Refractory metals have recently garnered significant interest as options for photonic applications due to their superior high-temperature stability and versatile optical properties. However, most previous studies only consider their room-temperature optical properties when analyzing these materials’ behavior as optical components. Here, we demonstrate structural color pixels based on three refractory metals (Ru, Ta, and W) for high-temperature applications. We quantify their optical behavior in an oxygenated environment and determine their dielectric functions after heating up to 600 °C. We use in situ oxidation, a fundamental chemical reaction, to form nanometer-scale metal oxide thin-film bilayers on each refractory metal. We fully characterize the behavior of the newly formed thin-film interference structures, which exhibit vibrant color changes upon high-temperature treatment. Finally, we present optical simulations showing the full range of hues achievable with a simple two-layer metal oxide/metal reflector structure. All of these materials have melting points >1100 °C, with the Ta-based structure offering high-temperature stability, and the Ru- and W-based options providing an alternative for reversible color filters, at high temperatures in inert or vacuum environments. Our approach is uniquely suitable for high-temperature photonics, where the oxides can be used as conformal coatings to produce a wide variety of colors across a large portion of the color gamut.

The oral cavity contains different microenvironments, as the non-shedding surface of the teeth and the epithelial mucosa, where oral barriers and microbial communities coexist. The interactions and balances between these two communities are responsible for oral tissue homeostasis or dysbiosis, that ultimately dictate health or disease. Disruption of this equilibrium is the first necessary step towards chronic inflammation and permanent tissue damage in the case of chronic periodontitis. There are currently no experimental models able to mimic the structural, physical, and metabolic conditions present in the oral gingival tissue to support the long-term investigation of host-pathogens unbalances. Herein, we report a 3D anatomical gingival in vitro model based on human primary culture that recapitulates the native tissue organization, and a native oxygen gradient within the gingival pocket to support human microbiome persistence with a physiologically relevant level of microbial diversity as well as native spatial organization. The modulation of inflammatory markers in the presence of oral microbiome suggested the humanized functional response of this model. The model will be used in future studies to investigate host-pathogen unbalances in gingivitis and periodontal disease.

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