Alison M. Skelley

Monolithic membrane valves and diaphragm pumps for practical large-scale integration into glass microfluidic devices

Abstract Monolithic elastomer membrane valves and diaphragm pumps suitable for large-scale integration into glass microfluidic analysis devices are fabricated and characterized. Valves and pumps are fabricated by sandwiching an elastomer membrane between etched glass fluidic channel and manifold wafers. A three-layer valve and pump design features simple non-thermal device bonding and a hybrid glass-PDMS fluidic channel; a four-layer structure includes a glass fluidic system with minimal fluid-elastomer contact for improved chemical and biochemical compatibility. The pneumatically actuated valves have

Sulfate minerals and organic compounds on Mars

Strong evidence for evaporitic sulfate minerals such as gypsum and jarosite has recently been found on Mars. Although organic molecules are often codeposited with terrestrial evaporitic minerals, there have been no systematic investigations of organic components in sulfate minerals. We report here the detection of organic material, including amino acids and their amine degradation products, in ancient terrestrial sulfate minerals. Amino acids and amines appear to be preserved for geologically long periods in sulfate mineral matrices. This suggests that sulfate minerals should be prime targets in the search for organic compounds, including those of biological origin, on Mars.

Practical Valves and Pumps for Large-Scale Integration into Microfluidic Analysis Devices

Pneumatically-actuated elastomer membrane valves and pumps for practical large-scale integration into glass μTAS devices are fabricated and characterized. The valves and pumps reliably manipulate nanoliter-scale volumes of fluid, introduce low dead volumes into the microfluidic system, and are compatible with a wide range of device chemistries. The integrated pneumatic manifold and practical microfabrication process facilitate the production and use of high-density arrays of the valves and pumps.

Mars Organic Detector III: a versatile instrument for detection of bio-organic signatures on Mars

Recent advances in the development of microfabricated lab-on-a-chip analysis systems have enhanced the feasibility and capabilities of in situ chemical and biochemical analyzers. While a wide variety of bio-organic molecules can be probed, we have focused our initial studies on the development of an amino acid analyzer with the hypothesis that extraterrestrial life would be based on homochiral amino acid polymers. In previous work, we developed a prototype electrophoresis chip, detection system and analysis method where the hydrolyzed amino acids were labeled with fluorescein and then analyzed in minutes via a capillary zone electrophoresis (CZE) separation in the presence of γ-cyclodextrin as the chiral recognition agent. In more recent work, we have demonstrated the feasibility of performing amino acid composition and chirality analyses using fluorescamine as the labeling reagent. Fluorescamine is advantageous because it reacts more rapidly with amino acids, has a low fluorescence background and because such a chemistry would interface directly with the Mars Organic Detector (MOD-I) concept being developed at Scripps. A more advanced analysis system called MOD-III is introduced here with the ability to analyze zwitterionic amino acids, nucleobases, sugars, and organic acids and bases using novel capture matrix chemistries. MOD-III, which is enabled by the nanoliter valves, pumps and reactors presented here, will provide a wide spectrum of organic chemical analyses and is suitable for a variety of in situ missions.

Integrated Amorphous Silicon Photodiode Detector for Microfabricated Capillary Electrophoresis Devices

We have demonstrated that hydrogenated amorphous Si (a-Si:H) photodiodes are sufficiently sensitive to be used as detectors for chemical and biological assays performed on microfabricated capillary electrophoresis devices. A limit of detection of 56 pM for fluorescein flowing in a 50-μrn deep microchannel is observed utilizing confocal optics. Moreover, the fluorescence has been successfully detected with a newly designed integrated a-Si:H detector, in which the detector and laser are placed on the same side of the microchip. This optical design is ideal for monolithic integration of the a-Si:H detector technology with VCSEL excitation.