A piezoelectric microactuator previously proposed by the authors for laser scanning in dual axes confocal endomicroscopy meets two primary challenges for dual axes confocal imaging: large out-of-plane actuation (~500μm) and a relatively high bandwidth (>100Hz). In order to further reach stage positioning error better than desired imaging resolution of 5 μm and to improve the robustness of actuator performance, a closed-loop controller and thus on-chip sensing, are being incorporated and integrated with system modeling.
This work presents these thin-film PZT based microstages where piezoelectric unimorphs are used not only to actuate its central platform but also to estimate its vertical motion. Initial results from on-chip piezoelectric sensing are presented. Although sensing output shows some feed-through from the actuation signal, testing shows detection of AC motion from various vibration modes of the stage. Meanwhile, 3D profiles of the entire actuator structure at different DC voltage levels were obtained and used to form a nonlinear optimization problem to estimate all forces and moments that each component of the device experiences for the prediction of its deflection. A comparison between modeled and experimental deflection of the actuation beams is included. These results will be used to describe the dynamic behavior of the actuation beams, where the sensors are embedded, and to estimate sensing outputs in order to implement a close-loop controller. Prototype stages are currently being assembled into a handheld dual axes confocal imaging system.