2018 / Published: 11 January 2018
Cited by 2 | Viewed by 1512 | PDF Full-text (5383 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, we for the first time have proposed and fabricated a self-propelled Janus foam motor for on-the-fly oil absorption on water by simply loading camphor/stearic acid (SA) mixture as fuels into one end of the SA-modified polyvinyl alcohol (PVA) foam. The
[...] Read more.
In this work, we for the first time have proposed and fabricated a self-propelled Janus foam motor for on-the-fly oil absorption on water by simply loading camphor/stearic acid (SA) mixture as fuels into one end of the SA-modified polyvinyl alcohol (PVA) foam. The as-fabricated Janus foam motors show an efficient Marangoni effect-based self-propulsion on water for a long lifetime due to the effective inhibition of the rapid release of camphor by the hydrophobic SA in the fuel mixture. Furthermore, they can automatically search, capture, and absorb oil droplets on the fly, and then be spontaneously self-assembled after oil absorption due to the self-propulsion of the motors as well as the attractive capillary interactions between the motors and oil droplets. This facilitates the subsequent collection of the motors from water after the treatment. Since the as-developed Janus foam motors can effectively integrate intriguing behaviors of the self-propulsion, efficient oil capture, and spontaneous self-assembly, they hold great promise for practical applications in water treatment. Full article
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Open AccessArticle Analysis of Correlation in MEMS Gyroscope Array and its Influence on Accuracy Improvement for the Combined Angular Rate Signal
Micromachines 2018, 9(1), 22; https://doi.org/10.3390/mi9010022
Received: 26 November 2017 / Revised: 23 December 2017 / Accepted: 5 January 2018 / Published: 9 January 2018
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Abstract
Obtaining a correlation factor is a prerequisite for fusing multiple outputs of a mircoelectromechanical system (MEMS) gyroscope array and evaluating accuracy improvement. In this paper, a mathematical statistics method is established to analyze and obtain the practical correlation factor of a MEMS gyroscope
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Obtaining a correlation factor is a prerequisite for fusing multiple outputs of a mircoelectromechanical system (MEMS) gyroscope array and evaluating accuracy improvement. In this paper, a mathematical statistics method is established to analyze and obtain the practical correlation factor of a MEMS gyroscope array, which solves the problem of determining the Kalman filter (KF) covariance matrix Q and fusing the multiple gyroscope signals. The working principle and mathematical model of the sensor array fusion is briefly described, and then an optimal estimate of input rate signal is achieved by using of a steady-state KF gain in an off-line estimation approach. Both theoretical analysis and simulation show that the negative correlation factor has a favorable influence on accuracy improvement. Additionally, a four-gyro array system composed of four discrete individual gyroscopes was developed to test the correlation factor and its influence on KF accuracy improvement. The result showed that correlation factors have both positive and negative values; in particular, there exist differences for correlation factor between the different units in the array. The test results also indicated that the Angular Random Walk (ARW) of 1.57°/h0.5 and bias drift of 224.2°/h for a single gyroscope were reduced to 0.33°/h0.5 and 47.8°/h with some negative correlation factors existing in the gyroscope array, making a noise reduction factor of about 4.7, which is higher than that of a uncorrelated four-gyro array. The overall accuracy of the combined angular rate signal can be further improved if the negative correlation factors in the gyroscope array become larger. Full article
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Open AccessArticle Dielectrophoresis Testing of Nonlinear Viscoelastic Behaviors of Human Red Blood Cells
Micromachines 2018, 9(1), 21; https://doi.org/10.3390/mi9010021
Received: 17 November 2017 / Revised: 11 December 2017 / Accepted: 8 January 2018 / Published: 9 January 2018
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Dielectrophoresis in microfluidics provides a useful tool to test biomechanics of living cells, regardless of surface charges on cell membranes. We have designed an experimental method to characterize the nonlinear viscoelastic behaviors of single cells using dielectrophoresis in a microfluidic channel. This method
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Dielectrophoresis in microfluidics provides a useful tool to test biomechanics of living cells, regardless of surface charges on cell membranes. We have designed an experimental method to characterize the nonlinear viscoelastic behaviors of single cells using dielectrophoresis in a microfluidic channel. This method uses radio frequency, low voltage excitations through interdigitated microelectrodes, allowing probing multiple cells simultaneously with controllable load levels. Dielectrophoretic force was calibrated using a triaxial ellipsoid model. Using a Kelvin–Voigt model, the nonlinear shear moduli of cell membranes were determined from the steady-state deformations of red blood cells in response to a series of electric field strengths. The nonlinear elastic moduli of cell membranes ranged from 6.05 µN/m to up to 20.85 µN/m, which were identified as a function of extension ratio, rather than the lumped-parameter models as reported in the literature. Value of the characteristic time of the extensional recovery of cell membranes initially deformed to varied extent was found to be about 0.14 s. Shear viscosity of cell membrane was estimated to be 0.8–2.9 (µN/m)·s. This method is particularly valuable for rapid, non-invasive probing of mechanical properties of living cells. Full article
(This article belongs to the collection Lab-on-a-Chip)
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Open AccessArticle A Changeable Lab-on-a-Chip Detector for Marine Nonindigenous Microorganisms in Ship’s Ballast Water
Micromachines 2018, 9(1), 20; https://doi.org/10.3390/mi9010020
Received: 31 October 2017 / Revised: 31 December 2017 / Accepted: 4 January 2018 / Published: 5 January 2018
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Abstract
The spread and invasion of many nonindigenous species in the ship’s ballast water around the world has been a hazard and threat to ecology, economy, and human health. The rapid and accurate detection of marine invasive species in ship’s ballast water is essential.
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The spread and invasion of many nonindigenous species in the ship’s ballast water around the world has been a hazard and threat to ecology, economy, and human health. The rapid and accurate detection of marine invasive species in ship’s ballast water is essential. This article is aimed at analysing ballast water quality by means of a changeable microfluidic chip detector thus comply with the D-2 standard of ship’s ballast water management and sediment convention. The detection system was designed through the integration of microfluidic chip technology, the impedance pulse sensing and LED light induced chlorophyll fluorescence (LED-LICF) detection. This system can measure the number, size, shape, and volume of targeted microorganisms, and it can also determine the chlorophyll fluorescence intensity, which is an important factor in analysing the activity of phytoplankton. The targeted samples were Chlorella volutis, Dunaliella salina, Platymonas subcordiformis, Chrysophytes, Escherichia coli, and Enterococci. The whole detection or operation can be accomplished through online detection in a few minutes with using micron volume of the sample solution. The valid data outputs are simultaneously displayed in terms of both impedance pulse amplitudes and fluorescent intensity signals. The detection system is designed for multi-sizes real time detection through changing the microchannel sizes on the microfluidic chip. Because it can successfully detect the label-free microorganisms, the system can be applicable to in-situ detections with some modifications to the system. Full article
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Open AccessArticle A Paper-Based Piezoelectric Accelerometer
Micromachines 2018, 9(1), 19; https://doi.org/10.3390/mi9010019
Received: 11 November 2017 / Revised: 26 December 2017 / Accepted: 30 December 2017 / Published: 2 January 2018
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Abstract
This paper presents the design and testing of a one-axis piezoelectric accelerometer made from cellulose paper and piezoelectric zinc oxide nanowires (ZnO NWs) hydrothermally grown on paper. The accelerometer adopts a cantilever-based configuration with two parallel cantilever beams attached with a paper proof
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This paper presents the design and testing of a one-axis piezoelectric accelerometer made from cellulose paper and piezoelectric zinc oxide nanowires (ZnO NWs) hydrothermally grown on paper. The accelerometer adopts a cantilever-based configuration with two parallel cantilever beams attached with a paper proof mass. A piece of U-shaped, ZnO-NW-coated paper is attached on top of the parallel beams, serving as the strain sensing element for acceleration measurement. The electric charges produced from the ZnO-NW-coated paper are converted into a voltage output using a custom-made charge amplifier circuit. The device fabrication only involves cutting of paper and hydrothermal growth of ZnO NWs, and does not require the access to expensive and sophisticated equipment. The performance of the devices with different weight growth percentages of the ZnO NWs was characterized. Full article
(This article belongs to the Special Issue Paper-Based Transducers and Electronics)
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Open AccessEditorial Application of Microfluidic Methodology for the Analysis of DNA
Micromachines 2018, 9(1), 18; https://doi.org/10.3390/mi9010018
Received: 15 December 2017 / Revised: 15 December 2017 / Accepted: 19 December 2017 / Published: 2 January 2018
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Abstract
Over the past 20 years, many of the developments and potential applications of microfluidic methodology have incorporated nucleic acid processes which have, in their own right, undergone a number of innovative changes [...]
Full article
(This article belongs to the Special Issue Application of Microfluidic Methodology for the Analysis of DNA)
Open AccessFeature PaperArticle A Wireless Implant for Gastrointestinal Motility Disorders
Micromachines 2018, 9(1), 17; https://doi.org/10.3390/mi9010017
Received: 6 December 2017 / Revised: 21 December 2017 / Accepted: 27 December 2017 / Published: 2 January 2018
Cited by 2 | Viewed by 1884 | PDF Full-text (3722 KB) | HTML Full-text | XML Full-text
Abstract
Implantable functional electrical stimulation (IFES) has demonstrated its effectiveness as an alternative treatment option for diseases incurable pharmaceutically (e.g., retinal prosthesis, cochlear implant, spinal cord implant for pain relief). However, the development of IFES for gastrointestinal (GI) tract modulation is still limited due
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Implantable functional electrical stimulation (IFES) has demonstrated its effectiveness as an alternative treatment option for diseases incurable pharmaceutically (e.g., retinal prosthesis, cochlear implant, spinal cord implant for pain relief). However, the development of IFES for gastrointestinal (GI) tract modulation is still limited due to the poorly understood GI neural network (gut–brain axis) and the fundamental difference among activating/monitoring smooth muscles, skeletal muscles and neurons. This inevitably imposes different design specifications for GI implants. This paper thus addresses the design requirements for an implant to treat GI dysmotility and presents a miniaturized wireless implant capable of modulating and recording GI motility. This implant incorporates a custom-made system-on-a-chip (SoC) and a heterogeneous system-in-a-package (SiP) for device miniaturization and integration. An in vivo experiment using both rodent and porcine models is further conducted to validate the effectiveness of the implant. Full article
(This article belongs to the Special Issue Wireless Microdevices and Systems for Biomedical Applications)
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Open AccessArticle Haptic-Based Manipulation Scheme of Magnetic Nanoparticles in a Multi-Branch Blood Vessel for Targeted Drug Delivery
Micromachines 2018, 9(1), 14; https://doi.org/10.3390/mi9010014
Received: 14 November 2017 / Revised: 25 December 2017 / Accepted: 28 December 2017 / Published: 1 January 2018
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Abstract
Magnetic drug targeting is a promising technique that can deliver drugs to the diseased region, while keeping the drug away from healthy parts of body. Introducing a human in the control loop of a targeted drug delivery system and using inherent bilateralism of
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Magnetic drug targeting is a promising technique that can deliver drugs to the diseased region, while keeping the drug away from healthy parts of body. Introducing a human in the control loop of a targeted drug delivery system and using inherent bilateralism of a haptic device at the same time can considerably improve the performance of targeted drug delivery systems. In this paper, we suggest a novel intelligent haptic guidance scheme for steering a number of magnetic nanoparticles (MNPs) using forbidden region virtual fixtures and a haptic rendering scheme with multi particles. Forbidden region virtual fixtures are a general class of guidance modes implemented in software, which help a human-machine collaborative system accomplish a specific task by constraining a movement into limited regions. To examine the effectiveness of our proposed scheme, we implemented a magnetic guided drug delivery system in a virtual environment using a physics-based model of targeted drug delivery including a multi-branch blood vessel and realistic blood dynamics. We performed user studies with different guidance modes: unguided, semi virtual fixture and full virtual fixture modes. We found out that the efficiency of targeting was significantly improved using the forbidden region virtual fixture and the proposed haptic rendering of MNPs. We can expect that using intelligent haptic feedback in real targeted drug delivery systems can improve the targeting efficiency of MNPs in multi-branch vessels. Full article
(This article belongs to the Special Issue Locomotion at Small Scales: From Biology to Artificial Systems)
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Open AccessCommunication Towards Miniaturization of Magnetic Gears: Torque Performance Assessment
Micromachines 2018, 9(1), 16; https://doi.org/10.3390/mi9010016
Received: 5 December 2017 / Revised: 20 December 2017 / Accepted: 30 December 2017 / Published: 31 December 2017
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Abstract
Magnetomechanical components can be a good solution in order to reduce, or even completely avoid, friction phenomena in micro-electro-mechanical systems (MEMS) since they can transmit forces through magnetic fields without contacts. In this communication, electromagnetic simulations of the expected specific torque of a
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Magnetomechanical components can be a good solution in order to reduce, or even completely avoid, friction phenomena in micro-electro-mechanical systems (MEMS) since they can transmit forces through magnetic fields without contacts. In this communication, electromagnetic simulations of the expected specific torque of a coaxial magnetic gear are given. The results show that micromagnetic gears (3 mm of diameter) could provide a specific torque up to 8.98 Nm/kg, several times larger than the specific torque that microgears (<9 mm of diameter) can provide. This implies that micromagnetic gears could provide speed conversion without contact in the teeth, avoiding corresponding friction, but also that it would even improve the specific torque transmission with respect to contact microgears. Full article
(This article belongs to the Special Issue Micro/Nano Robotics, Volume II)
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Open AccessArticle The Design, Fabrication, and Testing of an Electromagnetic Micropump with a Matrix-Patterned Magnetic Polymer Composite Actuator Membrane
Micromachines 2018, 9(1), 13; https://doi.org/10.3390/mi9010013
Received: 28 November 2017 / Revised: 19 December 2017 / Accepted: 21 December 2017 / Published: 31 December 2017
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Abstract
A valveless electromagnetic (EM) micropump with a matrix-patterned magnetic polymer composite actuator membrane structure was successfully designed and fabricated. The composite membrane structure is made of polydemethylsiloxane (PDMS) that is mixed with magnetic particles and patterned in matrix blocks. The matrix magnetic composite
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A valveless electromagnetic (EM) micropump with a matrix-patterned magnetic polymer composite actuator membrane structure was successfully designed and fabricated. The composite membrane structure is made of polydemethylsiloxane (PDMS) that is mixed with magnetic particles and patterned in matrix blocks. The matrix magnetic composite membrane was fabricated using a soft lithography process and expected to have a compact structure having sufficient magnetic force for membrane deformation and maintained membrane flexibility. The magnetic membrane was integrated with the microfluidic system and functionally tested. The experimental results show that a magnetic composite actuator membrane containing of 6% NdFeB is capable of producing a maximum membrane deflection up to 12.87 µm. The functionality test of the EM actuator for fluid pumping resulted in an extremely low sample injection flow rate of approximately 6.523 nL/min. It was also concluded that there is a correlation between the matrix structure of the actuator membrane and the fluid pumping flow rate. The injection flow rate of the EM micropump can be controlled by adjusting the input power supplied to the EM coil, and this is believed to improve the injection accuracy of the drug dosage and have potential in improving the proficiency of the existing drug delivery system. Full article
(This article belongs to the Special Issue Biomedical Microdevices: Design, Fabrication and Application)
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Open AccessArticle New MEMS Tweezers for the Viscoelastic Characterization of Soft Materials at the Microscale
Micromachines 2018, 9(1), 15; https://doi.org/10.3390/mi9010015
Received: 21 November 2017 / Revised: 17 December 2017 / Accepted: 27 December 2017 / Published: 30 December 2017
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Abstract
As many studies show, there is a relation between the tissue’s mechanical characteristics and some specific diseases. Knowing this relationship would help early diagnosis or microsurgery. In this paper, a new method for measuring the viscoelastic properties of soft materials at the microscale
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As many studies show, there is a relation between the tissue’s mechanical characteristics and some specific diseases. Knowing this relationship would help early diagnosis or microsurgery. In this paper, a new method for measuring the viscoelastic properties of soft materials at the microscale is proposed. This approach is based on the adoption of a microsystem whose mechanical structure can be reduced to a compliant four bar linkage where the connecting rod is substituted by the tissue sample. A procedure to identify both stiffness and damping coefficients of the tissue is then applied to the developed hardware. Particularly, stiffness is calculated solving the static equations of the mechanism in a desired configuration, while the damping coefficient is inferred from the dynamic equations, which are written under the hypothesis that the sample tissue is excited by a variable compression force characterized by a suitable wave form. The whole procedure is implemented by making use of a control system. Full article
(This article belongs to the Special Issue Locomotion at Small Scales: From Biology to Artificial Systems)
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Open AccessArticle A Graphene-Coated Mo Tip Array for Highly-Efficient Nanostructured Electron Field Emitters
Micromachines 2018, 9(1), 12; https://doi.org/10.3390/mi9010012
Received: 5 December 2017 / Revised: 18 December 2017 / Accepted: 19 December 2017 / Published: 29 December 2017
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Abstract
An efficient electron field emitter based on a monolayer graphene coated well aligned Mo tip array has been designed, fabricated, and evaluated. The advantages of this hybrid nanostructure film morphology are explored and discussed. Efficient and stable field emissions with low turn-on fields
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An efficient electron field emitter based on a monolayer graphene coated well aligned Mo tip array has been designed, fabricated, and evaluated. The advantages of this hybrid nanostructure film morphology are explored and discussed. Efficient and stable field emissions with low turn-on fields have been observed with the new devices. It is further found that the combination of graphene and Mo tip array leads to significant improvements in efficiency for the nanoscale heterostructure emitters. Full article
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Open AccessLetter Microwave Wire Interrogation Method Mapping Pressure under High Temperatures
Micromachines 2018, 9(1), 11; https://doi.org/10.3390/mi9010011
Received: 13 November 2017 / Revised: 17 December 2017 / Accepted: 28 December 2017 / Published: 29 December 2017
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Abstract
It is widely accepted that wireless reading for in-situ mapping of pressure under high-temperature environments is the most feasible method, because it is not subject to frequent heterogeneous jointing failures and electrical conduction deteriorating, or even disappearing, under heat load. However, in this
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It is widely accepted that wireless reading for in-situ mapping of pressure under high-temperature environments is the most feasible method, because it is not subject to frequent heterogeneous jointing failures and electrical conduction deteriorating, or even disappearing, under heat load. However, in this article, we successfully demonstrate an in-situ pressure sensor with wire interrogation for high-temperature applications. In this proof-of-concept study of the pressure sensor, we used a microwave resonator as a pressure-sensing component and a microwave transmission line as a pressure characteristic interrogation tunnel. In the sensor, the line and resonator are processed into a monolith, avoiding a heterogeneous jointing failure; further, microwave signal transmission does not depend on electrical conduction, and consequently, the sensor does not suffer from the heat load. We achieve pressure monitoring under 400 °C when employing the sensor simultaneously. Our sensor avoids restrictions that exist in wireless pressure interrogations, such as environmental noise and interference, signal leakage and security, low transfer efficiency, and so on. Full article
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