The Wyss Institute’s human breathing lung-on-a-chip, made using human lung and blood vessel cells, acts much like a lung in a human body. A vacuum re-creates the way the lungs physically expand and contract during breathing. [...] The scientists developed this prototype while keeping track of the natural design of our lungs. It is made of breathable silicone rubber acting as blood vessels that get as small as one-fourth of the width of a human hair. Because it works on the same scale as normal lung tissue, the team was able to shrink the distances for gas diffusion compared to current techniques. Tests using pig blood show oxygen exchange efficiency is three to five times better.