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Topology optimization applied to the design of multiactuated piezoelectric microtools

Micro-tools can have a wide range of application such as cell manipulation, microsurgery, nanotechnology equipment,etc. Micro-tools considered in this work consist of a multiflexible structure actuated by two or more piezoceramics that must generate different output displacements and forces in different specified points of the domain and directions, for different excited piezoceramics. The multiflexible structure acts as a mechanical transform by amplifying and changing the direction of the piezoceramics output displacements. Thus, the development of micro-tools requires to design micromechanisms with many degrees of freedom that perform complex movements without presence of joints and pins, due to manufacturing constraints of MEMS scale. In addition, when many piezoceramics are involved the coupling among movements becomes critical, that is, undesired movements may appear. This makes the design task very complex, which suggests that systematic design method, such as topology optimization, must be applied. Thus, in this work the topology optimization formulation was applied to design micro-tools actuated by many piezoceramics with minimum movement coupling. Essentially, the topology optimization method consists of finding the optimal material distribution in a design domain to extremize some objective function. The topology optimization method implemented is based on the CAMD approach where the pseudo-densities are interpolated in each finite element, providing a continuum material distribution in the domain. The optimization problem is posed as the design of a flexible structure that maximizes different output displacements (or grabbing forces) in different specified directions and points of the domain, for different excited piezoceramics. Different types of micro-tools can be obtained for a desired application. Among the examples, designs of a XY nanopositioner and a micro-gripper are considered.