Harnessing the power of structural colour in nature for photonic sensors

13 Jun 2023

Colm Delaney. Image: Paul Sharp/SHARPPIX

Trinity College Dublin’s Colm Delaney works on creating photonic sensors by exploiting a phenomenon known as ‘structural colour’ often found in birds, insects and chameleons.

Colm Delaney is an assistant professor in chemistry at Trinity College Dublin. He is a Marie Curie International Fellowship recipient and an European Research Council (ERC) Starting Grant awardee.

He works as part of a team in Trinity College Dublin on creating tiny colour-changing gas sensors using new materials and a high-resolution form of 3D printing.

While traditional physical sensors have bolstered the internet of things (IoT) and connected device market, there is still a lag in low-cost, adaptable chemical-sensing platforms that can be used.

Photonic sensors have made considerable in-roads into yielding accurate and robust alternatives, with minimal power consumption, low operating costs and high sensitivity.

The sensors Delaney is working on can be monitored in real-time and used for the detection of solvent vapours in air.

‘People have been mesmerised by structural colour for centuries’

Tell us about your current research.

Nature has enabled organisms to morph their colour and reflectivity to camouflage, signal, mimic, distract and regulate biological processes. This phenomenon, known as structural colour, is caused by combinations of complex nano and microstructures. Structural colour is found in the air (Paradise bird), on land (Panther chameleon), and soil (Hoplia Argentea beetle), and even under water (Neon Tetra fish).

Because of the complex nature of these structures, it has been extremely difficult to recreate, but achieving this would open a treasure trove of untapped potential. My research takes inspiration from this phenomenon.

The team exploits materials chemistry to harness dynamic and responsive structural colour, through the development of self-ordering nanoparticles (in place of keratin and chitin found in nature), the synthesis of responsive materials (mimicking motor proteins and actin filaments), and programmed nanoscale 3D printing (yielding ordered and disordered superstructures).

In your opinion, why is your research important?

Nature has had millions of years of evolutionary trial and error to master structural colour, and exploit it for camouflaging, signalling, mimicry, distraction and even temperature regulation.

Harnessing a fraction of this potential could allow us to make enormous leaps in making microscopic optical arrays that can respond to light, heat, vapour or chemical analytes, to instantly camouflage and encrypt or to sense and diagnose.

This will impact the way we design display technologies, the way we encrypt data and the way we fabricate low-cost sensing devices for medical and environmental monitoring.

What inspired you to become a researcher?

I am one of the lucky ones who always knew what I wanted to do. My dad would bring home old glassware and we would set up distillations in the kitchen over the Christmas holidays.

I can remember being a five or six-year-old, picturing myself doing this very job. It’s such a lucky position to be excited and amazed every day and to try and inspire the same feelings in others.

What are some of the biggest challenges or misconceptions you face as a researcher in your field?

At the moment, one of the biggest challenges is trying to persuade the best people to (or be able to) stay in Ireland. This is compounded by the meagre stipends that are offered through funding agencies. Trinity has taken a lead on this, in the hopes of being able to offer research students acceptable stipends.

Some of the most exciting and ground-breaking discoveries are achieved through frontier basic research. It is high risk but can also be high gain. This has repeated itself again and again throughout history. The impact and applications of the greatest discoveries are only visible long after fundamental breakthroughs are really understood.

It’s for this reason that funding of fundamental research is paramount. Unfortunately, many funding agencies are pushing us to lead our research through direct application. While this is very important, it can never be the driving force of innovation. I have been very fortunate to receive ERC funding that supports basic frontier research, that allows me to build up a team to explore and understand the fundamentals of structural colour and to create artificial analogues that can be exploited to create dynamic photonic devices.

Do you think public engagement with science has changed in recent years?

Public engagement and the democratisation of science was so important during the pandemic. In many ways, this is the direction research is moving towards, with open access data and pre-print publications. It can mean that we must defend our work amongst our peers, and often even across the general public. This has made scientists develop a whole new set of skills for engaging with the public.

In the research that I carry out on bioinspiration, I am lucky that there is very relatable element that engages people instantly. People have been mesmerised by structural colour for centuries. In fact, more than 400 years ago, Robert Hooke first investigated the vibrant colours of a peacock’s wing. Centuries later, scientists discovered that the effervescent colouration 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 metre in size.

It is a perfect platform to sell the virtues of nanoscience and materials chemistry to an unsuspecting audience.

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