(428e) Teaching Process Design Through Alginate Bead Synthesis

The creation and analysis of alginate beads has been found to be effective in teaching concepts of mass transfer [1].  We have designed and implemented a freshman-level teaching module in which students create an automated process for the production of alginate beads, introducing them to the principles of process design, conservation of mass, pump characteristics, and fluid dynamics.

Alginate beads are created by dripping alginic acid into a calcium chloride solution, transforming the outer shell of the droplet into a hydrogel. The resulting beads may be separated from the calcium chloride and loaded with a dye, creating a model drug-delivery system.  By placing the loaded beads into water, mass transfer of the dye out of the bead may be characterized.  Our teaching module uses this process to create an open-ended design project in which the students are able to be create a wide variety of processes of their own design. We explain the basic chemistry to the students and provide students with the chemicals, pumps, tubing, containers, a dye, and mesh. The students may also request additional equipment.

The design goals of the project are to create an automated system which produces uniform, spherical alginate beads with a specified size and release rate. The student’s process must be able to convert 5 ml of alginic acid solution into beads continuously without interference, separate out the resulting beads, and recycle the calcium chloride solution. After their beads are created, students may quickly determine size and eccentricity distributions using MATLAB’s image processing toolbox and a webcam. Then the rate of diffusion may be determined by tracking the amount of dye that diffuses out of the beads over time using a spectrophotometer. The students may go back and alter several parameters in order to create more uniform beads that are closer to the design goals. Some of the parameters that may be adjusted include the concentrations and flow rates of the alginate and calcium chloride solutions, the drip height and tip diameter, the residence time of the beads in the calcium chloride solution, and the flow rate of air around the alginic acid droplets.

Due to the number of goals and parameters that can be adjusted, this project may be adapted to various levels of difficulty. We have used this project for teaching freshman and senior students in the chemical engineering program, and for junior high and high school students as part of the Science Olympiad. The real-world applications of alginate beads make it attractive as a teaching module. According to a student survey in our chemical engineering freshman design laboratory, this was the most-enjoyed project out of seven, and it was also ranked the highest in the students’ assessment of which teaching modules were most educational.

 [1]         Farrell, Stephanie, and Jennifer Vernengo. "A Controlled Drug-Delivery Experiment Using Alginate Beads." Chemical Engineering Education 46.2 (2012): 97-109. Print.