New advances in cell engineering for personalized therapies can benefit from selection of individual cells based on their complex behaviors or time-dependent functions (such as cell killing, secretion, or movement). Current cell sorting technologies mainly use cell surface markers as a surrogate for cell function, observing these markers instantaneously during sorting processes, instead of looking at cell function itself.

To address this challenge, a UCLA-led interdisciplinary research team developed arrays of magnets to isolate magnetically-tagged cells, observe them, and then selectively release one based on a time-dependent behavior. Electromagnets at the scale of cells are two weak and consume too much power, so they instead looked to a new type of exotic magnetic material, Terfenol-D, that can maintain strong magnetic poles, but can be switched intermittently with an electric field. These types of materials are called multiferroic, and are the focus of the NSF Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems (TANMS) located at UCLA and directed by Greg Carman, Professor of Mechanical and Aerospace Engineering.

The study, published online in the journal Advanced Materials, was supervised by Dino Di Carlo, the Armond and Elena Hairapetian Professor of Engineering and Medicine, Greg Carman, Professor of Mechanical and Aerospace Engineering (MAE) and Rob Candler, Professor of Electrical Engineering (EE). Reem Khojah, a PhD student in the department of Bioengineering was the lead author. Co-first authors Zhuyun (Maggie) Xiao (EE) and Dr. Mohanchandra K. Panduranga (MAE) with additional collaborators included a team at UC Berkeley and the Lawrence Berkeley National Laboratory.

The team first fabricated Terfenol-D microstructures at scales the size of a cell over the surface of a wafer. They found that the structures possessed a single magnetic domain over a larger area than found in previous magnetic materials, leading to higher magnetic field strengths. These Terfenol-D microstructures enabled controlled trapping of magnetic beads with sub-micrometer precision.  Magnetically labeled cells were then captured by the large magnetic field gradients generated from the single-domain microstructures. The magnetic state on these microstructures was switched through applying voltage to another material adjacent to the Terfenol-D micro-magnets. The electric field caused that material to deform and therefore modulated the magnetic state of the Terfenol-D micro-magnets, releasing individual cells.