Development of Portable Sample-In-Answer-Out Microfluidic Systems for On-Site Analyte Detection

Microfluidic devices used in the field, whether for clinical or forensic applications, offer many advantages for translating conventional instrumentation to a portable, field-deployable platform. The scaled-down size of these devices offer advantages for rapid analysis, low cost substrates and instrumentation, low reagent and sample consumption, automated sample processing, and simple operating procedures. A core requirement of field technology is that the analysis technique can be performed independently of a centralized facility. To address this requirement, extensive research has been focused on the complete integration of all processes of an analysis technique that would normally be performed in the laboratory into a single microfluidic platform and making the operation of this platform automated for unskilled users. This dissertation presents two specific forensic applications for consideration, illicit drugs and explosives, for developing microfluidic technology.

The chapters that follow describe the development of microfluidic devices, and associated features, for various on-site colorimetric analyses. Chapter 1 provides the necessary background regarding trends in inexpensive microfluidic device fabrication techniques with discussion of complementary microfluidic platforms. Additionally, various examples of microfluidic devices used for analysis of explosives and illicit drugs are presented. The goal of the work presented in Chapter 2 was to determine a method towards presumptive on-site testing of illicit drugs using inexpensive, single-use centrifugal microfluidic devices. An objective colorimetric analysis technique for use with an Android cell phone application was evaluated for the detection of cocaine and methamphetamine from a unknown samples. The work described in Chapter 3 was to explore various chemical reagent storage methods to aid in the complete integration of microfluidic devices for increased portability. Initial chemical storage methods utilizing inkjet printing, custom glass capillary ampules, and hybrid polyester-paper devices were evaluated for the integration of the chemicals necessary for various colorimetric reactions. Described reagent storage techniques were utilized in Chapters 4 and 5 for explosives colorimetric analysis. Towards the development of an on-site analysis technique, a surface swab was determined for sampling residue from a surface to interface sampling with the microfluidic device. The final fully-integrated device exhibited a 90% success rate of 40 samples evaluated for the detection of 8 different explosive compounds within 8 minutes.