title: Measurement of microchannel fluidic resistance with a standard voltage meter.
abstract: A simplified method for measuring the fluidic resistance (R(fluidic)) of microfluidic channels is presented, in which the electrical resistance (R(elec)) of a channel filled with a conductivity standard solution can be measured and directly correlated to R(fluidic) using a simple equation. Although a slight correction factor could be applied in this system to improve accuracy, results showed that a standard voltage meter could be used without calibration to determine R(fluidic) to within 12% error. Results accurate to within 2% were obtained when a geometric correction factor was applied using these particular channels. When compared to standard flow rate measurements, such as meniscus tracking in outlet tubing, this approach provided a more straightforward alternative and resulted in lower measurement error. The method was validated using 9 different fluidic resistance values (from ∼40 to 600kPa smm(-3)) and over 30 separately fabricated microfluidic devices. Furthermore, since the method is analogous to resistance measurements with a voltage meter in electrical circuits, dynamic R(fluidic) measurements were possible in more complex microfluidic designs. Microchannel R(elec) was shown to dynamically mimic pressure waveforms applied to a membrane in a variable microfluidic resistor. The variable resistor was then used to dynamically control aqueous-in-oil droplet sizes and spacing, providing a unique and convenient control system for droplet-generating devices. This conductivity-based method for fluidic resistance measurement is thus a useful tool for static or real-time characterization of microfluidic systems.
authors.affiliation: Auburn University, Department of Chemistry and Biochemistry, Auburn, AL 36849, United States.
authors.forename: Leah A
authors.initials: LA
authors.lastname: Godwin
authors.forename: Kennon S
authors.initials: KS
authors.lastname: Deal
authors.forename: Lauren D
authors.initials: LD
authors.lastname: Hoepfner
authors.forename: Louis A
authors.initials: LA
authors.lastname: Jackson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Easley
mesh_terms: D002138:Calibration; D017097:Electric Impedance; D055615:Electrical Equipment and Supplies; D004867:Equipment Design; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D012996:Solutions
chemical_list: D012996:Solutions