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An award-winning Stanford University biology graduate, Mr McFadden uses rap music to communicate scientific concepts to children and to students at the American university.
He also creates innovative science music videos, which have gained international media coverage, including in England's Guardian newspaper.
His festival role would allow him to share his "contagious passion for biology, rap, and making science fun", he said.
Backed by the Otago Institute and Genetics Otago, he would visit Otago schools and work with pupils to turn science into rap music.
The seventh of the international science festivals, which runs from July 6 to July 11, will culminate with a rap competition to find New Zealand's first "science idol".
Festival director Sue Clarke said the festival would also focus on "Everyday Science: Food for Thought" , giving the public "a taste of science" and highlighting links between science and everyday life.
Its "dining in the dark" experience would include award-winning Auckland chef and author Julie Biuso and Dunedin motivational speaker and cook Julie Woods, also known as "that blind woman".
Dishes would be prepared by the guest chefs and the team at Otago Polytechnic's Technique Restaurant.
Ms Woods looked forward to the event, during which blindfolded members of the public would explore their sensory perceptions during an evening of fine dining.