The Electro-LEV system. Credit: Durmus Lab

It looks like a magic trick: Cells at the bottom of a liquid medium begin levitating, then hovering at a particular height. With no physical contact, an invisible force directs certain cells to float up or down in unison, like mini-submarines.

But there’s no sleight of hand going on here. It’s all taking place in a new cell-sorting device that uses electromagnetic levitation to precisely direct the movement of cells. Developed by Stanford Medicine researchers and collaborators, the device can be used to separate different types of cells—cancer cells from healthy cells, or live cells from dead cells, for example—with many potential applications in the lab and in the clinic.

“In the clinical setting, you may have a very low volume biopsy sample, and you want to look at certain cells and keep them viable for further genomic testing—that would be a perfect application for this technology,” said Gozde Durmus, Ph.D., assistant professor of radiology and senior author of a paper published in the Proceedings of the National Academy of Sciences describing the new technology.

The lead author is Malavika Ramarao, a former researcher in Durmus’ lab.

Unlike other cell sorting techniques, the new device, called Electro-LEV, does not require attaching fluorescent labels or antibodies to cells, or exposing them to harsh chemicals or centrifugal forces. Instead, cells are separated based on their density and magnetic susceptibility.

“We can sort them gently,” Durmus said.

Credit: Stanford University

A pair of magnets

Electro-LEV builds on a simple magnetic levitation system that Durmus developed more than a decade ago. In 2015, she published a paper showing that the system could levitate just about any type of cell.

“Cells can levitate because everything on Earth has some inherent magnetic properties,” Durmus said.

The magnetic levitation system consists of a pair of magnets, each about the size of a stick of gum and slightly stronger than ordinary refrigerator magnets, placed one on top of another, north pole to north pole and south pole to south pole.

A narrow glass capillary, 1 millimeter in diameter, is sandwiched between the two magnets. Cells in a paramagnetic solution flow through the capillary. (Paramagnetic solutions, such as the contrast agents used to enhance MRI scans, slightly amplify an external magnetic field.)

“The magnetic forces we work with are very small, around 0.4 Tesla,” Durmus said. “But the beauty of our system is that we put the magnets so close to each other that the magnetic field gradient is very big. That’s the trick.”

The magnetic field gradient is the change in magnetic field strength over distance, and increases when two magnets are closer together. The greater the gradient, the more force it applies to objects in the field.

In comparison, the powerful magnets in MRI machines are about 7 Tesla, but are roughly 1 meter apart. “The magnetic field gradient in an MRI machine is actually smaller than what we create in our teeny-tiny machine, in which the magnets are 1 millimeter apart,” Durmus said.

Inside the capillary, the magnetic field gradient causes the cells to levitate to an equilibrium point. The exact height depends largely on a cell’s density, which differs by cell type and condition.

Although the magnetic levitation system described in the 2015 paper allowed researchers to visually distinguish different types of cells, the differences were often too small to practically sort the cells. The setup was also static, meaning there was no way to adjust the conditions during an experiment.

“After you levitated a cell, if you wanted to levitate it further, you needed to prepare a new sample to adjust the paramagnetic properties. That was a challenge,” Durmus said.

Changing the current

The new device adds electromagnetic coils to both magnets. By adjusting the electric current running through the coils, the researchers can instantaneously modify the magnetic force applied to the cells.

“With our current design, you can very precisely manipulate the cells to separate them further,” Durmus said.

Cells levitating at distinct heights are sorted as they flow out of the capillary, which branches into a top outlet and bottom outlet.

“If the sorting is not going well, you just change the current,” Durmus said. “Everything is under your control in real time, so it’s more user-friendly.”

Dead or alive

In the new study, the researchers demonstrated that Electro-LEV could fine-tune the levitation of a variety of cell types, including breast cancer cells, lung cancer cells, fibroblasts and white blood cells.

They then tested the system’s ability to tackle a common problem in the preparation of biological samples—separating live cells from dead cells. For accurate single-cell RNA sequencing and drug toxicity screening, for example, dead cells need to be weeded out. And in stem cell transplantation, dead cells can trigger dangerous inflammatory responses.

Luckily, dead cells don’t fly as high as live ones. “Once cells are dead, usually their cell membranes are damaged and they are more leaky, so they take up more paramagnetic solution and become more dense,” Durmus said.

When the researchers began with a sample of 50% live cells, they found that Electro-LEV could sort live and dead cells well enough to achieve a sample of about 93% live cells. Even with a starting sample of only 10% live cells, Electro-LEV could achieve a sample of about 70% live cells.

The system may even have the potential to sort cells of similar density. The researchers discovered that, compared with single cancer cells, clusters of cancer cells reacted more quickly to changes in the magnetic field. That’s because single cells have more surface area relative to their volume and experience more drag force.

The phenomenon suggests that levitation speed could be a way to monitor for clusters of cancer cells, which tend to be more aggressive and more likely to cause metastasis, Durmus said.

She envisions far-ranging applications for electromagnetic levitation, sorting everything from cancer cells to microbes, assembling cells into organoids or even directing microrobots.

“It’s a broad, versatile platform,” Durmus said. “I think there will be applications that we haven’t even thought of yet.”

Mehmet Burcin Unlu, a researcher from Ozyegin University in Turkey, also contributed to the work.

More information: Malavika Ramarao et al, Dynamic and precise electromagnetic levitation of single cells, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2512246122

Citation: Electromagnetic device identifies cells by seeing how high they levitate (2025, October 24) retrieved 24 October 2025 from https://phys.org/news/2025-10-electromagnetic-device-cells-high-levitate.html

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