Design of a large-range rotary microgripper with freeform geometries using a genetic algorithm

This paper describes a novel electrostatically actuated microgripper with freeform geometries designed by a genetic algorithm. This new semiautomated design methodology is capable of designing near-optimal MEMS devices that are robust to fabrication tolerances. The use of freeform geometries designed by a genetic algorithm significantly improves the performance of the microgripper. An experiment shows that the designed microgripper has a large displacement (91.5 μm) with a low actuation voltage (47.5 V), which agrees well with the theory. The microgripper has a large actuation displacement and can handle micro-objects with a size from 10 to 100 μm. A grasping experiment on human hair with a diameter of 77 μm was performed to prove the functionality of the gripper. The result confirmed the superior performance of the new design methodology enabling freeform geometries. This design method can also be extended to the design of many other MEMS devices.

Design and Fabrication of a Ka Band RF MEMS Switch with High Capacitance Ratio and Low Actuation Voltage

In this paper a high capacitance ratio and low actuation voltage RF MEMS switch is designed and fabricated for Ka band RF front-ends application. The metal-insulator-metal (MIM) capacitors is employed on a signal line to improve the capacitance ratio, which will not degrade the switch reliability. To reduce the actuation voltage, a low spring constant bending folding beam and bilateral drop-down electrodes are designed in the MEMS switch. The paper analyzes the switch pull-in model and deduces the elastic coefficient calculation equation, which is consistent with the simulation results. The measured results indicated that, for the proposed MEMS switch with a gap of 2 μm, the insertion loss is better than −0.5 dB and the isolation is more than −20 dB from 25 to 35 GHz with an actuation voltage of 15.8 V. From the fitted results, the up-state capacitance is 6.5 fF, down-state capacitance is 4.3 pF, and capacitance ratios is 162. Compared with traditional MEMS capacitive switches with dielectric material Si3N4, the proposed MEMS switch exhibits high on/off capacitance ratios of 162 and low actuation voltage.

Novel ionic bioartificial muscles based on ionically crosslinked multi-walled carbon nanotubes-mediated bacterial cellulose membranes and PEDOT:PSS electrodes

High-performance bioartificial muscles with low-cost, large bending deformation, low actuation voltage, and fast response time have drawn extensive attention as the development of human-friendly electronics in recent years. Here, we report a high-performance ionic bioartificial muscle based on the bacterial cellulose (BC)/ionic liquid (IL)/multi-walled carbon nanotubes (MWCNT) nanocomposite membrane and PEDOT:PSS electrode. The developed ionic actuator exhibits excellent electro-chemo-mechanical properties, which are ascribed to its high ionic conductivity, large specific capacitance, and ionically crosslinked structure resulting from the strong ionic interaction and physical crosslinking among BC, IL, and MWCNT. In particular, the proposed BC-IL-MWCNT (0.10 wt%) nanocomposite exhibited significant increments of Young's modulus up to 75% and specific capacitance up to 77%, leading to 2.5 times larger bending deformation than that of the BC-IL actuator. More interestingly, bioinspired applications containing artificial soft robotic finger and grapple robot were successfully demonstrated based on high-performance BC-IL-MWCNT actuator with excellent sensitivity and controllability. Thus, the newly proposed BC-IL-MWCNT bioartificial muscle will offer a viable pathway for developing next-generation artificial muscles, soft robotics, wearable electronic products, flexible tactile devices, and biomedical instruments.

A seesaw-type MEMS switch with enhanced contact force: the first results

Outstanding working characteristics make microelectromechanical systems (MEMS) switches attractive for many applications. However, the lack of reliability prevents their commercial success. Due to the small size, MEMS switches develop low contact force compared to their macroscopic counterparts, which leads to instability and fast increase of the contact resistance. This work describes the switch providing significantly larger force than the previously reported device. The enlargement is achieved by the modified shape of the beam and electrodes with the same footprint and lower actuation voltage. Design, simulation, fabrication and first experimental results for the switch are presented.

Design, Evaluation and Analysis of a Novel H-Shaped Capacitive RF MEMS Switch

In this paper, absolute evaluation of Radio Frequency Micro Electromechanical System (RF MEMS) to improve parameters like high actuation voltage and low switching time, by introducing a new fixed - fixed RF MEMS capacitive switch. The proposed switch designed step-by-step evaluation of the plane beam, a novel structure of beam, and deposit the perforations and meanders to reducethe pull-in voltage. All the RF MEMS switch design parameters arestudy using the COMSOL Multiphysics FEM (Finite Element Model) tool. The proposed RF MEMS switch express low pull-in voltageof 4.75V and good return, insertion, and isolation losses in both upstate and downstate conditions are >10dB, below 0.1dB and 60dB, respectively. The dielectric layer as silicon nitride (Si3N4), beam as a gold material. The RLC values are extracted by using lumped model design. The RF MEMS shunt switch (capacitance, inductance, and resistance) of the MEMS bridge are accurately evaluated from the S-parameter analysis. The computational and simulated results are good agreement with each other, which indicates the validity of the proposed switch for K (18-26) GHz band applications.

Effectiveness of line type and cross type piezoelectric patches on active vibration control of a flexible rectangular plate

In the present work, vibration control of a simply supported plate with line type and cross type piezoelectric (PZT) patches are investigated with and without actuation voltage. The plate is modeled under the assumption of Kirchhoff’s Plate theory. The mass of PZT patches remain constant in all cases. In case of actuation, applied voltage considered are 1, 2 and 3 mV. The external excitation to the plate is in the form of harmonically varying point load of 1 mN. It is noticed that cross type PZT patch is more effective in deflection suppression of plate than that of line type PZT patch at 3 mV of actuation at patch thickness of 0.75 μm. Suppression of central deflection of plate for line type and cross type PZT patches are obtained in different frequency bands of (175–185 Hz) and (870–880 Hz) respectively.

Low-Voltage and High-Reliability RF MEMS Switch with Combined Electrothermal and Electrostatic Actuation

In this paper, we report a novel laterally actuated Radio Frequency (RF) Microelectromechanical Systems (MEMS) switch, which is based on a combination of electrothermal actuation and electrostatic latching hold. The switch takes the advantages of both actuation mechanisms: large actuation force, low actuation voltage, and high reliability of the thermal actuation for initial movement; and low power consumption of the electrostatic actuation for holding the switch in position in ON state. The switch with an initial switch gap of 7 µm has an electrothermal actuation voltage of 7 V and an electrostatic holding voltage of 21 V. The switch achieves superior RF performances: the measured insertion loss is −0.73 dB at 6 GHz, whereas the isolation is −46 dB at 6 GHz. In addition, the switch shows high reliability and power handling capability: the switch can operate up to 10 million cycles without failure with 1 W power applied to its signal line.

A MEMS Tunable Capacitor With Dual Deformation Modes and High Tunability and Linearity

MEMS tunable capacitors have applications in tunable filters and RF circuits where high tunability and Q-factor are desired. Conventional parallel-plate tunable capacitors have a highly nonlinear capacitance-voltage (C-V) response and limited tunability of up to 50% due to fundamental limitation and structural instability. In this work, we present a novel design idea for a parallel-plate tunable capacitor that increases the tuning ratio and provides a smoother (more linear) response. The design uses two modes of deformation, rigid-body displacement of a curved moving electrode before pull-in and deforming the plate after pull-in, and exploits nonlinear structural stiffness to improve the linearity (and the tunability) of the tunable parallel-plate capacitor. The capacitor structure is designed such that when actuation voltage is applied, first the beams holding the moving electrode deform, and capacitance increase similar to conventional design up to pull-in. After the pull-in, the top electrode (which has a curved geometry) is deformed and further increases the capacitance, as the voltage increases. The design may provide an overall simulated tunability of more than 380%, and also has a more linear C-V response. The design is modeled and simulated using ANSYS coupled-field multiphysics solver and the effect of different design parameters are investigated. The simulation results show much high tunability and better linearity than conventional parallel-plate capacitors.

Design and Simulation of Capacitive MEMS Switch for Ka Band Application

In this paper, RF MEMS switch with capacitive contact is designed and analyzed for Ka band application. A fixed-fixed beam/meander configuration has been used to design the switch for frequency band 10 GHz to 40 GHz. Electromagnetic and electromechanical analysis of three-dimensional (3D) structure/design has been analyzed in multiple finite element method (FEM) based full-wave simulator (Coventorware and high-frequency structure simulator). A comparative study has also been carried out in this work. The high resistivity silicon substrate ( tan δ = 0.010 , ρ > 8 k Ω − cm , ε r = 11.8 ) with a thickness of 675 ± 25 μ m has been taken for switch realization. The designed structure shows an actuation voltage of around 9.2 V. Impedance matching for the switch structure is well below 20 dB, loss in upstate, i.e., insertion loss >0.5 dB, and isolation of >25 dB throughout the frequency band is observed for the aforesaid structure. Furthermore, to increase the RF parameters, AIN dielectric material has been used instead of SiO2 resulting in capacitance in downstate that increases hence improved the isolation. The proposed switch can be utilized in various potential applications such as any switching/tunable networks phased-array radar, reconfigurable antenna, RF phase shifter, mixer, biomedical, filter, and any transmitter/receiver (T/R) modules.