Typically, engineers try to minimize residual stress in a piezoelectric stack. Silex has taken a different approach: developing the capability to engineer stress deliberately as part of the device design. Tuning the stress profile within the PZT stack from tensile to compressive makes it possible to influence how a membrane or beam behaves at rest and under actuation. This opens design possibilities that aren’t available with conventional fixed-stress processes, including pre-curved actuator geometries and structures optimised for specific force–displacement characteristics. “Stress in a multilayer stack is often seen as a problem to be solved,” Svedin adds. “We’ve made it something to be designed with. That shift gives our customers a degree of freedom in device architecture that most foundries simply cannot offer.”
