Addressable and perceptible dynamic reprogram of ferromagnetic soft machines.

Soft machines actuated by external magnetic fields have gained significant attention for their potential to interact with living organisms and complex environments. However, their adaptability and functionality are often limited by rigid magnetization during operation. In this work, we introduce dynamically reprogrammable magnetic soft machines with in situ reconfigurable magnetization profiles during operations, achieved through the synergy of various magnetic fields. A flexible resonant circuit is integrated into the machine body, enabling addressable and perceptible heating of specific regions via high-frequency fields of varying frequencies. The machine body is composed of microbeads made from a low-melting-point alloy and NdFeB microparticles. When heated, the alloy liquefies, allowing the rotation of NdFeB microparticles under a 40 mT pulsed programming field. Upon cooling, the new configuration is locked in place. This reprogramming process is equally effective for single or multiple machines, enabling versatile multi-pattern deformation of individual machines and cooperation of multiple ones. Furthermore, by incorporating addressable thermal actuation, we demonstrate in situ assembly of multiple robots. This work may enable a broad spectrum of magnetic soft machines with enhanced functionalities.