Scientists from Trinity College Dublin and AMBER, the SFI Research Centre for Advanced Materials and Bio­Engineering Research, have discovered a way to fabricate tiny colour-changing gas sensors using new materials and a high-resolution form of 3D printing. The sensors – responsive, printed, micr­oscopic optical structures – can be monitored in real-time, and used for the detection of solvent vapours in air. There is great potential for these sensors to be used in connected, low-cost devices for homes, or integrated in wearable devices used to monitor human health.

The work was led by Larisa Florea, Assistant Professor in Trinity’s School of Chemistry, and Principal Investigator at AMBER, in colla­boration with Louise Bradley, Professor in Trinity’s School of Physics, and carried out in CRANN, the Trinity Centre for Research on Adaptive Nano­structures and Nano­devices. An industrial collaborator and leader in the field of gas sensing, Radislav Potyrailo from GE Research, Niskayuna New York, has also been involved throughout. Colm Delaney said: “More than 300 years ago, Robert Hooke first inves­tigated the vibrant colors on a peacock’s wing. Only centuries later did scientists discover that the effer­vescent colora­tion was caused not by tradi­tional pigments but by the interaction of light with tiny objects on the feather, objects which were just a few millionths of a meterin size.”

“We have taken this biological design, seen all the way from a magpie to a chame­leon, to make some really exciting materials. We achieve this by using a technique known as Direct laser-writing (DLW), which allows us to focus a laser into an extremely small spot, and to then use it to make tiny structures in three dimensions from the soft polymers which we develop in the lab”, Delaney added. Louise Bradley, a funded investigator at AMBER, said: “The research we carry out between the two groups focuses on design, modelling, and fabri­cation of these tiny structures in stimuli-responsive materials. Jing Qian, a fantastic PhD student in my lab has spent a lot of time developing designs, and predicting the response of different structures, which we can have respond to light, heat, and humidity to create systems which can truly recreate the vividness, stealth response, and camou­flaging ability found in nature. The tiny responsive arrays, which are smaller than a freckle, can be used to tell us an enormous amount about the chemistry of their environment.”

While traditional physical sensors have bolstered a connected-living market, there exists a lag in low-cost, adaptable chemical-sensing platforms that can be used. Photonic sensors have made considerable inroads into yielding accurate and robust alternatives, with minimal power consump­tion, low operating costs and high sensi­tivity. Larisa Florea, from Trinity’s School of Chemistry and AMBER, said: “We have created responsive, printed, micro­scopic optical structures which can be monitored in real-time, and used for the detection of gases. The ability to print such an opti­cally responsive material has profound potential for their incorporation into connected, low-cost sensing devices for homes, or into wearable devices for monitoring analytes.”

“We spend the majority of our lives inside our homes, cars, or work environ­ments. Models suggest that the concen­tration of pollutants can be anywhere from 5-100 times the concentration found outside. This is a haunting thought when we consider that the World Health Orga­nisation suggests 90 % of the world’s population lives in areas which exceed acceptable air standard limits. These pollutants can be influenced by ambient air, chemical presence, fragrances, food quality, and human activity and have a profound effect on our health.

“To date, indoor gas sensors have focused almost solely on leak, smoke, and carbon dioxide detection. Even iterative advances, to include relative humidity, oxygen levels, carbon dioxide, volatile organic carbons (VOCs), and ammonia in a real-time manner could play an enormous role in the development of a domestic environ­mental monitoring ecosystem. This could ensure that health and wellbeing moni­toring become central to the future of home building and auto­mation”, Florea added. (Source: Trinity Col.)

Reference: C. Delanay et al.: Direct laser writing of vapour-responsive photonic arrays, J. Mater. Chem. C  9, 11674 (2021); DOI: 10.1039/d1tc01796a

Link: AMBER, The SFI Research Centre for Advanced Materials and BioEngineering Research, Trinity College Dublin, Dublin, Ireland