Microfluidic Production of Mechanochromic Photonic Fibers Containing Nonclose‐Packed Colloidal Arrays

Abstract

Photonic fibers are important raw materials for structurally colored fabrics. In particular, the mechanochromic fibers potentially provide color‐tunable clothes, like chameleon skins. Herein, microfluidic jetting to continuously produce mechanochromic fibers in a controlled manner is used. The jet is produced by flow‐focusing the photocurable dispersions in a surfactant‐laden carrier fluid using microfluidic devices. The dispersions contain monodispersed silica particles in an elastomer‐forming resin. As the silica particles have repulsive interparticle potential in the resin, they spontaneously organize into a nonclose‐packed regular array, developing structural colors. The jet of the dispersions is photocured in situ by irradiation of ultraviolet at the exit of the microfluidic channel, continuously producing the photonic fibers. As the interparticle separation among silica particles is shortened along the radial direction by stretching the elastic fibers, the structural colors are dynamically blue shifted. Also, the original colors are reversibly recovered by relaxing the fibers as the deformation is fully elastic. The nonclose‐packed array of inelastic silica particles provides a wide range of color tuning and high reversibility. Moreover, microfluidic jetting enables the production of Janus fibers composed of two distinct color domains, which enriches the available structural colors through color mixing.

Robust cholesteric liquid crystal elastomer fibres for mechanochromic textiles

“…Using a crystal of silica nanoparticles, Cheng et al obtained Δ λ ≈ 50 nm, from weakly red to green, before the material broke at 60% strain 21 . Kim et al made particle-loaded fibres that elongated 200% before breaking, but the red to green colour shift (Δ λ ≈ 0.1 μm) stopped at 80% elongation 22 . Kolle et al made one-dimensionally (1D) periodic lamellar fibres by rolling an elastomer bilayer around a glass rod 23 , but second-order reflections led to colour mixing, and mechanical durability and washability were not assessed, nor was scalability.…”

Recent advances in environmentally friendly structural colored fabrics

“…They even fabricated Janus photonic fibers by using two kinds of silica spheres with different sizes (Figure 7(d)). 83 Honaker et al adopted the microfluidic wet spinning method to fabricate core-shell fibers with structural colors, of which the core and shell were composed of liquid crystal material and rubber, respectively. 84 Electrophoretic deposition.…”

“…82 (d) Optical microscope of Janus fibers obtained by adjusting the proportion of silicon dioxide (SiO 2 ) with two sphere sizes. 83 (e) Schematic diagram of dyeing fabrics by electrophoretic deposition. 85 (f) Schematic diagram of mechanical rubbing test (i) and laundering test (ii), the optical photos and reflection spectra of structural colored fabrics before and after rubbing test (iii) and laundering test (iv).…”

“…(c) Schematic diagram of dyeing fabrics by microfluidic-spinning process 82. (d) Optical microscope of Janus fibers obtained by adjusting the proportion of silicon dioxide (SiO 2 ) with two sphere sizes 83. (e) Schematic diagram of dyeing fabrics by electrophoretic deposition 85.…”

Unclonable human-invisible machine vision markers leveraging the omnidirectional chiral Bragg diffraction of cholesteric spherical reflectors

“…Ideally, all circularly polarized light with the handedness of the helix is reflected across the full bandwidth 52 , but in practice, many samples show a gradual decay of reflectance for wavelengths departing from λ 0 53 . The selectivity of reflecting only one circular polarization, as determined by the unichiral make-up of the phase, makes cholesterics stand out from other structurally colored materials, such as periodic multilayer stacks of materials with different refractive indices 54 , block copolymers 55 , 56 or colloidal crystals 57 . As we will see below, this property is key to the application opportunities that we will discuss in this paper.…”