Can objects bruise like we do?

    Scientists are trying to develop things that bruise. The theory goes that if skin can tell us where it’s damaged by changing colour – indeed showing degrees of colour – it would be useful if objects could too.

    There’s a practical side to the fancy. When an object suffers an impact that is expected to cause damage, it is necessary to examine every centimetre of its surface to understand the extent of the damage, which takes time and money. Think of cars and planes in particular.

    And the idea isn’t fanciful. Researchers already are experimenting with spiropyran, a molecule that changes colour, due to a change in its chemical structure, when it is physically stimulated.

    When spiropyran is injected into concrete or silicone, it changes colour in response to mechanical stimuli such as force or deformation. The problem is that, until now, the sensitivity of the composite material has been too low for real-life applications.

    “Bruised” material. Credit: KIST

    Now a team led by Jaewoo Kim from the Korea Institute of Science and Technology (KIST) says it has improved the mechano-sensitivity to the extent that it could be applicable to wearable sensors and artificial skin.

    And it did it by coming at things in a different way. Previous studies, the researchers say, have been based around modifying the molecular structure of the spiropyran prior to synthesis according to the material with which it is going to be combined with.

    Their approach, described in a paper in the journal Macromolecules, is to synthesise the composite material first, then add a solvent to improve the sensitivity through what they describe as a sort of ageing process.

    The changes in colour and fluorescence of the composite material were observed, while controlling the absorption time with the solvent, and it was found that increasing the treatment time improved the sensitivity.

    The spiropyran-polymer developed through this new process showed 850% improvement in sensitivity compared to the previously developed materials, irrespective of whether deformations were caused by tension, compression and bending.

    The ageing process is possible, they say, because they are manipulating the final product, not each material separately. And it can be easily applied to various materials.

    “Based on this, we plan to devote ourselves to a follow-up study in which we apply the technology to futuristic wearable sensors and artificial skin,” Kim says.

    Chemical structure of the spiropyran mechanophore (a compound whose reaction is triggered by mechanical force) and its transformation into merocyanine form. Merocyanines are a class of polymethine dyes. Credit: KIST

    Read science facts, not fiction…

    There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.

    Latest articles

    Whodunit solved when ‘sword’ is found embedded in thresher shark

    Home News A swordfish (Xiphias gladius) left part of its "sword" sticking out of the shark it killed. (Image: © The Ichthyological Society of Japan 2020) When a...

    Wide-eyed prehistoric shark hid its sharpest teeth in nightmare jaws

    Home News Illustration of the prehistoric shark Ferromirum oukherbouchi. (Image: © Christian Klug, UZH) Imagine you're a fish swimming through the ocean millions of years ago, when a...

    ‘Superbolts’ are real, and they flash up to 1,000 times brighter than regular lightning

    Home News So-called superbolts are at least 100 times brighter than ordinary lighting, but can be more than 1,000 times brighter. (Image: © Shutterstock) Superbolts — flashes of...

    Changing behaviours of birds

    The sight of a sulphur-crested cockatoo raiding a household wheelie bin might do little more than irritate the average person left to clean up...

    Related articles