In 1873, Ayrton accepted an invitation from the Japanese government as Chair of Natural Philosophy and Telegraphy at the new Imperial College of Engineering, Tokyo.

He advised the college's architect on the design of the laboratory and demonstration rooms, and is credited with introducing the electric arc light to Japan in 1878.

[1] On his return to London, Ayrton became professor of applied physics at the Finsbury College of the City and Guilds of London Technical Institute, and, in 1884, he was chosen professor of electrical engineering, or of applied physics,[2] at the Central Technical College, South Kensington.

In 1872, Ayrton married his cousin, Matilda Chaplin (1846–1883), one of the Edinburgh Seven, the first group of matriculated undergraduate female students at any British university who fought for open medical education for women.

[3] In 1899, Ayrton supported Hertha on her way to being elected the first woman member of the Institution of Electrical Engineers and the Royal Society awarded her a Hughes Medal in 1906.