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Evaporation-Driven Micromixing in Sessile Droplets for Miniaturized Absorbance-Based Colorimetry.
Aditya Chandramohan1, Monojit Chakraborty1, Justin A Weibel1
1School of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, United States.
ACS Omega
|January 8, 2020
Summary
An evaporating droplet on a nonwetting surface acts as a micromixer for colorimetric assays, enabling protein concentration measurement. This novel approach offers a simpler, low-volume alternative to traditional microtiter plates.
Area of Science:
- Biochemistry
- Analytical Chemistry
- Microfluidics
Background:
- Colorimetric assays are crucial for quantifying biomolecules.
- Traditional methods often require larger sample volumes and complex equipment.
- Developing miniaturized, efficient mixing systems is essential for point-of-care diagnostics.
Purpose of the Study:
- To demonstrate an evaporating sessile droplet on a nonwetting substrate as a micromixer for absorbance-based colorimetry.
- To utilize buoyancy-induced mixing within the droplet for rapid reaction completion.
- To validate the system using the Bradford assay for protein concentration measurement.
Main Methods:
- Utilized an evaporating, sessile droplet on a nonwetting substrate as a microfluidic device.
- Employed buoyancy-induced mixing for in situ reaction and measurement.
- Performed absorbance measurements through the droplet during the Bradford assay.
- Investigated the effect of substrate heating on mixing efficiency.
Main Results:
- Established viability of absorbance measurement through droplets for colorimetric reactions.
- Observed a complex temporal absorbance signal influenced by mixing, reaction, and adsorption.
- Identified the second absorbance peak as most sensitive to protein concentration.
- Demonstrated substrate heating significantly accelerates the mixing process.
Conclusions:
- The evaporating droplet micromixer is a viable alternative to microtiter plates for colorimetric applications.
- This system enables sensitive protein concentration measurements with low reactant volumes.
- The method offers a simplified approach for miniaturized biochemical analysis.
