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Soft Sensors Map Skin Mechanics

Materials: Piezoelectric nanoribbons help create pliable devices

by Matt Davenport
May 21, 2015 | A version of this story appeared in Volume 93, Issue 21

Piezoelectric skin sensor
Credit: Nat. Mater.
This colorized electron micrograph shows a new piezoelectric device is composed of actuators (larger ribbons) and sensors (smaller ribbons).

An international research team led by John A. Rogers of the University of Illinois, Urbana-Champaign, has built electronic, flexible patches that can measure the mechanical properties of skin and other biological tissue (Nat. Mater. 2015, DOI: 10.1038/nmat4289).

The researchers mapped the skin elasticity of dozens of patients in the clinic, building up quantitative data on healthy and damaged tissue. The information could help doctors better assess conditions such as dermatitis and skin cancer. The team believes that similar sensors could be implanted inside the body to monitor blood vessels and other soft tissue for damage or dysfunction.

To measure tissue biomechanics, the team turned to nanoribbons of a piezoelectric material, lead zirconate titanate, which deforms when jolted with electrical energy and, conversely, produces electricity when it’s deformed. The ribbons were thin enough to flex, even after they were sandwiched between thin gold and platinum electrodes. The team connected the plated piezoelectrics to external power supplies and data collection systems using a mesh of narrow, serpentine wires.

Thanks to their geometries, these materials remained flexible when the team encapsulated them in polyimide, a polymer with mechanical properties similar to skin, Rogers says. Researchers could then affix a bandagelike device to a patient’s skin, where it would gently drum on the tissue with tiny piezoelectric actuators. Nearby piezoelectric sensors detected how skin vibrates in response to the drumming, allowing the team to determine stiffness of the tissue.

“The device’s response and overall acceptance across a large number of patients are particularly encouraging,” says Stéphanie P. Lacour of the Swiss Federal Institute of Technology (ETH), Lausanne, who was not involved in the study. For something like this to be useful, patients must be willing to try it in the doctor’s office, Rogers tells C&EN. He attributes the device’s early acceptance to its soft and flexible body, saying, “It’s a lot less daunting than the types of tools that one typically encounters in a doctor’s office.”



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