Zhuo Qing Yang

Fully integrated micro electromagnetic vibration energy harvesters with micro-patterning of bonded magnets

This paper presents the fabrication and characterization of a novel fully integrated micro electromagnetic vibration energy harvester using micro-patterning of bonded magnets. The magnetic material utilized is a polymer composite, consisting of a commercially available NdFeB powder dispersed in epoxy resin to a weight loading percentage of 90%. The prototype is fabricated using UV-LIGA technology and microelectroplating technology. The whole volume of the structure is about 20 mm3. Testing results show that the fabricated vibration energy harvesters can generate a maximum peak-peak voltage of 20.9 μV at the devices resonance frequency of 365 Hz and input acceleration of 1 g (9.8 m/s2).

Development of a shock acceleration microswitch with enhanced-contact and low off-axis sensitivity

In the present work, microswitches with different shapes have been fabricated by low-cost and convenient multi-layer electroplating in order to develop a shock acceleration microswitch with enhanced-contact and low off-axis sensitivity. Modal analysis based on FEM shows that the three kinds of new designed microswitches have lower off-axis sensitivity than our previous device, i.e., type I. The packaged microswitches were tested by the drop hammer system. The generated half-sine-like shocking acceleration with amplitude of 80g, lager than the threshold, was applied to the microswitches. The test contact time of the microswitch IV is about 55µs, whose contact effect is much better than conventional. A shock acceleration microswitch IV with a movable contact point utilizes the double spring-mass system to realize an enhanced-contact effect and is considered as a better selection for long duration contact and relatively low off-axis sensitivity.

A multidirectional-sensitive inertial microswitch with electrophoretic polymer-metal composite fixed electrode for flexible contact

A multidirectional-sensitive inertial microswitch with polymer-metal composite fixed electrode has been designed and fabricated based on non-silicon surface micromachining in the present work. The microswitch can sense the applied accelerations from any directions in xoy plane and positive z-axis. Its vertical composite fixed electrode is completed by electroplating and electrophoretic deposition, which can realize a flexible contact between the electrodes and eliminate the bouncing phenomenon and prolong the contact time. As a result, the stability and reliability of the inertial switch could be greatly improved. The test results show that the threshold acceleration of the fabricated prototype is generally uniform (~70g) in different sensitive directions in xoy plane and z-axis. The contact time of the microswitch with composite fixed electrode is ~110μs in vertical direction, which is longer than that (~65μs) of one without polymer.

Fabrication and Mechanical Characterization of a Microscale Electrophoretic Polymer Based on MEMS Technology

Microscale polyurethane modified epoxy resin film has been fabricated using MEMS tehnologies in the present paper. The effect of different process conditions on the thickness of fabricated film was discussed. The microscale film shows smooth and uniform surface morphology. The tensile test of the film by DMA indicates its tensile strength and Youngs modulus are approximately 55MPa and 1.8GPa, respectively. The fracture section of the film was characterized by SEM. In addition, the interface bonding strength of the fabricated film between Ni substrate is much higher than Parylene-C and SU-8. This microscale polymer film is promising in several smart MEMS fields, especially bio-MEMS structures.

Fabrication and Characterization of Bonded NdFeB Microstructures for Microelectromechanical Systems Applications

A micromachining technique has been developed for the fabrication of microscale polymer-bonded magnet. Two types of lithographically defined molds, photoresist mold and electroplated metal mold, were introduced. Photoresist mold is convenient, while electroplated metal mold can be fabricated on the glass or steel substrate which can bear much more compression. NdFeB films of thickness between 50 and 500 µm were prepared by micro-patterning of composites containing 83-95wt% of commercial NdFeB powder after curing at the room temperature. Magnetic properties mainly depend on the types and percentage of volume loading of magnetic powder. Coercivity of 772.4kA/m (9.70kOe), remanence of 275.1mT (2.751kG), and energy product of 22.6kJ/m3 (2.8MGOe) have been achieved. This easily developed magnet could be a promising candidate for applications in magnetic microelectromechanical systems (MEMS).

A Preparation Method of Patterned Nanoporous Copper

Graphic nanoporous copper (NPC) was prepared by a new method. Cu68Zn32 and Cu36Zn64 (atomic percentages) precursor alloy thin film was deposited by electro-deposition in acidic alloy plating solution and then dealloyed in hydrochloric acid to fabricate nanoporous copper (NPC) with pore size from 30nm to 100nm. The results show that the microstructure of NPC can be controlled by changing alloy plating solution and dealloying process, this process also maintains compatibility with micro-fabrication technique.

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 electrostatic force assistance and multi-step pull-in for eliminating bounce and prolonging contact time

A novel MEMS inertial switch with electrostatic force assistance and multi-step pull-in behavior has been designed, which can help the electrodes weaken the bounce and keep a long contact in the inertial switch before the leakage of electricity ends compared with the traditional rigid contact between electrodes. The dynamic switching and pull-in performance is simulated by finite element method. The designed structure is completed by multi-layer metal electroplating based on Surface micromachining technology. Finally, the fabricated device is tested by dropping hammer system. Its indicated that compared to the inertial switch with electrostatic force assistance has no bounce behavior, and realizes ∼512μs long stable contact compared to that without the applied electrostatic force.

A vertical driven inertial micro-switch with dual spring to prolong holding time

In this paper, a new model has been proposed for the design of inertial micro-switch. Compared with the traditional model consisted by movable-fixed electrode, the electrodes are designed as two movable springs. The dynamic response processes of electrodes can be controlled via the structure parameters. The simulation results indicated that the elastic contact can effectively prolong the holding time. The fabricated prototypes were tested by drop hammer system. The test results demonstrated that the holding time of improved inertial micro-switch much longer than the traditional designed one with the same threshold acceleration.

Design and Simulation of Fully Integrated Micro Electromagnetic Vibration Energy Harvester

A fully integrated micro electromagnetic vibration energy harvester based on MEMS technology is designed and its mechanical and electromagnetic characteristics are analyzed by using Finite Element method (FEM). Structure static, modal and harmonic analysis of spring-magnet system was carried out by ANSYS software. Ansoft Maxwell software was used to simulate the electromagnetic characteristics of the energy conversion system, especially the relationship between the output performances of the structure and parameters of the coil. The optimized model is designed and the optimization principles could provide a reference for the future electromagnetic vibration based harvester design.