Minimum Actuation Voltage Research Articles

Characterization of Inkjet-Printed Digital Microfluidics Devices.

Digital microfluidics (DMF) devices enable precise manipulation of small liquid volumes in point-of-care testing. A printed circuit board (PCB) substrate is commonly utilized to build DMF devices. However, inkjet printing can be used to fabricate DMF circuits, providing a less expensive alternative to PCB-based DMF designs while enabling more rapid design iteration cycles. We demonstrate the cleanroom-free fabrication process of a low-cost inkjet-printed DMF circuit. We compare Kapton and polymethyl methacrylate (PMMA) as dielectric coatings by measuring the minimal droplet actuation voltage for a range of actuation frequencies. A minimum actuation voltage of 5.6 V was required for droplet movement with the PMMA layer thickness of 0.2 μm and a hydrophobic layer of 0.17 μm. Significant issues with PMMA dielectric breakdown were observed at actuation voltages above 10 V. In comparison, devices that utilized Kapton were found to be more robust, even at an actuation voltage up to 100 V.

Optimization of the dielectric layer for electrowetting on dielectric

In this work the minimum actuation voltage Vmin for droplet actuation with electrowetting on dielectric (EWOD) is analyzed. At first, the theoretical background of drop transport with EWOD is shown. Then the impact of thin dielectric films deposited with atomic layer deposition (ALD) and super-hydrophobic layers on the minimum required actuation voltage for drop transport are presented. To this, contact angles are measured on both Al2O3 and fluorinated DLC each with a drop of water. For verify the hypothesis, the analytically calculated values for the minimum actuation voltage Vmin are compared with numerical simulation results using COMSOL Multiphysics®. The results show that the actuation voltage value from the simulation is lower than calculated analytically.

Design and Optimization of AlN based RF MEMS Switches

Radio frequency microelectromechanical system (RF MEMS) switch technology might have potential to replace the semiconductor technology in future communication systems as well as communication satellites, wireless and mobile phones. This study is to explore the possibilities of RF MEMS switch design and optimization with aluminium nitride (AlN) thin film as the piezoelectric actuation material. Achieving low actuation voltage and high contact force with optimal geometry using the principle of piezoelectric effect is the main motivation for this research. Analytical and numerical modelling of single beam type RF MEMS switch used to analyse the design parameters and optimize them for the minimum actuation voltage and high contact force. An analytical model using isotropic AlN material properties used to obtain the optimal parameters. The optimized geometry of the device length, width and thickness are 2000 µm, 500 µm and 0.6 µm respectively obtained for the single beam RF MEMS switch. Low actuation voltage and high contact force with optimal geometry are less than 2 Vand 100 µN obtained by analytical analysis. Additionally, the single beam RF MEMS switch are optimized and validated by comparing the analytical and finite element modelling (FEM) analysis.

The mechanism for large-volume fluid pumping via reversible snap-through of dielectric elastomer

Giant deformation of dielectric elastomers (DEs) via electromechanical instability (or the “snap-through” phenomenon) is a promising mechanism for large-volume fluid pumping. Snap-through of a DE membrane coupled with compressible air has been previously investigated. However, the physics behind reversible snap-through of a DE diaphragm coupled with incompressible fluid for the purpose of fluid pumping has not been well investigated, and the conditions required for reversible snap-through in a hydraulic system are unknown. In this study, we have proposed a concept for large-volume fluid pumping by harnessing reversible snap-through of the dielectric elastomer. The occurrence of snap-through was theoretically modeled and experimentally verified. Both the theoretical and experimental pressure-volume curves of the DE membrane under different actuation voltages were used to design the work loop of the pump, and the theoretical work loop agreed with the experimental work loop. Furthermore, the feasibility of reversible snap-through was experimentally verified, and specific conditions were found necessary for this to occur, such as a minimum actuation voltage, an optimal range of hydraulic pressure exerted on the DE membrane and a suitable actuation frequency. Under optimal working conditions, we demonstrated a pumping volume of up to 110 ml per cycle, which was significantly larger than that without snap-through. Furthermore, we have achieved fluid pumping from a region of low pressure to another region of high pressure. Findings of this study would be useful for real world applications such as the blood pump.

Screen‐printed mechanical switch based on stretchable PU‐foam film

A screen-printed mechanical switch based on an electrode structure on stretchable polyurethane (PU)-foam film, Platilon U 4021, combined with a piezoelectric actuator, Smart Material MFC M-4010-P1, is proposed. The minimum actuation voltage of the prepared component is 300 V. The measured resistance was 2 Ω while closed and >0.5 TΩ when open. The electrode structure endured on average of up to 15.5 M cycles with movement ≥100 times greater than the ≤1 µm required for actuation. The results suggest that the switch could be advantageous for various e-textile applications.

Improving the performance of electrowetting on dielectric microfluidics using piezoelectric top plate control

An intelligent EWOD top plate control system is proposed in this study. The dynamic top plate is controlled by a piezoelectric (PZT) cantilever structure. A High resolution laser displacement sensor is used to monitor the deflection of the top plate. The gap height optimization and the top plate vibration significantly improve the droplet velocity and decrease the droplet minimum threshold actuation voltage. The top plate vibration induced actuation velocity improvement is magnitude and frequency dependent. 100μm and 200μm vibrations are tested at 25Hz. Vibration frequencies at 5Hz, 10Hz, and 20Hz are tested while the magnitude is 200μm. Results show greater improvements are achieved at larger vibration magnitudes and higher vibration frequencies. With a vibrated top plate, the largest reduction of the actuation voltage is 76VRMS for a 2.0μl DI water droplet. The maximum droplet instantaneous velocity is around 9.3mm/s, which is almost 3 times faster than the droplet velocity without top plate vibration under insufficient driving voltages. Liquid that has different hysteresis such as acetonitrile with various concentrations are used as a control to show its compatibility with the proposed DMF chip. Contact line depinning under top plate vibration is observed, which indicates the underlying mechanism for the improvements in actuation velocity and threshold voltage. The top plate control technique reported in this study makes EWOD DMF chips more reliable when used for the clinical point-of-care diagnostic applications.

Design and development of a surface micro-machined push–pull-type true-time-delay phase shifter on an alumina substrate for Ka-band T/R module application

A radio frequency micro-electro-mechanical system (RF-MEMS) phase shifter based on the distributed MEMS transmission line (DMTL) concept towards maximum achievable phase shift with low actuation voltage with good figure of merit (FOM) is presented in this paper. This surface micro-machined analog DMTL phase shifter demonstrates low power consumption for implementation in a Ka-band transmit/receive (T/R) module. The push–pull-type switch has been designed and optimized with an analytical method and validated with simulation, which is the fundamental building block of the design of a true-time-delay phase shifter. Change in phase has been designed and optimized in push and pull states with reference to the up-state performance of the phase shifter. The working principle of this push–pull-type DMTL phase shifter has been comprehensively worked out. A thorough detail of the design and performance analysis of the phase shifter has been carried out with various structural parameters using commercially available simulation tools with reference to a change in phase shift and has been verified using a system level simulation. The phase shifter is fabricated on the alumina substrate, using a suspended gold bridge membrane with a surface micromachining process. Asymmetric behaviour of push–pull bridge configuration has been noted and a corresponding effect on mechanical, electrical and RF performances has been extensively investigated. It is demonstrated 114° dB−1 FOM over 0–40 GHz band, which is the highest achievable FOM from a unit cell on an alumina substrate reported so far. A complete phase shifter contributes to a continuous differential phase shift of 0°–360° over 0–40 GHz band with a minimum actuation voltage of 8.1 V which is the highest achievable phase shift with the lowest actuation voltage as per till date on the alumina substrate with good repeatability and return loss better than 11.5 dB over 0–40 GHz band.

Development of a PZT MEMS Switch Architecture for Low-Power Digital Applications

A lead zirconate titanate (PZT) microelectromechanical systems (MEMS) digital switch was designed as a low-power low-frequency control system intended to create energy-efficient microcontrollers, control higher voltage systems, and provide integrated control over other MEMS platforms. In addition, the technology is inherently insensitive to high energy radiation and has been shown to operate over a wide range of temperatures. Initial devices were fabricated with three design variables of interest-actuator length, width, and contact metallurgy (Au/Pt, Au/Ru, and Au/Au). To assess the impact of each variable on device performance, device wafers were measured using a SUSS semiautomated probe station and associated control hardware and software. Devices were evaluated based on contact resistance, actuation voltage, minimum actuation voltage using a voltage bias, propagation delay, dynamic power, and static power consumption. The measurements were then analyzed to determine the optimal switch geometry and contact material combination for digital applications. With the data collected, a software model was developed for accurate simulation of higher complexity circuits composed of these switches.

Effects of gap height, applied frequency, and fluid conductivity on minimum actuation voltage of electrowetting-on-dielectric and liquid dielectrophoresis

The effects of gap height, applied frequency, and fluid conductivity on the minimum actuation voltage of liquid dielectrophoresis (LDEP) and electrowetting on dielectric (EWOD) on two-plate devices are investigated. Gap heights ranging from 17 to 31 μm, electrical fluid conductivities of water of 10 −3 and 10 −4 S/m, and applied frequencies of 1, 10, and 100 kHz were used in the experiments. An electromechanical model with the modulus of the relative permittivity of water is derived to explain gap height, frequency, and conductivity effects on the minimum actuation voltage of EWOD and LDEP.

A novel low cost spring-less RF MEMS switch prototype

This work reports on the fabrication process and measurements of a novel radio frequency microelectromechanical system (RF MEMS) capacitive shunt switch prototype with a mechanically unconstrained armature. The prototype is fabricated in a low cost process based on a printed circuit board (PCB) bonded to a glass slide. The minimum actuation voltage (Vact) of the prototype is 93 V, with a switching time taken from the down to up state (Trise) and from the up to down state (Tfall) of 105 ms and 26 ms respectively.

Droplet creation using liquid dielectrophoresis

Dielectrophoresis (DEP) is defined as polarizable particles moving into regions of higher electric field intensity. In liquid DEP (LDEP), a dielectric liquid tends to flow toward regions of high electric field intensity under a non-uniform electric field. This work presents a theoretical model of LDEP based on parallel electrodes. The LDEP force is derived using the lump parameter electromechanical method. The relationship between the minimum actuation voltage and the electrode width is investigated experimentally and theoretically. We also propose a method for creating a 20 nl droplet of deionized water using LDEP. The creation of a water droplet containing 15 μm polystyrene beads is placed at the desired location from a continuous flow driven by LDEP using the developed method.

A stiff and flat membrane operated DC contact type RF MEMS switch with low actuation voltage

RF MEMS switches can be divided into electrostatic, magnetic, thermal, and piezoelectric types by their actuation mechanisms. Most research has focused on the electrostatic actuation types because of these types low power consumption, simple fabrication method, and good RF characteristics. However, these types of switches operate at high voltages compared with the other types. One of the main problems that affect the operation voltages is the bending of the membrane due to an internal stress gradient. To solve this problem, a thick and stiff membrane operated RF MEMS switch has been developed and is presented in this paper. This membrane consists of a flexible spring for an up-down actuation mode at low voltage and a pivot under the membrane for a seesaw mode on-off switch operation. This novel RF MEMS switch has been fabricated, and its RF characteristics measured. The minimum actuation voltage is approximately 10–12 V, the isolation approximately −50 dB, and the insertion loss is approximately −0.25 dB at 2 GHz, respectively.The bending range of the membrane has been measured by using an optical 3D profiler and the height is within 0.2 μm across the 800 μm length membrane. This bending range is uniform across all samples of an entire 4 in. wafer.

Robust Design of RF-MEMS Cantilever Switches Using Contact Physics Modeling

This paper presents the robust design optimization of an RF-MEMS direct contact cantilever switch for minimum actuation voltage and opening time, and maximum power handling capability. The design variables are the length and thickness of the entire cantilever, the widths of the sections of the cantilever, and the dimple size. The actuation voltage is obtained using a 3-D structural-electrostatic finite-element method (FEM) model, and the opening time is obtained using the same FEM model and the experimental model of adhesion at the contact surfaces developed in our previous work. The model accounts for an unpredictable variance in the contact resistance resulting from the micromachining process for the estimation of the power handling. This is achieved by taking the ratio of the root mean square power of the RF current (ldquosignalrdquo) passing through the switch to the contact temperature (ldquonoiserdquo) resulting from the possible range of the contact resistance. The resulting robust optimization problem is solved using a Strength Pareto Evolutionary Algorithm, to obtain design alternatives exhibiting different tradeoffs among the three objectives. The results show that there exists substantial room for improved designs of RF-MEMS direct-contact switches. It also provides a better understanding of the key factors contributing to the performances of RF-MEMS switches. Most importantly, it provides guidance for further improvements of RF-MEMS switches that exploit complex multiphysics phenomena.

Thick membrane operated rf microelectromechanical system switch with low actuation voltage

Most researcher who have studied the radio frequency (rf) microelectromechanical system (MEMS) switch has focused on the electrostatic actuation types switch because of this type’s low power consumption, simple fabrication method, and good rf characteristics compared to magnetic, thermal, and piezoelectric driving method. However, most of electrostatic actuation type switch needs high operation voltage compared to other types. One of the reasons that affect the high operation voltage is the bending of the membrane because of an internal stress gradient. This bending increases the gap between electrode and membrane. To solve this problem, the authors developed the thick membrane operated seesaw type rf MEMS switch. This membrane consisted of a pivot under single crystal thick silicon membrane for a seesaw mode operation and a flexible spring for an up-down actuation mode. After the fabrication of this switch, the authors measured its rf characteristics. The minimum actuation voltage was about 12V, the isol...

A low actuation voltage electrostatic actuator for RF MEMS switch applications

This paper presents the design, fabrication and characterization of an RF MEMS switch. Low actuation voltage and high isolation of the switch were achieved by exploiting buckling and bending effects induced by well-controlled residual stress. The effects of residual stress on improving the switch performance have been investigated using both analytical and numerical methods. The proposed RF switch has been fabricated by surface micromachining. The minimum actuation voltage of the fabricated switch was measured to be 10.2 V. At a 5 GHz signal frequency, the measured insertion loss and isolation are 0.21 dB and −44 dB, respectively. These results demonstrate that low voltage and high isolation of RF MEMS switches can be achieved with proper utilization of residual stresses.

Actuation potentials and capillary forces in electrowetting based microsystems

The minimum and maximum actuation voltages in electrowetting actuated microsystems are investigated in this paper. The minimum actuation voltage corresponds to the electric potential required to obtain motion of a droplet between two electrodes. Below this threshold, a droplet cannot be displaced due to contact angle hysteresis. The maximum actuation voltage corresponds to the electric potential above which there is no more gain in capillary forces because of the saturation effect. Based on the calculation of the electrocapillary forces on a drop in an EWOD system, and taking into account the contact angle hysteresis, an analytical relation is derived for the minimum actuation potential. On the other hand, the Peykov–Quinn–Ralston–Sedev model produces an approximate value of the maximum actuation voltage. Thus, a range of actuation potentials can be predicted depending on the liquid of the droplet, the surrounding gas or fluid and the nature of the solid substrate. The results of the two models are favorably compared with experimental results obtained using different liquids and substrates.