title: Hydrodynamic focusing of conducting fluids for conductivity-based biosensors.
abstract: Hydrodynamic focusing of a conducting fluid by a non-conducting fluid to form a constricted current path between two sensing electrodes is implemented in order to enhance the sensitivity of a 4-electrode conductance-based biosensor. The sensor has a simple two-inlet T-junction design and performs four-point conductivity measurements to detect particles immobilized between the sensing electrode pair. Computational simulations conducted in conjunction with experimental flow studies using confocal microscopy show that a flat profile for the focused layer is dependent on the Reynolds number for the chosen flow parameters. The results also indicate that a flat focused layer is desirable for both increased sensitivity as well as surface-binding efficiency. Proof of concept for conductance measurements in a hydrodynamically focused conducting fluid was demonstrated with entrapped magnetic beads.
authors.affiliation: Naval Research Laboratory, Center for Bio/Molecular Science and Engineering, Washington, DC 20375, USA.
authors.forename: Mansoor
authors.initials: M
authors.lastname: Nasir
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Ateya
authors.forename: Diana
authors.initials: D
authors.lastname: Burk
authors.forename: Joel P
authors.initials: JP
authors.lastname: Golden
authors.forename: Frances S
authors.initials: FS
authors.lastname: Ligler
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D017076:Computer-Aided Design; D004553:Electric Conductivity; D004563:Electrochemistry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D011312:Pressure; D012996:Solutions / Q000737:chemistry*
chemical_list: D012996:Solutions