Application of an accessible microfluidics platform to diffusion into dead-end pores*

In this work, we use a rapid prototyping technique to produce inexpensive, flexible microchannel chips out of double-sided adhesive tape using a craft-cutter in seconds with high precision. We then visualize the passive diffusion of fluorescein dye solution using an OpenFlexure microscope, which is an open-source device centered around a Raspberry Pi housed in a 3D-printed shell. We adapt the microscope to our application using the picamera python package and a color correction calibration method to quantitatively track the diffusion of fluorescein dye into micropores over a prolonged period of time. Our measurements are compared to analytical solutions of an effective 1D Fick-Jacobs equation for the case of both rectangular and trapezoidal cross-sectional geometries with good agreement. Open questions and future applications of our accessible microfluidics platform will be discussed.