Long-term testing of surface-micromachincd U-shaped thermal actuators has been carried out. Actuators operated at power levels lower than 8 mW (12 μm of displacement) operated satisfactorally for more than 100 million cycles at 660 Hz, with a failure defined as the point at which the displacement decreases by 20%. Plastic deformation had been observed in actuators operated above 8 mW, and the plastic deformation has been shown to be associated with the high temperatures encountered during operation. The failure rate of the actuators is dependent on the total time the actuators are at the elevated temperatures encountered during operation, rather than on the number of actuation cycles. This paper provides a guide for MEMS designers that shows the lifetime of a thermal actuator as a function of its drive power.

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