Microfluidic Molding of Photonic Microparticles with Engraved Elastomeric Membranes

Lee

et al. 2020

Adv Funct Materials

Colloidal crystals have been used for creating stimuli-responsive photonic materials. Here, macroporous hydrogels are designed, through a simple and reproducible protocol, that rapidly and reversibly switch between highly transparent and structurally colored states. The macroporous hydrogels are prepared by film-casting photocurable dispersions of silica particles in hydrogel-forming resins and selectively removing silica particles. The silica particles spontaneously form a nonclose-packed array due to repulsive interparticle interaction, which form the regular array of cavities after removal. However, the cavities are randomly collapsed by drying, losing a long-range order and rendering the materials highly transparent. When the hydrogels are swollen by either water, ethanol, or the mixture, the regular array is restored, which develops brilliant structural colors. This switching is completed in tens of seconds and repeatable without any hysteresis. The resonant wavelength depends on the composition of the water-ethanol mixture, where the dramatic shift occurs in one-component-rich mixtures due to the composition of the hydrogel. Micropatterns can be designed to have distinct domains of the macroporous hydrogels, which are transparent at the dried state and disclose encrypted graphics and unique reflectance spectra at the wet state. This class of solvent-responsive photonic hydrogels is potentially useful for alcohol sensors and user-interactive anti-counterfeiting materials.

Section: Resultsmentioning

confidence: 99%

Macroporous Hydrogels for Fast and Reversible Switching between Transparent and Structurally Colored States

Lee

et al. 2020

Adv Funct Materials

“…A series of functionalized photonic microspheres were prepared by Yang and co-workers based on microfluidic technology. 81,[124][125][126][127][128] Such photonic spheres show angle-independent structural colors because of the spherical symmetry and their internal structure by long-range ordered packing of colloidal particles. 43,[129][130][131][132][133][134] APCs structures can be generated by controlling the volume fraction of the colloids particles within the photonic microspheres.…”

Section: Space Confinement and Microfluidic Assemblymentioning

confidence: 99%

Self-assembly of colloidal particles into amorphous photonic crystals

Zhang

Yang

et al. 2021

Mater. Adv.

“…6,7 Several attempts have been proposed to solve this problem. [8][9][10][11][12] The Doyle group developed methods to generate hydrogel microparticles with specific shapes using continuous flow or stopflow lithography. 13 A droplet-based microfluidic system was proposed to construct alginate gel beads encapsulating cells.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Hydrogel Particles of Defined Shapes Using Superhydrophobic‐Hydrophilic Micropatterns

et al. 2016

We report a method to rapidly fabricate alginate hydrogel particles of specific sizes and shapes.Our method is based on the formation of arrays of droplets of pre-hydrogel solutions on superhydrophobic-hydrophilic patterns using the process of discontinuous dewetting, followed by their gelation via the parallel addition of CaCl 2 to the individual droplets via the sandwiching method. We demonstrate that viability of living cells incorporated within the hydrogel particles is higher during the long-term cultivation than in the case of cells cultured in the bulk threedimensional hydrogel matrix. Incorporation of magnetic particles into the free-standing hydrogel particles containing living cells enabled ease manipulation of the particles using an external magnetic field.