Zhuoqing Yang

Design, simulation and fabrication of a novel contact-enhanced MEMS inertial switch with a movable contact point

A novel inertial switch based on a micro-electro-mechanical system (MEMS) was designed, which consists of three main parts: a proof mass as the movable electrode, a cross beam as the stationary electrode and a movable contact point to prolong the contact time. A MATLAB/Simulink model, which had been verified by comparison with ANSYS transient simulation, was built to simulate the dynamic response, based on which the contact-enhancing mechanism was confirmed and the dependence of threshold acceleration on the proof mass thickness was studied. The simulated dynamic responses under various accelerations exhibit satisfactory device behaviors: the switch-on time is prolonged under transient acceleration; the switch-on state is more continuous than the conventional design under long lasting acceleration. The inertial micro-switch was fabricated by multilayer electroplating technology and then tested by a drop hammer experiment. The test results indicate that the contact effect was improved significantly and a steady switch-on time of over 50 µs was observed under half-sine wave acceleration with 1 ms duration, in agreement with the dynamic simulation.

A MEMS Inertia Switch With Bridge-Type Elastic Fixed Electrode for Long Duration Contact

A multilayer structural inertia microswitch with a bridge-type elastic fixed electrode for long duration contact has been designed and fabricated based on surface micromachining technology. The microswitch mainly consists of a suspended thick proof mass as a movable electrode and two parallel elastic beams with holes as a fixed electrode. The proof mass is designed to be much thicker than attached snake spring section. As a new type of fixed electrode, the bridge-type elastic beams can effectively improve the contact of the microswitch. The packaged microswitch (3.2 times 2.1 times1.3 mm3) has been tested and characterized by a dropping hammer system. The response time and the contact time of the microswitch are about 0.25 ms and 12 mus, respectively, when 100 g acceleration is applied, which indicates a better contact effect than current reported switches. Dependence of the contact time on the thickness of the parallel beam under applied acceleration of 100 g has been discussed. The contact time increases as the thickness of the parallel elastic beam decreases. The test data have an agreement with dynamic finite element simulation results.

Design, simulation and characterization of an inertia micro-switch fabricated by non-silicon surface micromachining

A multilayer structural inertia micro-switch with conjoined snake springs has been designed and successfully fabricated based on non-silicon surface micromachining technology. The micro-switch consists mainly of a suspended thick proof mass as a movable electrode that is located above the supporting layer, and an elastic beam with holes as a fixed electrode that is some distance above the proof mass. The designed proof mass is much thicker than the conjoined snake spring section. This conformation benefits the improvement of its sensitivity and the contact effect, while protecting the switch against severe shock damage from intensive impact of the switch contacts. The fabricated prototype micro-switch has been tested and characterized. The result indicates that the response time and the contact time of the micro-switch are about 0.40 ms and 12 µs, respectively, when a 100g acceleration is applied, which shows relatively better sensitivity and contact effect. This result agrees with that of dynamics finite-element contact simulation about the designed micro-switch. Besides, no severe plastic deformation occurs to springs or elastic beams after over 10 000 dropping tests in the optical profiling characterization. The fabricated micro-switch shows satisfactory mechanical behavior.

Design and fabrication of a magnetic bi-stable electromagnetic MEMS relay

This paper describes the principles, design, fabrication and performance of a new type of electromagnetic bistable MEMS relay. The microdevice is operated by a wiggling microactuator, which is symmetrically assembled with two integrated planar windings and one permanent rotor in the form of sandwich with coaxial sustained gaps between each other. The micromachined rotor moves to-and-fro around the axis and operates the joined brush to open or close external circuit. This hybrid MEMS relay has been provided with fast response and latching function owing to the special design. The response time is about 0.3ms and the maximum load current is 2A.

Development of a Novel MEMS Inertial Switch With a Compliant Stationary Electrode

A novel microelecromechnical system (MEMS) inertial switch based on the surface micromachining technology was developed, which mainly consists of a proof mass as the movable electrode and a compliant stationary electrode above the proof mass, whose deformation during the contact process would enhance the contact effect and prolong the switch-on time. Based on the original design which had already realized the enhancing effect to some extent, the device structure was redesigned as a centrosymmetric structure with the stationary electrode changed from two bridge-type beams to one cross beam in order to reduce the off-axis sensitivity. More importantly, a contact point was installed on top of the proof mass, changing the effective contact area of the stationary electrode from its end to the center, which undergoes the largest deformation. Therefore, the contact effect would be improved further, which has been confirmed by the ANSYS transient simulation. This simulation combined with the Simulink dynamic simulation described the device behavior, which were in agreement with the drop hammer tests. The threshold acceleration of the redesigned inertial microswitch was around 70 g, and the tested switch-on time reached 30 mus, more satisfactory than the original design.

Fabrication and characterization of a multidirectional-sensitive contact-enhanced inertial microswitch with a electrophoretic flexible composite fixed electrode

A multidirectional-sensitive inertial microswitch with a polymer?metal composite fixed electrode has been designed and fabricated based on surface micromachining in this work. The microswitch mainly consists of a suspended proof mass as a movable electrode and a T-shaped structure on the substrate with maple leaf-like top and cantilevers around the central cylinder as vertical and lateral fixed electrodes. It can sense the applied shock accelerations from any radial direction in the xoy plane and z-axis. The new vertical composite fixed electrode of the switch is completed by electroplating and electrophoretic deposition, which can realize a flexible contact between the electrodes and reduce the bounces and prolong the contact time. As a result, the stability and reliability of the inertial switch could be greatly improved. The fabricated microswitches have been tested and characterized by a standard dropping hammer system. It is shown that the threshold acceleration of the prototype is generally uniform in different sensitive directions in the xoy plane and z-axis, which is about 70 g. The contact time of the microswitch with the composite fixed electrode is ?110 ?s in the vertical direction, which is longer than that (?65 ?s) without a polymer. The test data are in agreement with dynamic finite-element simulation results.

Flexible Implantable Microtemperature Sensor Fabricated on Polymer Capillary by Programmable UV Lithography With Multilayer Alignment for Biomedical Applications

In this paper, we present and develop a programmable UV lithography system with multilayer alignment for cylindrical substrates. By using this system various microstructures with different patterns can be fabricated on the capillary surface, and ±1 μm alignment precision can be realized. A home-made spray coating system is also developed for capillary substrates. A flexible implantable microtemperature sensor for hyperthermia application has been designed and fabricated on the polymer capillary with 330 μm diameter. The finite-element transient simulation indicates the sensor can realize ~ 2 ms quick response. Magnetron sputtered platinum film is used as the sensing material considering its good resistance-temperature effect. The test temperature coefficient of resistance of the fabricated flexible microsensors is 0.0035/°C, which is close to the industry standard value of the bulk Pt resistor sensor. The current-voltage curves of the sensor at different temperatures have been tested. The test sensitivity of the temperature sensor is 1.485 Ω/°C. The present flexible implantable microtemperature sensor is promising to be used as an important interventional monitoring device for biomedical applications.

Modeling, Simulation and Characterization of a Micromachined Acceleration Switch With Anti-Stiction Raised Strips on the Substrate

Raised strips were introduced into the micromachined acceleration switch to avoid the stiction between the mass and the substrate. The system spring constant of the switch with serpentine springs was calculated. The influence of the introduced anti-stiction raised strips on squeeze-film damping of the switch was analyzed closed-form using reasonable boundary conditions. Based on the calculated systems parameters, a Simulink model was constructed to simulate the dynamic properties of the switch under different types of shock acceleration. It is indicated that the dynamic responses (threshold acceleration and response time) were almost not affected by those raised strips which are instead beneficial to reduce the oscillation of the moving mass and improve the yield of the switch. Dependence of dynamic properties on the distance between two electrodes, thickness of the mass and spring constant has also been simulated. The drop hammer experiment was conducted to characterize dynamic properties of the fabricated and packaged acceleration switch. Test threshold acceleration and response time are, respectively, about 41 g and 0.7 ms when the half-sine wave shock was applied, which are in accordance with simulated ones. The package strength of the switch was also evaluated and corresponding critical shear stress for failure is about 22 MPa.

Design and fabrication of a laterally-driven inertial micro-switch with multi-directional constraint structures for lowering off-axis sensitivity

This paper proposes a novel laterally-driven inertial micro-switch with multi-directional compact constraint structures for lowering off-axis sensitivity and improving shock-resistibility. The design utilizes constraint sleeve and reverse stop-block structures to limit too much displacement of proof mass in the micro-switch and avoid damage to the device under a high shock load. The dynamic contact simulation indicates that the designed inertial micro-switch can limit the movement of proof mass and lower the off-axis sensitivity by constraint sleeve and reverse block structures. The first collision response time between proof mass and constraint structures in the z-direction has been analyzed theoretically and simulated, which have indicated that the collision response time mainly depends on geometric parameters, applied shock acceleration amplitude and the inherent frequency of the mass-spring inertial system. Simulated dynamic response curves under applied reverse directional shock accelerations show the proposed inertial micro-switch also has a good shock-resistibility. The inertial micro-switch fabricated by surface micromachining technology has been evaluated using a drop hammer system. The test results indicate that spurious triggering is more likely to occur in the inertial micro-switch without constraint structures, and the designed constraint structures can effectively lower the off-axis sensitivity and improve the shock-resistibility.

A laterally-driven micromachined inertial switch with a compliant cantilever beam as the stationary electrode for prolonging contact time

A novel micro-electromechanical systems inertial switch based on non-silicon surface micromachining technology has been designed, fabricated and characterized in the present work. Compared with the traditional inertial switch, a compliant cantilever beam as a stationary electrode has been proposed to prolong the contact time, which can realize sufficient elastic deformation during the contact between the electrodes. The dynamic contact process is analyzed theoretically and the corresponding mechanical impact mechanism is also explained. To investigate the contact-enhancing mechanism of the cantilever beam, the switch applied half-sine acceleration with various amplitudes in the sensitive direction is simulated with ANSYS software. The dynamic simulation results confirm the contact-enhancing mechanism described by the theoretical analysis and it is shown that the contact time (i.e., the switch-on time) can be prolonged effectively by utilizing the elastic deformation of the cantilever beam and increased with the applied accelerations. The inertial switch is successfully fabricated by electroplating and sacrificial layer processes technologies. The prototype has been characterized by dropping hammer experiment. The test results indicate that the contact effect is improved significantly and the contact time is ~80 µs under the 297 g acceleration, and the maximum value is ~410 µs for the 672 g acceleration amplitude, which is in general accordance with the simulated results. The mechanical contact between the cantilever beam and the proof mass is evaluated following thousands of impacts. The scanning electron micrographs of the contact surfaces indicate that the all-metal switch still keeps a good mechanical property after suffering the hot contact, and the contact resistance is also stable.