Microfluidic devices, method for making and using same are disclosed. The microfluidic device can be made by applying a reagent in liquid form into a sample treatment site within a substrate base. The substrate base has hydrophilic properties bordering a flow channel, and has an application site, the sample treatment site and an analytical site. The flow channel is sized and configured so as to draw a sample applied into the application site to the analytical site through the sample treatment site by capillary action. The reagent is freeze-dried within the sample treatment site.