Design and fabrication of a planar three DOFs MEMS-based manipulator

The design, modeling and fabrication of a planar three degrees-of-freedom (DOFs) parallel kinematic manipulator, fabricated with a simple 2-mask process in conventional highly doped SCS wafers <100> is presented. The manipulator’s purpose is to provide accurate and stable positioning of a small sample (10 x 20 x 0.2 μm3) in e.g. a transmission electron microscope. The manipulator design is based on the principles of exact constraint design, resulting in high actuation-compliance combined with relatively high suspension-stiffness. A modal-analysis shows that the fourth vibration mode frequency is at least a factor 11 higher than the first three actuation related mode frequencies. The comb-drive actuators are modeled in combination with the shuttlesuspensions gaining insight in the side and rotational pull-in stability conditions. The two-mask fabrication-process enables high aspect ratio structures, combined with electrical trenchinsulation. Trench-insulation allows structures in conventional wafers to be mechanically connected, while being electrically insulated from each other. Device characterization shows high linearity of displacement w.r.t voltage squared over ± 10 μm stroke in x and y direction and ± 2° rotation at a maximum of 50 V driving voltage. Out-of-plane displacement cross-talk due to in-plane actuation in resonance is measured to be less than 20 pm. The hysteresis in SCS, measured using white light interferometry, shows to be extremely small.

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Fig. 2. Microscope image showing the top-view of a fabricated device. Inset: an enlargement of the platform.

Fig. 15 Graph of the measurements of the displacements in x- and y-direction as a function of the squared voltage.

For more information:

B. R. De Jong, D. M. Brouwer, H. V. Jansen, M. J. De Boer, T. G. Lammertink, S. Stramigioli, and G. J. M. Krijnen, “A planar 3 DOF sample manipulator for nano-scale characterization,” in MEMS, (Istanbul, Turkey), pp. 750–753, 2006.