Strain-Amplifiying Cellular Microstructure for Flexible Piezo-Powered Actuators

The goal of this project is to design flexible actuators that mimic the characteristics of biological muscle. Living creatures display tremendous capabilities of movement that cannot currently be recreated with mechanical systems. The structure and constitution of biological muscles allows organisms to move with awe-inspiring speed, fluidity, and precision. Furthermore, biological muscle can supply immense force relative to its size and weight. The reproduction of these qualities in mechanical systems will lead to serious advantages in many applications including robotics, prosthetics, and energy harvesting.

We are currently working on novel designs which seek to reproduce the features of biological muscle by mirroring its cellular structure. We are developping topologies in the form of a two- or three-dimensional arrays of single degree-of-freedom actuators. This allows the design to produce motion with degrees of freedom proportional to the number of individual cells. The proposed design relies on piezoelectric actuator technology due to its speed, accuracy, and mechanical simplicity. Each cell within the structure is fitted with a single piezoelectric element, each of which can be actuated independently. Because piezoelectric actuators can provide only small displacements relative to their size, the system is designed to amplify the piezoelectric strain rate to produce structural displacements commensurate with biological muscle.

We start this study by analyzing several two-dimensional models, based on a rigid pin-jointed lattice structures or on compliant monolithic structures. The latter model is studied by finite element analysis which helps shed light on the system’s behavior. In particular, we are able to identify values of the unit cell structural parameters that best serve particular applications, and to find optimal morphologies for given measure of performance. These finite element simulations are critical to the fabrication of a simple compliant, monolithic prototype whose performance must be evaluated experimentally.

We are also working on the feasibility of alternate two- or three-dimensional topologies and on applications of sensing and energy-harvesting.

Strain-Amplifying Cellular Microstructure for Flexible Piezo-Powered Actuator, E.J. Carron & R.V. Roy, 2018 ASME’s ICME, Pittsburgh, November 9-14, 2018.