The extraordinary controllability of DNA nanostructures provides great potential for nanotechnology and biotechnology, with diverse applications including drug delivery, sensing, and materials synthesis. However, DNA-based systems are limited in their realworld applications, particularly with respect to diagnostics. In particular, they are high complexity, require expensive equipment, and have specific operation conditions. To overcome these challenges, recent work has demonstrated the power of integrating DNA and microfluidics. The multifunctionality, controllability, and design versatility of DNA make it incredibly well suited for the detection of nucleic acid targets, chemicals, and small molecules. Moreover, microfluidic technology is ideal for clinical and point-of-care (POC) detection by providing small, highly controlled, self-contained systems for executing DNA-based reactions with high accuracy and precision. Thus, in this Dissertation I discuss two important themes underlying the use of DNA materials for diagnostics: 1) DNA is a remarkable structural polymer that enables controlled assembly of multifunctional probes for multiplexed detection, and 2) DNA's biological role in enzymatic amplification can be harnessed for engineering novel POC detection strategies. This fusion of "structure" and "function" exemplifies the power of DNA as both a genetic and generic material, and it will ultimately lead to great advancements in the field of nucleic acid diagnostics. iii