Counting and sequential information processing in mechanical metamaterials

Materials with an irreversible response to cyclic driving exhibit an evolving internal state which, in principle, encodes information on the driving history. Here we realize {irreversible metamaterials that count} mechanical driving cycles and store {the result} into easily interpretable internal states. We extend these designs to aperiodic metamaterials which are sensitive to the order of different driving magnitudes, and realize ‘lock and key’ metamaterials that only reach a specific state for a given target driving sequence. Our robust, scalable and extendable, and open new routes towards smart sensing, soft robotics and mechanical information processing.