Described herein are microfluidic devices and methods of detecting an analyte in a sample that includes flowing the sample though a microfluidic device, wherein the presence of the analyte is detected directly from the microfluidic device without the use of an external detector at an outlet of the microfluidic device. In a more specific aspect, detection is performed by incorporating functional nanopillars, such as detector nanopillars and/or light source nanopillars, into a microchannel of a microfluidic device.