Oyvind Nilsen

Holographic chemical vapor sensor.

A holographic interferometer senses vapor-induced optical path length changes in polymer or other chemically sensitive films. The interferometer is inherently sensitive to changes in chemical vapor content, self-compensates for drifts, and accommodates a large array of sensor elements. A sniff-locked-loop synchronous detection method takes advantage of the interferometers rapid response to achieve vapor concentration sensitivity in the parts-per-billion (ppb, parts in 10(9)) range. We demonstrate, for example, 40 ppb sensitivity to ethyl alcohol using poly(N-vinyl pyrrolidone) with a measurement time of 5 s.

Short non-coding RNAs as bacteria species identifiers detected by surface plasmon resonance enhanced common path interferometry

Small non-coding RNA sequences have recently been discovered as unique identifiers of certain bacterial species, raising the possibility that they can be used as highly specific Biowarfare Agent detection markers in automated field deployable integrated detection systems. Because they are present in high abundance they could allow genomic based bacterial species identification without the need for pre-assay amplification. Further, a direct detection method would obviate the need for chemical labeling, enabling a rapid, efficient, high sensitivity mechanism for bacterial detection. Surface Plasmon Resonance enhanced Common Path Interferometry (SPR-CPI) is a potentially market disruptive, high sensitivity dual technology that allows real-time direct multiplex measurement of biomolecule interactions, including small molecules, nucleic acids, proteins, and microbes. SPR-CPI measures differences in phase shift of reflected S and P polarized light under Total Internal Reflection (TIR) conditions at a surface, caused by changes in refractive index induced by biomolecular interactions within the evanescent field at the TIR interface. The measurement is performed on a microarray of discrete 2-dimensional areas functionalized with biomolecule capture reagents, allowing simultaneous measurement of up to 100 separate analytes. The optical beam encompasses the entire microarray, allowing a solid state detector system with no scanning requirement. Output consists of simultaneous voltage measurements proportional to the phase differences resulting from the refractive index changes from each microarray feature, and is automatically processed and displayed graphically or delivered to a decision making algorithm, enabling a fully automatic detection system capable of rapid detection and quantification of small nucleic acids at extremely sensitive levels. Proof-of-concept experiments on model systems and cell culture samples have demonstrated utility of the system, and efforts are in progress for full development and deployment of the device. The technology has broad applicability as a universal detection platform for BWA detection, medical diagnostics, and drug discovery research, and represents a new class of instrumentation as a rapid, high sensitivity, label-free methodology.

Detection and discrimination of low concentration gas contaminants by means of interferometrically-sensed polymers

Two optical techniques for bio- and chemical sensing were investigated. The methods are based on deviation of the optical properties of polymer transducers due to change in either index of refraction or dimension of the sensing element under molecular impact. The holographic interferometer technology developed at the University of Colorado observes interactions between an analyte and a transducers surface and bulk. The second approach, a common path interferometer proposed by Dr. John Hall, focuses on surface interactions only. The two techniques complement each other, enabling the separation of surface and bulk interactions. This is critical for accurate description of chemical uptake and release dynamics, and therefore for obtaining parameters necessary for the analyte identification process. Preliminary sensitivity level of the systems is on the order of 10-5 RTU (refractive index units) with possible improvement down to 10-7 RTU

The resonant micro fan gas pump for active breathing microchannels

This paper reports on the fluidic and mechanical performance of the resonant micro fan as an in-channel gas pump. Experiments with resonant fan arrays assembled within test channels were performed in order to observe the effects of changing fan length and resonant frequency with respect to volumetric flow rate in the channel. Flow rates of approximately 10 /spl mu/l/min were produced by single fans with the flow increasing to 25 /spl mu/l/min for three fans operated simultaneously in the same channel (the capability exists for many fans to be arrayed in a microchannel system). The ability of the micro fan to collect airborne suspended smoke particles was also experimentally examined.

Surface Plasmon Resonance enhanced Common Path Interferometry for high sensitivity label free biomolecule interaction analysis

A biomolecule interaction detection system using common path interferometry enhanced by surface plasmon resonance has been developed that provides multiplexed label free detection of biomolecule analytes at unprecedented sensitivities. Differential phase analysis of two orthogonally polarized components of a single laser beam gives interferometric measurement of refractive index changes at a biosensor surface. Surface plasmon resonance enhances the phase differential to give ultimate sensitivity below 5times10-8 RIU. Discreet two dimensional area analyses within the laser beam allow simultaneous interrogations of multiple analytes in a microarray format by using diode array detectors optically aligned with elements on the transducer. Preliminary results establish current sensitivity and dynamic range, and demonstrate detection of proteins and whole organisms such as bacteria. Differential signal acquisition from a multi-diode array with specifically functionalized transducers demonstrates multiplexed microarray analysis.

High sensitivity detection of bacteria by surface plasmon resonance enhanced common path interferometry

Real time monitoring of biowarfare agents (BWA) for military and civilian protection remains a high priority for homeland security and battlefield readiness. Available devices have adequate sensitivity, but the detection modules have limited periods of deployment, require frequent maintenance, employ single-use disposable components, and have limited multiplexing capability. Surface Plasmon Resonance enhanced Common Path Interferometry (SPR-CPI) is a label-free, high sensitivity biomolecular interaction measurement technology that allows multiplexed real-time measurement of biowarfare agents, including small molecules, proteins, and microbes. The technology permits continuous operation in a field-deployable detection module of an integrated BWA monitoring system. SPR-CPI measures difference in phase shift of polarized light reflected from the transducer interface caused by changes in refractive index induced by biomolecular interactions. The measurement is performed on a discrete 2-dimensional area functionalized with biomolecule capture reagents in a microarray format, allowing simultaneous measurement of up to 100 separate analytes. Output consists of simultaneous voltage measurements proportional to the phase differences resulting from the refractive index changes and is automatically processed and displayed graphically or delivered to a decision making algorithm. This enables a fully automatic field-deployable detection system capable of integration into existing modular BWA detection systems. Proof-of-concept experiments on surrogate models of anticipated BWA threats have demonstrated utility. Efforts are in progress for full development and deployment of the device.

Flow Characterization of an Electrostatic Resonant Plate Micropump-Mixer by a Scaled Model

Flow characterization of an electrostatically activated resonant-plate micropump-mixer was investigated. Detailed visualization of the mixing process at the tip of the resonant plate, which is almost impossible due to the high actuation frequency (10–30 kHz) and small scale of the resonant plate (250 micron) under normal conditions, was realized with a macro scale flow visualization experiment within the range of common visualization equipment such as a SLR camera. Flow phenomena such as distinct circulative regions, observed at the micro scale by Linderman et. al [1,2], were observed in this study. In addition, the transition between two different flow regimes was observed, corresponding to vortex shearing and vortex shedding respectively. This transition took place in a gradual manner over a range of Reynolds numbers between 20 and 98. Below this regime the resonant plate will only generate limited deformation of the interface between the two fluids. However, for larger Reynolds numbers, equivalent to higher plate frequencies, organized vortex roll-up is observed. Vortex roll-up indicates significant fluid entrainment, and consequently mixing. The visualization of the flow, generated by the resonating fan shed new light on the detailed flow phenomena involved, and may help guide future design and optimization of micro scale fans/mixers based on this principle.Copyright