Reversing the action of thermoelastic bimorphs using selective directional stiffeners

We present for the first time ever, a method for reversing the response of thermoelastic bimorph actuators, without changing the order of their layers. Our device is constructed from a flat stage that is suspended on three thermoelastic bimorph spiral arms. We demonstrate that the thermoelastic response of the spiral bimorphs can be affected by using directional stiffeners. We show that with no stiffeners, the thermoelastic response naturally displaces the stage downwards by 7μm. Stiffeners that are angled at 45° relative to the spiral tangent, enhance this response by a factor of 3, and increase the downward displacement to 23μm. Surprisingly, stiffeners which are angled at -45°, completely reverse the direction of the response, and result in an enhanced upward displacement of 23μm.