@article {287, title = {Time-of-flight flow imaging of two-component flow inside a microfluidic chip}, journal = {Physical Review Letters}, volume = {98}, year = {2007}, note = {Phys Rev Lett124OYTimes Cited:21Cited References Count:16}, month = {Jan 5}, abstract = {

Here we report on using NMR imaging and spectroscopy in conjunction with time-of-flight tracking to noninvasively tag and monitor nuclear spins as they flow through the channels of a microfluidic chip. Any species with resolvable chemical-shift signatures can be separately monitored in a single experiment, irrespective of the optical properties of the fluids, thereby eliminating the need for foreign tracers. This is demonstrated on a chip with a mixing geometry in which two fluids converge from separate channels, and is generally applicable to any microfluidic device through which fluid flows within the nuclear spin-lattice relaxation time.

}, keywords = {microchannels}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.98.017601}, url = {://WOS:000243379700050}, author = {Harel, E. and Hilty, C. and Koen, K. and McDonnell, E. E. and Pines, A.} } @article {304, title = {Auxiliary probe design adaptable to existing probes for remote detection NMR, MRI, and time-of-flight tracing}, journal = {Journal of Magnetic Resonance}, volume = {182}, year = {2006}, note = {J Magn Reson093XPTimes Cited:7Cited References Count:21}, month = {Oct}, pages = {260-272}, abstract = {

A versatile, detection-only probe design is presented that can be adapted to any existing NMR or MRI probe with the purpose of making the remote detection concept generally applicable. Remote detection suggests freeing the NMR experiment from the confinement of using the same radio frequency (RF) coil and magnetic field for both information encoding and signal detection. Information is stored during the encoding step onto a fluid sensor medium whose magnetization is later measured in a different location. The choice of an RF probe and magnetic field for encoding can be made based solely on the size and characteristics of the sample and the desired information quality without considering detection sensitivity, as this aspect is dealt with by a separate detector. While early experiments required building probes that included two resonant circuits, one for encoding and one for detection, a modular approach with a detection-only probe as presented here can be used along with any existing NMR probe of choice for encoding. The design of two different detection-only probes is presented, one with a saddle coil for milliliter-sized detection volumes, and the other one with a microsolenoid coil for sub-microliter fluid quantities. As example applications, we present time-of-flight (TOF) tracing of hyperpolarized Xe-129 spins in a gas mixture through coiled tubing using the microsolenoid coil detector and TOF flow imaging through a nested glass container where the gas flow changes its direction twice between inlet and outlet using the saddle coil detector. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {flow}, isbn = {1090-7807}, doi = {Doi 10.1016/J.Jmr.2006.06.024}, url = {://WOS:000241203900010}, author = {Han, S. I. and Granwehr, J. and Garcia, S. and McDonnell, E. E. and Pines, A.} } @article {315, title = {Microfluidic gas-flow profiling using remote-detection NMR}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {102}, year = {2005}, note = {P Natl Acad Sci USA977NZTimes Cited:41Cited References Count:26}, month = {Oct 18}, pages = {14960-14963}, abstract = {

We have used nuclear magnetic resonance (NMR) to obtain spatially and temporally resolved profiles of gas flow in microfluidic devices. Remote detection of the NMR signal both overcomes the sensitivity limitation of NMR and enables time-of-flight measurement in addition to spatially resolved imaging. Thus, detailed insight is gained into the effects of flow, diffusion, and mixing in specific geometries. The ability for noninvasive measurement of microfluidic flow, without the introduction of foreign tracer particles, is unique to this approach and is important for the design and operation of microfluidic devices. Although here we demonstrate an application to gas flow, extension to liquids, which have higher density, is implicit.

}, keywords = {mri}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.0507566102}, url = {://WOS:000232811800006}, author = {Hilty, C. and McDonnell, E. E. and Granwehr, J. and Pierce, K. L. and Han, S. I. and Pines, A.} } @article {311, title = {NMR analysis on microfluidic devices by remote detection}, journal = {Analytical Chemistry}, volume = {77}, year = {2005}, note = {Anal Chem995DDTimes Cited:25Cited References Count:36}, month = {Dec 15}, pages = {8109-8114}, abstract = {

We present a novel approach to perform high-sensitivity NMR imaging and spectroscopic analysis on microfluidic devices. The application of NMR, the most information-rich spectroscopic technique, to microfluidic devices remains a challenge because the inherently low sensitivity of NMR is aggravated by small fluid volumes leading to low NMR signal and geometric constraints resulting in poor efficiency for inductive detection. We address the latter by physically separating signal detection from encoding of information with remote detection. Thereby, we use a commercial imaging probe with sufficiently large diameter to encompass the entire device, enabling encoding of NMR information at any location on the chip. Because large-diameter coils are too insensitive for detection, we store the encoded information as longitudinal magnetization and flow it into the outlet capillary. There, we detect the signal with optimal sensitivity, using a solenoidal microcoil, and reconstruct the information encoded in the fluid. We present a generally applicable design for a detection-only microcoil probe that can be inserted into the bore of a commercial imaging probe. Using hyperpolarized Xe-129 gas, we show that this probe enables sensitive reconstruction of NMR spectroscopic information encoded by the large imaging probe while keeping the flexibility of a large coil.

}, keywords = {probes}, isbn = {0003-2700}, doi = {Doi 10.1021/Ac051320+}, url = {://WOS:000234079200034}, author = {McDonnell, E. E. and Han, S. L. and Hilty, C. and Pierce, K. L. and Pines, A.} }