Shaping micro-clusters via inverse jamming and topographic close-packing of microbombs

Abstract

Designing topographic clusters is of significant interest, yet it remains challenging as they often lack mobility or deformability. Here we exploit the huge volumetric expansion (up to 3000%) of a new type of building block, thermally expandable microbombs. They consist of a viscoelastic polymeric shell and a volatile gas core, which, within structural confinement, create micro-clusters via inverse jamming and topographical close-packing. Upon heating, microbombs anchored in rigid confinement underwent balloon-like blowing up, allowing for dense clusters via soft interplay between viscoelastic shells. Importantly, the confinement is unyielding against the internal pressure of the microbombs, thereby enabling self-assembled clusters, which can be coupled with topographic inscription to introduce structural hierarchy on the clusters. Our strategy provides densely packed yet ultralight clusters with a variety of complex shapes, cleavages, curvatures, and hierarchy. In turn, these clusters will enrich our ability to explore the assemblies of the ever-increasing range of microparticle systems.

Homeostatic growth of dynamic covalent polymer network toward ultrafast direct soft lithography

“…Soft lithography plays an essential role in a wide range of modern technologies, including electronics (1), optics (2), and biology (3). It relies on a soft stamp with surface microstructures to realize various operations, such as microcontact printing, micromolding, and microembossing (4)(5)(6). Since the surface microstructures on the soft stamp are replicated from a photolithographically defined master, soft lithography can be viewed as an extension of photolithography (4).…”

Discontinuous Dewetting in a Degassed Mold for Fabrication of Homogeneous Polymeric Microparticles

“…For this technique, the microparticle precursor is loaded into the replica mold's microwells and cured into microparticles with the positive patterns of the microwell. Because soft lithography allows the repeated production of an elastic mold comprising polydimethylsiloxane (PDMS), 13 perfluoropolyether (PFPE), 14 and polyurethane 15 from a micropatterned master template, the productivity of the particles can be expanded by using multiple mold templates. The advantages of this technique include enhanced productivity with roll-to-roll processing 16 and the control of microparticle geometry from laboratory scale to commercial scale.…”

Top-Down Heterogeneous Colloidal Engineering Using Capillary Assembly of Liquid Particles

“…Lithography-based approaches include: (1) directly generating a particle structure from photoresist and releasing it from a sacrificial substrate; − (2) imprinting a polymer or polyelectrolyte solution within stamps with patterned wetting regions; − and (3) creating a template in which to deposit particles into geometric clusters, which are then annealed and harvested. , The third strategy, typically known as template-assisted capillary assembly or capillarity-assisted particle assembly, relies on the controlled evaporation of a colloidal suspension within a patterned template . Capillary assembly has proven to be an indispensible tool for both controlling particle placement into patterned arrays − and fabricating anisotropic two- and three-dimensional clusters of polymer and metallic nano/microparticles, − as well as biomaterials. , …”