Bimorph

About: Bimorph is a research topic. Over the lifetime, 3339 publications have been published within this topic receiving 51880 citations.

Mems variable optical attenuator

Abstract: A MEMS (Micro Electro Mechanical System) variable optical attenuator is provided that is capable of optical attenuation over a full range of optical power. The MEMS variable optical attenuator comprises a microelectronic substrate, a MEMS actuator and an optical shutter. The MEMS variable optical attenuator may also comprise a clamping element capable of locking the optical shutter at a desired attenuation position. The variable light attenuator is capable of attenuating optical beams that have their optical axis running parallel and perpendicular to the substrate. Additionally, the MEMS actuator of the present invention may comprise an array of MEMS actuators capable of supplying the optical shutter with greater displacement distances and, thus a fuller range of optical attenuation. In one embodiment of the invention, the MEMS actuator comprises a thermal arched beam actuator. Additionally, the variable optical attenuator of the present invention may be embodied in a thermal bimorph cantilever structure. This alternate embodiment includes a microelectronic substrate and a thermal bimorph cantilever structure having at least two materials of different thermal coefficient of expansion. The thermal bimorph is responsive to thermal activation and moves in the direction of the material having the lower thermal coefficient expansion. Upon activation, the thermal bimorph intercepts the path of the optical beam and provides for the desired level of optical attenuation. The invention also provides for a method of optical attenuation and a method for fabricating an optical attenuator in accordance with the described structures.

Endoscopic optical coherence tomographic imaging with a CMOS-MEMS micromirror $

Abstract: This paper reports a single-crystalline silicon (SCS) micromirror used for laser beam scanning in an endoscopic optical coherence tomography (OCT) system. The micromirror is fabricated by using a deep reactive-ion-etch (DRIE) post-CMOS micromachining process. Thin bimorph actuation structures and movable bulk silicon structures are simultaneously achieved. The micromirror is 1 mm by 1 mm in size, coated with aluminum, and thermally actuated by an integrated polysilicon heater. The radius of curvature of the mirror surface is 50 cm. The mirror has a resonance frequency of 165 Hz and rotates 178 when a 15 mA d.c. current is applied. A discontinuity in the dynamic response curve is observed. By using a white-light profilometer, we found that the discontinuity is caused by localized buckling of the bimorph actuation mesh. Cross-sectional images of 500 � 1000 pixels covering an area of 2.9 mm by 2.8 mm are acquired at 5 frames/s by using an OCT system based on this micromirror. # 2003 Elsevier Science B.V. All rights reserved.

Harvested power and sensitivity analysis of vibrating shoe-mounted piezoelectric cantilevers

Abstract: This paper presents a preliminary investigation on energy harvesting from human walking via piezoelectric vibrating cantilevers. Heel accelerations during human gait are established by correlating data gathered from the literature with direct experimental measurements. All the observed relevant features are synthesized in a typical (standard) acceleration signal, used in subsequent numerical simulations. The transient electromechanical response and the harvested power of a shoe-mounted bimorph cantilever excited by the standard acceleration signal is computed by numerical simulations and compared with measurements on a real prototype. A sensitivity analysis is finally developed to estimate the mean harvested power for a wide range of scavenger configurations. Acceptability criteria based on imposed geometrical constraints and resistance strength limits (e.g. fatigue limit) are also established. This analysis allows a quick preliminary screening of harvesting performance of different scavenger configurations.

Rotational piezoelectric wind energy harvesting using impact-induced resonance

Abstract: To improve the output power of a rotational piezoelectric wind energy harvester, impact-induced resonance is proposed to enable effective excitation of the piezoelectric cantilevers' vibration modes and obtain optimum deformation, which enhances the mechanical/electrical energy transformation. The impact force is introduced by forming a piezoelectric bimorph cantilever polygon that is fixed at the circumference of the rotating fan's internal surface. Elastic balls are placed inside the polygon. When wind rotates the device, the balls strike the piezoelectric cantilevers, and thus electricity is generated by the piezoelectric effect. The impact point is carefully chosen to use the first bending mode as much as possible, and thus maximize the harvesting efficiency. The design enables each bimorph to be struck in a similar area and every bimorph is struck in that area at different moments. As a result, a relatively stable output frequency can be obtained. The output frequency can also be changed by choosing different bimorph dimensions, which will also make the device simpler and the costs lower. A prototype piezoelectric energy harvester consisting of twelve piezoelectric cantilevers was constructed. The piezoelectric cantilevers were made from phosphor bronze, the lead zirconium titanate (PZT)-based bimorph cantilever had dimensions of 47 mm × 20 mm × 0.5 mm, and the elastic balls were made from steel with a diameter of 10 mm. The optimal DC output power was 613 μW across the 20 kΩ resistor at a rotation speed of 200 r/min with an inscribed circle diameter of 31 mm.