Programmable Fluidic Production of Microparticles with Configurable Anisotropy

Abstract

We report a technique for continuous production of microparticles of variable size with new forms of anisotropy including alternating bond angles, configurable patchiness, and uniform roughness. The sequence and shape of the anisotropic particles are configured by exploiting a combination of confinement effects and microfluidics to pack precursor colloids with different properties into a narrow, terminal channel. The width and length of the channel relative to the particle size fully specify the configuration of the anisotropic particle that will be produced. The precursor spheres packed in the production zone are then permanently bonded into particles by thermal fusing. The flow in the production zone is reversed to release the particles for collection and use. Particles produced have linear chain structure with precisely configured, repeatable bond angles. With software programmable microfluidics, sequence and shape anisotropy are combined to yield synthesized homogeneous (type "A"), surfactantlike (type "A-B") or triblock (type "A-B-A") internal sequences in a single device. By controlling the dimensions of the microfluidic production zone, triangular prisms and particles with controlled roughness and patchiness are produced. The fabrication method is performed with precursors spheres with diameter as small as 3.0 microm.

Fabrication, Assembly, and Application of Patchy Particles

“…We would like to also highlight in this section a very different colloidal assembly approach reported by Solomon et al, [2] which involves the microfluidic trapping of particles in confined geometries and subsequent thermal fusing leading to the formation of colloidal particles with alternating bond angles, configurable patches and uniform roughness ( Figure 6). This method is interesting in that it allows the assembly of designer colloidal structures with precise control over the anisotropy dimensions of chemical ordering (F) and roughness (H).…”

“…A wide variety of anisotropic particles with diverse anisotropy in size, shape [1][2][3][4][5][6][7] and chemical functionality [8][9][10][11][12][13][14][15][16][17][18][19][20] has been explored. Within such a large diversity of anisotropic particles, significant attention has been given lately to the study of surface-anisotropic particles, that is, particles exhibiting multiple surface functionalities, while often having an isotropic polymer core.…”

Spontaneous shape reconfigurations in multicompartmental microcylinders

“…Thus, particle engineers have been accustomed to almost exclusively dealing with spherical polymer particles. Recent exceptions include the synthesis of certain inherently nonspherical polymer particles (9,(33)(34)(35)(36), energy-driven conversion of spherical particles into shaped particles via stretching at elevated temperatures (37)(38)(39), and the electrohydrodynamic cojetting procedure used herein to create microcylinders (30).…”

“…2B shows a population of PLGA-based microcylinders, which was stored below the glass transition temperature of the polymer for three days (T g > T P regimen, where T g ¼ glass transition temperature and T P ¼ polymer temperature). To induce shapeshifting, one can either increase T P or lower T g (39). Ultrasound treatment for two minutes in water converted the microcylinders completely and homogenously into spheres (Fig.…”

Direct determination of fluid-solid coexistence of square-well fluids confined in narrow cylindrical hard pores

“…Here we especially focus on the narrow pores, which can only hold one cylindrical layer of particles, and those are of great theoretical and experimental interest, as in such systems the particles can be self-assembled to form single helical or twisted helical structure. The systems resemble the colloids confined in very narrow channels for constructing nanowires, [21][22][23] peapod-related system such as C 60 encapsulated in Carbon-nanotube, 19,24 and even the double helices of DNA on the large molecular scale. 25 Also, better and more understanding of the fluid-solid behavior and structure of these systems ultimately help to find practical nanoapplications in capillarity, lubrication, gas purification and storage, fabrication of nanofluidic devices, and provide important insights on the self-assembly helical structure, which is commonly found in the nature.…”