Publications (91) View all
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Article: A scrape-through piezoelectric MEMS energy harvester with frequency broadband and up-conversion behaviors
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ABSTRACT: We propose a MEMS piezoelectric energy harvester with a wide operating frequency range by incorporating a high-frequency piezoelectric cantilever and a metal base as the top and bottom stoppers with a low-frequency piezoelectric cantilever. Frequency up-conversion of the piezoelectric energy harvester is realized when the low-frequency piezoelectric cantilever impacts and scrapes through the high-frequency piezoelectric cantilever. For an input acceleration of 0.6g, with top and bottom stopper distances of 0.75 and 1.1mm, respectively, the operating frequency ranges from 33 to 43Hz. The output voltage and power up to 95mV and 94 nW can be achieved. Experimental results indicate that the frequency up-conversion mechanism significantly improves the effective power.Microsystem Technologies 05/2012; 17(12):1747-1754. · 0.93 Impact Factor -
Article: Flexible structured-light-based three-dimensional profile reconstruction method considering lens projection-imaging distortion.
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ABSTRACT: Structured-light profilometry is a powerful tool to reconstruct the three-dimensional (3D) profile of an object. Accurate profile acquisition is often hindered by not only the nonlinear response (i.e., gamma effect) of electronic devices but also the projection-imaging distortion of lens used in the system. In this paper, a flexible 3D profile reconstruction method based on a nonlinear iterative optimization is proposed to correct the errors caused by the lens distortion. It can be easily extended to measurements for which a more complex projection-imaging distortion model is required. Experimental work shows that the root-mean-square (RMS) error is reduced by eight times and highly accurate results with errors of less than 1‰ can be achieved by the proposed method.Applied Optics 05/2012; 51(13):2419-28. · 1.41 Impact Factor -
Article: 3D Profile Simulation of Metal Nanostructures Obtained by Closely Packed Nanosphere Lithography
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ABSTRACT: Closely packed lithography is a versatile technology to fabricate different kinds of periodically arranged nanostructures on substrate or in solution. Due to its large diversities and versatilities, it is necessary to predict the shape of the nanostructures under various fabrication conditions. This paper gives a full simulation for the profile of metal nanostructures fabricated by closely packed nanosphere lithography. The simulation applies to both hexagonal and quadrangular nanosphere arrangements, and the nanospheres can be in one layer or stacked in two layers, with each layer having a different size. For metal evaporated at any angle onto the nanosphere mask, three-dimensional metal nanostructures on each layer of the nanosphere as well as the substrate are given. The simulation helps to obtain the desired metal nanostructures by predicting the profiles and facilitating the process design in closely packed lithography, and it is especially beneficial for finding out the profiles of the nanostructures hidden under the nanospheres, which are undetectable without removing the nanosphere layers. KeywordsNanosphere lithography (NSL)-Nanospheres-Simulation-NanostructuresPlasmonics 04/2012; 5(2):141-148. · 2.99 Impact Factor -
Article: Investigation of a MEMS piezoelectric energy harvester system with a frequency-widened-bandwidth mechanism introduced by mechanical stoppers
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ABSTRACT: This paper presents the design, microfabrication, modeling and characterization of a piezoelectric energy harvester (PEH) system with a wide operating bandwidth introduced by mechanical stoppers. The wideband frequency responses of the PEH system with stoppers on one side and two sides are investigated thoroughly. The experimental results show that the operating bandwidth is broadened to 18 Hz (30–48 Hz) and the corresponding optimal power ranges from 34 to 100 nW at the base acceleration of 0.6g and under top- and bottom-stopper distances of 0.75 mm and 1.1 mm, respectively. By adjusting the mechanical stopper distance, the output power and frequency bandwidth can be optimized accordingly.Smart Materials and Structures 02/2012; 21(3):035005. · 2.09 Impact Factor -
Article: Piezoelectric MEMS Energy Harvester for Low-Frequency Vibrations With Wideband Operation Range and Steadily Increased Output Power
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ABSTRACT: A piezoelectric MEMS energy harvester (EH) with low resonant frequency and wide operation bandwidth was designed, microfabricated, and characterized. The MEMS piezoelectric energy harvesting cantilever consists of a silicon beam integrated with piezoelectric thin film (PZT) elements parallel-arranged on top and a silicon proof mass resulting in a low resonant frequency of 36 Hz. The whole chip was assembled onto a metal carrier with a limited spacer such that the operation frequency bandwidth can be widened to 17 Hz at the input acceleration of 1.0 g during frequency up-sweep. Load voltage and power generation for different numbers of PZT elements in series and in parallel connections were compared and discussed based on experimental and simulation results. Moreover, the EH device has a wideband and steadily increased power generation from 19.4 nW to 51.3 nW within the operation frequency bandwidth ranging from 30 Hz to 47 Hz at 1.0 g. Based on theoretical estimation, a potential output power of 0.53 μW could be harvested from low and irregular frequency vibrations by adjusting the PZT pattern and spacer thickness to achieve an optimal design.Journal of Microelectromechanical Systems 11/2011; · 2.10 Impact Factor
