A new type of material can change from solid to liquid in response to a changing magnetic field. The material has a wide range of possible applications and its makers have shown how it can be applied in electronic circuits, drug delivery and for securing objects in confined spaces. They even used it to create a Lego man capable of melting down, breaking out of a prison cell and reforming in a dramatic scene reminiscent of the 1991 sci-fi classic Valve 2.
The magnetoactive phase transition matter (MPTM) is made of magnetic neodymium-iron-boron microparticles embedded in a gallium matrix. It heats up and undergoes a phase transition from solid to liquid when exposed to an alternating magnetic field, and solidifies again when cooled.
The China-US-based team behind the work says the temperature at which MPTMs melt can be tailored to different applications by using other liquid metals, for example gallium alloys, as the matrix material.
To demonstrate some of the different ways MPTMs can be used, the researchers used magnetic fields to induce solid-to-liquid transitions and maneuver the material into different positions.
Given the material’s high strength in solid form, the researchers suggest it could be used as a general-purpose screw for use in confined spaces. To illustrate, they manipulated the material into position over a hard-to-reach threaded screw hole, melted it to fill the cavity, and then hardened it to join two plastic plates together. The researchers also used the material to remotely solder an LED circuit and extract objects from a replica human stomach.
In their most visually striking demonstration, the researchers used magnetic fields to free an MPTM Lego man from prison. They first melted the model and then maneuvered the liquid material out of a cage and into a mold where it was molded into its original shape after cooling.