微机电系统在仿生学生学上的应用.docx

1、微机电系统在仿生学生学上的应用Design,and preliminary characterization of a novel MEMS bionic vector hydrophoneHua Mingya(School of mechanical engineering and automation Shanghai University, Shanghai 200072, China)Abstract: According to theprinciple ofthe fishlateral line organof hearing,a novel microelectromechani

2、cal systems(MEMS)bionic vector hydrophoneused for obtaining vectorinformation of underwater sound fieldis introduced.It is desirable thatthe application of MEMSpiezoresistive effectand bionicstructure can improve thelow frequencysensitivityof vector hydrophoneandits miniaturizationbased on.Bionicstr

3、ucture is composed of two parts: high precisionfourbeam structure and therigidplasticbarrel is fixed onthemicrostructure of thecenter.Hair cellslocated in thelaterallinevaristorsbeamsimulationandrigid plastic cylindricalsimulationcilia.When the plastictubeis by voice,strainvaristorto transform thedi

4、fferential voltageoutputsignal through theWheastone bridgecircuit.Microfabrication techniques have beenused to measuretissueresultsmade.Keywords: MEMS; Bionic; Vector hydrophone; Low frequency1. The characteristics of MEMS Miniature: MEMS deviceshas the advantages of small volume,light weight,low en

5、ergy consumption,small inertia,high resonance frequency,short response time. Silicon as the mainmaterial,mechanical and electricalproperties ofsiliconfine:strength,hardness and Youngs modulusanddensity ofiron,like aluminum,heat conductionrateclose to themolybdenum and tungsten. Mass production:micro

6、 machiningwithsiliconalsomakinghundreds ofmicroelectromechanicaldevice or acomplete MEMSina piece of silicontechnology.Mass productioncan greatly reduce the productioncost. Integration:can takedifferent functions andsensitivedirection or theactuating directionof multiplesensors or actuatorsare integ

7、rated,orthe formation of microsensor array,micro actuatorarray,even to thedeviceof multiple functionsare integrated together,forming acomplex microsystems.Micro sensors,micro actuatorsand microintegrationcan producereliability,high stabilityMEMS.2. Introduction In underwater acoustics, the applicati

8、on of vector hydrophone endows several advantages for detection of submarines: It can obtain both the sound pressure and particle velocity of sound field simultaneously, effectively reduce received intensity of isotropic hindrance, and so on. Therefore, all countries with noticeable navy force have

9、drawn unprecedented attention on the vector hydrophone and many works have been done about it. Although great achievements have been made, there are still some limitations in low-frequency detection, miniaturization, and high sensitivity. The miniaturization of mechanical systems offers unique oppor

10、tunities for scientific and technological progress, and will almost certainly open an entirely new industry 1. Microelectromechanical systems (MEMS) refer to microscopic devices that have a characteristic length of less than 1mm but more than 100nm and combine electrical and mechanical components 2.

11、 MEMS devices and systems are inherently smaller, lighter, more reliable, and faster than their macroscopic counterparts, and are usually more precise 1. The small dimensions of microcantilevers make them excellent sensors for very sensitive detection of many physical, chemical, and biological pheno

12、mena, including acoustic signals 35. Engineers, designers and architects often look to nature for inspiration. Biology has perfected its designs and formed many fruitful abilities such as its exquisite sensitivity, effectiveness, and reliability, through billions of years of evolution. So mimicking

13、its creations is a sureway of producing new technologies and new achievement that are both efficient and reliable 6.The advantage of piezoresistive effect is that it can be used to detect low-frequency signal even at 0 Hz. Therefore, it is of great advantage for research on vector hydrophone based o

14、n piezoresistive effect. In this paper, a novel MEMS vector hydrophone based on the theory of bionics and piezoresistive effect will be presented, with respect to the design, fabrication, and preliminary characterization. The targeted application region for these sensors is low-frequency detection o

15、f submarine sound Fig. 1. Lateral line of the fish. Fig. 2. Schematic view of fishs neuromast organ.3. Basic principle3.1 bionics principle An extraordinary but lesser known sensory system is the mechanosensory lateral line organ that enables the detection of minute water movements in the immediate

16、environment 7. The lateral line runs from the head to the tail of the fish and resembles a towed array with sensing organs (stitches) spaced at intervals along the nerve fiber (Fig. 1). Each stitch contains several neuromasts. Each neuromast comprises up to several hundred mechanosensory hair cells,

17、 more or less separated by supporting cells,and surrounding mantle cells. The apical part of the hair cell presents its stereocilia (mechanoreceptor structure) and kinocilium to the outside environment through the gelatinous cupula that covers the neuromast and makes contact with water 8,9. Fig. 2 i

18、s the schematic view of the neuromast. The stereocilia vibrate and act as sensors for flow noise as the fish swims through water. When stimulated by turbulence, the motion of the hair cell produces changes in the synapses which are in turn connected to the nerve fiber. The electric signal originates

19、 from impedance changes in cell walls which modulate the flow of K+ ions. The lateral line is especially sensitive to low frequency fluid motion parallel to the length of the fish. Sound, especially low frequency sound, travels faster and farther than in air.Near-field sound consists of small fluid

20、motions or vibrations and are characterized by a displacement direction. They are detected by the inner ear or by the lateral line 10.3.2. Acoustics theory of cylinder Acoustics theory research indicates that for an acoustically small cylinder immersed in fluid when the size of the acoustics cylinde

21、r is far smaller than the length of sound wave, under the action of sound wave, the relation of the velocity between the cylinder and the fluid particle is V (1)where V is the amplitude of the cylinder velocity, V0 the amplitude of the particle velocity, the density of the fluid, the density of cyli

22、nder, k =w/c the wave number, and a the crustaceous radius of the cylinder. When , (2)This shows that at low frequencies the motion of a cylinder whose density is equal to that of the fluid it displaces is identical to the motion of the fluid particles at this location when the cylinder is removed 1

23、113. Consequently, if the cylinder is fixed on an inertial transducer, a signal is produced and can be related to the acoustic particle motion.4. The process of design thought 14 According to the auditory principle of lateral line organ,we can see that the mechanoreceptor structure is the stereocili

24、a which acts as sensors for flow noise by stimulating the hair cell. Therefore, the bionic structure mainly includes the design of hair cell and its stereocilia. In this paper, the piezoresistor is simulated to hair cell and the rigid plastic cylinder is simulated to stereocilia. The structure of hy

25、drophone consists of two parts: four beam microstructure and rigid plastic cylinder which has the same density as that of water. Fig. 3 shows the actual design of this structure. Fig. 3(a) is the three-dimensional (3D) model of the design and Fig. 3(b) gives the two dimensional (2D) top view of the

26、design. The four-beam microstructure consists of four vertical cantilever beams. The rigid plastic cylinder is fixed at the center block of the four-beam microstructure. Both the center block and the beams have the same thickness. The whole structure has complete axial symmetry in the xoz plane and

27、yoz planes. According to acoustics theory, only when the cylinder and the surrounding medium have the same density can the cylinder and the medium particle have synchronous vibration, or else the acoustic information cannot be exactly memorized. In this paper, the rigid plastic cylinder not only has

28、 the same density as that of water but also has small geometric size (diameter: 200 mm, length: 5000 mm), meeting the vibration conditions well. When the plastic cylinder responds directly to the acoustic particle motion, the center block will have a horizontal displacement and an angular rotation.

29、Therefore, the structure will be subject to deformation, an amplified and concentrated strain is generated on the slim sensing beams. A full-active Wheatstone bridge is logically formed by locating eight piezoresistors which is used to sense the deformation of the beams. This bridge structure can in

30、crease the hydrophones sensitivity by about two orders of magnitude without sacrificing the natural frequency of the hydrophone. The resistance of the piezoresistor implanted into sensitive structure is changed when the signal is transmitted to it. When there is incentive direct current, the bridges

31、 change will be detected. Therefore, the vector underwater acoustic signal will be detected also. Considering the present fabrication technology, the center block of the modeled structure element is 500 mmlong, 500 mm wide, and 10 mm thick. The four beams are 1000 mm long, 120 mm wide, and 10 mm thi

32、ck. To verify the accuracy of the above model and evaluate its performance, the static behavior of the hydrophones structure is studied by means of finite element modeling (FEM) in this section. We used 45 solid, 3D elements. All the elements are standard cuboids; the ratio among length, width, and height is close to 1:1:1. Fig. 4(a) shows the distribution of simulated stress on a beam under static excitation. As expected, the maximal stress is located at the edg