Fig. 1: Generation of irregular architected materials with optimization-enabled stress modulation and its potential applications.

a Natural irregular materials found in wood, seashells, bones, spider silk, turtle shells, and bird feathers. b A material property optimizer governs the design variables, microstructures, and material properties (directional elasticity), guiding the evolution of the bulk material at both macro and micro scales to achieve the desired stress distribution. c A virtual growth simulator produces diverse disordered microstructures based on the input frequency combinations of basic building blocks. A machine learning model further maps the frequency combinations of the building blocks to their corresponding material properties, which are fed back into the material property optimizer in (c). d–g The generation and fabrication of irregular architected materials used for orthopedic femur restoration after a fracture. d The generation setup including a fractured femur and a support to be filled with four types of basic building blocks. e The initial, optimized, and target stresses in the control region around the fracture, where the initial stress corresponds to a homogeneous distribution of building blocks. f The generated support made of optimized irregular materials, which are further composed of disordered microstructures illustrated in the two insets. g The 3D-printed samples at varying scales.