Engineering news
Researchers from China have found a way to control the movement of microscopic crystals using magnetism, opening up the possibility of more targeted drug delivery in the body and “smart fluids”
Kezheng Chen and Ji Ma from Quingdou University of Science and Technology, Quingdou, China have successfully produced “superparamagnetic crystals” that are large enough to control with magnets.
When some magnetic materials, such as iron oxides, are small enough, such as a few millionths of a millimetre across, their magnetisation randomly flips as the temperature changes.
By applying a magnetic field to these crystals, scientists can make them almost as strongly magnetic as ordinary fridge magnets. This phenomenon, which is called superparamagnetism, is the strongest type of magnetism known.
Researchers believe that superparamagnetic particles would be ideal for drug delivery, as they can be directed to a tumor simply by using a magnetic field. However, their tiny size, has until now made them difficult to guide precisely.
Dr. Chen from Quingdou University of Science and Technology said: "The largest superparamagnetic materials that we have been able to make before now were clusters of nanocrystals that were together about a thousand times smaller than these.
"These larger crystals are easier to control using external magnetic fields, and they will not aggregate when those fields are removed, which will make them much more useful in practical applications, including drug delivery."
The crystals were formed under high temperature and pressure conditions causing them to form irregularities and defects which are responsible for their unusual magnetic properties. Magnetite crystals of a similar size that are grown at a lower temperature and under normal pressure are only very weakly magnetic.
This method of making larger superparamagnetic crystals paves the way for the development of superparamagnetic bulk materials that can be reliably controlled by moderate external magnetic forces, potentially revolutionising drug delivery to tumors and other sites in the body that need to be targeted precisely.
According to Chen the crystals might also be useful in many engineering projects that need "smart fluids" that change their properties when a magnetic field is applied. Potential applications may include vehicle suspension systems that automatically adjust as road conditions change, increasing comfort and safety, and to build more comfortable and realistic prosthetic limbs.
The research has been published in Physics Letters A and is free to download until May 2017.