Wenguo Chen

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.

The design, simulation and fabrication of a novel horizontal sensitive inertial micro-switch with low g value based on MEMS micromachining technology

A horizontal sensitive inertial micro-switch with low g value is proposed in this paper. It was simulated using ANSYS software and fabricated by MEMS micromachining technology. It consists of three parts: a suspended thick proof mass as a movable electrode, two novel elastic fixed beams as stationary electrodes to prolong the contact time and a barrier system, which constrains non-sensitive direction movement and eliminates reverse impact. The relationship between the threshold acceleration ath and the intrinsic frequency ω0 is discussed in a theoretical analysis and finite element simulation. The thickness of the proof mass (H) and the width of the springs (k) were designed to be variable to meet the requirement of the application environment. Two novel elastic stationary electrodes were designed specially to improve the contact effect. The fabricated micro-switch was characterized by a standard dropping test. The work frequency is about 33.3 Hz and the threshold acceleration of the sample is about 38g, which meet the simulation value very well. The response time was about 10−4 s and the contact time about 200 us.

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.

Design, simulation and characterization of a MEMS inertia switch with flexible CNTs/Cu composite array layer between electrodes for prolonging contact time

An inertia switch with flexible carbon nanotubes and copper (CNTs/Cu) composite array layer between movable and fixed electrodes has been designed, fabricated and characterized, which achieved long contact time compared to the traditional design using rigid-to-rigid impact between electrodes. The CNTs/Cu layer is fabricated using the composite electroplating method and the whole device is completed by multi-layer metal electroplating based on the micro-electro-mechanical systems (MEMS) process. The dynamic response of the designed inertia switch and the contact impact between single CNT and fixed electrode/another CNT have been both simulated by ANSYS finite element method. Finally, the fabricated MEMS inertia switch with flexible CNTs/Cu composite array layer between electrodes has been evaluated using a dropping hammer system. The test contact time is about 112μs, which has a good agreement with the simulation and is much longer than that of the traditional design.

Simulation and characterization of a laterally-driven inertial micro-switch

A laterally-driven inertial micro-switch was designed and fabricated using surface micromachining technology. The dynamic response process was simulated by ANSYS software, which revealed the vibration process of movable electrode when the proof mass is shocked by acceleration in sensitive direction. The test results of fabricated inertial micro-switches with and without anti-shock beams indicated that the contact process of micro-switch with anti-shock beams is more reliable than the one without anti-shock beams. The test results indicated that three contact signals had been observed in the contact process of the inertial switch without anti-shock beams, and only one contact signal in the inertial switch with anti-shock beams, which demonstrated that the anti-shock beams can effectively constrain the vibration in non-sensitive direction.

An inertial micro-switch with compliant cantilever fixed electrode for prolonging contact time

An inertial micro-switch with a compliant cantilever fixed electrode has been designed and fabricated by surface micromachining technology in the present work. The micro-switch can sense the applied acceleration in one horizontal direction. The dynamic contact process of the inertial micro-switch was simulated by finite element method (FEM). A compliant cantilever was proposed in the inertial system as fixed electrode, which can realize a flexible contact between the electrodes and eliminate the bouncing phenomenon for prolonging the contact time. A fabricated prototype inertial micro-switch was tested by dropping hammer system. The results demonstrate that the threshold acceleration of the fabricated prototype is ~180g. The test contact time is up to ~1050μs, which is much longer than that (~5μs) of one without the compliant cantilever.

Fabrication and Characterization of a Low-g Inertial Microswitch With Flexible Contact Point and Limit-Block Constraints

A novel contact-enhanced low-g inertial microswitch has been proposed and fabricated by surface micromachining technology in this paper. A novel segmental circle spring has been designed in the low-g inertial switch, which can decrease its stiffness compared with traditional semicircle spring. The dynamic response of the microswitch is simulated by ANSYS software, which has estimated its threshold acceleration and holding time. The vibrations of proof mass under the applied overload acceleration in the sensitive direction and the opposite direction are both simulated and analyzed, which demonstrates that the rebound of proof mass can be restrained effectively by the introduced limit blocks. The fabricated prototype has been tested by a dropping hammer system. The test results indicate that the threshold acceleration of fabricated inertial switch is ~25g with holding time ~650 μs. The overload acceleration of 80g, 120g have been applied on the fabricated prototype, and the test results indicate that the spurious trigger have been eliminated due to the limit blocks, which is in agreement with the simulation results. The acceleration of 100g is applied to the tested inertial microswitch with and without limit block in the opposite sensitive directions, respectively. The test result verifies the function of limit blocks.

AN ALL-METAL PASSIVE THRESHOLD SENSOR FOR OMNI-DIRECTIONAL VIBRATION MONITORING APPLICATION

This paper reports the design, fabrication and testing of an all-metal omni-directional passive threshold sensor for vibration monitoring. The entire structure is fabricated with nickel by low-temperature photoresist modeled electroplating technology. The fixed electrodes in horizontal and vertical direction have been designed as cantilever and multi-hole cross-beam, respectively, which can reduce the contact bouncing and damage effectively. The dynamic contact process is simulated by ANSYS software. The function of the proposed device has been demonstrated by dropping hammer system, which indicates that the threshold level in the horizontal direction is ~65g with holding time is ~40μs and 60g with holding time is ~150μs in the vertical direction.