Robust Trimorph Bulk SMA Microactuators for Batch Manufacturing and Integration

This paper introduces the concept of batch microfabrication and electrical contacting of bulk SMA microactuators. This concept addresses technical solutions for the main challenges related to using SMA actuators such as the necessary mechanical bias force, the difficult electrical contacting and the high power needed for actuation. We report on initial SMA-dielectric-metal trimorph test structures and their characteristics. The bias force is provided by a dielectric layer and the electrical contacting of the bulk SMA is avoided using indirect electrical heating via an additional metal layer. Three mm long beams can provide several hundreds of muN and deflect several hundreds of mum. The actuation power is reduced approx. 2.5 times compared to direct heating schemes.