At the Hull science festival in September 2018, we used wax crayons, food dye and filter paper to demonstrate how we make the paper analytical devices that we are developing for river water analysis. The devices we make in the lab make use of a wax barrier, which when heated, provides a barrier in paper which can contain liquid.
Using these barriers we can add liquid reagents to the paper devices where they can be dried and stored until they are needed to perform the tests on river water (see photos below).
At the festival we used wax crayons to draw these barriers onto filter paper circles and then used a hot plate to heat the wax allowing it to melt through the paper creating the barrier. This enabled people to understand the process that we follow in the lab where we use a commercial printer with wax ink and a laminator to create our devices. Once we have created the barrier we test the effectiveness with food dye. A good barrier will contain all the food dye in the patterned area and no food dye will leak.
Over the course of the two-day festival on the University of Hull campus, we engaged with over 770 children and adults.
Written by Samantha Richardson, PhD Student at the University of Hull
Top: PAD ready for use as a river water analysis tool. Bottom: PAD showing the presence of phosphate after testing.