The optofluidic ring resonator (OFRR) is a label-free refractive index biosensing platform that uses a glass capillary as a microfluidic sample delivery mechanism with an inherently integrated optical ring resonator. The device delivers molecular detection limits on par with the top-performing commercial label-free sensing technologies while reducing cost and complexity compared with fluorescence-based biosensing techniques as well as other label-free devices. The OFRR has been shown to quantify target molecules in a sample through specific biomolecular recognition events at the surface of the capillary. Examples presented here include protein detection, DNA sequence detection, and pathogen detection. The design of the OFRR makes it well-suited for integration into a lab-on-a-chip platform that will have significant implications for the diagnosis and understanding of disease.