Superelasticity and Shape Memory In Micro and Nano Devices of Cu-Al-Ni SMA

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Now a days MEMS are incorporating smart materials as sensors and actuators to improve their functional capabilities. Among the different smart materials candidates to be integrated in MEMS, shape memory alloys (SMA) exhibit the advantage of offering the highest work output per unit of mass (about 4 J/g). However, SMA development for potential applications in MEMS is based in thin films making use of shape memory properties on the large dimension of the films.

In the present work we present another approach for using SMA as tri-dimensional devices at micro and nano scale. Superelastic behavior has been demonstrated along hundred of cycles with a recovery resolution in the range of the nanometer, and shape memory has been also reported in simple devices as nano pillars of about 400 nm diameter [1,2]. Some previous results in Cu-Al-Ni single crystals micro pillars will be overviewed, and new results concerning the evolution of the mechanical behavior during compression cycling at nano scale will be presented. In addition these micro pillars exhibit an anomalous ultra-high damping at nano scale, which could be very useful to damp vibrations in MEMS, improving its reliability. So the potentiality of tri-dimensional features of SMA to be incorporated in MEMS technology will be presented and discussed. We believe that these results open new way for future research and development in SMA at micro-nano scale.

[1]  J. San Juan, M.L. Nó, C.A. Schuh. Advanced Materials 20, 272 (2008).

[2]  J. San Juan, M.L. Nó, C.A. Schuh. Nature Nanotechnology 4, 415 (2009).