V-shaped Electrothermal Actuators Research Articles

Design and numerical performance analysis of a microgravity accelerometer with quasi-zero stiffness

We report a nonlinear electrothermal-loaded accelerometer for microgravity measurement, achieving quasi-zero stiffness nearby its static equilibrium position. The high mechanical sensitivity is attributed to the compression of the spring, in addition to the geometric parameters matched with quasi-zero stiffness characteristic. To make the spring compressed effectively, a V-shape electrothermal actuator was adopted in the design. The FEA results in multiphysics clearly show the different performance of the accelerometer when it is at applied voltage or not, verifying that the electrothermal-loaded mechanism has an effective influence on the sensitivity of accelerometer. At the applied voltage of 22.3 V, the natural frequency of the accelerometer decreases from 501.95 Hz to 8.24 Hz, while the other two higher mode frequencies remain above 500 Hz. In addition, this mechanism realizes a quasi-zero stiffness approximately of 0.007 N m−1 within a linear working range of ±400 μg and the stiffness becomes larger beyond this range protecting the device being overloaded.

Design and research on large displacement bidirectional MEMS stage with interlock mechanism

The design, fabrication and characterization of a large displacement bidirectional MEMS stage is presented in this paper. The V-shape electro-thermal actuator, micro lever, pawl and slider are investigated respectively. With 11 V driven voltages, these basic components can generate 15 mN output force and realize pulling, disengaging and reengaging to move the stage forward and backward smoothly (1 mm displacement in bi-direction). The rack and interlock mechanism formed by the pawl and slider make the device to have the features of linear output displacement, low power consumption, input signal recognition and displacement sustaining. SOI wafer is introduced in the fabrication process, and the 1.2 × 3.5 mm2 movable plate can be actuated successfully.

Electrothermally actuated tunable clamped-guided resonant microbeams

Abstract We present simulation and experimental investigation demonstrating active alteration of the resonant and frequency response behavior of resonators by controlling the electrothermal actuation method on their anchors. In-plane clamped-guided arch and straight microbeams resonators are designed and fabricated with V-shaped electrothermal actuators on their anchors. These anchors not only offer various electrothermal actuation options, but also serve as various mechanical stiffness elements that affect the operating resonance frequency of the structures. We have shown that for an arch, the first mode resonance frequency can be increased up to 50% of its initial value. For a straight beam, we have shown that before buckling, the resonance frequency decreases to very low values and after buckling, it increases up to twice of its initial value. These results can be promising for the realization of different wide–range tunable microresonator. The experimental results have been compared to multi-physics finite-element simulations showing good agreement among them.

Design of a high‐speed electrothermal linear micromotor for microelectromechanical systems safety‐and‐arming devices

The design, fabrication and characterisation of a high-speed electrothermal linear micromotor for microelectromechanical systems safety-and-arming devices are presented. The micromotor consists of a microspring, a barrier plate and four V-shaped electrothermal actuators with microlever amplifications. The whole device is fabricated on a silicon-on-insulator wafer with a 50 µm device layer and the fabrication process is introduced. The micromotor has been successfully operated at a speed of 35.66 mm/s over a range of 500 µm with an output force of 5.27 mN under the applied voltage of 23 V. The chip area of the fabricated micromotor is about 19.20 mm2, which means the micromotor can be easily integrated with other microdevices. The linear micromotor performs well in driving force, mechanical strength and working speed, which signifies the proposed device is suitable for safety-and-arming devices.

Design, numerical simulation and experimental investigation of an SU-8 microgripper based on the cascaded V-shaped electrothermal actuators

This paper presents the numerical simulation results and the experimental investigations of a polymeric microgripper designed using the cascaded V-shaped electrothermal actuators. The microgripper was simulated using electro-thermo-mechanical finite element method (FEM) based on Coventorware 2014 software in order to check the performance of the gripper. As structural material of the microgripper, the SU-8 biocompatible polymer was used during the fabrication process. The metallic micro-heaters were encapsulated in the polymeric actuation structures of the microgrippers to reduce the undesirable out-of-plane displacement of the gripper tips, to reduce the mechanical stress and to improve the thermal efficiency. Experimental testing has been performed to determine the openings of the microgripper tips as function of electrical current. A displacement of the tips of more than 50 pm can be obtained at an electrical current of around 25-26 mA. Over 27-28 mA the heaters are still working but a softening and a damaging status in the polymer were observed.

Design and characterization of a microelectromechanical system electro-thermal linear motor with interlock mechanism for micro manipulators.

The design, fabrication, and testing of a novel electro-thermal linear motor for micro manipulators is presented in this paper. The V-shape electro-thermal actuator arrays, micro lever, micro spring, and slider are introduced. In moving operation, the linear motor can move nearly 1 mm displacement with 100 μm each step while keeping the applied voltage as low as 17 V. In holding operation, the motor can stay in one particular position without consuming energy and no creep deformation is found. Actuation force of 12.7 mN indicates the high force generation capability of the device. Experiments of lifetime show that the device can wear over two million cycles of operation. A silicon-on-insulator wafer is introduced to fabricate a high aspect ratio structure and the chip size is 8.5 mm × 8.5 mm × 0.5 mm.

Control of a Novel 2-DoF MEMS Nanopositioner With Electrothermal Actuation and Sensing

This paper presents the full characterization, modeling, and control of a 2-degrees-of-freedom microelectromechanical systems (MEMS) nanopositioner with fully integrated electrothermal actuators and sensors. Made from nickel Z-shaped beams, the actuators are able to move the device's stage in positive and negative directions (contrary to classical V-shaped electrothermal actuators) and along two axes ( $x$ and $y$ ). The integrated electrothermal sensors are based on polysilicon resistors, which are heated via Joule heating due to an applied electrical bias voltage. The stage displacement is effectively measured by variations in their resistance, which is dependent on the position of the stage. The characterization tests carried out show that the MEMS nanopositioner can achieve a range of displacement in excess of ${\pm}{\rm 5}~\mu{\rm m}$ for each of the $x$ and $y$ axes, with a response time better than 300 ms. A control scheme based on the combination of feedforward and internal model control-feedback is constructed to enhance the general performance of the MEMS device, and in particular to reject the cross-coupling between the two axes and to enhance the accuracy and the response time. The experimental results demonstrate the efficiency of the proposed scheme and demonstrate the suitability of the designed device for nanopositioning applications.

Mechanical Performance of a Cascaded V-Shaped Electrothermal Actuator

The function and performance of MEMS are affected by the output ability of the displacement and force of microactuators. The lateral deflection of cascaded V-shaped electrothermal actuators is modelled as a triple, statically indeterminate problem. An iteration algorithm is set up to calculate the output displacement and typical forces in anchors. The calculated results of this model agree well with our own simulation results as well as with the experimental and calculated results in the literature, and we conclude that the model is credible. The paper also discusses the effects of the structure parameters and temperature increments on the displacement production ability. Clear differences were found between single and cascaded V-shaped electrothermal actuators. For the former, the maximum deflection takes place in a 0.04 rad beam angle, while for the latter the beam angle is 0.19 rad. For both types of actuators, the deflection is unrelated to the beam thickness. The displacement of the cascaded V-shaped electrothermal actuator is proportional to the temperature increment and beam length, but is inversely proportional to the beam width. Experiments on the output ability of cascaded V-shaped electrothermal actuators validated the calculated and simulation results.

Spatially Resolved Temperature Mapping of Electrothermal Actuators by Surface Raman Scattering

In this paper, we report spatially resolved temperature profiles along the legs of working V-shaped electrothermal (ET) actuators using a surface Raman scattering technique. The Raman probe provides nonperturbing optical data with a spatial resolution of 1.2 /spl mu/m, which is required to observe the 3-/spl mu/m-wide actuator beams. A detailed uncertainty analysis reveals that our Raman thermometry of polycrystalline silicon is performed with fidelity of /spl plusmn/10 to 11 K when the peak location of the Stokes-shifted optical phonon signature is used as an indicator of temperature. This level of uncertainty is sufficient for temperature mapping of many working thermal MEMS devices which exhibit characteristic temperature differences of several hundred Kelvins. To our knowledge, these are the first quantitative and spatially resolved temperature data available for thermal actuator structures. This new temperature data set can be used for validation of actuator thermal design models and these new results are compared with finite-difference simulations of actuator thermal performance.