Recent advancements in the field of multi-material 3D printing have opened up new opportunities for the production of intricate structures capable of displaying distinct behaviours. The primary objective of this study is to develop adaptive multi-material lattice structures with customizable properties through thermal activation. This objective was accomplished by applying a conductive coating onto the surface of polymeric-based multi-material lattices. Subsequently, the structure was subjected to Joule heating, achieved by passing an electric current through it. To evaluate the electro-thermo-mechanical properties of these lattices, electrical and mechanical loads were simultaneously applied while monitoring the surface temperature. The findings indicate that by applying a 12V potential to the coated multi-material samples at room temperature, a significant average reduction of over 70% in the elastic modulus of the samples was observed, demonstrating the considerable potential inherent in this approach.