Due to the continued rise in drug abuse, there is a critical need for an enhanced on-site presumptive detection method for identifying the possession of illicit drugs. Presumptive field tests are most commonly colorimetric and are susceptible to various complications arising from manual operation these commercial color kits. Additionally, several different color tests are required for complete unknown sample identification, i.e., a separate test is used for identification of cocaine, methamphetamine, heroin, etc. A microfluidic device that can incorporate the multiple color tests utilized for unknown samples into a single device for cost-effectiveness and increased simplicity, and is amenable to objective analysis techniques, is well-suited to address the current on-site color testing limitations. Unfortunately, many of the validated color tests used for detecting illicit drugs contain harsh chemical reagents that are not compatible with inexpensive microfluidic device substrates, i.e., paper and thermoplastics, limiting microfluidic device developments for this application. Here, we propose a simple fabrication technique for generating custom capillary ampules for containing small volumes of chemical reagents that is compatible with cost-effective, thermoplastic centrifugal microfluidic devices, a platform that has shown to be advantageous for field use. Colorimetric reactions for the detection of methamphetamine, codeine, heroin, cocaine, 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) were utilized here for proof-of-principle. Additional utility of this reagent storage approach was evaluated for fluid movement towards the center of rotation within centrifugal devices, allowing for more complex sample processing. Inward fluid movement was performed over a radial distance of 50 mm within 3 s.
