This type of mirrors are ideally suitable for light weight ultra-large space telescopes. A set of such flexible mirror segments could be assembled to form the actual mirror. The surface quality is < 30nm. Stroke requirements for such adjustments is <2μm. Usually PZT actuators are bonded behind deformable silicon mirror membranes for this purpose. An electric field applied perpendicular to the piezoelectric layer plane will induce lateral contraction and thereby cause large out of plane deformation of the membrane.