TY - GEN
T1 - Reliability of cyclically actuated silicon microcantilevers in liquid environments
AU - Ali, S. Mubassar
AU - Mantell, Susan C.
AU - Longmire, Ellen K.
PY - 2006
Y1 - 2006
N2 - Microstructures are exposed to a variety of liquid environments in applications such as biosensors, BioMEMS, and microfluidic devices. Environmental interactions between the liquids and microstructures can undermine the reliability of MEMS in liquid environments. In this paper, reliability of silicon microcantilevers is investigated in two common liquids, de-ionized water and saline solution, and contrasted with results in air. These single crystal silicon microcantilevers have a magnetic Permalloy tip and are magnetically actuated. The microcantilevers are subjected to long-term cyclic actuation (108-109 cycles) in a liquid filled enclosure. Reliability of the microcantilevers is evaluated by periodically monitoring changes in resonance frequency. The microcantilevers are subjected to peak stresses of ∼5 MPa, which is typical for MEMS applications in liquids, e.g. AFM tips and biosensors. Since the tensile strength of silicon (1-3 GPa) is much higher than the applied stresses, structural fatigue failures were neither expected nor observed in air, water or saline. Changes in resonance frequencies of microcantilevers tested in air and water were insignificant to within the limits of experimental accuracy. However, environmental interactions influenced the reliability of microcantilevers tested in saline as indicated by a gradual decrease in resonance frequency. This decrease in resonance frequency is attributed to gradual mass adsorption of ionic species on the microcantilevers from the saline solution as indicated by scanning electron microscope imaging and electron dispersive spectroscopy.
AB - Microstructures are exposed to a variety of liquid environments in applications such as biosensors, BioMEMS, and microfluidic devices. Environmental interactions between the liquids and microstructures can undermine the reliability of MEMS in liquid environments. In this paper, reliability of silicon microcantilevers is investigated in two common liquids, de-ionized water and saline solution, and contrasted with results in air. These single crystal silicon microcantilevers have a magnetic Permalloy tip and are magnetically actuated. The microcantilevers are subjected to long-term cyclic actuation (108-109 cycles) in a liquid filled enclosure. Reliability of the microcantilevers is evaluated by periodically monitoring changes in resonance frequency. The microcantilevers are subjected to peak stresses of ∼5 MPa, which is typical for MEMS applications in liquids, e.g. AFM tips and biosensors. Since the tensile strength of silicon (1-3 GPa) is much higher than the applied stresses, structural fatigue failures were neither expected nor observed in air, water or saline. Changes in resonance frequencies of microcantilevers tested in air and water were insignificant to within the limits of experimental accuracy. However, environmental interactions influenced the reliability of microcantilevers tested in saline as indicated by a gradual decrease in resonance frequency. This decrease in resonance frequency is attributed to gradual mass adsorption of ionic species on the microcantilevers from the saline solution as indicated by scanning electron microscope imaging and electron dispersive spectroscopy.
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U2 - 10.1115/IMECE2006-16343
DO - 10.1115/IMECE2006-16343
M3 - Conference contribution
AN - SCOPUS:84920633458
SN - 0791837904
SN - 9780791837900
T3 - American Society of Mechanical Engineers, Micro-Electro Mechanical Systems Division, (Publications) MEMS
BT - Proceedings of 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006 - Microelectromechanical Systems
PB - American Society of Mechanical Engineers (ASME)
T2 - 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006
Y2 - 5 November 2006 through 10 November 2006
ER -