This is an open access article published by the IET under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/)
This Letter presents the design, fabrication and characterisation of an array of electrostatically actuated clamped–clamped microbeams. A large bottom actuation electrode and long beams with lengths ranging from 1 to 3.4 mm are the major features of the present device. The novelty of this Letter lies in the realisation of suspended and undeformed microstructures by controlling the process-induced stress during the fabrication process. This has been achieved by compensating the influence of the compressive and tensile stress components of the different deposited layers, resulting in ultralong beams with a relatively straight mechanical profile and an aspect ratio of ∼1:3400 of vertical deflection to the beam length. For the first time, ultralong microbeams of tantalum have been actuated electrostatically with AC and DC driving voltages to drive them into resonance and characterise their resonant frequencies. The lowest resonant frequency of 1.4 kHz is obtained for a 3.4 mm-long beam. The shift of the resonant frequency due to the effect of different DC biasing has been investigated experimentally. A spring softening effect has been induced through electrostatic tuning. A downward shift in the resonant frequency to 35,000 ppm for DC bias voltages increasing from 1 to 5 V has been demonstrated.
References
-
-
1)
-
4. Walser, S., Siegel, C., Winter, M., et al ‘MEMS microphones with narrow sensitivity distribution’, Sens. Actuat. A Phys., 2016, 247, pp. 663–670 (doi: 10.1016/j.sna.2016.04.051).
-
2)
-
8. Al-Masha'al, A., Bunting, A., Cheung, R.: ‘Evaluation of residual stress in sputtered tantalum thin-film’, Appl. Surf. Sci., 2016, 371, pp. 571–575 (doi: 10.1016/j.apsusc.2016.02.236).
-
3)
-
7. Fang, W., Lee, C.-H., Hu, H.-H.: ‘On the buckling behavior of micromachined beams’, J. Micromech. Microeng., 1999, 9, (3), pp. 236–244 (doi: 10.1088/0960-1317/9/3/304).
-
4)
-
1. Zhang, W.M., Yan, H., Peng, Z.K., et al ‘Electrostatic pull-in instability in MEMS/NEMS: A review’, Sens. Actuat. A Phys., 2014, 214, pp. 187–218 (doi: 10.1016/j.sna.2014.04.025).
-
5)
-
6. Liu, H., Pike, W.T.: ‘A micromachined angular-acceleration sensor for geophysical applications’, Appl. Phys. Lett., 2016, 109, (17), p. 173506 (doi: 10.1063/1.4966547).
-
6)
-
9. Al-masha'al, A., Mastropaolo, E., Bunting, A., et al ‘Fabrication and characterisation of suspended microstructures of tantalum’, J. Micromech. Microeng., 2017, 27, (1), p. 15020 (doi: 10.1088/0960-1317/27/1/015020).
-
7)
-
3. Chowdhury, S., Ahmadi, M., Miller, W.C.: ‘Design of a MEMS acoustical beamforming sensor microarray’, Sens. J., 2002, 2, (6), pp. 617–627 (doi: 10.1109/JSEN.2002.807773).
-
8)
-
5. Li, H., Tian, C., Deng, Z.D.: ‘Energy harvesting from low frequency applications using piezoelectric materials’, Appl. Phys. Rev., 2014, 1, (4), p. 41301 (doi: 10.1063/1.4900845).
-
9)
-
9. Krylov, S., Dick, N.: ‘Dynamic stability of electrostatically actuated initially curved shallow micro beams’, Continuum Mech. Thermodyn., 2010, 22, pp. 445–468 (doi: 10.1007/s00161-010-0149-6).
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