Will biometric implants become the norm?

Wearable device could be attached to the skin to measure tumours

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Stanford University engineers have developed a small, autonomous device that can be adhered to the skin to measure the changing size of tumours below.

The Flexible Autonomous Sensor measuring Tumors (FAST) device could represent a new, fast, inexpensive, hands-free, and accurate way to test the efficacy of cancer drugs, and even lead to promising new directions in cancer treatment, according to the researchers. 

The process of finding new therapies for the detection of subcutaneous tumours is slow because technologies for measuring tumour regression from drug treatment take weeks to read out a response, making drug screenings difficult and labour-intensive.

"In some cases, the tumours under observation must be measured by hand with callipers," says Alex Abramson, the project's lead researcher.

In contrast to the less-than-ideal use of metal pincer-like callipers to measure soft tissues, and radiological approaches that cannot deliver the data needed for real-time assessment, FAST can detect changes in tumour volume on the minute-timescale. 

The non-invasive, battery-operated device is sensitive to one-hundredth of a millimetre (10 micrometres) and can beam results to a smartphone app wirelessly in real time with the press of a button. The previously mentioned methods - calliper and bioluminescence measurements - often require weeks-long observation periods to read out changes in tumour size.

FAST's sensor is composed of a flexible and stretchable skin-like polymer that includes an embedded layer of gold circuitry. This sensor is connected to a small electronic backpack. The device measures the strain on the membrane—how much it stretches or shrinks—and transmits that data to a smartphone.

The breakthrough is in FAST's flexible electronic material. Coated on top of the skin-like polymer is a layer of gold, which, when stretched, develops small cracks that change the electrical conductivity of the material. When the material contracts, the cracks come back into contact and conductivity improves.

Using the FAST backpack, potential therapies that are linked to tumour size regression can quickly and confidently be excluded as ineffective or fast-tracked for further study.

After conducting experiments with mice, the researchers concluded that FAST had three advantages compared to other methods. First, it can provide continuous monitoring. Second, it is able to measure shape changes that are otherwise difficult to discern. Third, FAST is both autonomous and non-invasive.

The device is connected to the skin, battery-operated, and connected wirelessly. The mouse is free to move unencumbered by the device or wires, and scientists do not need to actively handle the mice following sensor placement. FAST packs are also reusable, cost just $60 (£50) or so to assemble, and can be attached to the mouse in minutes.

One hurdle the researchers had to overcome was the concern that the sensor itself might compromise measurements by applying undue pressure to the tumour, effectively squeezing it. To circumvent that risk, they carefully matched the mechanical properties of the flexible material to the skin itself to make the sensor as pliant and as supple as real skin.

"It is a deceptively simple design," Abramson says, "But these inherent advantages should be very interesting to the pharmaceutical and oncological communities. FAST could significantly expedite, automate, and lower the cost of the process of screening cancer therapies."

The researcher's findings were published in the journal Science Advances.

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