RainDance Technologies has taken a step toward completing its long-planned IPO by filing the paperwork for a $60 million offering. The Billerica, MA-based genomic tools business began talking up the prospect of an IPO back in 2013 when it raised $35 million in debt financing. Now, RainDance has decided the time is right to try to hop through the IPO window. The company has no particular plans for the money it raises, but is keen to list so it has access to public equity in the future. S-1