Micromachined piezoelectric force sensors based on PZT thin films

A micromachined lead zirconate titanate (PZT) force sensor for scanning force microscope (SFM) is conceptualized by its piezoelectricity. The fabrication procedure is interpreted, and mechanical characteristics of the micromachined PZT force sensors with various lengths are studied in this paper. A compact SFM is constructed by using the piezoelectric PZT sensor. A very clear image is taken by this SFM. The current study of the micromachined PZT force sensor can be considered as a breakthrough of design of SFM as well as a good example of integrated piezoelectric microdevices     

A scrape-through piezoelectric MEMS energy harvester with frequency broadband and up-conversion behaviors

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 0.6?g, with top and bottom stopper distances of 0.75 and 1.1?mm, respectively, the operating frequency ranges from 33 to 43?Hz. The output voltage and power up to 95?mV and 94 nW can be achieved. Experimental results indicate that the frequency up-conversion mechanism significantly improves the effective power.     

Nanophotonics Sensor Based on Microcantilever for Chemical Analysis

A Si-based cantilever sensor with photonic crystal (PC) resonator as readout for chemical sensing and analysis has been developed. The resonant wavelength shift of PC resonator is resulted from PC deformation induced by cantilever bending, in which this optical readout scheme facilitates cantilever deflection measurements in liquid. Through numerical simulation, we demonstrate that the detection capability of this micromechanical sensor operated in water is better than that of sensor operated in air. The minimum detectable Z-displacement and strain of Si/SiO₂ cantilever sensor are derived as 0.6 mum and 0.0098% in water and 0.812 mum and 0.0144% in air, respectively. This novel micromechanical sensor shows its promising future in applications such as detection of proteins and DNA in solution.     

Study of Low-Temperature Thermocompression Bonding in Ag-In Solder for Packaging Applications

Low-temperature solders have wide applications in integrated circuits and micro-electromechanical systems packaging. In this article, a study on Ag-In solder for chip-to-chip thermocompression bonding was carried out. The resulting joint consists of AgIn₂ and Ag₉In₄ phases, with the latter phase having a melting temperature higher than 400°C. Complete consumption of In solder into a Ag-rich intermetallic compound is achieved by applying a bond pressure of 1.4 MPa at 180°C for 40 min. We also observe that the bonding pressure effect enables a Ag-rich phase to be formed within a shorter bonding duration (10 min) at a higher pressure of 1.6 MPa. Finally, prolonged aging leads to the formation of the final phase of Ag₉In₄ in the bonded joints.     

Variable optical attenuator using planar light attenuation scheme based on rotational and translational misalignment

In the last decade, extensive developments of microelectromechanical systems based thermal actuator and/or electrothermal actuators have been dedicated to the applications, such as data storage devices, relays and optical switches, etc. In this paper, we demonstrated a novel planar micromechanism comprising a tilted mirror driven by a V-beam electrothermal actuator via a link beam. This electrothermally driven tilted mirror can have static displacement with a motion trace including rotational and translational movement. The rotational and translational misalignment of reflected light spot toward the core of output port fiber will lead to light attenuation. In other words, the attenuation is controlled in terms of the position of tilted mirror depending on driving dc voltage. This new micromechanism has granted us a more efficient way to perform the light attenuation regarding to the other kinds of planar variable optical attenuators. These devices were fabricated by the deep reactive ion etching process and can reach 30-dB attenuation at 7.5 V driving voltage. The polarization dependant loss is less than 0.1 dB within the 30-dB attenuation region. The static and transient characteristics of devices operated at ambient room temperature environment show good repeatability and stability.     

Design and Modeling of a Nanomechanical Sensor Using Silicon Photonic Crystals

Conventionally a line defect in the photonic crystal (PhC) is used to create a waveguide for light propagation through the PhC. A PhC based filter is designed by introducing micro-cavities within the line defect so as to form the resonant bandgap structure for PhC. Such a PhC waveguide (PhCWG) filter shows sharp resonant peak in output wavelength spectrum. We proposed a suspended silicon bridge structure comprising this PhCWG filter structure. Since the output resonant wavelength is sensitive to the shape of air holes and defect length of the micro-cavity. Shift of the output resonant wavelength is observed for suspended PhCWG beam structure under particular force loading. In other words, the induced strain modifies the shape of air holes and the spacing among them. Such an effect leads to shift of resonant wavelength. Under optical detection limitation of 0.1 nm for resonant wavelength shift, the sensing capability of this nanomechanical sensor is derived as that vertical deformation is 20-25 nm at the center and the smallest strain is 0.005% for defect length. This innovative design conceptualizes a new application area for PhCs, i.e., the nanometer-scale physical sensors for strains and forces.     

Microstructures for characterization of seebeck coefficient of doped polysilicon films

CMOS based thermoelectric micro-transducers have been demonstrated for various applications. To achieve better design and optimization of such micro-transducers, the Seebeck coefficient of doped polysilicon thin film needs to be measured accurately with respect to optimization effort in process and structure design of micro-transducers. A novel circular test structure is firstly presented to get accurate value of Seebeck coefficient in this paper, while the known planar and cantilever test structures are fabricated together and characterized separately to validate the measured Seebeck coefficient of samples with the same process conditions for comparison. Seebeck coefficient measured by the circular structure shows good agreement with the result measured by cantilever structure, while there is an error of about 14% for the result given by planar structure. The circular test structure is a good at accurate testing of the average absolute values of Seebeck coefficient of p-type and n-type. Strength and drawback for the three structures are summarized.     

Evolution of Microstructure and V-Shaped Positive Temperature Coefficient of Resistivity of (Pb0.6Sr0.4)TiO3 Materials

The effects of various liquid-phase sintering aids on (Pb_0.6SrO_0.4)TiO₃ ceramics have been investigated. The relationships between electrical properties and microstructures have been scrutinized. It has been found that, among the sintering aids studied, only SiO₂ exhibits a significant effect on the grain growth of (Pb_0.6SrO₄)TiO₃. The optimum firing profiles for sound microstructure and good electrical properties of (Pb_0.6SrO_0.4)TiO₃+ 5.0 mol% SiO₂ have been established. The V-shaped electrical behavior is prominent, and a PTCR jump of about 10^2.9 is observed. The formation of cation vacancies may increase the resistivity of the over-fired specimens. Various milling methods to pulverize the calcined powder and the optimum amount of packing protection powder during sintering are also discussed.     

Multiplexing Optical Images for Steganography by Single Metasurfaces

Image steganography based on intelligent devices is one of the effective routes for safely and quickly transferring secret information. However, optical image steganography has attracted far less attention than digital one due to the state-of-the-art technology limitations of high-resolution optical imaging in integrated devices. Optical metasurfaces, composed of ultrathin subwavelength meta-atoms, are extensively considered for flat optical-imaging nano-components with high-resolutions as competitive candidates for next-generation miniaturized devices. Here, multiplex imaging metasurfaces composed of single nanorods are proposed under a detailed strategy to realize optical image steganography. The simulation and experimental results demonstrate that an optical steganographic metasurface can simultaneously transfer independent secret image information to two receivers with special keys, without raising suspicions for the general public under the cloak of a cover image. The proposed optical steganographic strategy by metasurfaces can arbitrarily distribute a continuous grayscale image together with a black-and-white image in separate channels, implying the distinguishing feature of high-density information capacity for integration and miniaturization in optical meta-devices.     

A humidity resistant and high performance triboelectric nanogenerator enabled by vortex-induced vibration for scavenging wind energy

Wind energy is a promising renewable energy source for a low-carbon society.This study is to develop a fully packaged vortex-induced vibration triboelectric nan...