Micromachines

145 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Micromachines in 2015

by Micromachines Editorial Office

Micromachines 2016, 7(1), 16; https://doi.org/10.3390/mi7010016 - 21 Jan 2016

Viewed by 3211

The editors of Micromachines would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2015. [...] Full article

4201 KiB

Open AccessArticle

Love-Mode MEMS Devices for Sensing Applications in Liquids

by Cinzia Caliendo, Smail Sait and Fouad Boubenider

Micromachines 2016, 7(1), 15; https://doi.org/10.3390/mi7010015 - 21 Jan 2016

Cited by 10 | Viewed by 4681

Abstract

Love-wave-based MEMS devices are theoretically investigated in their potential role as a promising technological platform for the development of acoustic-wave-based sensors for liquid environments. Both single- and bi-layered structures have been investigated and the velocity dispersion curves were calculated for different layer thicknesses, [...] Read more.

Love-wave-based MEMS devices are theoretically investigated in their potential role as a promising technological platform for the development of acoustic-wave-based sensors for liquid environments. Both single- and bi-layered structures have been investigated and the velocity dispersion curves were calculated for different layer thicknesses, crystallographic orientations, material types and electrical boundary conditions. High velocity materials have been investigated too, enabling device miniaturization, power consumption reduction and integration with the conditioning electronic circuits. The electroacoustic coupling coefficient dispersion curves of the first four Love modes are calculated for four dispersive coupling configurations based on a c-axis tilted ZnO layer on wz-BN substrate. The gravimetric sensitivity of four Love modes travelling at a common velocity of 9318 m/s along different layer thicknesses, and of three Love modes travelling at different velocity along a fixed ZnO layer thickness, are calculated in order to design enhanced-performance sensors. The phase velocity shift and attenuation due to the presence of a viscous liquid contacting the device surface are calculated for different thicknesses of a c-axis inclined ZnO layer onto BN half-space. Full article

(This article belongs to the Special Issue Piezoelectric MEMS)

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4719 KiB

Open AccessReview

CMOS MEMS Fabrication Technologies and Devices

by Hongwei Qu

Micromachines 2016, 7(1), 14; https://doi.org/10.3390/mi7010014 - 21 Jan 2016

Cited by 94 | Viewed by 19056

Abstract

This paper reviews CMOS (complementary metal-oxide-semiconductor) MEMS (micro-electro-mechanical systems) fabrication technologies and enabled micro devices of various sensors and actuators. The technologies are classified based on the sequence of the fabrication of CMOS circuitry and MEMS elements, while SOI (silicon-on-insulator) CMOS MEMS are [...] Read more.

This paper reviews CMOS (complementary metal-oxide-semiconductor) MEMS (micro-electro-mechanical systems) fabrication technologies and enabled micro devices of various sensors and actuators. The technologies are classified based on the sequence of the fabrication of CMOS circuitry and MEMS elements, while SOI (silicon-on-insulator) CMOS MEMS are introduced separately. Introduction of associated devices follows the description of the respective CMOS MEMS technologies. Due to the vast array of CMOS MEMS devices, this review focuses only on the most typical MEMS sensors and actuators including pressure sensors, inertial sensors, frequency reference devices and actuators utilizing different physics effects and the fabrication processes introduced. Moreover, the incorporation of MEMS and CMOS is limited to monolithic integration, meaning wafer-bonding-based stacking and other integration approaches, despite their advantages, are excluded from the discussion. Both competitive industrial products and state-of-the-art research results on CMOS MEMS are covered. Full article

(This article belongs to the Special Issue CMOS-MEMS Sensors and Devices)

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17736 KiB

Open AccessReview

Thermocapillarity in Microfluidics—A Review

by Alireza Karbalaei, Ranganathan Kumar and Hyoung Jin Cho

Micromachines 2016, 7(1), 13; https://doi.org/10.3390/mi7010013 - 21 Jan 2016

Cited by 127 | Viewed by 18973

Abstract

This paper reviews the past and recent studies on thermocapillarity in relation to microfluidics. The role of thermocapillarity as the change of surface tension due to temperature gradient in developing Marangoni flow in liquid films and conclusively bubble and drop actuation is discussed. [...] Read more.

This paper reviews the past and recent studies on thermocapillarity in relation to microfluidics. The role of thermocapillarity as the change of surface tension due to temperature gradient in developing Marangoni flow in liquid films and conclusively bubble and drop actuation is discussed. The thermocapillary-driven mass transfer (the so-called Benard-Marangoni effect) can be observed in liquid films, reservoirs, bubbles and droplets that are subject to the temperature gradient. Since the contribution of a surface tension-driven flow becomes more prominent when the scale becomes smaller as compared to a pressure-driven flow, microfluidic applications based on thermocapillary effect are gaining attentions recently. The effect of thermocapillarity on the flow pattern inside liquid films is the initial focus of this review. Analysis of the relation between evaporation and thermocapillary instability approves the effect of Marangoni flow on flow field inside the drop and its evaporation rate. The effect of thermocapillary on producing Marangoni flow inside drops and liquid films, leads to actuation of drops and bubbles due to the drag at the interface, mass conservation, and also gravity and buoyancy in vertical motion. This motion can happen inside microchannels with a closed multiphase medium, on the solid substrate as in solid/liquid interaction, or on top of a carrier liquid film in open microfluidic systems. Various thermocapillary-based microfluidic devices have been proposed and developed for different purposes such as actuation, sensing, trapping, sorting, mixing, chemical reaction, and biological assays throughout the years. A list of the thermocapillary based microfluidic devices along with their characteristics, configurations, limitations, and improvements are presented in this review. Full article

(This article belongs to the Collection Lab-on-a-Chip)

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4193 KiB

Open AccessArticle

Dynamic Electromechanical Coupling of Piezoelectric Bending Actuators

by Mostafa R. A. Nabawy and William J. Crowther

Micromachines 2016, 7(1), 12; https://doi.org/10.3390/mi7010012 - 20 Jan 2016

Cited by 21 | Viewed by 5434

Abstract

Electromechanical coupling defines the ratio of electrical and mechanical energy exchanged during a flexure cycle of a piezoelectric actuator. This paper presents an analysis of the dynamic electromechanical coupling factor (dynamic EMCF) for cantilever based piezoelectric actuators and provides for the first time [...] Read more.

Electromechanical coupling defines the ratio of electrical and mechanical energy exchanged during a flexure cycle of a piezoelectric actuator. This paper presents an analysis of the dynamic electromechanical coupling factor (dynamic EMCF) for cantilever based piezoelectric actuators and provides for the first time explicit expressions for calculation of dynamic EMCF based on arrangement of passive and active layers, layer geometry, and active and passive materials selection. Three main cantilever layer configurations are considered: unimorph, dual layer bimorph and triple layer bimorph. The actuator is modeled using standard constitutive dynamic equations that relate deflection and charge to force and voltage. A mode shape formulation is used for the cantilever dynamics that allows the generalized mass to be the actual mass at the first resonant frequency, removing the need for numerical integration in the design process. Results are presented in the form of physical insight from the model structure and also numerical evaluations of the model to provide trends in dynamic EMCF with actuator design parameters. For given material properties of the active and passive layers and given system overall damping ratio, the triple layer bimorph topology is the best in terms of theoretically achievable dynamic EMCF, followed by the dual layer bimorph. For a damping ratio of 0.035, the dynamic EMCF for an example dual layer bimorph configuration is 9% better than for a unimorph configuration. For configurations with a passive layer, the ratio of thicknesses for the passive and active layers is the primary geometric design variable. Choice of passive layer stiffness (Young’s modulus) relative to the stiffness of the material in the active layer is an important materials related design choice. For unimorph configurations, it is beneficial to use the highest stiffness possible passive material, whereas for triple layer bimorph configurations, the passive material should have a low stiffness. In all cases, increasing the transverse electromechanical coupling coefficient of the active material improves the dynamic EMCF. Full article

(This article belongs to the Special Issue Piezoelectric MEMS)

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4966 KiB

Open AccessArticle

Temperature Sensing in Modular Microfluidic Architectures

by Krisna C. Bhargava, Bryant Thompson, Anoop Tembhekar and Noah Malmstadt

Micromachines 2016, 7(1), 11; https://doi.org/10.3390/mi7010011 - 18 Jan 2016

Cited by 10 | Viewed by 6174

Abstract

A discrete microfluidic element with integrated thermal sensor was fabricated and demonstrated as an effective probe for process monitoring and prototyping. Elements were constructed using stereolithography and market-available glass-bodied thermistors within the modular, standardized framework of previous discrete microfluidic elements demonstrated in the [...] Read more.

A discrete microfluidic element with integrated thermal sensor was fabricated and demonstrated as an effective probe for process monitoring and prototyping. Elements were constructed using stereolithography and market-available glass-bodied thermistors within the modular, standardized framework of previous discrete microfluidic elements demonstrated in the literature. Flow rate-dependent response due to sensor self-heating and microchannel heating and cooling was characterized and shown to be linear in typical laboratory conditions. An acid-base neutralization reaction was performed in a continuous flow setting to demonstrate applicability in process management: the ratio of solution flow rates was varied to locate the equivalence point in a titration, closely matching expected results. This element potentially enables complex, three-dimensional microfluidic architectures with real-time temperature feedback and flow rate sensing, without application specificity or restriction to planar channel routing formats. Full article

(This article belongs to the Collection Lab-on-a-Chip)

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3775 KiB

Open AccessArticle

Aspartate Aminotransferase and Alanine Aminotransferase Detection on Paper-Based Analytical Devices with Inkjet Printer-Sprayed Reagents

by Hsiang-Li Wang, Chien-Hung Chu, Sing-Jyun Tsai and Ruey-Jen Yang

Micromachines 2016, 7(1), 9; https://doi.org/10.3390/mi7010009 - 15 Jan 2016

Cited by 23 | Viewed by 7303

Abstract

General biochemistry detection on paper-based microanalytical devices (PADs) uses pipette titration. However, such an approach is extremely time-consuming for large-scale detection processes. Furthermore, while automated methods are available for increasing the efficiency of large-scale PAD production, the related equipment is very expensive. Accordingly, [...] Read more.

General biochemistry detection on paper-based microanalytical devices (PADs) uses pipette titration. However, such an approach is extremely time-consuming for large-scale detection processes. Furthermore, while automated methods are available for increasing the efficiency of large-scale PAD production, the related equipment is very expensive. Accordingly, this study proposes a low-cost method for PAD manufacture, in which the reagent is applied using a modified inkjet printer. The optimal reaction times for the detection of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are shown to be 6 and 7 min, respectively, given AST and ALT concentrations in the range of 5.4 to 91.2 U/L (R² = 0.9932) and 5.38 to 86.1 U/L (R² = 0.9944). The experimental results obtained using the proposed PADs for the concentration detection of AST and ALT in real human blood serum samples are found to be in good agreement with those obtained using a traditional spectrophotometric detection method by National Cheng Kung University hospital. Full article

(This article belongs to the Special Issue Paper-Based Microfluidic Devices for Point-of-Care Diagnostics)

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4883 KiB

Open AccessArticle

Design and Analysis of MEMS Linear Phased Array

by Guoxiang Fan, Junhong Li and Chenghao Wang

Micromachines 2016, 7(1), 8; https://doi.org/10.3390/mi7010008 - 15 Jan 2016

Cited by 3 | Viewed by 6353

Abstract

A structure of micro-electro-mechanical system (MEMS) linear phased array based on “multi-cell” element is designed to increase radiation sound pressure of transducer working in bending vibration mode at high frequency. In order to more accurately predict the resonant frequency of an element, the [...] Read more.

A structure of micro-electro-mechanical system (MEMS) linear phased array based on “multi-cell” element is designed to increase radiation sound pressure of transducer working in bending vibration mode at high frequency. In order to more accurately predict the resonant frequency of an element, the theoretical analysis of the dynamic equation of a fixed rectangular composite plate and finite element method simulation are adopted. The effects of the parameters both in the lateral and elevation direction on the three-dimensional beam directivity characteristics are comprehensively analyzed. The key parameters in the analysis include the “cell” number of element, “cell” size, “inter-cell” spacing and the number of elements, element width. The simulation results show that optimizing the linear array parameters both in the lateral and elevation direction can greatly improve the three-dimensional beam focusing for MEMS linear phased array, which is obviously different from the traditional linear array. Full article

(This article belongs to the Special Issue Piezoelectric MEMS)

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3818 KiB

Open AccessArticle

Single-Capacitor Electret Impact Microgenerator

by Igor Baginsky, Edward Kostsov and Alexey Sokolov

Micromachines 2016, 7(1), 5; https://doi.org/10.3390/mi7010005 - 15 Jan 2016

Cited by 5 | Viewed by 4832

Abstract

A new type of electrostatic microgenerator is presented that converts mechanical microvibrational energy into electric energy. The energy conversion mechanism is as follows. External microvibrations are transmitted to the device frame. The thin electret layer sputtered to the silicon substrate surface was fixed [...] Read more.

A new type of electrostatic microgenerator is presented that converts mechanical microvibrational energy into electric energy. The energy conversion mechanism is as follows. External microvibrations are transmitted to the device frame. The thin electret layer sputtered to the silicon substrate surface was fixed on the frame and the moving electrode was fixed by a weak suspension and comes into contact with the electret surface under the action of vibrations. A two-stage impact process is described: coming into contact with the spring stop that models the undulation of the contact surfaces, and direct impact on the electret surface. A numerical modeling of the generator operation is performed and analytic estimates of the generated power are obtained. It is shown that the energy generated by this motor is significantly higher than the energy generated by the classical mechanism based on the excitation of the forced vibrations of the moving plate. Experimental measurements of the microgenerator prototype parameters confirm the results of the theoretical modeling. Full article

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3636 KiB

Open AccessArticle

Rapid Detection of Salmonella enterica in Food Using a Compact Disc-Shaped Device

by Shunsuke Furutani, Mitsutoshi Kajiya, Narumi Aramaki and Izumi Kubo

Micromachines 2016, 7(1), 10; https://doi.org/10.3390/mi7010010 - 15 Jan 2016

Cited by 5 | Viewed by 5816

Abstract

Rapid detection of food-borne pathogens is essential to public health and the food industry. Although the conventional culture method is highly sensitive, it takes at least a few days to detect food-borne pathogens. Even though polymerase chain reaction (PCR) can detect food-borne pathogens [...] Read more.

Rapid detection of food-borne pathogens is essential to public health and the food industry. Although the conventional culture method is highly sensitive, it takes at least a few days to detect food-borne pathogens. Even though polymerase chain reaction (PCR) can detect food-borne pathogens in a few hours, it is more expensive and unsatisfactorily sensitive relative to the culture method. We have developed a method to rapidly detect Salmonella enterica by using a compact disc (CD)-shaped device that can reduce reagent consumption in conventional PCR. The detection method, which combines culture and PCR, is more rapid than the conventional culture method and is more sensitive and cheaper than PCR. In this study, we also examined a sample preparation method that involved collecting bacterial cells from food. The bacteria collected from chicken meat spiked with S. enterica were mixed with PCR reagents, and PCR was performed on the device. At a low concentration of S. enterica, the collected S. enterica was cultured before PCR for sensitive detection. After cultivation for 4 h, S. enterica at 1.7 × 10⁴ colony-forming units (CFUs)·g⁻¹ was detected within 8 h, which included the time needed for sample preparation and detection. Furthermore, the detection of 30 CFUs·g⁻¹ of S. enterica was possible within 12 h including 8 h for cultivation. Full article

(This article belongs to the Special Issue Centrifugal (Compact-Disc) Microfluidics for Extreme POC)

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4741 KiB

Open AccessArticle

Study on Improving Thickness Uniformity of Microfluidic Chip Mold in the Electroforming Process

by Liqun Du, Tong Yang, Ming Zhao, Yousheng Tao, Lei Luo, Lei Wang and Chong Liu

Micromachines 2016, 7(1), 7; https://doi.org/10.3390/mi7010007 - 13 Jan 2016

Cited by 19 | Viewed by 5465

Abstract

Electroformed microfluidic chip mold faces the problem of uneven thickness, which decreases the dimensional accuracy of the mold, and increases the production cost. To fabricate a mold with uniform thickness, two methods are investigated. Firstly, experiments are carried out to study how the [...] Read more.

Electroformed microfluidic chip mold faces the problem of uneven thickness, which decreases the dimensional accuracy of the mold, and increases the production cost. To fabricate a mold with uniform thickness, two methods are investigated. Firstly, experiments are carried out to study how the ultrasonic agitation affects the thickness uniformity of the mold. It is found that the thickness uniformity is maximally improved by about 30% after 2 h electroforming under 200 kHz and 500 W ultrasonic agitation. Secondly, adding a second cathode, a method suitable for long-time electroforming is studied by numerical simulation. The simulation results show that with a 4 mm width second cathode used, the thickness uniformity is improved by about 30% after 2 h of electroforming, and that with electroforming time extended, the thickness uniformity is improved more obviously. After 22 h electroforming, the thickness uniformity is increased by about 45%. Finally, by comparing two methods, the method of adding a second cathode is chosen, and a microfluidic chip mold is made with the help of a specially designed second cathode. The result shows that the thickness uniformity of the mold is increased by about 50%, which is in good agreement with the simulation results. Full article

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4402 KiB

Open AccessCommunication

Easily Fabricated Microfluidic Devices Using Permanent Marker Inks for Enzyme Assays

by Coreen Gallibu, Chrisha Gallibu, Ani Avoundjian and Frank A. Gomez

Micromachines 2016, 7(1), 6; https://doi.org/10.3390/mi7010006 - 12 Jan 2016

Cited by 24 | Viewed by 6161

Abstract

In this communication, we describe microfluidic paper analytical devices (μPADs) easily fabricated from commercially available Sharpie ink permanent markers on chromatography paper to colorimetrically detect glucose using glucose oxidase (GOx). Here, solutions of horseradish peroxidase (HRP), GOx, and potassium iodide (KI)were directly spotted [...] Read more.

In this communication, we describe microfluidic paper analytical devices (μPADs) easily fabricated from commercially available Sharpie ink permanent markers on chromatography paper to colorimetrically detect glucose using glucose oxidase (GOx). Here, solutions of horseradish peroxidase (HRP), GOx, and potassium iodide (KI)were directly spotted onto the center of the μPAD and flowed into samples of glucose that were separately spotted on the μPAD. Using an XY plotter (Roland DGA Corporation, Irvine, CA USA), several ink marks drawn in the paper act as the hydrophobic barriers, thereby, defining the hydrophilic fluid flow paths of the solutions. Two paper devices are described that act as independent assay zones. The glucose assay is based on the enzymatic oxidation of iodide to iodine whereby a color change from clear to brownish-yellow is associated with the presence of glucose. In these experiments, two designs are highlighted that consist of circular paper test regions fabricated for colorimetric and subsequent quantification detection of glucose. The use of permanent markers for paper patterning is inexpensive and rapid and does not require special laboratory equipment or technical skill. Full article

(This article belongs to the Special Issue Paper-Based Microfluidic Devices for Point-of-Care Diagnostics)

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Open AccessArticle

Design and Performance of a Focus-Detection System for Use in Laser Micromachining

by Binh Xuan Cao, Munju Bae, Hyonkee Sohn, Jiyeon Choi, Youngduk Kim, Jeng-o Kim and Jiwhan Noh

Micromachines 2016, 7(1), 2; https://doi.org/10.3390/mi7010002 - 04 Jan 2016

Cited by 16 | Viewed by 6827

Abstract

We describe a new approach for locating the focal position in laser micromachining. This approach is based on a feedback system that uses a charge-coupled device (CCD) camera, a beam splitter, and a mirror to focus a laser beam on the surface of [...] Read more.

We describe a new approach for locating the focal position in laser micromachining. This approach is based on a feedback system that uses a charge-coupled device (CCD) camera, a beam splitter, and a mirror to focus a laser beam on the surface of a work piece. We tested the proposed method for locating the focal position by using Zemax simulations, as well as physically carrying out drilling processes. Compared with conventional methods, this approach is advantageous because: the implementation is simple, the specimen can easily be positioned at the focal position, and the dynamically adjustable scan amplitude and the CCD camera can be used to monitor the laser beam’s profile. The proposed technique will be particularly useful for locating the focal position on any surface in laser micromachining. Full article

(This article belongs to the Special Issue Laser Micromachining and Microfabrication)

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1869 KiB

Open AccessArticle

Particulate Blood Analogues Reproducing the Erythrocytes Cell-Free Layer in a Microfluidic Device Containing a Hyperbolic Contraction

by Joana Calejo, Diana Pinho, Francisco J. Galindo-Rosales, Rui Lima and Laura Campo-Deaño

Micromachines 2016, 7(1), 4; https://doi.org/10.3390/mi7010004 - 30 Dec 2015

Cited by 33 | Viewed by 6912

Abstract

The interest in the development of blood analogues has been increasing recently as a consequence of the increment in the number of experimental hemodynamic studies and the difficulties associated with the manipulation of real blood in vitro because of ethical, economical or hazardous [...] Read more.

The interest in the development of blood analogues has been increasing recently as a consequence of the increment in the number of experimental hemodynamic studies and the difficulties associated with the manipulation of real blood in vitro because of ethical, economical or hazardous issues. Although one-phase Newtonian and non-Newtonian blood analogues can be found in the literature, there are very few studies related to the use of particulate solutions in which the particles mimic the behaviour of the red blood cells (RBCs) or erythrocytes. One of the most relevant effects related with the behaviour of the erythrocytes is a cell free layer (CFL) formation, which consists in the migration of the RBCs towards the center of the vessel forming a cell depleted plasma region near the vessel walls, which is known to happen in in vitro microcirculatory environments. Recent studies have shown that the CFL enhancement is possible with an insertion of contraction and expansion region in a straight microchannel. These effects are useful for cell manipulation or sorting in lab-on-chip studies. In this experimental study we present particulate Newtonian and non-Newtonian solutions which resulted in a rheological blood analogue able to form a CFL, downstream of a microfluidic hyperbolic contraction, in a similar way of the one formed by healthy RBCs. Full article

(This article belongs to the Special Issue Advances in Microfluidic Devices for Cell Handling and Analysis)

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3967 KiB

Open AccessArticle

Towards Independent Control of Multiple Magnetic Mobile Microrobots

by Sagar Chowdhury, Wuming Jing and David J. Cappelleri

Micromachines 2016, 7(1), 3; https://doi.org/10.3390/mi7010003 - 29 Dec 2015

Cited by 50 | Viewed by 12579

Abstract

In this paper, we have developed an approach for independent autonomous navigation of multiple microrobots under the influence of magnetic fields and validated it experimentally. We first developed a heuristics based planning algorithm for generating collision-free trajectories for the microrobots that are suitable [...] Read more.

In this paper, we have developed an approach for independent autonomous navigation of multiple microrobots under the influence of magnetic fields and validated it experimentally. We first developed a heuristics based planning algorithm for generating collision-free trajectories for the microrobots that are suitable to be executed by an available magnetic field. Second, we have modeled the dynamics of the microrobots to develop a controller for determining the forces that need to be generated for the navigation of the robots along the trajectories at a suitable control frequency. Next, an optimization routine is developed to determine the input currents to the electromagnetic coils that can generate the required forces for the navigation of the robots at the controller frequency. We then validated our approach by simulating an electromagnetic system that contains an array of sixty-four magnetic microcoils designed for generating local magnetic fields suitable for simultaneous independent actuation of multiple microrobots. Finally, we prototyped an m m -scale version of the system and present experimental results showing the validity of our approach. Full article

(This article belongs to the Special Issue Micro/Nano Robotics)

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3930 KiB

Open AccessReview

Miniature Microwave Notch Filters and Comparators Based on Transmission Lines Loaded with Stepped Impedance Resonators (SIRs)

by Lijuan Su, Jordi Naqui, Javier Mata-Contreras and Ferran Martín

Micromachines 2016, 7(1), 1; https://doi.org/10.3390/mi7010001 - 23 Dec 2015

Cited by 2 | Viewed by 5552

Abstract

In this paper, different configurations of transmission lines loaded with stepped impedance resonators (SIRs) are reviewed. This includes microstrip lines loaded with pairs of SIRs, and coplanar waveguides (CPW) loaded with multi-section SIRs. Due to the high electric coupling between the line and [...] Read more.

In this paper, different configurations of transmission lines loaded with stepped impedance resonators (SIRs) are reviewed. This includes microstrip lines loaded with pairs of SIRs, and coplanar waveguides (CPW) loaded with multi-section SIRs. Due to the high electric coupling between the line and the resonant elements, the structures are electrically small, i.e., dimensions are small as compared to the wavelength at the fundamental resonance. The circuit models describing these structures are discussed and validated, and the potential applications as notch filters and comparators are highlighted. Full article

(This article belongs to the Special Issue Microresonators)

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