He is best known for his patent, held jointly with Billy Gene Harper of Dow Chemical, that made the possible the production of modern "superabsorbent" disposable diapers.
He spent most of his childhood in Santa Clara, California, and he was a lifelong Mormon.
At age ten he took a job at a printing office for a man named Henry Roth.
The disposable diaper, in its original form invented by Victor Mills of Procter & Gamble, required a core of thick rolls of paper in order to adequately contain fluid and guard against diaper rash.
In 1966, Harmon and Harper each independently discovered that a small amount of a highly absorbent polymer could be more effectively used in place of rolls of paper in the diaper's core.