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Structural color is poorly known in plants relative to animals. In fruits, only a handful of cases have been described, including in Viburnum tinus where the blue color results from a disordered multilayered reflector made of lipid droplets. Here, we examine the broader evolutionary context of fruit structural color across the genus Viburnum. We obtained fresh and herbarium fruit material from 30 Viburnum species spanning the phylogeny and used transmission electron microscopy, optical simulations, and ancestral state reconstruction to identify the presence/absence of photonic structures in each species, understand the mechanism producing structural color in newly identified species, relate the development of cell wall structure to reflectance in Viburnum dentatum, and describe the evolution of cell wall architecture across Viburnum. We identify at least two (possibly three) origins of blue fruit color in Viburnum in species which produce large photonic structures made of lipid droplets embedded in the cell wall and which reflect blue light. Examining the full spectrum of mechanisms producing color in pl, including structural color as well as pigments, will yield further insights into the diversity, ecology, and evolution of fruit color.

Increasing the light scattering efficiency of nanostructured materials is becoming an active field of research both in fundamental science and commercial applications. In this context, the challenge is to use inexpensive organic materials that come with a lower refractive index than currently used mineral nanoparticles, which are under increased scrutiny for their toxicity. Although several recent investigations have reported different disordered systems to optimise light scattering by morphological design, no systematic studies comparing and explaining how different topological features contribute to optical properties have been reported yet. Using in silico synthesis and numerical simulations, we demonstrate that the reflectance is primarily determined by second order statistics. While remaining differences are explained by surface area and integrated mean curvature, an equal reflectance can be obtained by further tuning the structural anisotropy. Our results suggest a topological invariance for light scattering, demonstrating that any disordered system can be optimised for whiteness., Comment: submitted to a journal, 12 + 7 pages and 6 + 6 figures (manuscript + supporting information)

The ability to manipulate light-matter interaction to tailor the scattering properties of materials is crucial to many aspects of our everyday life, from paints to lighting, and to many fundamental concepts in disordered photonics. Light transport and scattering in a granular disordered medium are dictated by the spatial distribution (structure factor) and the scattering properties (form factor and refractive index) of its building blocks. As yet, however, the importance of anisotropy in such systems has not been considered. Here, we report a systematic numerical survey that disentangles and quanti es the role of different kinds and degrees of anisotropy in scattering optimization. We show that ensembles of uncorrelated, anisotropic particles with nematic ordering enables to increase by 20% the reflectance of low-refractive index media (n = 1.55), using only three-quarters of material compared to their isotropic counterpart. Additionally, these systems exhibit a whiteness comparable to conventionally used high-refractive index media, e.g. TiO2 (n = 2:60). Therefore, our findings not only provide an understanding of the role of anisotropy in scattering optimization, but they also showcase a novel strategy to replace inorganic white enhancers with sustainable and bio-compatible products made of biopolymers.

The study of light propagation in disordered media has attracted the interest of many researchers for its relevance to fundamental and applied problems, ranging from imaging through turbid media to the fabrication of white paint. Scattering in a disordered system is determined by the spatial distribution and the scattering properties of its building blocks. To date, most efforts on scattering optimisation have focused on isotropic, high refractive index systems. This thesis investigates the importance of anisotropy in increasing the scattering efficiency of a system, with a particular focus on low refractive index media and their use as sustainable, white materials. Nature provides a striking example of how to exploit anisotropy to achieve scattering optimisation: with the intra-scale chitin network of the beetle genus Cyphochilus. In this thesis, after showing that this network exhibits the highest scattering efficiency found in nature thus far, a systematic numerical investigation was performed to understand the importance of both single-particle and structural anisotropy in scattering optimisation. In particular, this numerical analysis unveiled that ensembles of anisotropic particles show higher reflectance compared to their isotropic counterpart, whilst using less material. Based on these findings, the optical properties of bioinspired, scattering systems ��� obtained both via polymer phase separation and a combination of sequential vacuum filtration and freeze-drying ��� were investigated. Notably, the reported materials achieve scattering properties comparable to those found in nature, showcasing the potential of using biopolymers to produce sustainable, biocompatible white materials. In addition, the presented bioinspired systems are an interesting platform for fundamental studies, allowing to investigate light transport in anisotropic media., European Research Council grant awarded to Dr Silvia Vignolini

International audience

Living organisms have developed a wide range of appearances from iridescent to matt textures. Interestingly, angular independent structural colors, where isotropy in the scattering structure is present, only produce coloration in the blue wavelength region of the visible spectrum. One might, therefore, wonder if such observation is a limitation of the architecture of the palette of materials available in nature. Here, by exploiting numerical modeling, we discuss the origin of isotropic structural colors without restriction to a specific light scattering regime. We show that high color purity and color saturation cannot be reached in isotropic short-range order structures for red hues. This conclusion holds even in the case of advanced scatterer morphologies, such as core-shell particles or inverse photonic glasses - explaining recent experimental findings reporting very poor performances of visual appearance for such systems.

This document contains all supplementary figures associated with the manuscript named "Complex photonic response reveals 3D self-organization of structural colored bacterial colonies" by Schertel et al.

Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. We demonstrate that the control of the interplay between order and disorder in the obtained photonic structure offers a powerful tool box for designing the optical appearance of the polymer resins in terms of reflected wavelength and scattering properties. The obtained materials exhibit excellent mechanical properties with hardness up to 172 MPa and Young's modulus over 2.9 GPa, indicating great potential for practical uses as photonic coatings on a variety of surfaces.

The understanding of the interaction between light and complex, random structures is the key for designing and tailoring the optical appearance and performance of many materials that surround us, ranging from everyday consumer products, such as those for personal care, paints, and paper, to light diffusers used in the LED-lamps and solar cells. Here, it is demonstrated that the light transport in membranes of pure cellulose nanofibrils (CNFs) can be controlled to achieve bright whiteness in structures only a few micrometers thick. This is in contrast to other materials, such as paper, which require hundreds of micrometers to achieve a comparable appearance. The diffusion of light in the CNF membranes is shown to become anomalous by tuning the porosity and morphological features. Considering also their strong mechanical properties and biocompatibility, such white coatings are proposed as a new application for cellulose nanofibrils.

Monte Carlo code to simulate the coherent backscattering effect in anisotropic media

The introduction of eGovernment services and applications leads to major changes in the structure and operation of public administrations. In this paper we describe the work in progress in an Italian project called “SPO.T.” aimed at the analysis, development, deployment and evaluation of tools and environments to support the people who plan, deliver, use and evaluate user-centred provision of One-Stop-Shop services to citizens. The “SPO.T.” project has focused on two requirements: 1. the support tools and environments must facilitate the active involvement of all stakeholders in the definition and evolution of eGovernment applications and services, and it is argued that through participatory design changes of structure, process and culture can be delivered effectively; 2. they must embody a set of architecturally coherent resources which reflect the new roles and relationships of public administration and which are sufficiently generic to be relevant to a wide range of local contexts across the community.

Strong-coupling between excitons and confined photonic modes can lead to the formation of new quasi-particles termed exciton-polaritons which can display a range of interesting properties such as super-fluidity, ultrafast transport and Bose-Einstein condensation. Strong-coupling typically occurs when an excitonic material is confided in a dielectric or plasmonic microcavity. Here, we show polaritons can form at room temperature in a range of chemically diverse, organic semiconductor thin films, despite the absence of an external cavity. We find evidence of strong light-matter coupling via angle-dependent peak splittings in the reflectivity spectra of the materials and emission from collective polariton states. We additionally show exciton-polaritons are the primary photoexcitation in these organic materials by directly imaging their ultrafast (5 �� 106 m s-1), ultralong (~270 nm) transport. These results open-up new fundamental physics and could enable a new generation of organic optoelectronic and light harvesting devices based on cavity-free exciton-polaritons., EPSRC (EP/R025517/1), EPSRC (EP/M025330/1), ERC Horizon 2020 (grant agreements No 670405 and No 758826), ERC (ERC-2014-STG H2020 639088), Netherlands Organisation for Scientific Research, Swedish Research Council (VR, 2014-06948), Knut and Alice Wallenberg Foundation 3DEM-NATUR (no. 2012.0112), Royal Commission for the Exhibition of 1851, CNRS (France), US Department of Energy, Office of Science, Basic Energy Sciences, CPIMS Program, Early Career Research Program (DE-SC0019188).

Corals have evolved as optimised photon augmentation system, leading to space-efficient microalgal growth and outstanding photosynthetic quantum efficiencies. Light attenuation due to algal self-shading is a key limiting factor for the upscaling of microalgal cultivation. Coral-inspired light management systems could overcome this limitation and facilitate scalable bioenergy and bioproduct generation. Here, we develop 3D printed bionic corals capable of growing microalgae with high spatial cell densities of up to 109 cells mL-1. The hybrid photosynthetic biomaterials are produced with a 3D bioprinting platform which mimics morphological features of living coral tissue and the underlying skeleton with micron resolution, including their optical and mechanical properties. The programmable synthetic microenvironment thus allows for replicating both structural and functional traits of the coral-algal symbiosis. Our work defines a class of bionic materials that is capable of interacting with living organisms and can be exploited for applied coral reef research and photobioreactor design.

Corals have evolved as optimized photon augmentation systems, leading to space-efficient microalgal growth and outstanding photosynthetic quantum efficiencies. Light attenuation due to algal self-shading is a key limiting factor for the upscaling of microalgal cultivation. Coral-inspired light management systems could overcome this limitation and facilitate scalable bioenergy and bioproduct generation. Here, we develop 3D printed bionic corals capable of growing microalgae with high spatial cell densities of up to 109 cells mL-1. The hybrid photosynthetic biomaterials are produced with a 3D bioprinting platform which mimics morphological features of living coral tissue and the underlying skeleton with micron resolution, including their optical and mechanical properties. The programmable synthetic microenvironment thus allows for replicating both structural and functional traits of the coral-algal symbiosis. Our work defines a class of bionic materials that is capable of interacting with living organisms and can be exploited for applied coral reef research and photobioreactor design.

Photonic materials with angular-independent structural color are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles, or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. Here, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic bottlebrush block copolymer. This is achieved by exploiting a novel "controlled micellization" self-assembly mechanism within an emulsified toluene-in-water droplet. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally colored pigments. Furthermore, the reflected color can be tuned to reflect across the full visible spectrum using only a single polymer (Mn = 290 kDa) by altering the initial emulsification conditions. Such "photonic pigments" have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves color purity without the need for either refractive index matching or the inclusion of a broadband absorber., National Natural Science Foundation of China [51873098] Winton Programme for the Physics of Sustainability

Strong-coupling between excitons and confined photonic modes can lead to the formation of new quasi-particles termed exciton-polaritons which can display a range of interesting properties such as super-fluidity, ultrafast transport and Bose-Einstein condensation. Strong-coupling typically occurs when an excitonic material is confided in a dielectric or plasmonic microcavity. Here, we show polaritons can form at room temperature in a range of chemically diverse, organic semiconductor thin films, despite the absence of an external cavity. We find evidence of strong light-matter coupling via angle-dependent peak splittings in the reflectivity spectra of the materials and emission from collective polariton states. We additionally show exciton-polaritons are the primary photoexcitation in these organic materials by directly imaging their ultrafast (5 �� 106 m s���1), ultralong (~270 nm) transport. These results open-up new fundamental physics and could enable a new generation of organic optoelectronic and light harvesting devices based on cavity-free exciton-polaritons

Photonic materials with angular independent structural colour are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. In this article, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic bottlebrush block copolymer. This is achieved by exploiting a novel controlled micellization self-assembly mechanism within emulsified toluene-in-water droplets. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally coloured pigments. Furthermore, the reflected colour can be tuned to reflect across the full visible spectrum using only a single polymer (Mn = 290 kDa) by altering the initial emulsification conditions. Such photonic pigments have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves colour purity without the need for either refractive index matching or the inclusion of a broadband absorber., National Natural Science Foundation of China [51873098] Winton Programme for the Physics of Sustainability

Funder: European Union Horizon 2020 scheme, Corals have evolved as optimized photon augmentation systems, leading to space-efficient microalgal growth and outstanding photosynthetic quantum efficiencies. Light attenuation due to algal self-shading is a key limiting factor for the upscaling of microalgal cultivation. Coral-inspired light management systems could overcome this limitation and facilitate scalable bioenergy and bioproduct generation. Here, we develop 3D printed bionic corals capable of growing microalgae with high spatial cell densities of up to 109 cells mL−1. The hybrid photosynthetic biomaterials are produced with a 3D bioprinting platform which mimics morphological features of living coral tissue and the underlying skeleton with micron resolution, including their optical and mechanical properties. The programmable synthetic microenvironment thus allows for replicating both structural and functional traits of the coral-algal symbiosis. Our work defines a class of bionic materials that is capable of interacting with living organisms and can be exploited for applied coral reef research and photobioreactor design.

Strong-coupling between excitons and confined photonic modes can lead to the formation of new quasi-particles termed exciton-polaritons which can display a range of interesting properties such as super-fluidity, ultrafast transport and Bose-Einstein condensation. Strong-coupling typically occurs when an excitonic material is confided in a dielectric or plasmonic microcavity. Here, we show polaritons can form at room temperature in a range of chemically diverse, organic semiconductor thin films, despite the absence of an external cavity. We find evidence of strong light-matter coupling via angle-dependent peak splittings in the reflectivity spectra of the materials and emission from collective polariton states. We additionally show exciton-polaritons are the primary photoexcitation in these organic materials by directly imaging their ultrafast (5 × 106 m s−1), ultralong (~270 nm) transport. These results open-up new fundamental physics and could enable a new generation of organic optoelectronic and light harvesting devices based on cavity-free exciton-polaritons, Exciton-polaritons are typically formed in organic systems when the molecules are confined between metallic or dielectric mirrors. Here, the authors reveal that interactions between excitons and moderately confined photonic states within the bare organic film can also lead to polariton formation, making them the primary photoexcitation.

Scattering enhancers are a class of nanomaterials used in every colored or white material surrounding us: from paints and inks to food and cosmetics to packaging and paper. Such hiding pigments usually consist of non-absorbing, high refractive index nanoparticles, for example spherically shaped titanium dioxide nanopowders. However use of TiO2 carries a high environmental burden. To offset the carbon footprint and health concerns inherent with the use of titanium dioxide, one could approach the challenge of scattering optimization by modifying the morphology of the scattering elements rather than their refractive index. Here, inspired by the bright anisotropic scattering system found in nature, we demonstrate that anisotropic sphero-cylindrical particles can outperform the scattering efficiency of their isotropic counterparts – obtaining an excellent scattering performances across the visible electromagnetic spectrum. We developed a class of micron-sized scattering enhancers composed only of silica. We show that these cylindrical colloids are easily assembled into scattering supracolloidal balls, a new class of pigment microspheres which can be used in formulations for ultrabright coatings.

International audience; 16 Viburnum tinus is an evergreen shrub that is native to the Mediterranean region but cultivated 17 widely in Europe and around the world. It produces ripe metallic blue fruits throughout winter [1]. 18 Despite its limited fleshy pulp,[2] its high lipid content[3] makes it a valuable resource to the small 19 birds[4] that act as its seed-dispersers[5]. Here, we find that the metallic blue appearance of the 20 fruits is produced by globular lipid inclusions arranged in a disordered multilayer structure. This 21 structure is embedded in the cell walls of the epicarp and underlaid with a dark layer of anthocyanin 22 pigments. The presence of such large, organised lipid aggregates in plant cell walls represents a new 23 mechanism for structural colouration and may serve as an honest signal of nutritional content. 24 Results and Discussion 25 The colours of fleshy fruits are thought to serve primarily to attract animal dispersers, and 26 understanding the origins and diversity of fleshy fruit colours provides insight into the ecological 27 interactions between plants and their dispersers.[7] Viburnum tinus (Adoxaceae) is a shrub native to 28 the Mediterranean region that is now cultivated around the world.[8] It produces large numbers of 29 metallic blue fruits throughout the year. Although a variety of bird dispersers consume V. tinus 30 fruits,[2] these serve as an especially important food source for birds during winter, including the 31 Eurasian blackcap (Sylvia atricapilla)[9] and the European robin (Erithacus rubecola).[10] While the 32 remarkable blue metallic appearance of V. tinus fruits (Figure 1) is commonly known and previously 33 reported,[11] the mechanism by which such blue colour is produced has not been elucidated. In a 34 review of earlier literature,[12] the colour of V. tinus has been attributed to the presence of 35 anthocyanin pigments. 36

Living organisms have developed a wide range of appearances from iridescent to matte textures. Interestingly, angular independent structural colors, where isotropy in the scattering structure is present, only produce coloration in the blue wavelength region of the visible spectrum. One might, therefore, wonder if such observation is a limitation of the architecture of the palette of materials available in nature. Here, by exploiting numerical modeling, we discuss the origin of isotropic structural colors without restriction to a specific light scattering regime. We show that high color purity and color saturation cannot be reached in isotropic short-range order structures for red hues. This conclusion holds even in the case of advanced scatterer morphologies, such as core-shell particles or inverse photonic glasses — explaining recent experimental findings reporting very poor performances of visual appearance for such systems.

Vivid colours found in living organisms are often the result of scattering from hierarchical nanostructures, where the interplay between order and disorder in their packing defines visual appearance. In the case of Flavobacterium IR1, the complex arrangement of the cells in polycrystalline three-dimensional lattices is found to be a distinctive fingerprint of colony organization. By combining analytical analysis of the angle-resolved scattering response of in vivo bacterial colonies with numerical modelling, we show that we can assess the inter-cell distance and cell diameter with a resolution below 10 nm, far better than what can be achieved with conventional electron microscopy, suffering from preparation artefacts. Retrieving the role of disorder at different length scales from the salient features in the scattering response enables a precise understanding of the structural organization of the bacteria. © 2020 The Author(s) Published by the Royal Society. All rights reserved.

Corals have evolved as optimized photon augmentation systems, leading to space-efficient microalgal growth and outstanding photosynthetic quantum efficiencies. Light attenuation due to algal self-shading is a key limiting factor for the upscaling of microalgal cultivation. Coral-inspired light management systems could overcome this limitation and facilitate scalable bioenergy and bioproduct generation. Here, we develop 3D printed bionic corals capable of growing microalgae with high spatial cell densities of up to 109 cells mL−1. The hybrid photosynthetic biomaterials are produced with a 3D bioprinting platform which mimics morphological features of living coral tissue and the underlying skeleton with micron resolution, including their optical and mechanical properties. The programmable synthetic microenvironment thus allows for replicating both structural and functional traits of the coral-algal symbiosis. Our work defines a class of bionic materials that is capable of interacting with living organisms and can be exploited for applied coral reef research and photobioreactor design., Corals have evolved as finely tuned light collectors. Here, the authors report on the 3D printing of coral-inspired biomaterials, that mimic the coral-algal symbiosis; these bionic corals lead to dense microalgal growth and can find applications in algal biotechnology and applied coral science.

Photonic materials with angular independent structural colour are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. In this article, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic bottlebrush block copolymer. This is achieved by exploiting a novel controlled micellization self-assembly mechanism within emulsified toluene-in-water droplets. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally coloured pigments. Furthermore, the reflected colour can be tuned to reflect across the full visible spectrum using only a single polymer (Mn = 290 kDa) by altering the initial emulsification conditions. Such photonic pigments have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves colour purity without the need for either refractive index matching or the inclusion of a broadband absorber., 32 pages, 18 figures, 1 table

Hydroxypropyl cellulose (HPC) is a biocompatible cellulose derivative capable of self assembling into a lyotropic chiral nematic phase in aqueous solution. This liquid crystalline phase reflects right-handed circular polarized light of a specific color as a function of the HPC weight fraction. Here, we demonstrate that, by introducing a crosslinking agent, it is possible to drastically alter the visual appearance of the HPC mesophase in terms of the reflected color, the scattering distribution and the polarization response, resulting in an exceptional matte appearance in dry solid-state films. By exploiting the interplay between order and disorder, a robust and simple methodology towards the preparation of polarization and angular independent color was developed, which constitutes an important step towards the development of real-world photonic colorants., This work is funded by EPSRC grant EP/R511675/1 to B.F.-P., S.V.; by EPSRC grant EP/L016087/1 to C.A.W.; by BBSRC David Phillips fellowship BB/K014617/1 to G.J., S.V.; by EU’s Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant agreement No. 722842 (ITN Plant-inspired Materials and Surfaces – PlaMatSu) to G.T.K., S.V.; by Swiss National Science Foundation #165176 to R.V.; by Croucher Cambridge International Scholarship to C.L.C.C.; by ERC grant ERC 2014 STG H2020 639088 to M.M.B., G.J., S.V.; by ERC grant ERC 2017 POC 790518 to R.M.P., S.V.

Both vertebrates and invertebrates commonly exploit photonic structures adjacent to their photoreceptors for visual benefits. For example, use of a reflecting structure (tapetum) behind the retina increases photon capture, enhancing vision in dim light [1–5]. Colored filters positioned lateral or distal to a photoreceptive unit may also be used to tune spectral sensitivity by selective transmission of wavelengths not absorbed or scattered by the filters [6–8]. Here we describe a new category of biological optical filter that acts simultaneously as both a transmissive spectral filter and narrowband reflector. Discovered in the larval eyes of only one family of mantis shrimp (stomatopod) crustaceans (Nannosquillidae), each crystalline structure bisects the photoreceptive rhabdom into two tiers and contains an ordered array of membrane-bound vesicles with sub-wavelength diameters of 153 ± 5 nm. Axial illumination of the intrarhabdomal structural reflector (ISR) in vivo produces a narrow band of yellow reflectance (mean peak reflectivity, 572 ± 18 nm). The ISR is similar to several synthetic devices, such as bandgap filters, laser mirrors, and (in particular) fiber Bragg gratings used in optical sensors for a wide range of industries. To our knowledge, the stomatopod larval ISR is the first example of a naturally occurring analog to these human-made devices. Considering what is known about these animals’ visual ecology, we propose that these reflecting filters may help improve the detection of pelagic bioluminescence in shallow water at night. Video Abstract: Feller et al. report how one family of mantis shrimp larvae uses visual filtering structures to selectively reflect and transmit light within photoreceptors. These reflective filters likely enhance bioluminescence detection underwater at night and are similar to human-made optical devices such as fiber Bragg gratings or band gap filters.

The scattering strength of a random medium relies on the geometry and spatial distribution of its components as well as on their refractive index. Anisotropy can, therefore, play a major role in the optimization of the scattering efficiency in both biological and synthetic materials. In this study, we show that, by exploiting the coherent backscattering phenomenon, it is possible to characterize the optical anisotropy in Cyphochilus beetle scales without the need to change their orientation or their thickness. For this reason, such a static and easily accessible experimental approach is particularly suitable for the study of biological specimens. Moreover, estimation of the anisotropy in Cyphochilus beetle scales might provide inspiration for improving the scattering strength of artificial white materials.

The understanding of the interaction between light and complex, random structures is the key for designing and tailoring the optical appearance and performance of many materials that surround us, ranging from everyday consumer products, such as those for personal care, paints, and paper, to light diffusers used in the LED-lamps and solar cells. Here, it is demonstrated that the light transport in membranes of pure cellulose nanofibrils (CNFs) can be controlled to achieve bright whiteness in structures only a few micrometers thick. This is in contrast to other materials, such as paper, which require hundreds of micrometers to achieve a comparable appearance. The diffusion of light in the CNF membranes is shown to become anomalous by tuning the porosity and morphological features. Considering also their strong mechanical properties and biocompatibility, such white coatings are proposed as a new application for cellulose nanofibrils.

In this paper we introduce an artistic artefact "NeonAlbers" which is a part of a larger system prototype in which traditional human-computer interface is hidden inside electronic art pieces in the home environment. In that prototype an electronic art piece acts as a communication device as well as an artistic artefact. "NeonAlbers" is an interactive artwork constructed with light and sound levelsensors and two displays, which are hanging on the wall. The audience can alter the digipainting's colors by triggering the light sensors in the environment. The artwork includes also loudspeakers. The purpose of the work is to study new ways to visualise information in the home environment and create new ubiquitous human-artefact interfaces.

This paper describes a hand controlled interactive light installation, “Aurora Borealis”. User can select a light color by performing a certain gesture with the control device and control its intensity by tilting the device. The selection of color is presented to the user with audiovisual indication.

In this paper we explore the similarities and differences of participatory design and action research in a cross-disciplinary fashion. We briefly outline two distinct studies: (1) a design study that examines mobile interactions of backpackers, and (2) an urban sociology study to better understand social networks of apartment residents. The first study follows a participatory design approach. The second study is guided by action research principles. We reflect on the research practice of these two studies in order to discuss the key methodological features of each. We would like to invite the larger participatory design community to continue the comparison and exploration we have begun here. By outlining the tools and techniques, and the application thereof we hope to promote the usefulness of action research for participatory design projects and vice versa.

Beyond the initial phases of systems design Participatory Design has potentiality to include operation and maintenance of IT systems in organizations. The paper presents this argument through reports from case studies of local IT-support, here coined 'participatory IT-support'. The paper presents characteristics of participatory ITsupport and suggests a method for identifying qualified candidates for the support position in organizations.

Aqueous suspensions of cellulose nanocrystals (CNCs) are known to self-assemble into a chiral nematic liquid crystalline phase, leading to solid-state nanostructured colored films upon solvent evaporation, even in the presence of templating agents. The angular optical response of these structures, and therefore their visual appearance, is completely determined by the spatial arrangement of the CNCs when the drying suspension undergoes a transition from a flowing and liquid crystalline to a kinetically arrested state. Here, we demonstrate how the angular response of the final film allows for retrieval of key physical properties and the chemical composition of the suspension at the onset of the kinetic arrest, thus capturing a snapshot of the past. To illustrate this methodology, we investigated a dynamically evolving sol-gel co-assembly process by various amounts of organosilica precursor addition, namely 1,2-bis(trimethoxysilyl)ethane (BTMSE). We were able to track the influence of the organosilica condensation on the kinetic arrest and thus explain the angular response of the resulting films. Our a posteriori and in situ approach is general, it can be applied to a variety of additives in CNC-based films and it allows accessing key rheological information of the suspension without using any dedicated rheological technique.