3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

Abstract

Living organisms in nature have amazing control over their color, shape, and morphology in response to environmental stimuli for camouflage, communication, or reproduction. Inspired by the camouflage of the octopus via the elongation or contraction of its pigment cells, oblate cholesteric liquid crystal droplets are dispersed in a polymer matrix, serving as the role of pigment cells and showing structural color due to selective Bragg reflection by their periodic helical structure. The color of 3D‐printed biomimetic systems can be tuned by changing the helical pitch via the chiral dopant concentration or temperature. When the oblate liquid crystal droplets are heated up to isotropic, the opaque and colored biomimetic systems become transparent and colorless. Meanwhile, the isotropic liquid crystal droplets tend to become spherical, causing volume contraction along the film plane and volume dilation in the perpendicular direction. The internal strain combined with the gradient distribution of the oblate isotropic liquid crystal droplets result in corresponding shape transformations. The camouflage of a biomimetic octopus and the blossom of a biomimetic flower, both of which show synergetic color and shape responses, are demonstrated to inspire the design of functional materials and intelligent devices.

Attractive Pickering Emulsion Gels

“…The excellent performances and unique viscoelastic properties of the APEG systems enable the facile processing and customized design of functional materials by direct 3D printing, [ 32–34 ] as shown in Figure S13, Supporting Information. Under shearing, the APEGs can continuously be extruded out of the nozzle with the viscous modulus G ″ larger than the elastic modulus G ′.…”

Temperature‐Responsive Photonic Devices Based on Cholesteric Liquid Crystals

“…www.advancedsciencenews.com www.adpr-journal.com Over-saturation of chiral dopant [53,80,81] %450À1000 nm [53] %23 C À45 C [53] PDLC with small mesogenic molecules HTP changing [44,45,94,97] 400À700 nm [97] %25 C À35 C [97] Fast response Suffer from scattering Cells…”

“…The resulting reflective CLC coatings [96,97] contain CLC droplets size dependent on the mixing rate during emulsification. [98] A recent example of such emulsion-based PDLC coatings that exhibit a TR-RC response is based on CLCs having a SmÀCh transition upon heating embedded in polyvinyl alcohol.…”

“…[98] A recent example of such emulsion-based PDLC coatings that exhibit a TR-RC response is based on CLCs having a SmÀCh transition upon heating embedded in polyvinyl alcohol. [97] Additional methods have been developed to achieve PDLC systems, but to our knowledge, the emulsion-based procedure is the most common method for rapidly obtaining thermosensitive reflective PDLC devices in a single production step. However, compared with the CLC capsules, the size distribution of the CLC droplets is broader, which induces light scattering that reduces the transparency of the PDLC films.…”

“…[ 98 ] A recent example of such emulsion‐based PDLC coatings that exhibit a TR‐RC response is based on CLCs having a Sm−Ch transition upon heating embedded in polyvinyl alcohol. [ 97 ]…”