After moving to Maine, Farnsworth became increasingly interested in nuclear fusion. He believed that fusion offered a clean and abundant source of energy. This became his primary focus for many years.

Farnsworth developed the 'Fusor,' a device designed to achieve nuclear fusion through inertial electrostatic confinement. Although his early designs were not commercially viable for power generation, the Fusor concept has found applications in research and industrial fields.

Farnsworth formed Philo T. Farnsworth Associates, a company focused on developing and marketing his fusion technology. However, the company faced financial challenges and was unable to secure sufficient funding to fully commercialize his fusion research.

Farnsworth also developed other inventions, which included an infant incubator, a metal fastener, and improved telescopes.