Humanity has entered an era where computing technology is virtually ubiquitous. From websites and mobile devices to computers embedded in appliances on our kitchen counters and automobiles parked in our driveways, information and communication technologies (ICTs) and IT artifacts are fundamentally changing the ways we interact with our world. Indeed, the world itself changing, becoming ever more artificial. It is a designed world that we have created for ourselves. Human-computer interaction (HCI) scholars are concerned with the interactions that occur between people and technology in this new world: how do IT artifacts impact the human experience, and how can knowledge of the human experience impact the design of new computer-based systems? At the same time, HCI is design-oriented, a community where scholars seek to shape the design of new IT artifacts, and make real improvements to the world we live in. It remains an unresolved challenge to bring these scholarly and design perspectives together. Various models and approaches have been proposed, but current thinking on a "design science" for HCI is in flux. This multi-paper dissertation draws upon existing literature from HCI, various design communities, and information systems (IS) to develop a new model of design science: the theory, design, and evaluation (TDE) model. The TDE model, informed by an included research paper, envisions that scholarly activities and design activities can occur in parallel across the three stages of theory, design, and evaluation. The TDE model is demonstrated using an additional three included papers, each one taken from a separate TDE design science project. These ongoing projects occur in widely varied contexts--gaming for citizen science, online nuisances, and military history education--but each has the TDE model as its central organizing structure. The papers are examples of TDE knowledge outcomes, but also address design outcomes from each project. The three projects are analyzed and connected directly to various elements of the TDE model itself. In addition, the final chapter describes future directions for the three projects and the TDE model, as well as thinking on the importance of design science in HCI scholarship. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]