Faculty Bibliography

A novel shock switch based on a micro-electro-mechanical system (MEMS) for vibration monitoring was designed and fabricated by non-silicon surface micromaching technology. It consisted of three main parts: the proof mass as the movable electrode, the cross beam as the stationary electrode and the movable contact point to prolong the contact time. The ANSYS model was built, by which the modal analysis was carried out showing that the new design reduced the sensitivity to off-axis accelerations compared with the previous design, and the physical parameters were extracted from the structure so they could be used in the Simulink model. Through the dynamic simulation, the contact-enhancing mechanism was verified and compared with the traditional design. The fabricated micro shock switch was tested with a dropping hammer experiment. Test results indicated that the threshold acceleration was about 145 g and a stable contact time of over 50 μs was observed under a half-sine wave shock load acceleration with 1ms duration, in agreement with the simulation results. The contact effect was improved significantly as expected and the proposed model was able to describe the device's behavior correctly.

Based on non-silicon surface micromachining technology, a simple but reliable micro electro-mechanical system (MEMS) electrical inertia micro-switch with single sensitive direction and reverse impact protection is designed and fabricated on glass substrate. In this design, conjoined serpentine springs are used to fix and suspend the mobile electrode (mass) and blocks are used to protect the device against reverse impulse. The switch is laterally driven (i.e. its sensitive direction is parallel to the substrate). Fabrication is carried out by low-cost and convenient multi-layer electroplating technology. The relationship between threshold acceleration and mass thickness has been investigated by theoretical analysis and finite element analysis (FEA) simulation. After fabrication and packaging, micro-switches are tested by using drop weight. The results show that the threshold accelerations distribute between 58 g and 72 g, which basically fulfils the expected 60 g; and the response time to 100 g half-sine waved shock is in the order of 10^-4 s, which is in agreement with simulation result.

Vertically and laterally driven MEMS inertia switches are designed. The solid modeling and finite element dynamics analysis of the Nickel micro-spring in the switch are conducted. The stress distribution and the displacement-time response curve of the micro-spring under dynamic load are obtained. The influence of configuration parameters on the spring constants (including klevel and kvertic) are compared under static and dynamic loads. The finite element dynamics analysis is considered to be a useful method in evaluating the spring constant in MEMS devices, especially for the spring in inertia micro devices working under the dynamic load.

A novel MEMS inertia micro-switch has been designed basing on non-silicon surface micromachining technology. The switch mainly consists of a thicker mass block as mobile electrode and a suspended elastic beam as fixed electrode locating above the mass block. The designed switch structure not only benefits the improvement of the sensitivity and the contact effect, but also protects the switch against shock damage owing to too much deviation of the mass block and the snake springs. The dynamics finite element contact simulation about the designed switch has been done. The results show that the response time and the contact time of the switch is about 0.24ms and 10 μs respectively when 100g acceleration was applied, which is relatively better sensitivity and contact effect. The response time of the inertia micro-switch would decrease when applied acceleration was increased, and the contact effect between two electrodes would be enhanced.

A novel design of MEMS electrical inertia micro-switch was proposed. In the design, an elastic beam with holes was used as the fixed electrode, and a suspended thicker mass block with conjoined snake springs was used as the mobile electrode locating between the supporting layer and the elastic beam. This designed switch structure benefits the improvement of the sensitivity, the contact effect, and protects the switch against intensive shock damage. The micro-switch had been fabricated using cost-effective electroplating nickel and tested subsequently. 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 100 g acceleration is applied, which shows relatively better sensitivity and contact effect. This result has an agreement with that of dynamics finite element contact simulation about the designed micro-switch.