Alginate-Based UV Sensor: A Simple and Inexpensive Tool for Educational Purposes

Abstract

This document presents a simple yet highly effective demonstration for creating UV radiation sensors using alginate molecules. This demonstration can easily be aligned with the Next Generation Science Standards (NGSS) for classroom use. Moreover, the demonstration requires only a few easily obtainable materials, and the process involved is straightforward. When exposed to UV light or sunlight, the spheres' color changes, offering a fascinating observation that is sure to capture the imagination of students of all ages. This encourages curiosity and inspires further exploration of the scientific world. It is easily understandable and suitable for people of all ages. This experiment represents a valuable addition to the scientific community's educational tools, and its potential to inspire a new generation of scientists is truly limitless.

Figure 1

Schematic illustration of a photochromic pigment-based sensor. The “Input” shows photochromic pigment exposed to UV light, initiating the “Process” where a color change occurs due to UV exposure. The “Output” demonstrates the visible result of this process: the pigment’s color change. The “Feedback” loop indicates the reversible nature of the photochromic reaction, allowing the pigment to return to its original state in the absence of UV radiation, ready for subsequent cycles of detection.

Figure 2

Egg-box model for the alginate spherification process. This model allows us to explain how the membrane is formed when exposed to calcium ions.

Figure 3

Simplified outline of the demonstration procedure, starting with the preparation of the solutions, spherification, rinse, and at last the irradiation of the beads with UV-light.

Figure 4

(A) A dropper or transfer pipet was used to form the beads. The spoon-stirrer was also used to drop bigger beads. (B) Top view of the beads formed when the drops of alginate solution were added to the calcium solution. A string of alginate can be seen. This occurs when the alginate solution is added too quickly with the dropper.

Figure 5

(A) Rinsed alginate beads under room light. They look white as the alginate solution. (B) The alginate beads are exposed to UV light using a UV light flashlight. Another source that can be used is sunlight. (C) Alginate beads after a quick exposure to UV light. It can be seen that the beads changed color to purple since the photochromic pigment was white changing to purple. The color of the beads after exposing them to UV depends on the photochromic pigment used.