Shape-morphing systems, which can perform complex tasks through morphological transformations, are of high interest for future applications in minimally invasive medicine 1,2 , soft robotics 3-6 , active metamaterials 7 , and smart surfaces 8. With current fabrication methods, shapemorphing configurations have been embedded into structural design, for example by spatially distributing heterogeneous materials 9-14 , which cannot be altered once fabricated. The systems are therefore restricted to a single type of transformation that is predetermined by their geometry. In this work, we have developed a strategy to encode multiple shape-morphing information into a micromachine by programming the magnetic configurations of arrays of single-domain nanomagnets on connected panels. By tailoring the switching fields of the nanomagnets, the magnetic configurations can be programmed using a specific sequence of magnetizing fields and, with customised micromachine designs, these magnetic configurations result in specific shape transformations in an applied magnetic field. Using this concept, we have built an assembly of modular units that can be programmed to morph into alphabetic letters, and we have constructed a microscale 'bird' capable of complex behaviours, including 'flapping', 'hovering', 'turning' and 'side-slipping'. This establishes a route for the creation of future intelligent microsystems that are reconfigurable and reprogrammable in situ, and can therefore adapt to complex situations.

With a specific stimulus, shape‐memory materials can assume a temporary shape and subsequently recover their original shape, a functionality that renders them relevant for applications in fields such as biomedicine, aerospace, and wearable electronics. Shape‐memory in polymers and composites is usually achieved by exploiting a thermal transition to program a temporary shape and subsequently recover the original shape. This may be problematic for heat‐sensitive environments, and when rapid and uniform heating is required. In this work, a soft magnetic shape‐memory composite is produced by encasing liquid droplets of magneto‐rheological fluid into a poly(dimethylsiloxane) matrix. Under the influence of a magnetic field, this material undergoes an exceptional stiffening transition, with an almost 30‐fold increase in shear modulus. Exploiting this transition, fast and fully reversible magnetic shape‐memory is demonstrated in three ways, by embossing, by simple shear, and by unconstrained 3D deformation. Using advanced synchrotron X‐ray tomography techniques, the internal structure of the material is revealed, which can be correlated with the composite stiffening and shape‐memory mechanism. This material concept, based on a simple emulsion process, can be extended to different fluids and elastomers, and can be manufactured with a wide range of methods.

Magnetically-switchable adhesion of a two-phase composite to non-magnetic objects is achieved by magnetically addressing the material dissipative properties.