Sustainable colours

Clothing, walls, art and utensils like your crockery: people love things with a beautiful colour. However, many ways of colouring are not sustainable. They pollute groundwater and introduce heavy metals into the soil. Our collaboration partner Colin Ingham of Hoekmine BV has discovered bacteria that can reflect colour, and that are biodegradable in an easy way. Together, we are exploring how these bacteria can replace polluting pigments and dyes in the future. 

"The colour effect of the bacteria is similar to the colour of the carapace of green beetles, blue butterflies or the feathers of a peacock," said Ingham. "These actually have no colour of their own but consist of micron-sized scales. Those scales, which are all exactly the same distance apart, cause the light falling on them to reflect multiple colours. This is called 'iridescence'. The bacteria I study also stack that way. This offers great opportunities. Not only because the paint currently on the market does not produce this iridescent effect as intensely as these bacteria. But also because the bacteria are not toxic or harmful to the environmentally. However, there are still challenges: growing bacteria in a sterile petri dish is relatively easy, but how do you apply the bacteria to something without damaging the structure, and how do you then protect this fragile layer?"

Students help Ingham search for a topcoat. "Because I want to find a sustainable alternative to dyes and pigments, such a topcoat must of course be completely sustainable. Furthermore, it should not damage the bacteria, it should not be too thick, and if it does influence the colour of the bacteria, this effectshould always be the same. If the students' market research shows that the right protective layer is not yet in the available, I will guide them in developing such a layer."

Ingham: "We are currently still in an experimental phase. In this phase, it is hard work to keep our efforts financed. This collaboration helps us a lot. Hoekmine BV uses a lab at the HU and gets help from students. In return, Hoekmine guides students in the lab in their professional development. By doing so, the HU helps us in our development of sustainable colouring, and we help the HU in training innovative students with practical experience, who are valuable in the labour market."

Lecturer and researcher Patrick Baesjou is also enthusiastic: “I guide students at the HU and have extensive experience in research and product development in chemistry myself. So I can tell them a lot. However, I see that a truly hands-on research environment, where they are well mentored and where their research is really used, is the most instructive and motivating. And when iridescent blue electric cars drive around in a few years' time, or when bacteria-coloured shoes are trendy, it's nice that they can say: 'I worked on that'."