Jul 19 2019
Conventional magnets are rigid and hard but have contributed in great measure to society and contemporary industry, says materials scientist Thomas Russell of the University of Massachusetts Amherst. This award-winning visionary decided to do more. He visualized soft magnets that are flowable as liquid and malleable to conform to a narrow space.
Three liquid magnets float in the oil phase, spinning and dancing with each other in the rotating external magnetic field. Red dye records the track induced by flowing vortex. (Courtesy Berkeley National Lab/Xubo Liu)
In an article published recently in Science, he and first author Xubo Liu from Beijing University of Chemical Technology, with others at Lawrence Berkeley National Laboratory and the University of California, Berkeley, talk about a simple method they formulated to change paramagnetic ferrofluids—plain metal particles in suspension—into a magnetic state. The new ferromagnetic liquid droplets “represent a milestone for the further development of magnetic materials,” Russell says.
This means that when an external magnetic field is applied, researchers can manipulate liquid devices designed this way, like waving Harry Potter’s wand, he puts forth, “which opens promising research and application areas such as liquid actuators, liquid robotics, and active-matter delivery.”
As the polymer scientist explains, he, Liu, and the team used iron oxide nanoparticles in a distinctive oil-polymer mixture to convert paramagnetic ferrofluid into the ferromagnetic state at room temperature. Due to nanoparticle-polymer mix interactions, the resulting ultra-soft droplet has magnetic properties akin to solid magnets but with liquid features.
At the nanoscale, traditional ferromagnetic materials become magnetic only when exposed to a magnetic field. Based on these exceptional physical properties, ferrofluids are already used in mechanical engineering, medical applications, electrical devices, and materials science research, he observes.
Russell, who is also a visiting professor at the Berkeley National Lab, adds that the method enriches the scientific knowledge of magnetic materials, and should inspire research into the deep-seated mechanism of how liquid magnets develop.
This will facilitate the development of relative advanced instruments and new material theories. These amazing liquid magnetic materials will attract attention in biology, physics, and chemistry.
Thomas Russell, Materials Scientist, University of Massachusetts Amherst
A thousand years ago, he reflects, European explorers used compasses they made using magnetite dug from the Earth to search and discover new continents. For centuries, people learned to design smart magnetic devices to enhance the quality of life. “Such jumps in science and technology are always followed by a sudden emergence of a new material or theory,” Russell notes.
He and contemporaries anticipate that the new, reconfigurable ferromagnetic liquid droplets they describe will offer more such prospects, such as liquid vessels for delivering active matter, magnetically actuated liquid robotics, and information technology with programmable liquid droplet patterns.
This research was backed by the U.S. Department of Energy, the Office of Science at Lawrence Berkeley National Lab including Molecular Foundry and National Center for Electron Microscopy, the Beijing National Science Foundation, the Beijing Advanced Innovation Center for Soft Matter Science and Engineering at Beijing University of Chemical Technology and the China Scholarship Council.