The multi-scale structures are commonly found in nature, such as plants and bones. Such multi-scale structures
can be divided into macro-scale, micro-scale and further sub-scale structures. In this study, we aim to design
optimised two-scale structures for multifunctional composites, specifically by enhancing the structural stiffness
and the ionic conductivity simultaneously. To tackle this problem, a novel strategy for achieving optimised multiscale structures is presented. A database of optimised micro-scale structures and simple placement criterion for
the micro-scale structure were applied. We demonstrate the efficiency of our strategy by designing, optimising
and evaluating two-scale structures composed of macro-and micro-scales. The advantage of our strategy for
optimised multi-scale structures is presented and discussed by comparing the structural stiffness and the ionic
conductivity of several two-scale structures composed of different microstructures such as the solid-void, uniform
and varied microstructures.