Low Actuation Voltage Research Articles

Switchable diffractive optics using patterned PEDOT:PSS based electrochromic thin-films

We demonstrate switchable, thin film diffractive optical gratings and Fresnel zone plate lenses fabricated using a micro-patterned electrochromic polymer and gel electrolyte. Electrochemically switching the conductive polymer PEDOT:PSS causes the patterned layer to change between a low-absorption to high absorption state, acting as an amplitude diffractive optical element. The switchable lens and gratings were fabricated using a lithographically patterned electrochromic polymer, a gel electrolyte, and an ITO-coated glass substrate. Within an applied voltage of −1 V to 1 V, the diffraction efficiency of the switchable lens can be varied 4.1-fold between the ‘on’ and ‘off’ states. Due to their low actuation voltage and biocompatibility, electrochemically actuated diffractive optics have potential applications in low power and implantable biomedical devices.

Experimental investigation of resonant MEMS switch with ac actuation

In this letter, modeling, analysis, and experimental investigation for a resonant MEMS switch are presented. The resonant switch harnesses its mechanical resonance to lower the required actuation voltage by a substantial factor over the switch with static actuation. With alternating actuation voltage at its mechanical resonance frequency of 6.6 kHz, the average capacitance is tuned by changing the gap between fixed and movable electrodes. Based on the proposed actuation method, the device offers 57.44% lower actuation voltage compared with the switch with static actuation.

A Tunable Capacitor Based on MEMS Technology for RF Applications

A tunable capacitor based on MEMS technology is presented in this paper. The proposed structure consists of two fixed-fixed parallel movable plates with 4 supports. Movability of two plates makes it possible to actuate the plates with a small voltage. When the actuation is applied, two plates move together and their distance is decreased, hence the capacitance is increased and tuning is achieved. The structure is simulated through the finite element method using COMSOL and ANSOFT HFSS software. Simulation results show that the actuation voltage required to access the 59% tuning, is 7 V. The effective area of the designed tunable capacitor is 200 x 200 µm2 with a thickness of 2 µm. The quality factor is 91 at 11 GHz which is sufficient for various RF communication applications such as filters, transceivers and so on. The low stress induced on the plates and low actuation voltage, are the main advantages of the design.

Fabrication of an RF-MEMS-Switch on a hybrid Si-Ceramic substrate

Abstract The integration of MEMS sensors, microelectronics and RF circuits including RF-MEMS is still a challenging task but becomes crucial for the Internet of Things. A wafer-level silicon-ceramic composite substrate (called SiCer, Silicon-on-Ceramics) allows new options in smart system integration. SiCer substrates combine the benefits of two different worlds of materials. The silicon substrate is a suitable material to build active MEMS devices such as switches and resonators. The ceramic substrate, a Low Temperature Cofired Ceramic (LTCC), is well-known for RF circuit integration including resistors, capacitors and coils. Both materials are co-sintered into a monolithically composite substrate. Chemical and physical modification of the silicon interface allows a low-pressure sintering and therefore new techniques for generating buried cavities at the bond interface. A carbon paste is applied on the LTCC via screen printing. After sintering, this results in a defined cavity. To demonstrate the advantages of the buried cavities within SiCer substrates the fabrication process of a RF-MEMS switch is shown. The switch is intended for a switching matrix to select frequency bands in a mobile LTE receiver. A parallel-plate electrostatic actuation with in-plane movement has been selected. This type of switch allows a large displacement range and a low actuation voltage can be achieved.

Design and simulation of a novel RF MEMS shunt capacitive switch with low actuation voltage and high isolation

This paper presents a new RF MEMS capacitive shunt switch with low voltage, low loss and high isolation for K-band applications. In this design, we have proposed the step structure to reduce the air gap between the bridge and the signal line, thus the actuation voltage is reduced to 2.9 V. Furthermore, to reach more isolation, we used aluminum nitride (AlN) as a dielectric layer instead of conventional dielectric materials such as $$Sio_{2}$$Sio2 and $$Si_{3} N_{4}$$Si3N4 which has more $$\varepsilon_{r}$$?r led to increase the down-state capacitance and increase the isolation of switch. Moreover, to reach more isolation, a kind of meander have designed to increase the inductance of switch, therefore, the resonant frequency is shifted to the desired frequency band. The results show that the switch in up position involve $$S_{11}$$S11 less than ?10 dB from 1 to 40 GHZ and $$S_{21}$$S21 more than ?0.72 dB from 1 to 22 GHZ. In down state, switch has an excellent isolation at the frequency range of K-band. The maximum isolation of ?58 dB is obtained at resonance frequency of 27 GHZ.

Mixing enhancement by degenerate modes in electrically actuated sessile droplets

The dependence of oscillation dynamics of a sessile droplet on the actuation parameters (voltage and frequency) in AC electrowetting which leads to the manifestation of non-axisymmetric oscillation patterns were investigated through experiments and theoretical modeling. The symmetrical nature of the electrowetting force leads to a circular three phase contact line for low actuation voltages. At higher actuation voltages, despite of symmetrical actuation force the contact line showed a transition from axisymmetric to non-axisymmetric oscillations. We found a good match between the experimentally determined region in the actuation parameter space where non-axisymmetric modes are dominant and the theoretically modeled parametric instability region derived from the Mathieu equation. The results showed that these non-axisymmetric modes are degenerate sectoral modes defined by the spherical harmonic functions. In contrast to axisymmetric oscillations, for non-axisymmetric oscillations the variation of contact angle and base radius remained in-phase between successive resonant modes. Finally, mixing by these parametric oscillations was investigated and the best mixing time was approximately 2% of the diffusive mixing time.

A single-layer micromachined tunable capacitor with an electrically floating plate

This paper reports a novel micromachined tunable capacitor with an electrically floating movable plate. The device has been fabricated from a single metal layer based on a low-cost standard process. Tunable capacitors with electrically floating and non-floating plates have been characterized and compared with each other by using the same fabricated device with different configurations. The floating tunable capacitor exhibits a higher quality factor (Q-factor) compared to a non-floating capacitor by eliminating the spring’s resistance loss in radio frequency signal path. The device is actuated by an electro-thermal actuator to achieve high capacitance tuning range without the pull-in effect issue of parallel-plate electrostatic actuators. Experimental results show that the tunable capacitor has a wide capacitance tuning range of 631% with a low actuation voltage of 0.72 V. The floating tunable capacitor has a Q-factor at 1 GHz of 24.4, which is 5.5 times higher than that of a non-floating traditional tunable capacitor fabricated on the same chip.

Functionally graded carbon nanotube and nafion/silica nanofibre for electrical actuation of carbon fibre reinforced shape memory polymer

Purpose – This paper aims to study the synergistic effect of self-assembled carboxylic acid-functionalised carbon nanotube (CNT) and nafion/silica nanofibre nanopaper on the electro-activated shape memory effect (SME) and shape recovery behaviour of shape memory polymer (SMP) nanocomposite. Design/methodology/approach – Carboxylic acid-functionalised CNT and nafion/silica nanofibre are first self-assembled onto carbon fibre by means of deposition and electrospinning approaches, respectively, to form functionally graded nanopaper. The combination of carbon fibre and CNT is introduced to enable the actuation of the SME in SMP by means of Joule heating at a low electric voltage of 3.0-5.0 V. Findings – Nafion/silica nanofibre is used to improve the shape recovery behaviour and performance of the SMP for enhanced heat transfer and electrical actuation effectiveness. Low electrical voltage actuation and high electrical actuation effectiveness of 32.5 per cent in SMP has been achieved. Research limitations/implications – A simple way for fabricating electro-activated SMP nanocomposites has been developed by using functionally graded CNT and nafion/silica nanofibre nanopaper. Originality/value – The outcome of this study will help to fabricate the SMP composite with high electrical actuation effectiveness under low electrical voltage actuation.

Fabrication and characterization of MEMS cantilever array for switching applications

The electromechanical switches have been playing an important role in technology particularly in the industrial applications. Along with many components, this switch is also miniaturized and showing many interesting properties. In this work, the design and development of micro-cantilevers switch array for increasing the current handling capacity of the device for switching applications is presented. The aim is to design an array of MEMS cantilever beam switch with low actuation voltage for large current handling applications. The aluminum interconnects having current density in the endurable range is the backbone for the designed cantilever switch. These switches are arranged in parallel to split the current in multiple interconnect. The switch is fabricated and electrically tested to compare the experimental values and theoretical model. The characterization results show an increase in current handling capacity with lower actuation voltage in these switches. This switch can also be configured for multiple numbers of cantilever beams for scaling up the current capacity with low actuation voltage. Thus MEMS-based switch can be used for various power electronic circuits and applications with added advantages.

Analysis and test of a new MEMS micro-actuator

A large-deformation and low-voltage micro actuator is proposed in this paper to overcome the problems of high voltage and undersized deformation of electrostatic micro actuator. The principle of the proposed actuator is based on vertical-horizontal bending. Dynamic equations of the micro actuator under axial and horizontal loading are built based on Lagrange---Maxwell electromechanical dynamics equations. In addition, the influences of thermal stress, axial electrostatic force and squeezing force are analyzed. Furthermore, the horizontal distributed load and axial load are equivalent to horizontal centralized load based on the Runge---Kutta algorithm and finite difference method. The relationships of deformation with driving voltage, regulation voltage, and axial compression quantity and temperature difference are achieved by simulation. Simulation results show that the deformation of the proposed actuator is as high as 10.861 μm when the driving voltage is 16 V. The deformation of proposed micro actuator is larger than that of the existing one. Finally, the simulation results are verified by experiment and agree well with experiment results.

Low-voltage, High-tuning Range MEMS Variable Capacitor Using Closed-loop Control

A low-voltage, high-tuning range variable MEMS capacitor using parallel-plates electrostatic microactuators operated in close-loop is introduced in this paper. The structures were fabricated using an in-house 2-masks process on SOI wafers and the use of a closed-loop controller increases the stable displacements of the structure beyond the pull-in limitation along the full available gap (the limitation are the mechanical stoppers). Additionally, the structure has two pairs of actuators, in opposing directions, enabling bi-directional displacement leading to extended tuning range. The fabricated capacitors have a designed tuning range close to 17. A lower actuation voltage is also a main benefit for future integration on low-power devices (measured pull-in voltage of approximately 3.25V). The devices were characterized and a capacitance variation of 2.3pF was experimentally verified.

RF MEMS Perforated Shunt Switch Design on Hafnium Oxide Substrate for Low Actuation Voltage

RF MEMS Perforated Shunt Switch Design on Hafnium Oxide Substrate for Low Actuation Voltage

Nonlinear Model Predictive Control for Thermal Management in Plug-in Hybrid Electric Vehicles

A nonlinear model predictive control (NMPC) for the thermal management (TM) of plug-in hybrid electric vehicles (PHEVs) is presented. TM in PHEVs is crucial to ensure high components’ performance and durability in all possible climate scenarios. A drawback of accurate TM solutions is the higher electrical consumption due to the increasing number of low-voltage actuators used in the cooling circuits. Hence, more complex control strategies are needed for minimizing components’ thermal stress and, at the same time, electrical consumption. In this context, NMPC proves to be a powerful method for achieving multiple objectives in multiple input multiple output systems. This paper proposes an NMPC for the TM of the high-voltage battery and the power electronics cooling circuit in a PHEV. It distinguishes itself from the previously NMPC reported methods in the automotive sector by the complexity of its controlled plant, which is highly nonlinear and controlled by numerous variables. The implemented model of the plant, which is based on experimental data and multidomain physical equations, has been validated using six different driving cycles logged in a real vehicle, obtaining a maximum error, in comparison with the real temperatures of 2 $^\circ$ C. For one of the six cycles, an NMPC software-in-the loop (SIL) is presented, where the models inside the controller and for the controlled plant are the same. This simulation is compared with the finite-state machine-based strategy performed in the real vehicle. The results show that NMPC keeps the battery at healthier temperatures and reduces the cooling electrical consumption by more than 5%. In terms of the objective function, which is an accumulated and weighted sum of the two goals, this improvement amounts to 30%. Finally, the online SIL presented in this paper suggests that the used optimizer is fast enough for a future implementation in the vehicle.

Analysis of DC-Metal Contact RF MEMS Switch with Split Beam Structure for Wireless Application

This paper presents a design of low actuation voltage radio frequency (RF) micro-electromechanical system (MEMS) switch with its Electro-Mechanical and RF characteristics simulation, as well as its virtual fabrication process. The RF MEMS switch employs a series metal contact switch on a coplanar waveguide (CPW) transmission line. The proposed switch is a single meander cantilever beam with split beam structure. The developed RF-MEMS switch has a very low Pull-in voltage of 5V and the maximum Mises stress under actuated condition is 22.8344 MPa. Its insertion loss and isolation is of -0.276 dB to -0.82 db and -79.3 dB to -77.1 dB at 8 to 12 GHz respectively. A simple four-mask process with photo resist (PR-S1800) as sacrificial layer to release the membrane is proposed in the design; and a virtual fabricated device is simulated using IntelliFab v8.7@ software.

Experimental investigation of an active twist model rotor blade with a low voltage actuation system

AbstractSmart materials that are directly embedded in the rotor blade structure are an attractive concept for active blade control. A promising approach is the use of anisotropic piezoelectric strain actuators embedded in the rotor blade skin. Especially in Europe and the US this concept has been intensively investigated over the past years. A major drawback of all configurations studied so far is the high operation voltage of up to 2,000V of state of the art piezoelectric actuators. Within the Green Rotorcraft Project of the European Joint Technology Initiative Clean Sky, a new approach with a low voltage piezoelectric actuation system is investigated to demonstrate the feasibility of this technology.A first major step in this direction was completed by conducting a centrifugal test with a model rotor blade. The objective of the centrifugal test was to demonstrate the performance of the actuation system and the structural concept under centrifugal loads by showing that the expected twist deformation can be achieved at the nominal rotation speed and different actuation frequencies.It was demonstrated that the new actuation system is capable of operating under representative centrifugal loads. In comparison to state-of-the-art actuators (operation voltage 500V to +1500V) the new actuation system (operation voltage -20V to 120V) exhibits higher active twist performance per active area.

High performance electromechanical actuators based on ionic liquid/poly(vinylidene fluoride)

Due to the increasing need of low voltage actuators, independent from electrochemical processes, electroactive actuators based on poly(vinylidene fluoride) composites with 10, 25 and 40% of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C2mim] [NTf2], ionic liquid are prepared by solvent casting and melting. We show that the charge structure of [C2mim] [NTf2] induces the complete piezoelectric β-phase crystallization of the PVDF within the composite and decreases its crystallinity fraction significantly. [C2mim] [NTf2] also works as a plasticizer of PVDF, reducing the elastic modulus down to 12% of the initial value. Moreover, the composites show significant displacement and bending under applied voltages of 2, 5 and 10 Vpp. The displacement and bending of the composite membranes are also evaluated as a function of [C2mim] [NTf2] content and sample thickness. Increasing amounts of ionic liquid result in larger deformations independently of the applied voltage.

Design and modeling of a novel RF MEMS series switch with low actuation voltage

This paper presents the design, analysis, modeling and simulation of a novel RF MEMS series switches with low actuation voltage. A mechanical modeling is presented to describe the behavior of the series switch. The switch is designed with special mechanical structures. The novel mechanical and mathematical modeling of the switch leads to calculation of the accurate actuation voltage. The spring constant has been calculated in relation to the presence of the residual stress in the beam. The calculated spring constant for this beam is used to determine the accurate actuation voltage. The size of the switch is 60 ? 110 µm2. The designed RF MEMS series switch was simulated using Intellisuite MEMS tool. He calculated actuation voltage is 4.05 V and simulated one is 4.2 V for 0.6 µm beam thickness. The calculated result is also very close with simulated one. The proposed switch compared with other electrostatic switches has low actuation voltage and small size. The RF characteristics were simulated using HFSS software and the switch has good RF performance. The insertion loss of 0.067 dB, return loss of 26 dB and isolation of 16 dB were achieved at 40 GHz.

Tubular dielectric elastomer actuator for active fluidic control

We report a novel low-profile, biomimetic dielectric elastomer tubular actuator capable of actively controlling hydraulic flow. The tubular actuator has been established as a reliable tunable valve, pinching a secondary silicone tube completely shut in the absence of a fluidic pressure bias or voltage, offering a high degree of resistance against fluidic flow, and able to open and completely remove this resistance to flow with an applied low power actuation voltage. The system demonstrates a rise in pressure of ∼3.0 kPa when the dielectric elastomer valve is in the passive, unactuated state, and there is a quadratic fall in this pressure with increasing actuation voltage, until ∼0 kPa is reached at 2.4 kV. The device is reliable for at least 2000 actuation cycles for voltages at or below 2.2 kV. Furthermore, modeling of the actuator and fluidic system yields results consistent with the observed experimental dependence of intrasystem pressure on input flow rate, actuator prestretch, and actuation voltage. To our knowledge, this is the first actuator of its type that can control fluid flow by directly actuating the walls of a tube. Potential applications may include an implantable artificial sphincter, part of a peristaltic pump, or a computerized valve for fluidic or pneumatic control.

Low-Actuation Voltage MEMS Digital-to-Analog Converter with Parylene Spring Structures.

We propose an electrostatically-actuated microelectromechanical digital-to-analog converter (M-DAC) device with low actuation voltage. The spring structures of the silicon-based M-DAC device were monolithically fabricated using parylene-C. Because the Young’s modulus of parylene-C is considerably lower than that of silicon, the electrostatic microactuators in the proposed device require much lower actuation voltages. The actuation voltage of the proposed M-DAC device is approximately 6 V, which is less than one half of the actuation voltages of a previously reported M-DAC equipped with electrostatic microactuators. The measured total displacement of the proposed three-bit M-DAC is nearly 504 nm, and the motion step is approximately 72 nm. Furthermore, we demonstrated that the M-DAC can be employed as a mirror platform with discrete displacement output for a noncontact surface profiling system.

Ultra low actuation voltage RF MEMS switch

In this brief a new low actuation voltage RF MEMS switch is presented which can be integrated and controlled with available CMOS technologies. Despite the advantages in the design of RF MEMS switches designing a low actuation voltage RF MEMS switch is still a challenging task. To overcome this problem, a small size RF MEMS switch utilizing a moving plate with multiple holes supported by a low spring constant beam is presented in this work. Experimental measurement results indicate pull-in voltage of 0.5 V and lift-off voltage of 0.3 V for 1.5 μm displacement. The measured return loss and insertion loss are better than −20 dB and −0.1 dB respectively for a frequency range extending from 3 kHz to 3GHz. The switching time is less than 0.22 ms when the switch is turned on with a CMOS buffer from TSMC-65 nm technology with 1.00 V supply voltage.