Heart patches grown from stem cells on biodegradable scaffolds could one day help treat heart attacks or congenital heart problems. But heart tissue is a mechanical marvel that's hard to mimic. Any substitute must be flexible enough to permit the contractions that drive blood through the body but strong enough to withstand them.

A new scaffold material developed by researchers at MIT approximates the mechanical, structural, and electrical properties of natural heart tissue. It's made of a biodegradable, rubber-band-like polymer carved with a laser into an accordionlike honeycomb pattern. The scaffold encourages cells grown on it to align themselves in the same direction, as they do in natural heart tissue. Because of the honeycomb pattern, the material is stiffer in the direction in which the cells are aligned than it is in the perpendicular direction, so it's both strong and flexible. When stimulated with electricity, muscle grown on the honeycomb scaffold beats just like heart tissue. So far, by seeding their scaffolds with heart cells from newborn rats, the researchers have made thin tissues that very closely mimic the properties of the heart's right ventricle.