Plans for Microbial Biology Experiments on the Gateway

STI is for a presentation being given by Tony Ricco to the European Space Agency's Topical Team on Astrobiology

Detection and Quantification of Multi-Analyte Mixtures Using a Single Sensor and Multi-Stage Data-Weighted RLSE

This work reports the development and experimental verification of a sensor signal processing technique for online identification and quantification of aqueous mixtures of benzene, toluene, ethylbenzene, xylenes (BTEX) and 1, 2, 4-trimethylbenzene (TMB) at ppb concentrations using time-dependent frequency responses from a single polymer-coated shear-horizontal surface acoustic wave sensor. Signal processing based on multi-stage exponentially weighted recursive leastsquares estimation (EW-RLSE) is utilized for estimating the concentrations of the analytes in the mixture that are most likely to have produced a given sensor response. The initial stages of EW-RLSE are used to eliminate analyte(s) that are erroneously identified as present in the mixture; the final stage of EW-RLSE with the corresponding sensor response model representing the analyte(s) present in the mixture is used to obtain a more accurate quantification result of the analyte(s). The success of this method in identifying and quantifying analytes in real-time with high accuracy using the response of just a single sensor device demonstrates an effective, simpler, lower-cost alternative to a sensor array that includes the advantage of not requiring a complex training protocol

Analysis of biopharma raw materials by electrophoresis microchips with contactless conductivity detection

Detailed information concerning the composition of the raw materials employed in the production of biologics is important for the efficient control and optimization of bioprocesses. We demonstrate the application of electrophoresis microchips with capacitively-coupled contactless conductivity detection (C4D) to the analysis of wa-ter-soluble vitamins and metal cations in raw material solutions that are subse-quently fed into bioreactors for the production of biologics

Monolithic centrifugal microfluidic platform for bacteria capture and concentration, lysis, nucleic-acid amplification, and real-time detection

We report the design, fabrication, and characterization of a polymer centrifugal microfluidic system for the specific detection of bacterial pathogens. This single-cartridge platform integrates bacteria capture and concentration, supernatant solution removal, lysis, and nucleic-acid sequence-based amplification (NASBA) in a single unit. The unit is fabricated using multilayer lamination and consists of five different polymer layers. Bacteria capture and concentration are accomplished by sedimentation in five minutes. Centrifugation forces also drive the subsequent steps. A wax valve is integrated in the cartridge to enable high-speed centrifugation. Oil is used to prevent evaporation during reactions requiring thermal cycling. Device functionality was demonstrated by real-time detection of E. coli from a 200-muL sample

Liquid recirculation in microfluidic channels by the interplay of capillary and centrifugal forces

We demonstrate a technique to recirculate liquids in a microfluidic device, maintaining a thin fluid layer such that typical diffusion times for analytes to reach the device surface are < 1 min. Fluids can be recirculated at least 1000 times across the same surface region, with no change other than slight evaporation, by alternating the predominance of centrifugal and capillary forces. Mounted on a rotational platform, the device consists of two hydrophilic layers separated by a thin pressure-sensitive adhesive (PSA) layer that defines the microfluidic structure. We demonstrate rapid, effective fluid mixing with this device

Enhanced Microfluidic Electromagnetic Measurements

Techniques for enhanced microfluidic impedance spectroscopy include causing a core fluid to flow into a channel between two sheath flows of one or more sheath fluids different from the core fluid. Flow in the channel is laminar. A dielectric constant of a fluid constituting either sheath flow is much less than a dielectric constant of the core fluid. Electrical impedance is measured in the channel between at least a first pair of electrodes. In some embodiments, enhanced optical measurements include causing a core fluid to flow into a channel between two sheath flows of one or more sheath fluids different from the core fluid. An optical index of refraction of a fluid constituting either sheath flow is much less than an optical index of refraction of the core fluid. An optical property is measured in the channel

Optically addressable single-use microfluidic valves by laser printer lithography

We report the design, fabrication, and characterization of practical optofluidic valves fabricated using laser printer lithography. Valves are opened by directing optical energy from a solid-state laser, with similar power characterisitcs to those used in CD/DVD drives, to a spot of printed toner where localized heating melts an orifice in the polymer layer in as little as 500 ms, connecting previously isolated fluidic components or compartments. Valve functionality, response time, and laser input energy dependence of orifice size are reported for cyclo-olefin copolymer (COC) and polyethylene terephthalate (PET) films. Implementation of these optofluidic valves is demonstrated on pressure-driven and centrifugal microfluidic platforms. In addition, these “one-shot” valves comprise a continuous polymer film that hermetically isolates on-chip fluid volumes within fluidic devices using low-vapor-permeability materials; we confirmed this for a period of one month. The fabrication and integration of optofluidic valves is compatible with a range of polymer microfabrication technologies and should facilitate the development of fully integrated, reconfigurable, and automated lab-on-a-chip systems, particularly when reagents must be stored on chip for extended periods, e.g. for medical diagnostic devices, lab-on-a-chip synthetic systems, or hazardous biochemical analysis platforms

Thin film diffusion barrier formation in PDMS microcavities

We describe a method to form glass like thin film barrier in polydimethylsiloxane (PDMS) microcavities. The reactive fragments for the surface reaction were created from O2 and hexamethyldisiloxane (HMDS) in RF plasma environment. The reaction is based on migration of the reactive fragments into the microcavities by diffusion, to form a glass like thin film barrier to conceal the naked surface of PDMS. The barrier successfully blocked penetration of a fluorescent dye rhodamine B (RhB) into PDMS. The thickness of the barrier could be controlled by the time of reaction and the pressure inside the reaction chamber. There is a wide range of applications of such a technique in various fields, e.g. for coating the covered surfaces of microfluidic channels, tubes, capillaries, medical devices, catheters, as well as chip-integrated capillary electrophoresis and advanced electronic and opto-fluidic packaging

Sensor-Based Estimation of BTEX Concentrations in Water Samples Using Recursive Least Squares and Kalman Filter Techniques

This work investigates sensor signal processing approaches that can be used with a sensor system for direct on-site monitoring of groundwater, enabling detection and quantification of BTEX (benzene, toluene, ethylbenzene and xylene) compounds at μg/L (ppb) concentrations in the presence of interferents commonly found in groundwater. A model for the sensor response to water samples containing multiple analytes was first formulated based on experimental results. The first signal processing approach utilizes only RLSE (recursive least squares estimation) whereas the second, a two-step processing technique, utilizes both RLSE and bank of Kalman filters for the estimation process. The estimation techniques were tested using actual sensor responses to contaminated groundwater samples. Results indicate that relatively accurate concentration estimates (within ±15–23% for benzene) can be obtained in near-real time using these techniques. The two-step processing technique gave more accurate results. This approach allows the use of a single sensor, even for multiple analyte detection and quantification