Periodic Reporting for period 2 - COLOUR (bio-inspired full-speCtrum blOck-copoLymer phOtonic strUctuRal pigments)
Berichtszeitraum: 2024-12-01 bis 2025-11-30
COLOUR addresses the need for sustainable, vibrant, and non-toxic pigments for applications such as coatings, cosmetics, packaging and optical devices. Conventional pigments can be toxic, fade over time, and rely on environmentally burdensome production routes. In contrast, many of nature’s most brilliant colours arise from structural colouration, where periodic nanostructures manipulate light to generate intense, durable hues without relying on molecular dyes. COLOUR therefore set out to develop bio-inspired photonic pigments based on the self-assembly of block copolymers (BCPs), with the long-term goal of enabling colourants that are non-fading, non-toxic and environmentally compatible.
The project pathway to impact is based on establishing a scalable materials platform and progressively increasing optical performance and application readiness. COLOUR pursued four scientific objectives:
(1) developing and optimising confined BCP self-assembly routes to produce photonic microparticles with controllable nanostructure and tunable colour;
(2) enhancing brightness by increasing refractive-index contrast through organic/inorganic high-index strategies and hybrid photonic structures;
(3) improving colour saturation by integrating absorption approaches that suppress incoherent scattering while preserving reflectance;
(4) translating the resulting pigments into macroscopic coatings/paint demonstrators.
In the final project phase, the work consolidated robust fabrication protocols, expanded morphology control (including anisotropic architectures enabling angle-dependent optical response), demonstrated higher loading of inorganic nanomaterials while maintaining photonic order, and produced application-oriented coating/paint demonstrators. COLOUR integrates concepts and methods from polymer chemistry, soft-matter physics, photonics and materials science. Its expected impacts are technological and societal: replacing hazardous or fading pigment chemistries with structurally coloured alternatives that support sustainability-driven industrial transitions. In the European policy context, the project aligns with the European Green Deal and broader circular-economy objectives by advancing safer materials and scalable approaches that can reduce environmental harm. Potential impact at scale includes adoption in sectors where colourants are used in large volumes (decorative coatings, packaging) as well as higher-value applications (functional surfaces, sensing and anti-counterfeiting concepts enabled by photonic materials). No specific integration of social sciences and humanities was required for this topic.
The project pathway to impact is based on establishing a scalable materials platform and progressively increasing optical performance and application readiness. COLOUR pursued four scientific objectives:
(1) developing and optimising confined BCP self-assembly routes to produce photonic microparticles with controllable nanostructure and tunable colour;
(2) enhancing brightness by increasing refractive-index contrast through organic/inorganic high-index strategies and hybrid photonic structures;
(3) improving colour saturation by integrating absorption approaches that suppress incoherent scattering while preserving reflectance;
(4) translating the resulting pigments into macroscopic coatings/paint demonstrators.
In the final project phase, the work consolidated robust fabrication protocols, expanded morphology control (including anisotropic architectures enabling angle-dependent optical response), demonstrated higher loading of inorganic nanomaterials while maintaining photonic order, and produced application-oriented coating/paint demonstrators. COLOUR integrates concepts and methods from polymer chemistry, soft-matter physics, photonics and materials science. Its expected impacts are technological and societal: replacing hazardous or fading pigment chemistries with structurally coloured alternatives that support sustainability-driven industrial transitions. In the European policy context, the project aligns with the European Green Deal and broader circular-economy objectives by advancing safer materials and scalable approaches that can reduce environmental harm. Potential impact at scale includes adoption in sectors where colourants are used in large volumes (decorative coatings, packaging) as well as higher-value applications (functional surfaces, sensing and anti-counterfeiting concepts enabled by photonic materials). No specific integration of social sciences and humanities was required for this topic.
Over the course of COLOUR, substantial progress was achieved in developing bio-inspired photonic pigments based on the confined self-assembly of block copolymers (BCPs). The project established scalable fabrication routes for structurally coloured microparticles and advanced their optical performance through refractive-index engineering, scattering suppression, and translation towards macroscopic demonstrators.
(1) Optimising BCP self-assembly and expanding structural control.
A robust fabrication methodology was developed using oil-in-water emulsions as confinement templates to trigger BCP self-assembly during solvent exchange/evaporation. Systematic optimisation of polymer selection, interfacial conditions and processing parameters enabled reproducible photonic microparticles with well-defined internal ordering and tuneable colour across the visible spectrum. In the final project phase, the work moved beyond concentric lamellae to deliberately access additional morphologies, including anisotropic particles with stacked lamellae, enabling materials with angular-dependent optical responses alongside the original angular-independent designs.
(2) Enhancing refractive-index contrast via organic/inorganic strategies.
To increase brightness and colour purity, the refractive-index contrast between lamellar domains was strengthened through domain-selective incorporation of high-index components. Building on the strategies developed earlier (high-index organic additives and nanoparticle co-assembly), the final phase focused on increasing inorganic nanoparticle loading while preserving photonic ordering, thereby strengthening the hybrid photonic pigment platform and extending it to additional functional nanomaterials.
(3) Combining structural colour with absorption to suppress incoherent scattering.
COLOUR addressed the key limitation of incoherent scattering by integrating absorption in a controlled manner. Alongside a dye-in-domain strategy that reproducibly improved colour saturation, the final phase refined this approach using a two-dye scheme with absorption bands positioned outside the photonic bandgap, improving contrast without the brightness penalties associated with fully broadband black dyes. In parallel, core–shell concepts were advanced using an improved microfluidic approach, enabling preliminary core–shell photonic capsules with control over core and shell dimensions and providing a pathway towards more sophisticated absorption/photonic architectures.
(4) Translation to macroscopic coatings and demonstrators.
Optimised photonic microparticles were incorporated into binder-based formulations to produce structurally coloured macroscopic coatings. Building on formulation guidelines established earlier (particle loading, binder selection and concentration, substrate effects, and absorber use), the project delivered functional photonic paint/coating demonstrators using optimised binder–particle systems, demonstrating the feasibility of translating COLOUR pigments into application-relevant surfaces.
Overall, COLOUR delivered a versatile photonic pigment platform with controllable structure–optics relationships, improved brightness through refractive-index engineering, enhanced saturation through scattering suppression strategies, and credible macroscopic demonstrators, supporting the development of sustainable, non-fading alternatives to conventional pigment technologies.
(1) Optimising BCP self-assembly and expanding structural control.
A robust fabrication methodology was developed using oil-in-water emulsions as confinement templates to trigger BCP self-assembly during solvent exchange/evaporation. Systematic optimisation of polymer selection, interfacial conditions and processing parameters enabled reproducible photonic microparticles with well-defined internal ordering and tuneable colour across the visible spectrum. In the final project phase, the work moved beyond concentric lamellae to deliberately access additional morphologies, including anisotropic particles with stacked lamellae, enabling materials with angular-dependent optical responses alongside the original angular-independent designs.
(2) Enhancing refractive-index contrast via organic/inorganic strategies.
To increase brightness and colour purity, the refractive-index contrast between lamellar domains was strengthened through domain-selective incorporation of high-index components. Building on the strategies developed earlier (high-index organic additives and nanoparticle co-assembly), the final phase focused on increasing inorganic nanoparticle loading while preserving photonic ordering, thereby strengthening the hybrid photonic pigment platform and extending it to additional functional nanomaterials.
(3) Combining structural colour with absorption to suppress incoherent scattering.
COLOUR addressed the key limitation of incoherent scattering by integrating absorption in a controlled manner. Alongside a dye-in-domain strategy that reproducibly improved colour saturation, the final phase refined this approach using a two-dye scheme with absorption bands positioned outside the photonic bandgap, improving contrast without the brightness penalties associated with fully broadband black dyes. In parallel, core–shell concepts were advanced using an improved microfluidic approach, enabling preliminary core–shell photonic capsules with control over core and shell dimensions and providing a pathway towards more sophisticated absorption/photonic architectures.
(4) Translation to macroscopic coatings and demonstrators.
Optimised photonic microparticles were incorporated into binder-based formulations to produce structurally coloured macroscopic coatings. Building on formulation guidelines established earlier (particle loading, binder selection and concentration, substrate effects, and absorber use), the project delivered functional photonic paint/coating demonstrators using optimised binder–particle systems, demonstrating the feasibility of translating COLOUR pigments into application-relevant surfaces.
Overall, COLOUR delivered a versatile photonic pigment platform with controllable structure–optics relationships, improved brightness through refractive-index engineering, enhanced saturation through scattering suppression strategies, and credible macroscopic demonstrators, supporting the development of sustainable, non-fading alternatives to conventional pigment technologies.
COLOUR delivered results beyond the state of the art in bio-inspired photonic pigments by moving from proof-of-principle structural colours to a controllable, hybrid and application-oriented pigment platform. The project established robust emulsion-confined block copolymer self-assembly routes for photonic microparticles and demonstrated multiple technical advances that address key limitations of existing photonic pigments (insufficient brightness, scattering-induced “whiteness”, limited functional integration and weak routes to coatings).
Key results beyond the state of the art include:
(1) Morphology-by-design for tailored optical response. Beyond concentric lamellae, COLOUR developed control over additional architectures, including anisotropic particles with stacked lamellae, enabling angular-dependent optical behaviour as a new degree of freedom for photonic pigment design.
(2) Hybrid refractive-index engineering while preserving photonic order. The project demonstrated that high-index components can be incorporated in a domain-selective manner while maintaining lamellar ordering, strengthening brightness and extending the platform towards multifunctional hybrid photonic pigments (including routes to incorporate different classes of inorganic nanomaterials).
(3) Improved strategies to suppress incoherent scattering without sacrificing brightness. COLOUR refined absorption integration by moving from a single broadband absorber concept to a bandgap-tailored approach (using complementary dyes positioned outside the photonic bandgap), improving colour contrast whilst largely preserving photonic peak intensity.
(4) More controllable routes to complex architectures. Core–shell concepts were advanced using microfluidics, enabling controlled generation of core–shell photonic capsules and additional control through osmotic effects, providing a credible pathway to architectures that combine absorption and structural colour in a reproducible manner.
(5)Translation to macroscopic demonstrators. Optimised pigments were integrated into binder-based formulations and used to produce structurally coloured coatings/paint demonstrators, supporting the feasibility of application in surfaces and coatings.
These results have potential impacts across sustainability-driven markets where colourants are used at scale. Structurally coloured pigments can reduce reliance on hazardous or fading dye chemistries and enable durable, non-toxic colour solutions aligned with European sustainability priorities. Beyond colour, the demonstrated hybrid and responsive routes open opportunities in higher-value applications such as functional surfaces, sensing concepts and anti-counterfeiting approaches.
To ensure further uptake and success, several next steps are needed: (i) scale-up and process engineering, including pilot-scale production (e.g. intensified/parallelised microfluidics and continuous processing) and quality control of colour metrics; (ii) performance validation of coatings under relevant mechanical and environmental conditions (abrasion, weathering, chemical resistance) and formulation optimisation for industrial application methods (spraying, roll-to-roll, printing); (iii) standardised characterisation protocols for structural-colour pigments (colour stability, angular response, durability), supporting comparability and market acceptance; and (iv) exploitation support, including IP strategy where appropriate, engagement with industrial partners for demonstrator validation, and access to financing for pilot production and market entry. Overall, COLOUR provides a strong scientific and technological foundation for sustainable photonic pigments and their translation towards real-world coatings and functional materials.
Key results beyond the state of the art include:
(1) Morphology-by-design for tailored optical response. Beyond concentric lamellae, COLOUR developed control over additional architectures, including anisotropic particles with stacked lamellae, enabling angular-dependent optical behaviour as a new degree of freedom for photonic pigment design.
(2) Hybrid refractive-index engineering while preserving photonic order. The project demonstrated that high-index components can be incorporated in a domain-selective manner while maintaining lamellar ordering, strengthening brightness and extending the platform towards multifunctional hybrid photonic pigments (including routes to incorporate different classes of inorganic nanomaterials).
(3) Improved strategies to suppress incoherent scattering without sacrificing brightness. COLOUR refined absorption integration by moving from a single broadband absorber concept to a bandgap-tailored approach (using complementary dyes positioned outside the photonic bandgap), improving colour contrast whilst largely preserving photonic peak intensity.
(4) More controllable routes to complex architectures. Core–shell concepts were advanced using microfluidics, enabling controlled generation of core–shell photonic capsules and additional control through osmotic effects, providing a credible pathway to architectures that combine absorption and structural colour in a reproducible manner.
(5)Translation to macroscopic demonstrators. Optimised pigments were integrated into binder-based formulations and used to produce structurally coloured coatings/paint demonstrators, supporting the feasibility of application in surfaces and coatings.
These results have potential impacts across sustainability-driven markets where colourants are used at scale. Structurally coloured pigments can reduce reliance on hazardous or fading dye chemistries and enable durable, non-toxic colour solutions aligned with European sustainability priorities. Beyond colour, the demonstrated hybrid and responsive routes open opportunities in higher-value applications such as functional surfaces, sensing concepts and anti-counterfeiting approaches.
To ensure further uptake and success, several next steps are needed: (i) scale-up and process engineering, including pilot-scale production (e.g. intensified/parallelised microfluidics and continuous processing) and quality control of colour metrics; (ii) performance validation of coatings under relevant mechanical and environmental conditions (abrasion, weathering, chemical resistance) and formulation optimisation for industrial application methods (spraying, roll-to-roll, printing); (iii) standardised characterisation protocols for structural-colour pigments (colour stability, angular response, durability), supporting comparability and market acceptance; and (iv) exploitation support, including IP strategy where appropriate, engagement with industrial partners for demonstrator validation, and access to financing for pilot production and market entry. Overall, COLOUR provides a strong scientific and technological foundation for sustainable photonic pigments and their translation towards real-world coatings and functional materials.