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Noble metal nanostructures have been widely explored as an effective method to increase photon absorption and charge separation in plasmonic photocatalysis. In this study, we integrated two differe...

In this paper, a bump-forming method for flip chip bonding using ink-jet printing technology is proposed. A flip chip bonded transmission line using ink-jet printed silver bumps consisting of conductive ink containing silver nanoparticles was fabricated to verify the electrical characteristics after the flip chip bonding process. The transmission line was designed according to microstrip theory for a frequency range of 300 kHz to 3 GHz, with the size of fabricated line being 35 (width) × 8.64 (length) × 0.5 (thickness) mm3. The electrical characteristics of a reference microstrip and the flip chip bonded line were compared with FEM simulation and measurement results. Direct current (DC) resistances of both the reference line and the flip chip bonded line were measured to be 3.1 Ω and 3.2 Ω, respectively. The discrepancy between measured insertion loss and the simulation result was only 0.04 dB at 3 GHz, and the return loss was greater than 15 dB in the measurement frequency range. As a result of the analysis, it was confirmed that the DC resistance of ink-jet printed bumps account for 0.56% of the total DC resistance, and the ink-jet printed bumps hardly affected the radio frequency (RF) characteristics of the RF transmission line at low frequencies. The results demonstrate that ink-jet printed silver bumps can be used for a simple and low-cost flip chip bonding process. We expect that the proposed method can be applied to the packaging of various electronics such as flexible, wearable devices and RF applications.

A simple and cost-effective fabrication process of a flexible-based inverse micro-cone array (i-MCA) structure textured on flexible transparent conductive electrodes (TCEs) was successfully demonstrated via a micro-imprinting process. The flexible i-MCA films exhibited an extremely high total transmittance of ∼93% and a haze of ∼95% with reduced reflectance while simultaneously demonstrating water-repellent properties. Introducing i-MCA on the illuminating side of organic solar cells (OSCs)- and perovskite solar cells-rigid glass substrate showed improved power conversion efficiencies (PCEs) due to the light trapping effect by multiple light bounces between cone array structures (forward scattering). This results in an increase of the optical path length in the photoactive layer. Similarly, flexible TCEs embedded with textured i-MCA increased the PCE by 14% for flexible OSCs. More importantly, i-MCA-TCE-based OSCs were highly flexible with 98% retention from the initial PCE at both 0° and at 60° even after 2000 bending cycles at a radius of 2 mm. This finding demonstrates that textured i-MCA is promising for improving: (a) the light harvesting efficiency of solar cells when installed in low-/high-latitude locations and (b) the wearable technology where a flexible device attached on curved objects could retain the PCE, even at an oblique angle, with respect to the normal incidence angle.

This paper reviews the application of microwave signal-interference techniques to interferometers for frequency measurement and filters. The microwave interference takes place when the input-signal components pass through two different electrical paths to be then recombined and produce an interference pattern. Path lengths define the interference-based power-transmission maximum and minimum, which are calculated to obtain the desired device frequency response. Reconfigurable interferometers, wide-band, and dual-band filters designed using interference principles are described in this overview paper.

In this paper we propose Otto surface plasmon resonance (SPR) system with tunable air-gap using piezoactuator for the first time. The proposed Otto configuration based SPR system include a piezoactuator for varying an air-gap distance between a prism and gold surface. We verified effects of air-gap variation in Otto SPR system and the measured results show that the Otto SPR sensor can be realized with a metal film and prism by using a microactuator without complex microfabrication process for specific air-gap distance.

In this study, a micromachined chip in Otto configuration with multiple air-gaps (1.86 µm, 2.42 µm, 3.01 µm, 3.43 µm) was fabricated, and the resonance characteristics for each air-gap was measured with a 980 nm laser source. To verify the variability of the reflectance characteristics of the Otto configuration and its applicability to multiple gas detection, the air-gap between the prism and metal film was adjusted by using a commercial piezoactuator. We experimentally verified that the SPR characteristics of the Otto chip configuration have a dependence on the air-gap distance and wavelength of the incident light. When a light source having a wavelength of 977 nm is used, the minimum reflectance becomes 0.22 when the displacement of the piezoactuator is about 9.3 µm.

In this paper, microstrip lines that are directly patterned by Ag ink-jet printing are discussed and their RF performance is investigated on both rigid and flexible substrates, which are FR-4 and polyimide (PI) film substrates, respectively. Microstrip lines are designed by computational simulation, and the simulated results are compared with the measured RF results of the fabricated microstrip lines. The measured transmission losses of the microstrip lines are 0.24 dB/cm for the FR-4 substrate and 0.66 dB/cm for the PI film substrate at 3 GHz. To measure the RF performance of the printed microstrip lines undergoing bending tests, the distances between the ends of the bended microstrip line are varied from 5 cm to 9.2 cm. The microstrip lines are twisted by torsion angles in the range of 0–40°. The RF performance and characteristics remain nearly unchanged under bending and torsion tests except for negligible variation caused by impedance mismatching occurred during the measurement process. The measured RF performance demonstrates that the printed Ag conductive lines can be utilized in RF application such as wearable and flexible systems, which require low-cost and low-end antennae at low frequencies.

We firstly show the prototype of an ohmic contact Single-Pole Double-Throw Radio Frequency Micro-Electro-Mechanical Systems (SPDT RF MEMS) switch operating at 50-100GHz. The fabricated ohmic contact SPDT RF MEMS silicon switch moves both laterally and vertically, to improve the isolation at high frequencies by initially misaligning the contact part of the switch over a Coplanar Waveguide (CPW) transmission line. The lateral and vertical movement of the switch is operated by using comb and parallel plate actuators, respectively. The proposed switch was fabricated using Silicon-On-Glass (SiOG) bonding process. The insertion loss of the fabricated switch is measured according to the different operation states of the switch, in the range from 50 to 100GHz. The fabricated length of the transmission line is 4.6mm and the measured insertion loss and isolation are 9.13dB and 24.37dB at 70GHz, respectively. Display Omitted A SPDT RF MEMS metal-contact switch for 50-100GHz applications is proposed.The switch is driven by a bidirectional comb actuator and parallel plate actuator.The RF characteristics of the switch are measured in the lateral and vertical movement sequentially.The measurement results show that the isolation can be increased using the proposed design.

In this paper, we report an X-band 3D printed two-way rectangular waveguide power divider made up of electroless plated non-conductive material. In contrast to conventional metal machining fabrication processes, such as computerized numerically controlled (CNC) milling and laser beam machining (LBM), it is verified that 3D printing methods can be used to fabricate rectangular waveguide power dividers with low cost and low weight in short time.

This paper reports an experimental study focused on the characterization of the Otto chip device. These devices are structures sealed with a glass window, having a gold film, which is separated from the window surface by a well-defined gap. The gap is designed for the surface plasmon resonance effect. In this study, gap profiles were scanned by optical reflectometry. A preliminary analysis of reflectance curve patterns allows mapping the topography of the different regions of the chip. The results of the study can be used to optimize the manufacturing process of this type of structure.

In this study, a MEMS acceleration switch using mechanical hooked latch is designed, fabricated, and measured. A mechanical latching mechanism and switching characteristic are analyzed using FEM simulation. The acceleration switch with a size of 1.8×3.2×0.55mm3 was fabricated using a Silicon-on-Glass (SiOG) process. A resonance frequency of the fabricated switch and an acceleration threshold are measured to be 1.022kHz and 43.7g, respectively. The fabricated switch is latched when an applied external acceleration is higher than the threshold value of 43.7g. After latching "on", the "on" state of the switch is reliably sustained regardless of the applied external acceleration. Display Omitted We analyze switching characteristic of a MEMS acceleration switch with latching function.Fabricated switch is latched by applied acceleration which is higher than 43.7g.Measurement result agrees well with simulation result based on fabricated switch.After latching on, the "on" state is reliably sustained regardless of the applied acceleration.

In this study, we suggested a method to fabricate a coplanar waveguide with high resolution using an inkjet printing process. A glass substrate was selectively coated with fluorocarbon film, which makes the coated region hydrophobic. Silver nanoparticle colloid ink was printed on the hydrophilic region using an inkjet printer, where the fluorocarbon film effectively hindered the ink from dispersing onto the film. As a result, a coplanar waveguide with a uniform gap of 16.1 μm was fabricated, where the thickness of the structure was higher than 2 μm. The conductivity of the printed structure was about eight times lower than that of bulk silver. The transmission loss of the coplanar waveguide was measured to be 0.61 dB/cm and 2.01 dB/cm at 1 GHz and 10 GHz, respectively, and the return loss was mostly better than 15 dB at the frequency ranging from 100 MHz to 40 GHz. The measurement results show that the proposed method is not only cost-effective and simpler than conventional processes, but is also suitable for the fabrication of microstructures with high-resolution and high-thickness.

We report DNA-mediated simple synthetic methods to obtain anisotropic plasmonic nanostructures with a tailorable intra-nanogap distance ranging from 0.9 to 4.0 nm. Anisotropic half-shell structures with sub-1.0 nm intra-nanogaps showed a wavelength-independent surface-enhanced Raman scattering (SERS) intensity and a highly sensitive SERS response to NIR light. We found that the reaction conditions such as pH and NaCl concentration are responsible for the resulting shell structures and intra-nanogap distances. Three noticeable plasmonic nanostructures [i.e., half-shell with sub-1.0 nm nanogaps, closed-shell with a wide nanogap (2.1 nm) and star-shaped with an irregular nanogap (1.5–4.0 nm)] were synthesized, and solution-based and single particle-based Raman measurements showed a strong relationship between the plasmonic structures and the SERS intensity. An understanding of DNA-mediated control for nanogap-engineered plasmonic nanostructures and studies of SERS-activity relationships using single particle-correlated measurements can provide new insights into the design of new plasmonic nanostructures and SERS-based biosensing applications.

A MEMS acceleration switch capable of tuning threshold acceleration to either higher or lower levels is designed and implemented with comb drive actuators as a mechanism of threshold tuning. A small sized switch (1.6 × 3.1 × 0.55 mm 3 ) is successfully realized by patterning silicon structures on a glass wafer. The resonant frequency of fabricated switches agrees well with a designed frequency of 1.1 kHz. The threshold acceleration at no tuning voltage is 10.25 g and it is subsequently tuned to 2.0 g and 17.25 g by applying 30 V to pushing comb and pulling comb, respectively. The rising time is measured to be 9.8 ms. Additional functionalities such as safe/armed position convertibility and single use latching switch are also described for diverse applications of the tunable acceleration switches.

This paper introduces Radio Frequency Microelectromechanical Systems (RF MEMS) devices, including a switch, resonator, filter and antenna for applications that require reconfigurable RF components.

An Otto chip device fabricated on silicon and sealed with a quartz window has recently been demonstrated as a potential alternative for the traditional Kretschmann based configuration for the development of surface plasmon resonance - SPR - sensors. We have fabricated open Otto chip structures as well and have characterized the surface plasmon resonance - SPR - effect at a wavelength of 975.1 nm. In this paper we report on the potential of these structures to act as pressure sensors.

In this paper, nano-silver ink-jet printed transmission lines were fabricated to investigate RF performance on both flame retardant (FR-4) and polyimide (PI) as rigid and flexible substrates. The transmission lines were printed by using the ink-jet printer with velocity of 3.5 mm/s and were sintered in a convection oven with 250 °C. The RF performance of transmission lines was simulated and measured at low frequencies. The transmission loss is measured to be 0.22 dB@1 GHz and 0.32 dB@1 GHz, respectively, for the FR-4 and PI substrates, respectively. The return loss has over 16 dB for FR-4 substrate and over 12 dB for PI substrate. The RF performance of transmission line was investigated and discussed in regard to an influence by two substrates. The measured RF performance of fabricated transmission lines results in the possibility that flexible device is explored in low frequencies application.

This paper presents a comparison between fixed and reconfigurable 4-bit microwave discriminators. The fixed discriminator is implemented by using multi-band-stop filters to define bits used for frequency identification. The reconfigurable discriminator is implemented by using delay lines and two SPQT switches. Both designs operate at L and S bands, a comparison between both devices is provided, including simulated and measured responses for both designs.

A sealed Otto chip device has recently been demonstrated as a potential alternative for the traditional Kretschmann based configuration for the development of surface plasmon resonance - SPR - sensors. We have fabricated an open Otto chip structure on silicon and have characterized the SPR effect at a wavelength of 975.1 nm. In this paper we report on an open Otto chip pressure transducer.

In this paper, an Otto coupling configuration based SPR chip is designed, simulated and fabricated using a silicon-on-quartz (SoQ) bonding process. The simulation of the SPR effect is conducted using COMSOL Multiphysics simulator (Altsoft Co.) using the designed chip dimensions, the optical constants are interpolated from data available in the literature. The size of the fabricated SPR chip is $$30\; \times \;30\; \times \;1 {\text{mm}}^{3}$$30×30×1mm3. Resonance angle and reflectance are measured to be 42.19° and 0.411°, respectively, using an automated reflectometer. Discrepancy between measurement and simulation results is discussed by optical constant of the gold layer used as a thin metal film. The SoQ bonding process is a feasible approach for implementation of Otto coupling configuration based SPR chips.

In this paper, we propose a feed-through reduction technique for a micro-resonator with a push–pull configuration that is based on the analysis of electrical characteristics of a direct driving micro-resonator. We show that the feed-through capacitance is decreased by reducing the sizes of the driving and sensing electrodes, inserting bias electrodes between them, and by surrounding them with a bias electrode. Using the proposed methods, we succeeded in reducing the feed-through capacitance and improving the performance of the micro-resonator with a push–pull configuration. We propose designs for the push–pull configuration with small electrodes, small electrodes and the insertion of bias electrodes between the driving and sensing electrodes, and surrounding the electrodes with a bias electrode. The feed-through capacitance of the small electrode model is 41.9 fF, an approximately 50% decrease from the general model (90.1 fF). The feed-through capacitance of the model with inserted bias electrodes is 17.9 fF. The feed-through capacitance of the model surrounded with an inserted bias electrode is 10.9 fF. The electrical transmission according to the feed-through capacitance was measured for each model. The efficiency in the electrical transmission is increased from 7.83 dB (the general model) to 8.94 dB (the small electrodes), 9.18 dB (inserting bias electrodes model) and 9.40 dB (surrounded with bias electrode model). We experimentally verified that the feed-through capacitance is decreased by reducing the sizes of the driving and sensing electrodes, inserting bias electrodes, and surrounding the electrodes with bias electrodes. The feed-through capacitance reduction technique would be useful for sensors, such as a micro-resonator requiring high performance, and radio frequency (RF) devices operating at high frequencies.

This paper presents a single antenna platform steered by an external magnetic field where a monolithic microwave integrated circuit (MMIC) and capacitors are vertically integrated. Unique process skills are successfully optimized to implement a newly proposed microelectromechanical systems antenna. A silicon grid is patterned on the processing wafer to prevent the destruction of the antenna by benzocyclobutene delamination due to the stress applied to the wafers. Moreover, the stress barrier patterns are designed to increase the fabrication yield by protecting the structure failure during the back-side silicon release step. All the electrical elements, such as the MMIC, capacitors, patch antenna, and signal lines, are integrated on a single silicon chip; thus, the fabricated antenna system has smaller size and higher productivity than the conventional ones. The vertically integrated MMIC particularly results in a uniform gain at entire steering angles and reduced signal losses. The fabricated antenna is driven by a magnetic field externally applied with copper coils, and the antenna beam patterns are obtained with various tilting angles. The scanning angles are -14°, 0°, and +18° in the H-plane and -18°, -12°, 0°, +12°, and +16° in the E-plane, and the center frequency of the fabricated antenna is 59.8 GHz which is close to the designed resonance frequency of 60 GHz.

This article reports on a low temperature cofired ceramic (LTCC)-based RF MEMS packaging and its electrical modeling using lumped elements and microstrip lines. An LTCC cap with vertical vias was flip-chip bonded with a glass substrate, where a coplanar waveguide (CPW) formed to measure the RF characteristics of packaging structure. We measured return loss (S11) and insertion loss (S21) of the fabricated packaging structure in a frequency range of 1 to 30 GHz. The parameters of two different equivalent circuits using lumped elements and physical microstrip lines were extracted from the measured results. The mean absolute errors (MAEs) were calculated to show the agreement between measured properties and electrical equivalent circuits. The calculated MAEs were 0.591 dB (S11) and 0.146 dB (S21) for lumped elements, and 0.926 dB (S11) and 0.179 dB (S21) for microstrip lines, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 252–257, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24895

In this paper, we describe a self-aligned fabrication method for a nano-patterned bottom electrode using flood exposure from the backside. Misalignments between layers could cause the final devices to fail after the fabrication of the nano-scale bottom electrodes. A self-alignment was exploited to embed the bottom electrode inside the glass substrate. Aluminum patterns act as a dry etching mask to fabricate glass trenches as well as a self-aligned photomask during the flood exposure from the backside. The patterned photoresist (PR) has a negative sidewall slope using the flood exposure. The sidewall slopes of the glass trench and the patterned PR were 54.00° and 63.47°, respectively. The negative sidewall enables an embedment of a gold layer inside 0.7㎛ wide glass trenches. Gold residues on the trench edges were removed by the additional flood exposure with wet etching. The sidewall slopes of the patterned PR are related to the slopes of the glass trenches. Nano-scale bottom electrodes inside the glass trenches will be used in beam resonators operating at high resonant frequencies.

In this article, we proposed the novel monolithic microwave integrated circuit (MMIC) protection technique in plasma etching process for MMIC mounted mechanically movable RF MEMS antenna. We could eliminate the distortion of radiation pattern caused by RF feed line on antenna frame and torsional hinge as using MMIC direct mounting on antenna plate instead of using external RF power source. Silicon-based mechanically movable RF MEMS antenna was released using DRIE process, which was performed on the backside of silicon substrate after MMIC mounting on RF MEMS antenna plate. An aluminum layer on the front side of RF MEMS antenna plays a role of etch stop layer for DRIE process. We measured the radiation pattern as rotating the moving plate along the vertical- and horizontal-direction hinge mechanically. We could obtain the radiation pattern without gain reduction and distortion of radiation pattern. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3089–3093, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23870

In this paper, we proposed a planar type micromachined probe with low uncertainty and showed its feasibility in practical biomedical applications through the in vivo measurements of cancerous tissue xenografted on nude mice. We have succeeded in increasing the fringe capacitance at low frequencies by locating an aperture on the top side of probe. Furthermore, we showed experimental proof of low uncertainty at low frequencies through measurements of known liquid samples below 1 GHz. Measured results using the proposed probe showed superior agreement with the reference values of the Cole-Cole equation in comparison to measurements made using an open-ended coaxial probe. Muscle and tumor tissue samples of mice, as well as 0.9% saline as a liquid sample, were measured using the proposed probe from 1 GHz to 20 GHz, thus demonstrating the feasibility of this method as a practical biomedical application.

Surface plasmon resonance (SPR) based sensors are usually designed using the Kretschmann prism coupling configuration in which an input beam couples with a surface plasmon through a thin metal film. This is generally preferred by sensor developers for building planar devices instead of the Otto prism coupling configuration, which, for efficient coupling, requires the metal surface to be maintained at a distance on the order of the wavelength from the input prism surface. In this paper, we report on the microfabrication and characterization of an Otto chip device, which is suitable for applications of the SPR effect in gas sensing and biosensing.

This paper discusses key issues related to the design of large processing volume chip architectures and high speed system interconnects. Design methodologies and techniques are discussed, where recent trends and considerations are highlighted.

This paper presents a building block approach for the design of frequency identification receivers. The devices are based on a Reconfigurable Discriminator (RD) for frequency measurement, operating from 1 to 4 GHz. The RD is a two-port device used to identify the frequency of an unknown signal. The devices use RF switches, which are implemented with PIN diodes to select different bits used for frequency identification.

This paper describes two types of novel compact low-loss millimeter-wave filters using an overlay coplanar waveguide (OCPW) line for lowpass filters and an inverted overlay coplanar waveguide (IOCPW) line for bandpass filters with periodic defected ground structures (DGSs). The OCPW and IOCPW lines are utilized to reduce the conductor and the substrate dielectric loss of the transmission lines. Also, these lines can provide a wide impedance range by controlling the overlapped area. The DGSs implemented on the transmission line have the role of size reduction and harmonic suppression of the filters. The combination of transmission lines having suspended structures and DGSs can provide great potential in terms of compact size, band rejection property and low-loss characteristics. The proposed filters are fabricated by using a micromachining technology and their RF performances are measured and analyzed. One of the proposed filters is a lowpass filter with a five-section stepped impedance topology having a periodic high?low impedance section. In this filter, the low impedance section is composed of the OCPW line with dumbbell-shaped DGSs and its length can be reduced by 52.7% compared to the OCPW line without DGSs. The measured insertion loss of this filter is lower than 0.2 dB up to 9 GHz, and significant spurious bands are not observed up to 40 GHz, resulting in a wide stop band. The other work that is presented here deals with a pi-shaped bandpass filter. This filter consists of three high impedance sections and two low impedance sections, and the line length of the high impedance section can be reduced by using the IOCPW line with spiral-shaped DGSs. The measured center frequency of the fabricated filter is 19 GHz, and the passband loss is 2.3 dB at the measured center frequency. The use of DGSs on the transmission line also enables us to suppress effectively the third-order harmonic component at 57 GHz.

This paper reports two types of compact dual-band bandpass filters for wireless local area network (WLAN) applications operating at two frequency bands of 2.4 and 5.2 GHz. The two types of filters (contact-type and capacitive-type) are focused on their digital mode operations in order to alternatively select the operational frequency band of the WLAN. Different types of micromachined frequency-tuning elements having only two states are implemented on each filter to control the center frequencies of the filters. Two digitally operated WLAN filters are fabricated using a surface micromachining technology, which enables us to make simple planar structures of the filters, resulting in easy integration with other planar circuits. Besides, external switching devices for frequency selection are not required, since they are already implemented on the filter's own structures. One of the proposed filters is a contact-type filter using switched inductors with direct-contact MEMS switches. In this filter, a precise and stable frequency-tuning ratio can be obtained because the center frequency is changed by total inductance change due to ON/OFF actuations of the switch. The measured center frequencies of the filter were 2.5 and 5.1 GHz (49% tuning ratio), and the passband insertion loss and return loss were 4.7 dB and 21.5 dB at 2.5 GHz, and 5.2 dB and 21 dB at 5.1 GHz, respectively. The other is a low-loss capacitive-type filter using micromachined variable capacitors. The frequency tunability of this filter is controlled by discrete change of a capacitance according to simultaneous actuations of a total of 12 variable capacitors. This filter shows lower loss compared to the contact-type filter, since loss due to contact resistance of the switch is not included in this filter configuration. The initial center frequency was measured to be 5.4 GHz and it was shifted to 2.6 GHz (48% tuning ratio) with the applied voltage. The total insertion loss and return loss were 2.8 dB and 24.4 dB at 5.4 GHz and 3.3 dB and 20.1 dB at 2.6 GHz, respectively.

In this paper, a packaging method utilizing an LTCC (low temperature co-fired ceramic) substrate and a BCB (benzocyclobutene) adhesive layer has been developed for RF MEMS devices, and the RF performance and characteristic parameters of the package have been evaluated. LTCC substrates have good RF characteristics in high-frequency applications, and via feedthroughs can be easily incorporated during the manufacturing process. In this paper, an LTCC substrate is used as a capping wafer to reduce the complex processes for vertical interconnections. A layer of BCB, in the form of sealing rims, is used as an adhesive to bond the MEMS substrate with the LTCC cap due to the excellent properties of BCB as a packaging material. A CPW (coplanar waveguide) line has been fabricated on a quartz substrate and packaged to demonstrate the performance of the proposed packaging method. After forming the CPW lines, a 28 µm thick BCB layer is patterned by double-coating photolithography for an adhesive bonding. On the backside of the LTCC cap, a 150 µm deep cavity is formed to improve the RF characteristics. The CPW and the contact pad are connected electrically through the silver via-post in the LTCC substrate by screen-printed silver epoxy. The RF characteristics of the CPW line have been measured before and after packaging. The insertion loss of a bare CPW is 0.047 dB at 2 GHz and 0.092 dB at 20 GHz. After packaging, the insertion loss of the packaged CPW is 0.091 dB at 2 GHz and 0.312 dB at 20 GHz. A leak test has been performed using both IPA (isopropyl alcohol) soaking and the He leak tester. Most of the samples show no leakage for the IPA test, and a measured leak rate of 10−8 atm cc s−1 for the He leak test. In addition, the shear strength of the package was measured to be 25–35 MPa. From the experimental results, we showed the feasibility of a low-loss RF MEMS package from dc to 20 GHz with acceptable package performances.

This paper describes a single-aperture MEMS probe and a MEMS probe array for the measurement of biological properties. We designed and fabricated the single-aperture MEMS probe using surface micromachining and verified it by measuring the permittivity of a standard liquid before introducing the MEMS probe array. The actual aperture size of the single-aperture MEMS probe is only 390 µm × 80 µm, which is very small in comparison with the conventional laser-machined coaxial probe. In order to show the feasibility of the proposed single-aperture MEMS probe for permittivity measurements, we performed in vitro measurements of 0.9% saline. Once the single-aperture probe was verified, we proposed the concept of a probe array for biological measurements and experimentally showed the suitability of the MEMS probe array for biological applications through experiments using pork. The MEMS probe array consists of five microstrip feed lines, each of which is followed by open-ended strip lines, and the permittivity measurement of each port is separately performed through the use of a conventional multiport coaxial switch (Agilent, HP 87106 C), followed by a network analyzer (HP 8510 C). Through broadband measurements of 0.9% saline and pork using the MEMS probe array, we were able to discriminate the muscle and fat of pork through just one contact by placing the MEMS probe array on the boundary of muscle and fat. This newly proposed MEMS probe array has great potential in terms of disposability, low cost, integration with planar circuits and a short detection time for biological measurements.

We developed a silicon MEMS probe for permittivity measurements using an adhesive bonding process. Only two photolithographic masks are required to fabricate the probe, which can be implemented through simple bonding processes using silicon substrates and a benzo cyclo butene (BCB) adhesive layer. Undoped silicon substrates with thicknesses of 300 ?m are used as the dielectric layers of the proposed probe. BCB layers, which have good electrical properties at high frequencies as well as adhesive properties for the bonding process, play the role of bonding materials between the two silicon substrates. The length of the probe is 30 mm, and the aperture located at the tip of the probe is 1.1 mm ? 0.62 mm. The permittivity of 0.5% saline was measured, and the results agreed with the values obtained through the Cole?Cole equation. To validate the feasibility of this probe for practical biological applications, we also performed in vivo measurements of the muscle, skin and blood of mice. Due to the simple fabrication process, the cost of the probe can be reduced in comparison with the previous micromachined probe (Kim et al 2005 J. Micromech. Microeng. 15 543?50) as well as the conventional laser machined probe. Low cost leads to disposability, which is an important factor for practical biomedical applications; and thus, coupled with the probe's capabilities of MMIC integration and CMOS compatibility, this probe has excellent potential in the field of microwave permittivity measurements.

This paper reports the first demonstration of a single crystalline silicon(SCS)-based vertical gap-tuning MEMS variable capacitor with high mechanical reliability using the SiOG (silicon-on-glass) process. The proposed variable capacitor was fabricated by silicon-based micromachining technology, and its mechanical and electrical performances were tested. By adopting SCS, which has nearly zero stresses and superior thermal characteristics as a structural material, we can improve the manufacturability, reproducibility and mechanical reliability of the fabricated devices compared with a conventional metallic variable capacitor. The variable capacitor described in this paper is fabricated on a coplanar waveguide (CPW) transmission line and the top electrode in the driving part is incorporated with a SCS actuating membrane, resulting in a highly rigid structure without structural deformations. The designed SCS variable capacitor is actuated by an electrostatic force, and the total chip size is 1.05 mm × 0.72 mm. The measured pull-in voltage was 37 V, and the RF characteristics of the fabricated SCS variable capacitor from dc to 40 GHz were measured. With and without an applied dc bias voltage, the measured S11 and S21 were changed from −15.6 to −5.1 dB, and from −0.49 to −2.3 dB at 30 GHz, respectively. The measured capacitance at the up and the down states was 30 and 140 fF, respectively, which corresponds to the capacitance ratio of 4.67. The mechanical lifetime of the fabricated variable capacitor was also measured. RF performance degradation and stiction problems were not observed, even after 108 cycles of repeated actuations.

In this paper, fully monolithic reconfigurable millimeter-wave filters are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass and band-pass filters were designed, fabricated, and tested. Three cascaded CPW-based periodic structures, with low-pass and band-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. By using the multiple-contact MEMS switches, the insertion loss can be reduced and the operating frequency ranges are extended to millimeter-waves with little increase of loss. Additionally, the number of the switching elements has been reduced and the bias-decoupling circuits are not required, resulting in a very small chip size. The measured results of the reconfigurable low-pass filter show the 3-dB cutoff frequency change from 67 to 28 GHz with very small change in the insertion loss from 0.32 to 0.27 dB. The center frequency of the reconfigurable band-pass filter is tuned from 55 to 20 GHz, and the measured 3-dB cutoff bandwidth changed from 32 to 12 GHz, while the average insertion loss changed from 1.27 to 1.61 dB. The chip size of the low-pass and band-pass filter including dc bias line is 1.2 mm /spl times/ 1.5 mm and 1.2 mm /spl times/ 4.5 mm, respectively.

We implemented a micromachined probe for the measurement of biological properties using MEMS technology, and experimentally showed the suitability of the micromachined probe in biological applications. The micromachined probe was fabricated on a silicon substrate, and to remove wave transmission through the silicon substrate, we etched the silicon substrate from beneath a lower ground and made the etched silicon surface conducting by using thermal evaporation of Cr/Au and a coating of conductive epoxy. The micromachined probe consists of a CPW and strip line between benzo cyclo butene (BCB) layers, which is known to be a material with high resistivity, low loss tangent, and low permittivity at high frequency. We measured the permittivity of a number of well-known liquids—0.5%, 0.9% and 1.3% saline, acetone, ethanol, and muscle and fat of pork—as biological samples using the micromachined probe after liquid calibration. The measured permittivity of 0.9% saline agreed well with the expected value of the Cole–Cole equation. In this paper, we first demonstrate that the micromachined probe can provide broadband measurement of measurable solid materials, such as biological samples, and also of well-known liquids at microwave frequencies. The size of the micromachined probe is 2000 µm (width) × 580 µm (thickness) × 30 000 µm (length), and the aperture size of the micromachined probe is only 650 µm × 70 µm. Therefore, we can extract the biological information from very small biological tissues and reduce radiation effects. Thus we show the feasibility of low-cost, small and portable permittivity measurement systems using a micromachined open-ended coaxial RF MEMS probe.

Broad-band analog and digital reflection-type phase shifters (RTPSs), showing constant phase shift over 1:3 bandwidth, have been developed using microelectromechanical systems (MEMS) technology. Two-unit RTPSs centered at two different frequencies have been cascaded to achieve flat phase responses over a wide frequency band. Each phase shifter uses air-gap overlay coplanar-waveguide couplers for low-loss 3-dB coupling and bridge-type MEMS capacitors for reflective terminations. The fabricated analog phase shifter shows the average insertion loss of 3.5 dB, and maximum phase error of /spl plusmn/4.9/spl deg/ from 15 to 45 GHz. The 2-bit digital RTPS shows reduced maximum phase error of /spl plusmn/2.8/spl deg/ together with a comparable insertion loss of 3.1 dB from 5 to 15 GHz. The details of the circuit design, analysis, and fabrication procedures are presented together with the measurement results. Compared with the similar constant phase shifters using semiconductor diodes and transistors, the micromachined RTPS of this study shows superior performance in terms of phase errors, insertion losses, and bandwidth.

An SU8-quartz composite photoresist has been fabricated and characterized from 1.2 to 1.4 THz; the material contains quartz particles from 0 to 50 wt%. The composite can reduce the inherent losses of SU8 photoresist at terahertz frequencies. Calculated and measured data is presented and compared with SU8 without quartz inclusions. The results show a reduction in losses and an increase in permittivity in the composite material as the density of quartz particles increases. This initial experiment proves the possibility of modifying the electrical parameters of SU8; increasing the quartz density of the composite will modify these parameters further at THz frequencies. (c) 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2329-2330, 2016

This paper presents a new type of antenna fabricated by micromachining technology for mechanical beam steering with two degrees of freedom of motion. A V-band two-dimensional mechanical beam-steering antenna was designed and fabricated on a single high-resistivity silicon substrate using microelectromechanical systems technologies. A fabricated antenna is driven by magnetic force to overcome the limit of electrostatic actuation, and a polymer-based hinge structure is used to increase the maximum scanning angle to as much as 40/spl deg/. Simulation result for validating the mechanical beam-steering concept is presented. In addition, mechanical properties such as static actuation angles are investigated together with microwave properties such as the return loss and radiation pattern at the V-band.

Low-loss digital distributed phase shifters have been developed using micromachined capacitive shunt switches for V-band applications. Instead or conventional metal-insulator-metal capacitors, high-Q metal-air-metal capacitors were used in series with the microelectromechanical system (MEMS) shunt capacitive switches to minimize the dielectric loss. The operation voltage for the phase shifters was also reduced by applying the bias directly to the MEMS shunt switches through choke spiral inductors. Fabricated 2-b (270/spl deg/) and 4-b (337.5/spl deg/) distributed phase shifters showed low average insertion losses of 2.2 dB at 60 GHz and 2.8 dB at 65 GHz, respectively. The average phase errors for 2-b and 4-b phase shifters were 6.5% and 1.3%, respectively. The return losses are better than 10 dB over a wide frequency range from 40 to 70 GHz. Most of the circuits operated at 15-35-V bias voltages. These phase shifters present promising solution to low-loss integrated phase shifting devices at the V-band and above.

This paper presents a novel 4-bit reconfigurable discriminator for frequency measurement, operating from 1 to 4 GHz. The discriminator is a two-port device used to identify the frequency of an unknown signal by switching between its 4 states. The device is formed by a fixed reference line and a switchable delay line. The device is implemented using microstrip lines and PIN diodes. Simulated and measured results are presented for the four states of the reconfigurable discriminator.

In this paper, a new type of reconfigurable inductor is proposed for mm-waves based on the reconfiguration of slow-wave coplanar waveguide (CPW) lines using multiple-contact switches. It is then employed together with micro-electro-mechanical systems (MEMS) capacitive shunt switches to realize a reconfigurable low-pass filter, where the values of both inductors and capacitors are changed independently to achieve optimum filter characteristics. The measured 3-dB cut-off frequency of the reconfigurable low-pass filter changes from 53 GHz to 20 GHz while maintaining Tchebycheff low-pass prototype characteristics. The out-of-band rejection characteristics are also improved in this way. To our knowledge, this is among the first demonstrations that both types of MEMS contact switches and capacitive switches are used simultaneously to construct a monolithic tunable filter with independent L/C controlling capability.

A high-performance reconfigurable low-pass filter based on the quasifractal self-similar structures has been developed at millimeter-waves using multiple-contact MEMS switches. Three-cell cascaded low-pass structure was reconfigured to one-cell low-pass counterpart by activating the micromachined switches to achieve 3:1 frequency scaling. Two types of special multiple-contact MEMS switches were developed to reduce the number of switching elements as well as to reduce the insertion loss and, thus, extend the operating frequencies to mm-waves. In addition, bias-decoupling circuits were eliminated, resulting in a small chip size of 1.2 mm /spl times/ 1.5 mm. The measured 3-dB cut-off frequency of the reconfigurable low-pass filter changed from 67 GHz to 28 GHz with minor change in the insertion loss from 0.32 dB to 0.27 dB. This work demonstrates the possibility of high-performance compact-size reconfigurable filters at mm-waves using multiple-contact micromachined switches.

This work presents a novel fabrication method for {111} dual mirror and optical bench using double-sided anisotropic wet etching of oriented silicon wafer. The roughness of the wet etched {111} plane is 8 nm.

This paper suggests a complete solution for thermal isolation which hinders a stable fabrication of silicon micro-structures with a large proof mass and long springs when the device is released using silicon deep etching process. Comprehensive analysis on a thermal equivalent circuit and the implementation of thin metal layers have successfully reduced a temperature rise down to 6.16 °C whereas conventional fabrication method shows 217 °C temperature rise in simulation. The reduction of the temperature rise leads to an improved spring width of 34.2 μm (20 μm without the metal layer) in case of the designed width of 40 μm. As a result, the resonant frequency of a proposed model is improved to 678 Hz while a reference model shows 439 Hz, where the simulated frequency of design is 754 Hz.

This paper describes design guidance for a compensation method of spring width loss during silicon deep RIE (reactive ion etch) process. We found that a compensation factor (CF), defined by circumference (C) of unit etch hole divided by its area (A), is directly related to the variation of resonant frequencies of silicon MEMS resonators. We proposed 5 models with different etch hole shapes and investigated the effect of etch holes on resonant frequencies. The model with proposed etch holes showed three fold smaller variation of resonant frequencies than other models with conventional etch holes.

We firstly propose the concept of a frequency agile electromagnetic decoupling MEMS-based device. We experimentally show the feasibility of such an apparatus, and further work consists in cascading more than one decoupling device to achieve stronger electromagnetic decoupling values. The structure consists of a freestanding half-wavelength resonator mounted on a movable shuttle connected with large displacement comb actuators. The lateral movement of the shuttle over the main transmission line produces different electromagnetic decoupling values with a variable center frequency. The freestanding resonator plays the role of a loading capacitor as well as the decoupling mechanism in the proposed structure. The device is able to produce diverse decoupling and center frequency effects depending on the overlapping region between the main line and the movable shuttle.

This paper reports on a micromachined planar type probe based on a novel hybrid shielded stripline. The proposed structure is for a broadband transverse electromagnetic (TEM) single-mode propagation using substrate integrated waveguide (SIW) and conventional shielded stripline. We suggested a novel probe structure that composed of half-SIW and half-shielded stripline, which combined through a benzocyclobutene (BCB) bonding layer. The structural concept and simple fabrication method has been introduced, and the S11 in air was measured from 0.5 GHz to 30 GHz. The permittivity measurement of 0.9 % saline has been performed to validate the proposed structure at frequencies from 0.5 GHz to 20 GHz.