Design and uncertainty assessment of a setup for calibration of microfluidic devices down to 5 nL min⁻¹

Abstract

This work focuses on the design and characterization of a system for measuring and calibration of liquid micro-flows down to 5 nL min−1. The experimental setup relies on a telecentric imaging system mounted on a high-precision, computer controlled linear stage to track a moving liquid meniscus in a glass capillary. The position of the linear stage can be automatically adjusted to track the motion of the liquid front over distances of up to 15 cm. All fluidic components were placed inside a temperature regulated chamber at 36.0 ± 1.1 °C with a maximum variability ΔT = ± 0.1 °C for time intervals shorter than 1 h. The combined flow-rate uncertainty has been evaluated for measurement times from 15 s to 1 h and nominal flow rates between 5 and 50 nL min−1. At 5 nL min−1, an extended flow-rate uncertainty better that 8.3% can be attained for measurement times equal to or longer than 60 s. The uncertainty approaches asymptotically 5.4% for measurement times longer than 300 s or flow rates higher than 50 nL min−1.

Dynamic Measurement of Nanoflows: Analysis and Theory of an Optofluidic Flowmeter

“…As an interesting aside, we note that under certain experimentally attainable conditions, the flow-profile u can be independent of the radial coordinates. [12] If the laser profile φ(r) = φ(z) is likewise only a function of the axial variable, it is possible to integrate Eq. (8) directly in x and y without the need to perform a perturbation expansion in the spirit of Eq.…”

Micro-flow facility for traceability in steady and pulsating flow

“…Another possibility is to track directly the meniscus of the waterfront flowing through a capillary as a function of time. This method strongly depends on the traceable calibration of the diameter of the capillary, which is the main contribution to the uncertainty [8]. A third possibility is to use a known expansion of a liquid to realize a flow generator.…”

Dynamic Measurement of Nanoflows: Realization of an Optofluidic Flow Meter to the Nanoliter-per-Minute Scale

“…11,12 Uncertainties as low as 5% at 5 nL/min have been achieved with 5 min integration time. 13 However, these and related techniques 14−17 are increasingly constrained by practical limitations associated with geometry, temperature, or interfacial properties at the microscale. Moreover, they suffer from an inability to simultaneously achieve both real-time and high-precision measurement.…”

“…Such approaches have achieved high-precision flow measurements on the order of 1 μL/min, and further optimization has allowed for measurement of >10 nL/min to within a few percent error (Table ). , Uncertainties as low as 5% at 5 nL/min have been achieved with 5 min integration time . However, these and related techniques − are increasingly constrained by practical limitations associated with geometry, temperature, or interfacial properties at the microscale.…”