Qiu Xu

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.

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.

Shock-Resistibility of MEMS-Based Inertial Microswitch under Reverse Directional Ultra-High g Acceleration for IoT Applications

This paper presents a novel MEMS-based inertial microswitch design with multi-directional compact constraint structures for improving the shock-resistibility. Its shock-resistibility in the reverse-sensitive direction to ultra-high g acceleration (~hunderds of thousands) is simulated and analyzed. The dynamic response process indicates that in the designed inertial microswitch the proof mass weight G, the whole system’s stiffness k and the gap x2 between the proof mass and reverse constraint blocks have significant effect on the shock-resistibility. The MEMS inertial microswitch micro-fabricated by surface micromachining has been evaluated using the drop hammer test. The maximum allowable reverse acceleration, which does not cause the spurious trigger, is defined as the reverse acceleration threshold (athr). Test results show that athr increases with the decrease of the gap x2, and the proposed microswitch tends to have a better shock-resistibility under smaller gap. The measured responses of the microswitches with and without constraint structure indicates that the device without constraint structure is prone to spurious trigger, while the designed constraint structures can effectively improve the shock-resistibility. In this paper, the method for improving the shock-resistibility and reducing the spurious trigger has been discussed.

Design and Optimization of a Stationary Electrode in a Vertically-Driven MEMS Inertial Switch for Extending Contact Duration

A novel micro-electro-mechanical systems (MEMS) inertial microswitch with a flexible contact-enhanced structure to extend the contact duration has been proposed in the present work. In order to investigate the stiffness k of the stationary electrodes, the stationary electrodes with different shapes, thickness h, width b, and length l were designed, analyzed, and simulated using ANSYS software. Both the analytical and the simulated results indicate that the stiffness k increases with thickness h and width b, while decreasing with an increase of length l, and it is related to the shape. The inertial micro-switches with different kinds of stationary electrodes were simulated using ANSYS software and fabricated using surface micromachining technology. The dynamic simulation indicates that the contact time will decrease with the increase of thickness h and width b, but increase with the length l, and it is related to the shape. As a result, the contact time decreases with the stiffness k of the stationary electrode. Furthermore, the simulated results reveal that the stiffness k changes more rapidly with h and l compared to b. However, overlarge dimension of the whole microswitch is contradicted with small footprint area expectation in the structure design. Therefore, it is unreasonable to extend the contact duration by increasing the length l excessively. Thus, the best and most convenient way to prolong the contact time is to reduce the thickness h of the stationary electrode while keeping the plane geometric structure of the inertial micro-switch unchanged. Finally, the fabricated micro-switches with different shapes of stationary electrodes have been evaluated by a standard dropping hammer system. The test maximum contact time under 288 g acceleration can reach 125 µs. It is shown that the test results are in accordance with the simulated results. The conclusions obtained in this work can provide guidance for the future design and fabrication of inertial microswitches.

A novel inertial microswitch with synchronous follow-up compliant electrodes for extending output switch-on pulse width

This paper reports a novel inertial microswitch with synchronous follow-up compliant electrodes for extending output switch-on pulse width. The flexible movable electrode and stationary electrode are proposed to keep a continuous duration contact by double-stair and spring-shape structures, which can not only extend the output switch-on pulse width but also reduce the impact bounces. Then the inertial microswitch has been fabricated using surface micromachining and multilayer electroplating technology. The comparison testing results show that there is no contact bouncing behavior can be observed under ∼466g half sine-wave shock acceleration and the test output switch-on pulse width can reach 390μs, which is longer than that in the traditional design.

A MEMS inertial switch with compact constraint structures for lowering off-axis sensitivity

This paper proposes two novel laterally-driven inertial switches with multi-directional constraint structures for lowering off-axis sensitivity. First one is the inertial switch with one layer of serpentine springs. The second is the inertial switch with two layers of serpentine springs. ANSYS software was used to simulate the dynamic contact process of inertial switch, and the simulation results reveal that the design of symmetrical distribution of double layers serpentine springs plays an important role in resisting small acceleration disturbance from off-axis sensitive z-direction, and the constraint structures can resist large acceleration disturbance. The fabricated inertial switch by surface micromachining technology has been evaluated using a drop hammer system. The test results show that the symmetrical distribution of double layers serpentine springs reduce the displacement of proof mass in the off-axis sensitive direction under a small acceleration disturbance. Therefore, The combined efforts of double layers suspended springs and constraint structures effectively lower the off-axis sensitivity of the MEMS inertial switch.

A high efficient integrated heat dissipation systems with CNT array based heat lines and microchannel heat sink in 3D ICs

This work mainly focused on the heat dissipation of the 3D integrated circulates (ICs). In order to satisfy the urgent heat dissipation needs, the optimal design of heat sink and optimized path for transmitting heat is one of the most promising and effective ways. Two methods have been proposed for solving the heat dissipation issues. First one was the optimized microchannel with pin fin integrated with the high-power chips or interposers. The influence of dimension of the pin fin on the heat dissipation was analyzed and optimized by FEM. The demotion of microchannel with the optimized pin fin achieved to more than 50 W/cm2 when fluid (water) speed was 1 m/s. The secondary was a novel heat line design with a cold end, which was composed of a copper plate containing nano arrays and pin fin. With the heat line integrated with Cu-pad connected with pin fin and CNT arrays, the temperature of hotspot has dropped by 17.89% (fluid cooling mode) and 9.95% (air cooling mode).