MICROFLUIDIC ASSAY PERFORMANCE ENHANCEMENT USING POROUS VOLUMETRIC DETECTION ELEMENTS FOR IMPEDEMETRIC AND OPTICAL SENSING

Microfluidic technologies have great potential to help create automated, cost-effective, portable devices for rapid point of care (POC) diagnostics in diverse patient settings. Unfortunately commercialization is currently constrained by the materials, reagents, and instrumentation required and detection element performance. While most microfluidic studies utilize planar detection elements, this dissertation demonstrates the utility of porous volumetric detection elements to improve detection sensitivity and reduce assay times. Impedemetric immunoassays were performed utilizing silver enhanced gold nanoparticle immunoconjugates (AuIgGs) and porous polymer monolith or silica bead bed detection elements within a thermoplastic microchannel. For a direct assay with 10 µm spaced electrodes the detection limit was 0.13 fM AuIgG with a 3 log dynamic range. The same assay was performed with electrode spacing of 15, 40, and 100 µm with no significant difference between configurations. For a sandwich assay the detection limit was10 ng/mL with a 4 log dynamic range. While most impedemetric assays rely on expensive high resolution electrodes to enhance planar senor performance, this study demonstrates the employment of porous volumetric detection elements to achieve similar performance using lower resolution electrodes and shorter incubation times. Optical immunoassays were performed using porous volumetric capture elements perfused with refractive index matching solutions to limit light scattering and enhance signal. First, fluorescence signal enhancement was demonstrated with a porous polymer monolith within a silica capillary. Next, transmission enhancement of a direct assay was demonstrated by infusing aqueous sucrose solutions through silica bead beds with captured silver enhanced AuIgGs yielding a detection limit of 0.1 ng/mL and a 5 log dynamic range. Finally, ex situ functionalized porous silica monolith segments were integrated into thermoplastic channels for a reflectance based sandwich assay yielding a detection limit of 1 ng/mL and a 5 log dynamic range. The simple techniques for optical signal enhancement and ex situ element integration enable development of sensitive, multiplexed microfluidic sensors. Collectively the demonstrated experiments validate the use of porous volumetric detection elements to enhance impedemetric and optical microfluidic assays. The techniques rely on commercial reagents, materials compatible with manufacturing, and measurement instrumentation adaptable to POC diagnostics.

The New Bottom Line: Black Women Cultural Entrepreneurs Re-Define Success in The Connected Economy

Black women cultural entrepreneurs are a group of entrepreneurs that merit further inquiry. Using qualitative interview and participant observation data, this dissertation investigates the ways in which black women cultural entrepreneurs define success. My findings reveal that black women cultural entrepreneurs are a particular interpretive community with values, perspectives and experiences, which are not wholly idiosyncratic, but shaped by collective experiences and larger social forces. Black women are not a monolith, but they are neither disconnected individuals completely devoid of group identity. The meaning they give to their businesses, professional experiences and understandings of success are influenced by their shared social position and identity as black women. For black women cultural entrepreneurs, the New Bottom Line goes beyond financial gain. This group, while not uniform in their understandings of success, largely understand the most meaningful accomplishments they can realize as social impact in the form of cultural intervention, black community uplift and professional/creative agency. These particular considerations represent a new paramount concern, and alternative understanding of what is typically understood as the bottom line. The structural, social and personal challenges that black women cultural entrepreneurs encounter have shaped their particular perspectives on success. I also explore the ways research participants articulated an oppositional consciousness to create an alternative means of defining and achieving success. I argue that this consciousness empowers them with resources, connections and meaning not readily conferred in traditional entrepreneurial settings. In this sense, the personal, social and structural challenges have been foundational to the formation of an alternative economy, which I refer to as The Connected Economy. Leading and participating in The Connected Economy, black women cultural entrepreneurs represent a black feminist and womanist critique of dominant understandings of success.