Artists impression over photo:

“Cardiac tissue is very special,” said Jun Yao of UMass Amherst’s college of engineering. “It has a mechanical activity – contractions and relaxations that pump blood through our body – coupled to an electrical signal that controls that activity.”

‘Cardiac micro-tissue’ is the material of interest, according to the university, which is grown from human stem cells and is vulnerable to damage if sensors are inserted after growth. Hence the need to grow on a pre-existing matrix of sensors, in a way that allows it to grow unimpeded.

Monitoring ‘excitation-contraction coupling’ in the sample was the aim of the experiment, by measuring both the self-generated electrical stimulus from the tissue and any resulting movement.

The team designed 20 x 20μm graphene transistors – roughly the size of a cell – to do the sensing, with their channels modulated by local electrical potentials through the field effect, while simultaneously detecting mechanical movement because they are naturally piezo-resistive.

“Because graphene is impossibly thin, it can register even the tiniest flutter of muscle contraction or relaxation, and can do so without impeding the heart’s function,” according to the university.