Anjie Ming

Multi-resonant wideband energy harvester based on a folded asymmetric M-shaped cantilever

This article reports a compact wideband piezoelectric vibration energy harvester consisting of three proof masses and an asymmetric M-shaped cantilever. The M-shaped beam comprises a main beam and two folded and dimension varied auxiliary beams interconnected through the proof mass at the end of the main cantilever. Such an arrangement constitutes a three degree-of-freedom vibrating body, which can tune the resonant frequencies of its first three orders close enough to obtain a utility wide bandwidth. The finite element simulation results and the experimental results are well matched. The operation bandwidth comprises three adjacent voltage peaks on account of the frequency interval shortening mechanism. The result shows that the proposed piezoelectric energy harvester could be efficient and adaptive in practical vibration circumstance based on multiple resonant modes.

Fabrication of patternable nanopillars for microfluidic SERS devices based on gap-induced uneven etching

In this work, a lithography-free approach for fabricating patternable nanopillars is reported. The key technique of the approach is to introduce a gap over the substrate by covering it with a cap, which contains through holes and the material on its lower surface has similar etching rate with the substrate. By this means, uneven etching of the substrate is induced under the through holes, consequently, nanopillars are fabricated into patterns corresponding to the holes. By sputtering a thin layer of Ag on the nanopillar patterns, obvious Raman enhancement can be observed. Since the large areas around the patterns are protected from anisotropic etching and metal sputtering, they are flat enough to be bonded with PDMS caps thus to form microfluidic Surface-enhanced Raman Scattering devices, and the whole fabrication process for the devices is simplified.

CMOS MEMS infrared source based on black silicon

In this work, a MEMS infrared source applied to compact Non-Dispersive Infrared (NDIR) gas sensor is reported. Compared to other related things, the source coats integrated nanostructure black silicon compatible with CMOS technique on the poly-silicon. Hence the emissivity is as high as 98% at 3~5μm wave range; relatively the radiation efficiency is increased by 40% through calculation. Suspension structure and DRIE release process of the back side are used in the design to reduce the heat conduction losses, and the source is only sized 3×3mm2 suitable for mass production. After being packed, the source can rapidly heat in 20 ms, besides the modulation depth can reach 30% below 50Hz, which all meet the requirements of the NDIR gas sensor.

Nanofiber forests as a humidity-sensitive material

Nanofiber forests with high hydrophilicity and humidity-sensitivity are reported in this work. They are fabricated from polyimide (PI) by a plasma-stripping technique, and are utilized as a humidity-sensitive material in humidity sensors. In a relative humidity range of 50%-80%, nanofiber forest-based devices have capacitance ~50% larger than that of PI-based sensors. Meanwhile, as the nanofibers construct a non-closed layer, the internal nanostructures are fully exposed to external environment, thus the absorption and desorption of moisture consume only a short time. Since the fabrication processes for both nanofiber forests and the devices are simple and fast, thus such a method may provide possibility for development of novel humidity sensors with high sensitivity and short response time.

Nanofiber forests with high infrared absorptance

In this work, nanofiber forests with high infrared (IR) absorptance are reported. In wavelength range from 1.5 to 5 μm, the absorptance of the nanofiber forests reaches a minimum of 96%, which is much higher than that of Si3N4-based IR absorbers and the polymer coatings from which the nanofibers are obtained. Such nanofiber forests are fabricated by using a plasma-stripping-of-polymer technique, which is fast, high-yield and applicable to a wide range of polymers. Moreover, the technique is highly compatible with micro-fabrication. As a result, the nanofiber forests can be introduced into MEMS (Micro-Electro-Mechanical systems) IR devices, and it is expected that the performance of such devices can be improved.

MEMS compressed tunable grating

Currently, MEMS tunable grating draws a lot of attentions due to its promising applications in display, spectrometer, external cavity laser, programmable mask, optical telecommunication, etc. Among phase-tunable and incident-angletunable grating, period-tunable grating distinguishes itself by relative simple structure, ease-to-fabrication, good performance, and ability to be integrated with IC. In this paper, a novel approach based on compressed period grating is demonstrated. Based on a developed comb-drive actuator working in a low voltage of 37V, our grating period was compressed for 12.5%. The first resonant mode of the comb-drive actuator was simulated to be 3.8 kHz by finite element modeling.

A double-end-beam based infrared device fabricated using CMOS-MEMS process

Purpose Thermopile infrared (IR) detectors are one of the most important IR devices. Considering that the surface area of conventional four-end-beam (FEB)-based thermopile devices cannot be effectively used and the performance of this type of devices is relatively low, this paper aims to present a double-end-beam (DEB)-based thermopile device with high duty cycle and performance. The paper aims to discuss these issues. Design/methodology/approach Numerical analysis was conducted to show the advantages of the DEB-based thermopile devices. Findings Structural size of the DEB-based thermopiles may be further scaled down and maintain relatively higher responsivity and detectivity when compared with the FEB-based thermopiles. The authors characterized the thermoelectric properties of the device proposed in this paper, which achieves a responsivity of 1,151.14 V/W, a detectivity of 4.15 × 108 cm Hz1/2/W and a response time of 14.46 ms sensor based on DEB structure. Orginality/value The paper proposed a micro electro mechanical systems (MEMS) thermopile infrared sensor based on double-end-beam structure.

The packaging technology of optical switch arrays

Optical switch is one of key supporting technologies in all-optical-network (AON). And electrostatic MOEMS (Micro-Optical-Electro-Mechanical Systems) switch plays a very important role in all the researched switches, because of their excellent features, including low insertion, low crosstalk and scalability. But the packaging technology has been limiting the development of optical switch. In this paper, the authors study the laser beam propagating during the free space and select collimator, design the pedestal to packaging and address aspects of the insertion loss that are most important loss mechanisms for the 2D cross-connect switch.

The study on the compound X-ray refractive lens using LIGA technique

A theoretical method of focusing X-rays by the compound X-ray refractive lens is presented in this paper. The authors report their resent theoretical results including the material selection and structure parameters for such a device. As an example, a compound X-ray refractive lens with PMMA material is designed. The detailed fabrication process of the PMMA compound lens by LIGA technology is described. Moreover, some measured results by means of SEM are also shown. The structure height of one of the PMMA compound lens is measured to be 500μm.

Pyroelectric infrared detector based on LiTaO 3 crystal with novelty nanostructured amorphous carbon film

This work introduced a novelty MEMS pyroelectric infrared detector based on LiTaO3 (LT) crystal with high absorptivity amorphous carbon film layer. The LT crystal is thined and polished to 100um thickness and double mentaled for electical connection which will be suspened upon rectangle cave of silicon substrate with mental ring. Amorphous carbon(a-C) could be produced by magnetron sputtering on the top of LT layer and nanostructured by Inductively Coupled Plasma(ICP) etching with advantages of lower process temperature and simple fabrication process. Test results shows that the absorptivity of 1.9um a-C was not less than 80% at 2.5–6um wavelength after etching 5 minutes. The performance of developed infrared detector with high absorption rate nanostructured amorphous carbon film is 27 times than that without absorbing layer in theory as well feasible in fabrication process and low cost.