title: Gradient-free microfluidic flow labeling using thin magnetic films and remotely detected MRI.
abstract: Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) may be employed as noninvasive measurements yielding detailed information about the chemical and physical parameters that define microscale flows. Despite these advantages, magnetic resonance has been difficult to combine with microfluidics, largely due to its low sensitivity when detecting small sample volumes and the difficulty of efficiently addressing individual flow pathways for parallel measurements without utilizing large electric currents to create pulsed magnetic field gradients. Here, we demonstrate that remotely-detected MRI (RD-MRI) employing static magnetic field gradients produced by thin magnetic films can be used to encode flow and overcome some of these limitations. We show how flow path and history can be selected through the use of these thin film labels and through the application of synchronized, frequency-selective pulses. This obviates the need for large electric currents to produce pulsed magnetic field gradients and may allow for further application of NMR and MRI experiments on microscale devices.
authors.affiliation: Materials Sciences Division, E.O. Lawrence Berkeley National Lab, Berkeley, CA, USA; College of Chemistry, University of California, Berkeley, CA, USA.
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Halpern-Manners
authors.affiliation: Materials Sciences Division, E.O. Lawrence Berkeley National Lab, Berkeley, CA, USA; Biophysics Graduate Group, University of California, Berkeley, CA, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Kennedy
authors.affiliation: Materials Sciences Division, E.O. Lawrence Berkeley National Lab, Berkeley, CA, USA; College of Chemistry, University of California, Berkeley, CA, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Trease
authors.affiliation: Materials Sciences Division, E.O. Lawrence Berkeley National Lab, Berkeley, CA, USA; Graduate Program in Bioengineering, University of California, Berkeley and University of California, San Francisco, USA.
authors.forename: Thomas Z
authors.initials: TZ
authors.lastname: Teisseyre
authors.affiliation: Materials Sciences Division, E.O. Lawrence Berkeley National Lab, Berkeley, CA, USA; College of Engineering, University of California, Berkeley, CA, USA.
authors.forename: Nicolas S
authors.initials: NS
authors.lastname: Malecek
authors.affiliation: Materials Sciences Division, E.O. Lawrence Berkeley National Lab, Berkeley, CA, USA; College of Chemistry, University of California, Berkeley, CA, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Pines
authors.affiliation: Materials Sciences Division, E.O. Lawrence Berkeley National Lab, Berkeley, CA, USA; College of Chemistry, University of California, Berkeley, CA, USA; Department of Radiology, Stanford University School of Medicine, USA. Electronic address: vikbajaj@gmail.com.
authors.forename: Vikram S
authors.initials: VS
authors.lastname: Bajaj
keywords: Flow imaging; MRI; Microfluidics; NMR; Remote detection