Design and visual servo control of a three-axis piezo-flexural micro/nano-manipulator with suppressed coupling motions.

Compliant-mechanism-based precision positioning stages are widely employed in micro/nano manipulation applications. However, cross-coupling motions are major sources of positioning errors, particularly in multi-axis, multi-stage systems. Here, we develop a visual sensing-based compliant dual-stage nano-manipulator driven by piezoelectric actuators for decoupled motion control. It comprises a XY stage for lateral motion and a Z stage for axial motion, both designed using symmetrical four-bar flexure mechanisms. The load-displacement relationships of both stages were analyzed theoretically and their dimensions were optimized according to a maximum-stiffness criterion. A visual sensing-based position measurement and closed-loop control system was implemented to enable real-time motion compensation. Experimental results demonstrate good decoupling performance, with cross-coupling errors below 0.4% and 0.7% for the XY and Z stages, respectively. These errors can be further compensated in real time via visual servo control. The system capability was demonstrated by fabricating a micro-droplet array through droplet sliding on a hydrophobic surface.