It may be latched and unlatched by pushing one lever or the other with a micromanipulator. In this version, actuation was not accomplished by TiNi microribbon because the point of attachment, the small perpendicular extension, is a vertical step up from the substrate, and difficulty was encountered in depositing and patterning TiNi film over such steps. The third photograph shows a TiNi microribbon attached to the lever. The photograph shows hinged spacers fabricated of multiple layers of polysilicon on a substrate. The spacer is 200 microns long and approximately 40 microns wide.
Rectangular objects are lifter devices to help initiate rotation of the hinge.
We believe that TiNi thin film shape memory actuators will become the core technology for providing actuation of MEMS devices. The recovery stress and strain of the shape-memory effect can be very large. The deliverable work typical of the nickel-titanium SMA is one joule per gram per cycle. By contrast, an electrostatic actuator of the same volume might generate 10 -3 microjoule, and a comparable piezoelectric device is limited to approximately 0.1 microjoule per cycle. Because of the phase transformation the actuation takes place in a small temperature range.