Flexible sensor measures changes in subcutaneous tumors

Engineers at Stanford University and Georgia Institute of Technology have created a small, autonomous device with a stretchable, flexible sensor that attaches to the skin and measures changes in the size of underlying tumors. The battery-powered, non-invasive device has a signal sensitivity of 10 microns and can wirelessly transmit the results in real time to a smartphone app at the push of a button.

The researchers said that this "Flexible Autonomous Sensor for Measuring Tumors" (FAST) represents a new, fast, cheap, portable and accurate method to test the efficacy of anti-cancer drugs. In the long run, it may point out new directions for cancer treatment. The FAST sensor can detect changes in tumor volume on a minute scale, while caliper and bioluminescence measurements usually require weeks of observation to measure changes in tumor size.

FAST consists of a flexible and stretchable skin-like polymer that includes a layer of embedded gold circuitry. The sensor is attached to a small electronic backpack. The device measures the tension (degree of stretch or contraction) on the film and transmits the data to a smartphone. Using the FAST backpack, potential therapeutic efficacy associated with tumor size regression can be quickly and accurately determined or fast-tracked for further study.

The researchers say the new device offers at least three significant advances. First, it provides continuous monitoring because the sensors are physically connected to the mouse and remain in place throughout the experiment. Second, the flexible sensors wrap around the tumor, making it possible to measure shape changes that would be difficult to discern with other methods. Third, FAST is both autonomous and non-invasive. It attaches to the skin like a Band-Aid, is battery-operated, and wirelessly connected. The mouse can move freely without being hindered by the device or wires, and scientists do not need to actively operate the mouse after placing the sensors. The FAST backpack is also reusable, costs only about $60 to assemble, and can be connected to the mouse in a few minutes.

“It’s a deceptively simple design,” said Alex Abramson, lead author of the study, a postdoctoral fellow in Zhenan Bao’s lab at Stanford’s School of Engineering and now an assistant professor at Georgia Tech. “But the pharmaceutical and oncology communities should be very interested in the advantages. FAST is automated, which could greatly speed up and reduce the cost of the cancer therapy screening process.”