One‐Way Particle Transport Using Oscillatory Flow in Asymmetric Traps

One challenge of integrating of passive, microparticles manipulation techniques into multifunctional microfluidic devices is coupling the continuous‐flow format of most systems with the often batch‐type operation of particle separation systems. Here, a passive fluidic technique—one‐way particle transport—that can conduct microparticle operations in a closed fluidic circuit is presented. Exploiting pass/capture interactions between microparticles and asymmetric traps, this technique accomplishes a net displacement of particles in an oscillatory flow field. One‐way particle transport is achieved through four kinds of trap–particle interactions: mechanical capture of the particle, asymmetric interactions between the trap and the particle, physical collision of the particle with an obstacle, and lateral shift of the particle into a particle–trapping stream. The critical dimensions for those four conditions are found by numerically solving analytical mass balance equations formulated using the characteristics of the flow field in periodic obstacle arrays. Visual observation of experimental trap–particle dynamics in low Reynolds number flow (<0.01) confirms the validity of the theoretical predictions. This technique can transport hundreds of microparticles across trap rows in only a few fluid oscillations (<500 ms per oscillation) and separate particles by their size differences.Passive fluidic particle transport using asymmetric traps in nonacoustic oscillatory flow is developed. The conditions to achieve this technique are based on the mass balance of fluid flows, the theory of deterministic lateral displacement of microparticles, and experimental validation. This technique can transport or separate microparticles in a closed chamber and facilitate the integration of the microparticle system into portable lab‐on‐a‐chip devices.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142443/1/smll201702724-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142443/2/smll201702724.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142443/3/smll201702724_am.pd

An Overview of Recent Strategies in Pathogen Sensing

Pathogenic bacteria are one of the major concerns in food industries and water treatment facilities because of their rapid growth and deleterious effects on human health. The development of fast and accurate detection and identification systems for bacterial strains has long been an important issue to researchers. Although confirmative for the identification of bacteria, conventional methods require time-consuming process involving either the test of characteristic metabolites or cellular reproductive cycles. In this paper, we review recent sensing strategies based on micro- and nano-fabrication technology. These technologies allow for a great improvement of detection limit, therefore, reduce the time required for sample preparation. The paper will be focused on newly developed nano- and micro-scaled biosensors, novel sensing modalities utilizing microfluidic lab-on-a-chip, and array technology for the detection of pathogenic bacteria

An integrated, self-contained microfluidic cassette for isolation, amplification, and detection of nucleic acids

A self-contained, integrated, disposable, sample-to-answer, polycarbonate microfluidic cassette for nucleic acid-based detection of pathogens at the point of care was designed, constructed, and tested. The cassette comprises on-chip sample lysis, nucleic acid isolation, enzymatic amplification (polymerase chain reaction and, when needed, reverse transcription), amplicon labeling, and detection. On-chip pouches and valves facilitate fluid flow control. All the liquids and dry reagents needed for the various reactions are pre-stored in the cassette. The liquid reagents are stored in flexible pouches formed on the chip surface. Dry (RT-)PCR reagents are pre-stored in the thermal cycling, reaction chamber. The process operations include sample introduction; lysis of cells and viruses; solid-phase extraction, concentration, and purification of nucleic acids from the lysate; elution of the nucleic acids into a thermal cycling chamber and mixing with pre-stored (RT-)PCR dry reagents; thermal cycling; and detection. The PCR amplicons are labeled with digoxigenin and biotin and transmitted onto a lateral flow strip, where the target analytes bind to a test line consisting of immobilized avidin-D. The immobilized nucleic acids are labeled with up-converting phosphor (UCP) reporter particles. The operation of the cassette is automatically controlled by an analyzer that provides pouch and valve actuation with electrical motors and heating for the thermal cycling. The functionality of the device is demonstrated by detecting the presence of bacterial B.Cereus, viral armored RNA HIV, and HIV I virus in saliva samples. The cassette and actuator described here can be used to detect other diseases as well as the presence of bacterial and viral pathogens in the water supply and other fluids

Non Parametric Estimation of Inhibition for Point Process Data

For a single geyser one eruption may inhibit another eruption. The objective is to estimate the inhibition function of geyser eruptions using a non parametric algorithm by extending the non parametric estimation method of Marsan and Lenglin?(2008) for clustered Hawkes processes to the case where there may be inhibition. The proposed method is tested using simulated geyser eruption data from known densities: Exponential, Pareto, Normal, and Uniform. The method is then applied ot the actual data from the Lone Pine Geyser in Yellowstone National Park. The data consists of 163 eruptions from 2011. The results indicate that geyser eruptions do inhibit other eruptions to some degree

Immunomagnetic bead-based cell concentration microdevice for dilute pathogen detection

A cell concentration microdevice for immunomagnetic pathogen isolation from a dilute sample is presented. Cells are driven by integrated on-chip pumps through a fluidized bed of immobilized immunomagnetic beads. Off-chip polymerase chain reaction and capillary electrophoretic analysis are used to determine capture efficiencies of E. coli and to optimize the system. Beads are immobilized after each split in a bifurcated channel system to ensure a balanced distribution of beads in all the capture channels. The addition of a pumping flutter step to repeatedly drive sample through the bead bed was found to enhance capture. Capture efficiencies of 70% and a limit of detection of 2 cfu/mu L were achieved; specific capture of E. coli at a concentration of 100 cfu/mu L in a 100-fold background of S. aureus is shown. This capture/concentration system is an important step in overcoming the macro-to-micro interface challenge in the development of microdevices for pathogen detection.the NIH (#U01AI056472

Integrated portable polymerase chain reaction-capillary electrophoresis microsystem for rapid forensic short tandem repeat typing

A portable forensic genetic analysis system consisting of a microfluidic device for amplification and separation of short tandem repeat (STR) fragments as well as an instrument for chip operation and four-color fluorescence detection has been developed. The microdevice performs polymerase chain reaction (PCR) in a 160-nL chamber and capillary electrophoresis (CE) in a 7-cm-long separation channel. The instrumental design integrates PCR thermal cycling, electrophoretic separation, pneumatic valve fluidic control, and four-color laser excited fluorescence detection. A quadruplex Y-chromosome STR typing system consisting of amelogenin and three Y STR loci (DYS390, DYS393, DYS439) was developed and used for validation studies. The multiplex amplification of these 4 loci with 35 PCR cycles followed by CE separation and 4-color fluorescence detection was completed in 1.5 h. All the amplicons can be detected with a limit of detection of 20 copies of male standard DNA in the reactor. Real-world forensic analyses of oral swab and human bone extracts from case evidence were also successfully performed. Mixture analysis demonstrated that a balanced profile can be obtained even at a male-to-female template ratio of 1:10. The successful development and operation of this portable PCR-CE system establishes the feasibility of rapid point-of-analysis DNA typing of forensic casework, of mass disaster samples or of individuals at a security checkpoint.Grant 2004-DN-BX-K216 awarded by the NAtional Institute of Justic