Electromechanical analysis of a self-sensing torsional micro-actuator based on CNTs reinforced piezoelectric composite with damage

Electromechanical microstructures are increasingly attractive for various applications of smart devices. However, electrostatic actuator is sensitive to pull-in instability caused by microscopic dispersion forces, taking risks of stiction, adhesion, and even failure. Making micro-actuators self-sensing is a promising strategy for active modulation of device design. Although some progress has been made for respective sensing and actuating, it is still challenging to build integrating sensing-actuating device. In this work, we proposed one self-sensing actu-ating composite structure for constructing an electrostatic torsional actuator. We modelled composite nanobeams capable of self-adjusting pull-in titling angle of micro-actuator based on strain gradient theory with size de-pendency and damage. Theoretical and numerical results showed good agreements and verified the accuracy of proposed model in this paper. The variation of CNTs volume fraction can tune torsional stiffness of torsional nanobeam, and thus increase the stable working range of micromirror. By introducing piezoelectric layers into laminated torsional structures, the working state and the damage of device can be sensed and driven by piezoelectric effect, and the stability can be adjusted and predicted to avoid pull-in instability. This work can contribute to structural optimization of electromechanical devices.