A simple method for the evaluation of microfluidic architecture using flow quantitation via a multiplexed fluidic resistance measurement

Abstract

Quality control of microdevices adds significant costs, in time and money, to any fabrication process. A simple, rapid quantitative method for the post-fabrication characterization of microchannel architecture using the measurement of flow with volumes relevant to microfluidics is presented. By measuring the mass of a dye solution passed through the device, it circumvents traditional gravimetric and interface-tracking methods that suffer from variable evaporation rates and the increased error associated with smaller volumes. The multiplexed fluidic resistance (MFR) measurement method measures flow via stable visible-wavelength dyes, a standard spectrophotometer and common laboratory glassware. Individual dyes are used as molecular markers of flow for individual channels, and in channel architectures where multiple channels terminate at a common reservoir, spectral deconvolution reveals the individual flow contributions. On-chip, this method was found to maintain accurate flow measurement at lower flow rates than the gravimetric approach. Multiple dyes are shown to allow for independent measurement of multiple flows on the same device simultaneously. We demonstrate that this technique is applicable for measuring the fluidic resistance, which is dependent on channel dimensions, in four fluidically connected channels simultaneously, ultimately determining that one chip was partially collapsed and, therefore, unusable for its intended purpose. This method is thus shown to be widely useful in troubleshooting microfluidic flow characteristics.

Measurement of microchannel fluidic resistance with a standard voltage meter

“…From the linear velocity of the meniscus in the tubing connecting the syringe to the device, the volumetric flow rate was calculated using the cross-sectional area of the tubing. The vacuum pressure applied by the 100-mL glass syringe was determined using the ideal gas law, as previously described and validated with ~2% error [4,15]. From the volumetric flow rate ( Q ) and pressure ( ΔP ) measurements, the fluidic resistance ( R fluidic ) was determined with the equation $R_{\mathit{fluidic}}=\frac{\mathrm{\Delta }P}{Q}$.…”

“…One of the most facile methods, meniscus tracking through outlet tubing, requires only water, a pressure source, and a timer [4,14], yet this approach requires ~15 minutes for each measurement and is highly sensitive to user error. Another method is to quantify flux of colored solutions through devices [15], but this approach requires syringe pumps and UV spectroscopy to accomplish. These examples highlight the need to further simplify the measurement of fluidic resistance, ideally reducing the measurement system to the analogous electrical voltage meter.…”

Quantitative full-colour transmitted light microscopy and dyes for concentration mapping and measurement of diffusion coefficients in microfluidic architectures

“…2 Offline UV-visible absorbance measurements have been used for microfluidic flow rate determination. 3 Quantitative measurements of concentration profiles [4][5][6][7] in microfluidics are mostly achieved using fluorescence imaging and fluorescent probes which requires sensitive detectors and suitable microscope optics and hardware.…”

The μSCAPE System: 3-Dimensional Profiling of Microfluidic Architectural Features Using a Flatbed Scanner

“…In this report, we describe our findings on the use of an office flatbed scanner to detect the 3D profiles of microfluidic structures. In 2010, we reported that, by measuring the absorbance of dye solution after it passed through the microchannels, the quality of the channels could be easily determined spectroscopically 16 . Here, we exploit absorbance of dye-filled channels again, but in a very different way.…”