Microfluidics for High School Chemistry Students

Abstract

We present a laboratory experiment that introduces high school chemistry students to microfluidics while teaching fundamental properties of acid-base chemistry. The procedure enables students to create microfluidic systems using nonspecialized equipment that is available in high school classrooms and reagents that are safe, inexpensive, and commercially available. The experiment is designed to ignite creativity and confidence about experimental design in a high school chemistry class. This experiment requires a computer program (e.g., PowerPoint), Shrinky Dink film, a readily available silicone polymer, weak acids, bases, and a colorimetric pH indicator. Over the span of five 45-min class periods, teams of students design and prepare devices in which two different pH solutions mix in a predictable way to create five different pH solutions. Initial device designs are instructive but rarely optimal. During two additional half-class periods, students have the opportunity to use their initial observations to redesign their microfluidic systems to optimize the outcome. The experiment exposes students to cutting-edge science and the design process, and solidifies introductory chemistry concepts including laminar flow, neutralization of weak acids-bases, and polymers.

Keywords: Acids/Bases; Aqueous Solution Chemistry; Collaborative/Cooperative Learning; Hands-On Learning/Manipulatives; High School/Introductory Chemistry; Inquiry-Based/Discovery Learning; Laboratory Instruction; Liquids; Microscale Lab; Problem Solving/Decision Making.

Figure 1

Fabrication and operation of the microfluidic device. (A) A microfluidic design is double printed (approximately 1.6× larger than the final desired dimensions) onto Shrinky Dink film using a laser printer. (B) The printed patterns are cut to size and submerged in hot oil (150 °C) until the film shrinks completely (30–60 s). (C) The shrunken design is removed quickly from the oil and gently flattened between two glass plates. (D) The cleaned and dry design is taped to the bottom of a Petri dish, and (E) PDMS elastomer is poured in the dish to completely cover the design. (F) A vacuum pump is used to degas the PDMS elastomer before it is cured in a 60 °C oven overnight. (G) Once the PDMS has fully cured, the microfluidic device is cut to the desired size using a razor. Inlets and outlets are created using a biopsy punch, and the final device is assembled by attaching the PDMS device to a glass slide with double-sided tape. (H) Liquid samples are added to the device (shown here as yellow and blue droplets covering the inlets) using a pipet. Flow is achieved by attaching a syringe to the outlet of the device using a short piece of flexible tubing. Gently pulling the syringe plunger creates a vacuum that draws the samples through the device toward the outlet.

Figure 2

Summative assessment results. We surveyed two independent classes of chemistry students in the same school, with the same teacher for the same course (different semesters), who either participated (N = 52; labeled as participants) or did not participate (N = 78; labeled as nonparticipants) in the microfluidics experiment.