The University of Regina Library established a research partnership with a computer science researcher with expertise in interactive information retrieval. This partnership leverages the Primo Search API to facilitate design-oriented research (Fallman, 2003) in digital library search interfaces. For several years, graduate students in computer science have used the Primo Search API to develop and test exploratory search interface prototypes for their thesis research. In this presentation, we will discuss the key principle underlying this approach and how it differs from how libraries and vendors typically approach design questions. We will provide several examples of research projects completed or underway, including some of the benefits for graduate students and the challenges they face when working with the Primo Search API. Finally, we will describe a student project that has moved beyond the research prototype phase and is now deployed as an enhancement to Ex Libris Primo at our institution.