Piezoelectric 3D actuator for micro-manipulation based on [011]-poled PMN-PT single crystal

- A net transverse elongation is achievable for [011]-poled anisotropic PMN-PT.
- Duo-bimorph cantilevered structures based on PMN-PT [011] allow for 3D actuation.
- A six-DoF (degrees of freedom) gripper is proposed for dexterous micromanipulation tasks.
- Complete pick-and-place operations are thus possible without external stages.

This paper sets forth to study and demonstrate the usability of an emerging piezoelectric material, called Lead Magnesium Niobate-Lead Titanate (PMN-PT), as a potential actuator for dexterous micro-manipulation. For this purpose, a generic structure called a duobimorph cantilever is studied. The proposed design takes advantage of a specific transverse elongation property of the PMN-PT poled in the [011] crystalline direction. A static 3D analytical model is presented, that links the applied voltage signals to the displacement and blocking force along each axis. Experimental characterization is conducted on 21.0 × 0.6 × 0.41 mm3 cantilevers to validate the analytical 3D model. The transverse and longitudinal displacement range (not counting end-effectors) is over 460 μm and 40 μm respectively, while still generating high forces typically in the range of 16.5-48.2 mN, values which are significantly higher than in the case of regular Lead Zirconate Titanate (PZT) ceramics. Results also show that PMN-PT has a good linearity, i.e. a very low hysteresis in the range of 2.8-6%, which is around 5 times lower than in the case of PZT. Next, in order to test the potential of this material for micro-manipulation devices, a pair of duobimorph cantilevers is used to build a microgripper. This device is used to conduct a 3D pick-and-place exercise without assistance from external motorized stages. A number of six useful Degrees of Freedom (DoF) are thus achieved, which is a novelty for cantilevered piezoelectric grippers. The results prove that PMN-PT is a great candidate for precise motion generation while still generating large displacement, which is a key factor for any Micro Electro Mechanical Systems (MEMS) implementation. Furthermore, PMN-PT of [011] type particularly can be used in complex, yet more compact, multi-DoF micro-manipulation applications.