Search for: All records

Abstract Programming rapid, repeatable motions in soft materials has remained a challenge in active matter and biomimetic design. Here, we present a light-controlled chemomechanical network based onTetrahymena thermophilacalcium-binding protein 2 (Tcb2), a Ca²⁺-sensitive contractile protein. These networks—driven by Ca²⁺-triggered structural rearrangements—exhibit dynamic self-assembly, spatiotemporal growth, and contraction rates comparable to actomyosin systems. By coupling light-sensitive chelators for optically triggered Ca²⁺release, we achieve precise growth and repeatable mechanical contractility of Tcb2 networks, revealing emergent phenomena such as boundary-localized active regions and density gradient-driven reversals in motion. A coupled reaction-diffusion and elastic model explains these dynamics, highlighting the interplay between chemical network assembly and mechanical response. We further demonstrate active transport of particles via network-mediated forces in vitro and implement reinforcement learning to program seconds-scale spatiotemporal actuation in silico. These results establish a platform for designing responsive active materials with rapid chemomechanical dynamics and tunable optical control, with applications in synthetic cells, sub-cellular force generation, and programmable biomaterials. 

Abstract Strong shear thickening and jamming in dense suspensions are driven by friction as particles are sheared into contact. Control over these frictional interactions can be achieved via particle shape and roughness, and also via the particles’ surface chemistry and interactions with the surrounding solvent. We report on experiments with cornstarch suspensions where effective friction is modified by solvent-induced interactions, focusing on the effect of hydrogen bonding between solvent molecules and hydroxyl groups on the particle surface. We systematically vary the hydrogen bonding propensity by increasing the size of the backbone of the solvent molecule, from water to diols with up to 4 carbon atoms. For a fixed particle weight fraction, we find a sudden transition from strong shear thickening (in water and ethylene glycol) to shear thinning (in propanediol and butanediol). Combining data from rheology, density functional theory simulations, and fixed-rate pull tests, our results show how changes in the solvent’s molecular structure affect both particle–solvent and solvent–solvent interactions, and how this can be used to tailor the shear-thickening and jamming behavior of suspensions. 

Abstract Conjugated polymers are essential for flexible organic thermoelectrics (OTEs). Herein, we demonstrate that polymorphism in 3,3‴-poly(didodecyl-quaterthiophene) (PQT) significantly dictates doping efficiency and charge transport upon 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) vapor doping. Using X-ray scattering, ellipsometry, and molecular dynamics simulations, we characterize how thermal annealing induces distinct side-chain and backbone orientations. 130 °C annealed samples reach a conductivity (σ) of 8.6 ± 0.1 S/cm, while 100 °C samples only exhibit a conductivity of 0.3 ± 0.2 S/cm due to inhibited doping from the polymorph with stronger interdigitation of the side chains. Leveraging these findings, we fabricated functionally graded (FG) PQT films using a custom thermal annealing station to induce spatial microstructural gradients. Modeling the cooling performance via linear constitutive relations and experimental transport profiles reveals that FG films outperform equivalent uniform counterparts in cooling performance (ΔTc = TH − Tc). Overall, this work establishes a robust strategy to enhance OTE performance by leveraging thermally induced microstructural gradients in semiconducting polymers. 

Abstract Mechanical metamaterials can be designed to exhibit unique mechanical properties, including tunable auxetic behavior as well as multistability, which arise from the geometry and configuration of the constituent building blocks. Lattice-based metamaterials, in particular, provide lightweight platforms where local instabilities can dictate the global response, with applications in energy routing and vibration isolation. In underdamped structures, perturbations have been found to propagate as nonlinear waves, e.g. transition waves or solitons. Here we investigate the opposite limit of overdamped, highly dissipative lattice metamaterials. Focusing on 3D structures, we uncover how buckling instabilities, triggered by compression, propagate as fronts that shape the macroscopic behavior. We demonstrate in experiments on 3D-printed simple cubic lattices how global and local buckling modes can be controlled via the lattice geometry. By incorporating viscoelastic dissipation into a 3D-continuum model, we show that strain-driven buckling fronts obey coupled reaction–diffusion equations. The diffusion and reaction coefficients, determined by local geometry, material properties, and strain, select the propagation direction and enable steering of the fronts. This establishes a predictive and experimentally validated framework for the control of cascading mechanical instabilities in lattice-based metamaterials. 

ABSTRACT Conventional covalent and supramolecular crosslinks impose inherent trade‐offs between mechanical robustness and environmental adaptability in polymer networks. Mechanically interlocked junctions offer an alternative route by enabling topological motion without compromising structural integrity. Here, a modular approach is reported to construct topology‐engineered gels by copolymerizing 2‐hydroxyethyl acrylate (HEA) with doubly threaded (dt‐) pseudo[4]rotaxane crosslinkers, formed via the complexation of γ‐cyclodextrin (γ‐CD) and acrylate‐end‐capped pyrene derivatives. By tuning the HEA/water ratio in pre‐gel formulations, the supramolecular assembly can be shifted from dt‐ to singly threaded (st‐) entities, enabling access to gels with the same chemical composition but different architectures—dt‐slide ring network versus st‐polyrotaxane covalent network. The dt‐network exhibits solvent‐dependent fluorescence, swelling, and viscoelasticity that is not observed in either the st‐network or a covalent control gel. Mechanical testing of the bulk networks reveals that the dt‐network exhibits high extensibility (>1050% strain at break), strain rate‐dependent stiffening and rupture, and a favorable combination of high toughness and comparatively low hysteresis under cyclic deformation that is not observed in the networks lacking the dt‐architecture. Overall, these results establish a structure–property relationship dictated by crosslinking topology, demonstrating how dt‐interlocked motifs can encode both mechanical performance and environmental responsiveness in soft materials. 

Abstract Ongoing efforts to design stable, ionically conductive solid-state electrolytes (SSEs) for next-generation solid-state batteries make it clear that both long and short-range structural order strongly influence materials performance. However, clear structure–property relationships are generally lacking, making it difficult to develop design rules for improving the (electro) chemical stability of SSEs. In this work, we synthesize epitaxial, single-crystal lithium lanthanum titanium oxide (LLTO) films and demonstrate that the kinetics of Ti4+ reduction and lithium intercalation depend sensitively on the crystal orientation, with electrochemical stability increasing as LLTO (001) < (110) ∼ (112) < (100). However, thermodynamic stability is ultimately unaffected─all orientations fully reduce after extended contact with Li metal. In contrast, amorphous LLTO films exhibit minimal, self-limiting reactivity that results in an interface that is stable to extended contact with Li metal. The results demonstrate the potential to engineer crystal lattice strain and long-range order to differentially tune the stability of the solid electrolyte toward reactive lithium metal and cathode materials, suggesting strategies for enabling the wider deployment of LLTO and other ionically conductive ceramic films in advanced energy storage technologies. 

Abstract The principles behind the sharp, singular structures in a crumpled sheet are well understood. Here we discuss more general ways of exploiting such sharp structures to control the shape of a sheet by deforming or forcing it elsewhere. Often, the induced shape leads to further sharp structures—“sub-singularities.” Though weaker and softer than the primary singularities, they nevertheless provide robust ways of shaping a sheet. In simple cases, we understand the reason for these and their strength. This paper surveys a broad range of other sub-structure phenomena and reports recent progress in understanding some of them. 

Abstract Guided elastic waves are a truly cross-disciplinary key enabling technology. For more than five decades, surface acoustic wave (SAW) and bulk acoustic wave devices find widespread applications. Nowadays, different types of guided elastic waves cover the wide spectrum of applications spanning from quantum technologies to the life sciences, from controlling single excitations to macroscopic collective states in condensed matter. Six years after the first 2019 SAW roadmap, we believe it is time to make a step back and take a fresh look at the status of the field and its future challenges. Since the first roadmap in 2019, the spectrum clearly expanded and this new edition presents a current snapshot of the status of this vibrant field and prospects for potential future developments. 

Abstract The spatial and temporal control of material properties at a distance has yielded many unique innovations including photo-patterning, 3D-printing, and architected material design. To date, most of these innovations have relied on light, heat, sound, or electric current as stimuli for controlling the material properties. Here, we demonstrate that an electric field can induce chemical reactions and subsequent polymerization in composites via piezoelectrically-mediated transduction. The response to an electric field rather than through direct contact with an electrode is mediated by a nanoparticle transducer, i.e., piezoelectric ZnO, which mediates reactions between thiol and alkene monomers, resulting in tunable moduli as a function of voltage, time, and the frequency of the applied AC power. The reactivity of the mixture and the modulus of a naïve material containing these elements can be programmed based on the distribution of the electric field strength. This programmability results in multi-stiffness gels. Additionally, the system can be adjusted for the formation of an electro-adhesive. This simple and generalizable design opens avenues for facile application in adaptive damping and variable-rigidity materials, adhesive, soft robotics, and potentially tissue engineering. 

ABSTRACT Recent interest in manipulating the chemistry of block copolymers (BCPs) to manage the covarying properties necessary to meet manufacturing criteria in nanolithography has resulted in the development and expansion of the A‐block‐(B‐random‐C) BCP architecture, where the random block allows for the decoupling of thermodynamic and wetting properties. Previous reports of such BCPs have used click chemistry to create the desired random block, but all such instances possess additional functional groups that are susceptible to undesirable side reactions upon annealing, such as cross‐linking and surface grafting. This study reports the substitution reaction of polystyrene‐block‐poly(pentafluorophenyl methacrylate) (PS‐b‐PPFMA) with primary amines. The resulting methacrylamide structure of the functionalized random block has only an amide linkage between the attached functional group and the polymer backbone, thereby omitting any sources of side reactions within the BCP. The outcomes of this report also demonstrate the enhanced thermal stability of these materials by virtue of their stable amide bonds. A range of random copolymer compositions is assessed to develop BCPs in which the random block has approximately the same surface energy as the PS block. These BCPs can self‐assemble into perpendicular lamellae and are therefore promising candidates for directed self‐assembly.