Design of piezoelectric multi-actuated microtools using topology optimization

Abstract

Microtools offer significant promise in a wide range of applications such as cellmanipulation, microsurgery, nanotechnology processes, and many other fields.The development of these microtools is still in the initial stages and it can bestrongly enhanced by using design tools. The microtools considered in this paperessentially consist of a multi-flexible structure actuated by two or more piezoceramicdevices such that when each piezoceramic is actuated, it generates an outputdisplacement and force in a specified point of the domain and direction. Themulti-flexible structure acts as a mechanical transform by amplifying and changing thedirection of the piezoceramic output displacements. Thus, the development ofmicrotools requires the design of actuated flexible structures that can perform complexmovements. In addition, when multiple piezoceramic devices are involved, couplingeffects in their movements become critical, especially the appearance of undesiredmovements, which makes the design task very complex. One way to avoid suchundesirable effects is the use of a systematic design method, such as topologyoptimization, with appropriate formulation of the optimization problem. Here, a topologyoptimization formulation is developed for the design of microtools actuated bymultiple piezoceramics that minimizes the effects of movement coupling. Thismethod is implemented based on the CAMD (continuous approximation of materialdistribution) approach where fictitious densities are interpolated in each finite element,providing a continuum material distribution in the domain. In addition, in previouspiezoelectric actuator topology optimization works the piezoceramics were excited bycharge, which is not realistic, even though it simplifies the sensitivity analysis.In this work, the piezoceramics are excited by voltage and the correspondingsensitivity analysis is presented. Different types of microtools required for variousapplications are designed to demonstrate the usefulness of the proposed method.Although the presented examples are limited to two-dimensional models, this isappropriate since most of the applications for such microtools are planar devices.