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15 May 2007 Feedback loops with electrically driven microcantilevers
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Proceedings Volume 6589, Smart Sensors, Actuators, and MEMS III; 65890N (2007)
Event: Microtechnologies for the New Millennium, 2007, Maspalomas, Gran Canaria, Spain
The electronic feedback used with microcantilevers (&mgr;CLs) to obtain their best performances requires a precise driving method to exert on them a force proportional to an electrical signal. One of these methods is Electrostatic Driving (ED) easily achieved on &mgr;CLs placed some mm apart from a conductive surface. This easy appearance of ED is the reason to find it unexpectedly, coming from electrical fields not properly shielded, in setups designed for other driving as Magnetic Driving (MD). When feedback loops designed for MD suffers from this ED contamination due to an unshielded solenoid for example, the tight phase control of the driving is lost. As a result, self-oscillation of the loop does not take place at f0, the resonance frequency of the &mgr;CL, or an appealing shift in the resonance frequency from f0 without feedback to fFB=f0±&Dgr;f with feedback appears in non-oscillating loops. A feedback force proportional to the displacement (DF) or to the speed (SF) of &mgr;CLs has been studied and it is demonstrated that SF sets an apparent temperature for the thermal motion of a &mgr;CL without changing its native f0 (a desired feature for high stability &mgr;CL-based oscillating sensors) whereas the fFB±f0 produced by DF allows an electrical tuning of fFB very useful for &mgr;CL-based Voltage Controlled Oscillators.
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Javier Malo and José-Ignacio Izpura "Feedback loops with electrically driven microcantilevers", Proc. SPIE 6589, Smart Sensors, Actuators, and MEMS III, 65890N (15 May 2007);

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