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Molecular motors are essential to the living, generating fluctuations that boost transport and assist assembly. Active colloids, that consume energy to move, hold similar potential for man-made materials controlled by forces generated from within. Yet, their use as a powerhouse in materials science lacks. Here we show a massive acceleration of the annealing of a monolayer of passive beads by moderate addition of self-propelled microparticles. We rationalize our observations with a model of collisions that drive active fluctuations and activate the annealing. The experiment is quantitatively compared with Brownian dynamic simulations that further unveil a dynamical transition in the mechanism of annealing. Active dopants travel uniformly in the system or co-localize at the grain boundaries as a result of the persistence of their motion. Our findings uncover the potential of internal activity to control materials and lay the groundwork for the rise of materials science beyond equilibrium. Active particles added to a material control its internal activity. Here the authors investigate such a system and control the annealing of a colloidal crystal, the dynamics of which depend on the persistence of the motion of active particles.

A classic paradigm of soft and extensible polymer materials is the difficulty of combining reversible elasticity with high fracture toughness, in particular for moduli above 1 MPa. Our recent discovery of multiple network acrylic elastomers opened a pathway to obtain precisely such a combination. We show here that they can be seen as true molecular composites with a well–cross-linked network acting as a percolating filler embedded in an extensible matrix, so that the stress–strain curves of a family of molecular composite materials made with different volume fractions of the same cross-linked network can be renormalized into a master curve. For low volume fractions (<3%) of cross-linked network, we demonstrate with mechanoluminescence experiments that the elastomer undergoes a strong localized softening due to scission of covalent bonds followed by a stable necking process, a phenomenon never observed before in elastomers. The quantification of the emitted luminescence shows that the damage in the material occurs in two steps, with a first step where random bond breakage occurs in the material accompanied by a moderate level of dissipated energy and a second step where a moderate level of more localized bond scission leads to a much larger level of dissipated energy. This combined use of mechanical macroscopic testing and molecular bond scission data provides unprecedented insight on how tough soft materials can damage and fail.

Self-assembling colloidal particles in the cubic diamond crystal structure could potentially be used to make materials with a photonic bandgap 1 – 3 . Such materials are beneficial because they suppress spontaneous emission of light 1 and are valued for their applications as optical waveguides, filters and laser resonators 4 , for improving light-harvesting technologies 5 – 7 and for other applications 4 , 8 . Cubic diamond is preferred for these applications over more easily self-assembled structures, such as face-centred-cubic structures 9 , 10 , because diamond has a much wider bandgap and is less sensitive to imperfections 11 , 12 . In addition, the bandgap in diamond crystals appears at a refractive index contrast of about 2, which means that a photonic bandgap could be achieved using known materials at optical frequencies; this does not seem to be possible for face-centred-cubic crystals 3 , 13 . However, self-assembly of colloidal diamond is challenging. Because particles in a diamond lattice are tetrahedrally coordinated, one approach has been to self-assemble spherical particles with tetrahedral sticky patches 14 – 16 . But this approach lacks a mechanism to ensure that the patchy spheres select the staggered orientation of tetrahedral bonds on nearest-neighbour particles, which is required for cubic diamond 15 , 17 . Here we show that by using partially compressed tetrahedral clusters with retracted sticky patches, colloidal cubic diamond can be self-assembled using patch–patch adhesion in combination with a steric interlock mechanism that selects the required staggered bond orientation. Photonic bandstructure calculations reveal that the resulting lattices (direct and inverse) have promising optical properties, including a wide and complete photonic bandgap. The colloidal particles in the self-assembled cubic diamond structure are highly constrained and mechanically stable, which makes it possible to dry the suspension and retain the diamond structure. This makes these structures suitable templates for forming high-dielectric-contrast photonic crystals with cubic diamond symmetry. Self-assembly of cubic diamond crystals is demonstrated, by using precursor clusters of particles with carefully placed ‘sticky’ patches that attract and bind adjacent clusters in specific geometries.

DNA-coated colloids hold great promise for self-assembly of programmed heterogeneous microstructures, provided they not only bind when cooled below their melting temperature, but also rearrange so that aggregated particles can anneal into the structure that minimizes the free energy. Unfortunately, DNA-coated colloids generally collide and stick forming kinetically arrested random aggregates when the thickness of the DNA coating is much smaller than the particles. Here we report DNA-coated colloids that can rearrange and anneal, thus enabling the growth of large colloidal crystals from a wide range of micrometre-sized DNA-coated colloids for the first time. The kinetics of aggregation, crystallization and defect formation are followed in real time. The crystallization rate exhibits the familiar maximum for intermediate temperature quenches observed in metallic alloys, but over a temperature range smaller by two orders of magnitude, owing to the highly temperature-sensitive diffusion between aggregated DNA-coated colloids. DNA-coated colloids have failed to achieve their promise of programmable self-assembly because they stick to each other like Velcro. Here Wang et al. overcome this problem by making clickable smooth colloids that are coated with short single-stranded DNA at high density.

Self-assembly is a powerful approach for constructing colloidal crystals, where spheres, rods or faceted particles can build up a myriad of structures. Nevertheless, many complex or low-coordination architectures, such as diamond, pyrochlore and other sought-after lattices, have eluded self-assembly. Here we introduce a new design principle based on preassembled components of the desired superstructure and programmed nearest-neighbour DNA-mediated interactions, which allows the formation of otherwise unattainable structures. We demonstrate the approach using preassembled colloidal tetrahedra and spheres, obtaining a class of colloidal superstructures, including cubic and tetragonal colloidal crystals, with no known atomic analogues, as well as percolating low-coordination diamond and pyrochlore sublattices never assembled before. Complex colloidal crystal structures can be obtained by a combination of preassembled units and DNA-mediated interactions. This enables, for instance, the generation of a MgCu 2 structure with interpenetrating diamond and pyrochlore sublattices.

Elastomers are widely used because of their large-strain reversible deformability. Most unfilled elastomers suffer from a poor mechanical strength, which limits their use. Using sacrificial bonds, we show how brittle, unfilled elastomers can be strongly reinforced in stiffness and toughness (up to 4 megapascals and 9 kilojoules per square meter) by introducing a variable proportion of isotropically prestretched chains that can break and dissipate energy before the material fails. Chemoluminescent cross-linking molecules, which emit light as they break, map in real time where and when many of these internal bonds break ahead of a propagating crack. The simple methodology that we use to introduce sacrificial bonds, combined with the mapping of where bonds break, has the potential to stimulate the development of new classes of unfilled tough elastomers and better molecular models of the fracture of soft materials.

Liquid-liquid phase separation (LLPS) has emerged as a key biological paradigm, playing a critical role in cellular compartmentalization and potentially contributing to the origins of life. Lipid membranes are equally important in these processes, serving as selective barriers that define and protect cellular environments. Recent studies have revealed a dynamic interaction between LLPS and lipid membranes, both in cellulo and in biomimetic systems. In vitro studies typically use simplified model membranes, while biological membranes are far more complex, often exhibiting phase-separated domains. Despite growing interest, the relationship between lipid phase separation within membranes and LLPS remains largely unexplored. Here, we explore how coacervates interact with membranes composed of liquid-ordered or liquid-disordered lipid phases using giant unilamellar vesicles (GUVs). We show that coacervate-membrane interactions are modulated by coacervate composition and lipid domain properties. Notably, we report the selective wetting of lipid domains in phase separated GUVs. Different coacervates exhibit distinct wetting behaviors, with variations in their composition influencing whether they preferentially wet liquid-disordered or liquid-ordered lipid domains, highlighting the coacervate-specific nature of these interactions. These findings highlight how lipid phase separation can mediate selective membrane wetting, offering insights into condensate-membrane interactions in cells and in simplified cell-like model systems.

Patchy particles have received great attention due to their ability to develop directional and selective interactions and serve as building units for the self-assembly of innovative colloidal molecules and crystalline structures. Although synthesizing particles with multiple dissimilar patches is still highly challenging and lacks efficient methods, these building blocks would open paths towards a broader range of ordered materials with inherent properties. Herein, we describe a new approach to pattern functional DNA patches at the surface of particles, by the use of colloidal stamps. DNA inks are transferred only at the contact zones between the target particles and the stamps thanks to selective strand-displacement reactions. The produced DNA-patchy particles are ideal candidates to act as advanced precision/designer building blocks to self-assemble the next generation of colloidal materials.

Here, the general design and properties of new multiple network elastomers with an exceptional combination of stiffness, toughness, and elasticity are reported. In this paper, it is reported in more detail how the increase in strain at break resulting from the toughening can be used to provide great insight in the large strain properties of otherwise brittle acrylic well crosslinked networks. The networks have been prepared by sequences of polymerization and swelling with monomers. The parameters that have been varied are the nature of the base monomers and the degree of crosslinking of the first network. Here, the small strain properties, equilibrium swelling, and large strain properties in uniaxial tension are characterized. It is shown here that the large strain properties of the multiple networks are quantitatively controlled by the large strain properties of the stretched first network which acts as a percolating filler, while the small and intermediate properties are controlled by the entanglement density which can be largely superior to that of homogeneous networks. Different brittle and prestretched elastomer networks are embedded at a low volume fraction in a soft extensible matrix. The increase in toughness of the final material is directly controlled by the nonlinear elastic properties of the prestretched network and its volume fraction, providing a general design rule for tough soft materials

Molecular motors are essential to the living, they generate additional fluctuations that boost transport and assist assembly. Self-propelled colloids, that consume energy to move, hold similar potential for the man-made assembly of microparticles. Yet, experiments showing their use as a powerhouse in materials science lack. Our work explores the design of man-made materials controlled by fluctuations, arising from the internal forces generated by active colloids. Here we show a massive acceleration of the annealing of a monolayer of passive beads by moderate addition of self-propelled microparticles. We rationalize our observations with a model of collisions that drive active fluctuations to overcome kinetic barriers and activate the annealing. The experiment is quantitatively compared with Brownian dynamic simulations that further unveil a dynamical transition in the mechanism of annealing. Active dopants travel uniformly in the system or co-localize at the grain boundaries as a result of the persistence of their motion. Our findings uncover the potential of man-made materials controlled by internal activity and lay the groundwork for the rise of materials science beyond equilibrium.