Influence of interlocking blocks assembly on the actuation time, shape change, and reversibility of voxel-based multi-material 4D structures

Interlocking blocks have been explored to solve assembly issues in large and complex structures, and are increasingly being used in additive manufacturing (AM) to build objects with multiple properties and dissimilar materials. 4D printing, which combines AM and smart materials, is being investigated to upgrade objects in terms of shape and/or property changes once stimulated with energy. A trend in 4D printing is to strategically arrange active and passive materials for better control and performance. Multi-material AM is challenging, but one alternative solution is to develop interlocking mechanisms to print dissimilar materials. This work deepens the approach of interlocking blocks assembly by investigating their effect on the behavior of multi-material 4D printed structures. Using a computational design approach, which converts a material distribution into interlocking blocks intended to be printed separately and then assembled to achieve a desired shape change, the study compares structures printed in one go versus interlocking ones. The mechanical/stimulation tests and numerical simulations conducted demonstrate that interlocking structures exhibit relevant mechanical performance while enhancing better actuation response than multi-material structures within a single print.