More Like this

1. Directing and reconfiguring colloidal assembly by disclination networks in nematic liquid crystal as templates

   https://doi.org/10.1016/j.giant.2023.100228  

   Guo, Yubing; Jiang, Miao; Afghah, Sajedeh; Peng, Chenghui; Selinger, Robin LB; Lavrentovich, Oleg D; Wei, Qi-Huo (March 2024, Giant)

   Exotic structures with interesting physical and chemical properties can be achieved by self-organizing engineered building blocks. The central aim for self-assembly is to precisely control the position and orientation of individual building blocks. In this work, we use topological defects (disclinations) in nematic liquid crystals as templates to direct the self-assembly of colloidal particles into designable 3D structures. By photopatterning preprogrammed molecular orientations at two confining surfaces, we created pre-designable disclination networks and characterized their interactions with spherical colloidal particles. We find that colloidal particles are attracted to different disclinations depending on the orientation of the point defect (elastic dipole) around the colloids. We demonstrate that the positions, network structures, and orientation of the elastic dipoles of the colloidal chains can be pre-designed and reconfigured with remote illumination of polarized light. 

   more » « less
2. Shape-driven entropic self-assembly of an open, reconfigurable, binary host–guest colloidal crystal

   https://doi.org/10.1039/d0sm02073g  

   Moore, Timothy C.; Anderson, Joshua A.; Glotzer, Sharon C. (March 2021, Soft Matter)

   null (Ed.)

   Entropically driven self-assembly of hard anisotropic particles, where particle shape gives rise to emergent valencies, provides a useful perspective for the design of nanoparticle and colloidal systems. Hard particles self-assemble into a rich variety of crystal structures, ranging in complexity from simple close-packed structures to structures with 432 particles in the unit cell. Entropic crystallization of open structures, however, is missing from this landscape. Here, we report the self-assembly of a two-dimensional binary mixture of hard particles into an open host–guest structure, where nonconvex, triangular host particles form a honeycomb lattice that encapsulates smaller guest particles. Notably, this open structure forms in the absence of enthalpic interactions by effectively splitting the structure into low- and high-entropy sublattices. This is the first such structure to be reported in a two-dimensional athermal system. We discuss the observed compartmentalization of entropy in this system, and show that the effect of the size of the guest particle on the stability of the structure gives rise to a reentrant phase behavior. This reentrance suggests the possibility for a reconfigurable colloidal material, and we provide a proof-of-concept by showing the assembly behavior while changing the size of the guest particles in situ . Our findings provide a strategy for designing open colloidal crystals, as well as binary systems that exhibit co-crystallization, which have been elusive thus far. 

   more » « less
3. Numerical simulations of electric-field-driven assembly of binary colloids into colloidal molecules and crystals

   https://doi.org/10.1063/5.0287245  

   Zhang, Yuanxing; Wu, Ning (November 2025, The Journal of Chemical Physics)

   Colloidal molecules (CMs)—clusters of colloidal particles with directional interactions—offer a versatile platform for the programmable assembly of complex soft materials. While both static and dynamic CMs have been synthesized to mimic molecular geometries, assembling them from simple colloidal building blocks via controllable interactions remains a challenge. Here, we employ Brownian dynamics simulations with experimentally realizable interaction models to investigate the electric-field-directed assembly of binary colloidal mixtures. By modulating electrohydrodynamic attraction and dipolar repulsion between particles and leveraging particle size ratios, we demonstrate the formation of two-dimensional and pseudo-two-dimensional CMs with various valences and geometric shapes. This valence-assisted strategy further supports the bottom-up construction of open colloidal lattices, including square and honeycomb arrangements. It also enables the simultaneous stabilization of both square packing and triangular packing at high particle concentrations. Our findings present a reversible and tunable approach to designing colloidal architectures with programmable interactions, offering new opportunities for the development of photonic materials, reconfigurable metamaterials, and functional soft-matter systems. 

   more » « less
4. Disorder and demixing in bidisperse particle systems assembling bcc crystals

   https://doi.org/10.1063/5.0219037  

   Kennard, Jasmin J; Zelaya_Solano, H Jonathan; Biddulph, Caleb D; Prager, Ryan C; Dshemuchadse, Julia (August 2024, The Journal of Chemical Physics)

   Colloidal and nanoparticle self-assembly enables the creation of ordered structures with a variety of electronic and photonic functionalities. The outcomes of the self-assembly processes used to synthesize such structures, however, strongly depend on the uniformity of the individual nanoparticles. Here, we explore the simplest form of particle size dispersity—bidispersity—and its impact on the self-assembly process. We investigate the robustness of self-assembling bcc-type crystals via isotropic interaction potentials in binary systems with increasingly disparate particle sizes by determining their terminal size ratio—the most extreme size ratio at which a mixed binary bcc crystal forms. Our findings show that two-well pair potentials produce bcc crystals that are more robust with respect to particle size ratio than one-well pair potentials. This suggests that an improved self-assembly process is accomplished with a second attractive length scale encoded in the particle–particle interaction, which stabilizes the second-nearest neighbor shell. In addition, we document qualitative differences in the process of ordering and disordering: in bidisperse systems of particles interacting via one-well potentials, we observe a breakdown of order prior to demixing, while in systems interacting via two-well potentials, demixing occurs first and bcc continues to form in parts of the droplet down to low size ratios. 

   more » « less
5. Single-Step Self-Assembly and Physical Crosslinking of PEGylated Chitosan Nanoparticles by Tannic Acid

   https://doi.org/10.3390/polym11050749  

   Smith, Raven A.; Walker, Rebecca C.; Levit, Shani L.; Tang, Christina (May 2019, Polymers)

   Chitosan-based nanoparticles are promising materials for potential biomedical applications. We used Flash NanoPrecipitation as a rapid, scalable, single-step method to achieve self-assembly of crosslinked chitosan nanoparticles. Self-assembly was driven by electrostatic interactions, hydrogen bonding, and hydrophobic interactions; tannic acid served to precipitate chitosan to seed nanoparticle formation and crosslink the chitosan to stabilize the resulting particles. The size of the nanoparticles can be tuned by varying formulation parameters including the total solids concentration and block copolymer to core mass ratio. We demonstrated that hydrophobic moieties can be incorporated into the nanoparticle using a lipophilic fluorescent dye as a model system. 

   more » « less