From Discovery News: Artificial muscles can be made with cables on pulleys, driven by heat, or twisted together from carbon nanotubes. But it’s been hard to duplicate the way muscle cells contract and relax at the cellular level, driven by little more than the impulses from the brain. That is starting to change. A recent study by a team headed by Nicolas Giuseppone at France’s Université de Strasbourg shows it’s possible to make molecules that respond to changes in the acidity of a solution. By stringing the molecules together, they got a chain that contracted when the pH was higher and expanded when the pH was low.