Bioengineers and physicians have created an artificial ear -- using 3-D printing and injectable molds -- that looks and acts like a natural ear, giving new hope to thousands of children born with a congenital deformity called microtia. Scientists have described how 3-D printing and injectable gels made of living cells can fashion ears that are practically identical to a human ear. Over a three-month period, these flexible ears grew cartilage to replace the collagen that was used to mold them.