A sticky, stretchy semiconductor for bioelectronics

Biological tissues rely on electrical or ionic signals for many functions—but because tissues are irregularly shaped, wet, and constantly in motion, those signals can be difficult to monitor. Researchers have developed materials that can adhere to tissue, but combining that adhesion with semiconducting remains a challenge. In a paper published in Science and a presentation on Monday at the ACS Fall 2023 meeting, researchers at the University of Chicago and Argonne National Laboratory reported a new tissue-adhesive semiconductor material that can combine these properties to measure signals like the ones that power brain and muscle activity (2023, DOI: 10.1126/science.adg8758).

Designers led by Sihong Wang, an engineer at the University of Chicago, had previously developed a stretchy, semiconductive polymer (Science 2017, DOI: 10.1126/science.aah4496). In the current work, the authors blended it with a polymer based on other bioadhesives that combines carboxylic acid and N-hydroxysuccinimide (NHS) functional groups. The carboxylic acid moieties temporarily dry the tissue surface and form electrostatic interactions with it; removing the water enables the NHS to form covalent bonds with primary amines in proteins on the surface of tissues. The two polymers form together, in what’s known as a double-network architecture.

“The double-network system the authors used was a brilliant choice,” Yuhan Lee of Harvard University, who was not involved in the study, wrote in an email. He added that the material “mixes the adhesive and semi-conductor properties down to the molecular level.”

The resulting material can remain stuck even through a gentle pull, and can be stretched and abraded without losing performance. When implanted into an animal, they found, it causes less scar tissue formation than other semiconductor materials. The researchers used the material to build a sensor that only has to be gently pressed into place to record electrical activity from the heart or skeletal muscles in live animals without sliding out of position. According to Wang, this is the first time anyone has combined bioadhesion and semiconducting properties successfully.