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

International audienceThis 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