Transporting molecules across biological membranes is essential for life. In nature, this can occur through passive transport, known as diffusion. “Biological systems often use mechanical motion to accomplish tasks that cannot be achieved by diffusion alone,” says Professor Laura Na Liu, director of the 2nd Physics Institute at the University of Stuttgart. For example, certain bacteria use extracellular contractile injection systems. These molecular nanomachines puncture target cells and deliver molecular cargo.
