Microfluidics-Based Analysis of Controlled Mixing and Bubble Formation in Soda Solutions for Education

Abstract

This study describes a microfluidics experiment with ready classroom applications, designed to enhance students' understanding of fluid dynamics, controlled mixing, and bubble formation. The materials employed are safe and readily accessible, such as vinegar and baking soda, combined with PDMS microfluidic chips and a high-resolution microscope, to provide real-time observation of gas-liquid interactions. A syringe pump delivers the reactants into a micro-channel through which the fluid flow behavior and bubble formation can be visualized and quantified.(/p)The focus of the experiment is on elucidating the effects of different soda concentrations on bubble generation in a controlled laminar flow. The results show a nonlinear trend between soda concentration and bubble features: lower concentrations produce fewer but larger bubbles, moderate concentrations produce small bubbles more frequently. At 0.2 M, the average bubble area was approximately 389 μm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, and at 0.4 M, there were smaller bubbles but more frequent occurrences. As concentrations increased above 0.6 M, bubbles became more uniform in size and more circular.Flow rates were varied from 3 to 15 μL/min to assess bubble behavior. Most bubbles functioned as wall bubbles in the micro-channel and were not perfectly spherical because of the influence of the local flow field and concentration gradients. The size distribution and circularity of the bubbles were measured using image analysis tools developed in Python.This affordable and visually appealing platform provides an alternative hands-on experience for students to learn the fundamental principles of microfluidics, thereby connecting classroom concepts with real-world observations. The lab activity promotes data analysis, hypothesis testing, and deepening understanding of concepts—skills essential for both academic and applied research.