Mechanochromism in Structurally Colored Polymeric Materials

Mechanochromic effects in structurally coloured materials are the result of deformation-induced changes to their ordered nanostructures. Polymeric materials which respond in this way to deformation offer an attractive combination of characteristics, including continuous strain-sensing, high strain resolution and a wide strain-sensing range. Such materials are potentially useful for a wide range of applications, which extend from pressure-sensing bandages to anti-counterfeiting devices. Focusing on the materials design aspects, this review summarises recent developments in this field. The article starts with an overview of different approaches to achieve mechanochromic effects in structurally coloured materials, before the physical principles governing the interaction of light with each of these materials types are summarised. Diverse methodologies to prepare these polymers are then discussed in detail, and where applicable, naturally occurring materials that inspired the design of artificial systems are discussed. The capabilities and limitations of structurally coloured materials in reporting and visualising mechanical deformation are examined from a general standpoint and also in more specific technological contexts. To conclude, current trends in the field are highlighted and possible future opportunities are identified.