The Tiniest of RFID Chips

Scientists say they've created tags small enough to fit inside human cells.
14 August, 2017
Scientists say they've created tags small enough to fit inside human cells.
RFID tags are at work whether they're checking out books from a library, working in a warehouse, or sailing through the toll plaza with their car's payment device. The tags work by emitting small signals from an antenna mounted to a microchip. That's streamlined the way identity and other data can be exchanged.

What most people haven't seen yet is an RFID tag so small that it's only 22 microns wide, about a fifth of a human hair, and so tiny that they can fit inside a human cell – a potential game-changer for medical research and health care. Scientists at Stanford University in California who described their new RFID tags in the journal Physical Review Applied said they've not only proved the wireless RFID tags work, but demonstrated that melanoma cells in mice can "swallow" the tag while it still remains intact.
The tags also fit into human melanoma, breast cancer and colorectal cancer cells, and healthy human connective tissue cells too, says lead study author Jasmine Xiaolin Hu. Most disease processes start at a single- to few-cell level, but there is no current technology to monitor a few cells inside the living body of a person, she added in a recent interview. Tracking and monitoring single cells may enable the early detection of diseases and targeted treatments that may lead to better outcomes. It also means that cell behavior can be scrutinized without destroying it or altering its processes.

One layer of the microscopic tags is made of a 5-nanometer-thick titanium and 200-nanometer-thick gold film. A second layer is made with a 1,000-nanometer-wide aluminum sheet, trapping a layer of hafnium dioxide insulation between them. They're currently in octagonal shapes, but Hu told science writer Charles Choi that they'd ideally be circular; so far, the octagons are the closest they can get.
The tiny tags carry two RFID antenna instead of one to boost their signal, and are sealed in silicon dioxide, which makes them safe to use in medical scenarios. They operate at 60 GHz, with a high signal magnitude up to −50 dB and a sensitivity of 0.2. What the researchers will do next is put them in motion in the lab, solving problems on how to read them accurately and tell the signals apart.

Stanford team member H.-S. Philip Wong, a professor in electrical engineering, notes that without real-time access to understand what's happening in cells, medical professionals have little information about chemical, electrical and other changes that are part of any disease process. The technology has advanced so that reliable monitoring and drug delivery can be achieved at the organ level, but not at the cellular.
Image: Stanford
"Progress in nanofabrication and wireless communication has opened up the potential of delivering miniaturized circuit components into living cells," Wong said while discussing his early-stage work. The advancements in that research now mean that a pH sensor might monitor acidity at the cellular level, providing a key indicator of overall health as well as a specific diagnostic finding; or it might keep a real-time record of glucose use, and the cell's energy level, efficiency or access to the cellular fuels.

How the RFID tags are used remains to be seen, but they're a big development for such tiny little devices.
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