While shape-memory materials do have some interesting potential applications, many of them require the application of heat in order to change shape – and that could cause problems, in temperature-sensitive environments such as the human body. A new material, however, relies instead on a magnetically-responsive liquid.

The substance consists of a silicone-based polymer with liquid droplets encapsulated within it. That "magnetorheological liquid" is in turn made up of water, glycerine and tiny particles of carbonyl iron – the liquid's composition is similar to that of milk, in which fat droplets are dispersed within an aqueous solution. When not being exposed to a magnetic field, the material remains soft and flexible. Once such a field is applied, though, the droplets become elongated, and the iron particles align themselves along the magnetic field lines. These two factors cause an almost 30-fold increase in the material's stiffness. In practise, this means that if the soft material is manually formed into a certain shape and then subjected to a magnetic field, it becomes rigid and holds that shape until the field is removed. When the latter happens, the material reverts to its original shape, and to its soft state.

[Source: New Atlas. 5 June 2019. Ben Coxworth]