Hayes told ESPN that he wanted to "create conversation" about compensation for college athletes. All funds will be given to the Boys & Girls Clubs of Dane County, according to Hayes.
The Badgers star said he's using a friend's account on Venmo -- the company describes itself as a "digital wallet that lets you make and share payments" with others -- and never intended to make money for himself.
"Obviously, me accepting money is illegal," he told ESPN. "Therefore, I used my friend's account. And as I said, all proceeds will be going to the Boys & Girls Club. The sign was strictly to generate conversation."
Hayes told ESPN's Darren Rovell his action was simply the electronic equivalent of what he did earlier in the season at Wisconsin's Camp Randall Stadium, where he campaigned for donations for charity.
Hayes has previously spoken out about the NCAA and Big Ten's financial treatment of student-athletes. On Friday, he sent a series of tweets comparing the revenue taken in for college athletics to the value of his scholarship.
You make a company millions. They "pay" you with only a college education (estimated UW $160,000).— Nigel Hayes (@NIGEL_HAYES) October 14, 2016
Fair, right? https://t.co/Hy3yKP42hH
He followed up Saturday by saying student-athletes deserve more than their current stipends, and that each institution -- not the NCAA -- should have the power to pay its athletes appropriate compensation.
"Allowing the schools to decide payment would be the best option," he said.
"This conversation will continue to be had. It's my hopes that one day ALL college kids decide to sit out of sport and school until someone negotiates new circumstances for them," Clarett wrote. "When you disrupt the money you get people's attention."
Hayes, a senior, was named the preseason Big Ten Player of the Year after averaging 15.7 points and 5.8 rebounds per game last season. Wisconsin opens its regular season Nov. 11 against Central Arkansas.
Information from ESPN.com's Myron Medcalf was used in this report.