Dynamic functions of biological organisms often rely on arrays of actively deformable microstructures undergoing a nearly unlimited repertoire of predetermined and self-regulated reconfigurations and ...motions, most of which are difficult or not yet possible to achieve in synthetic systems. Here, we introduce stimuli-responsive microstructures based on liquid-crystalline elastomers (LCEs) that display a broad range of hierarchical, even mechanically unfavored deformation behaviors. By polymerizing molded prepolymer in patterned magnetic fields, we encode any desired uniform mesogen orientation into the resulting LCE microstructures, which is then read out upon heating above the nematic–isotropic transition temperature (TN–I) as a specific prescribed deformation, such as twisting, in- and out-of-plane tilting, stretching, or contraction. By further introducing light-responsive moieties, we demonstrate unique multifunctionality of the LCEs capable of three actuation modes: self-regulated bending toward the light source at T < TN–I, magnetic-field–encoded predetermined deformation at T > TN–I, and direction-dependent self-regulated motion toward the light at T > TN–I. We develop approaches to create patterned arrays of microstructures with encoded multiple area-specific deformation modes and show their functions in responsive release of cargo, image concealment, and light-controlled reflectivity. We foresee that this platform can be widely applied in switchable adhesion, information encryption, autonomous antennae, energy harvesting, soft robotics, and smart buildings.
The release of chemicals following either pulsatile or continuous release modes is important for various potential applications, including programmed chemical reactions, mechanical actuation, and ...treatments of various diseases. However, the simultaneous application of both modes in a single material system has been challenging. Here, two chemical loading methods are reported in a liquid‐crystal‐infused porous surface (LCIPS) that enables both a pulsatile and continuous release of chemicals simultaneously. Specifically, chemicals loaded in the porous substrate exhibit a liquid crystal (LC) mesophase‐dependent continuous release, whereas the chemicals dissolved in micrometer‐sized aqueous droplets dispersed in the LC surface follow a pulsatile release activated by a phase transition. Moreover, the loading method of distinct molecules can be controlled to program their release mode. Finally, the pulsatile and continuous release of two distinct bioactive small molecules, tetracycline and dexamethasone, are demonstrated which display antibacterial and immunomodulatory activities for applications such as chronic wound healing and biomedical implant coating.
The loading of chemicals in a porous polymeric coating prior to lubrication leads to a diffusion‐based continuous release of chemicals, whereas the loading of dissolved water‐soluble chemicals that disperse in the lubricated liquid crystals in the form of micrometer‐sized aqueous droplets gives rise to a pulsatile release triggered by a liquid crystal phase transition.
Interactions between side chains of polymers have been utilized to tune the thermal and mechanical properties of polymeric materials. In liquid crystal (LC) elastomers (LCEs), previous studies have ...demonstrated that the configuration of LC monomers, specifically oblate or prolate, determines the direction of macroscopic material deformations relative to the orientational ordering of the LC functional groups. However, the effects of the copolymerization between different configurations of LC monomers on the phase behaviors and thermomechanical properties of LCEs have not been explored. Here, we reveal that statistically random copolymers of LC monomers with different configurations destabilize the orientational order of the LC functional groups, whereas the random insertion of LC monomers with the same configuration preserves the packing of the constituent mesogenic functional groups. We further demonstrate how this fundamental understanding can be applied to control both the direction and magnitude of the thermally triggered mechanical deformations of LC copolymer networks.
The structure-driven assembly of multimeric protein complexes and the formation of intracellular phase-like protein condensates have been the subject of intense research. However, the assembly of ...larger superstructures comprising cellular components, such as protein nanoparticles driven by general physical rather than specific biochemical interactions, remains relatively uncharacterized. Here, we use gas vesicles (GVs)—genetically encoded protein nanoparticles that form ordered intracellular clusters—as a model system to study the forces driving multiparticle assembly under cytoplasm-like conditions. Our calculations and experimental results show that the ordered assembly of GVs can be achieved by screening their mutual electrostatic repulsion with electrolytes and creating a crowding force with dissolved macromolecules. The precise balance of these forces results in different packing configurations. Biomacromolecules such as polylysine and DNA are capable of driving GV clustering. These results provide basic insights into how physically driven interactions affect the formation of protein superstructures, offer guidance for manipulating nanoparticle assembly in cellular environments through synthetic biology methods, and inform research on the biotechnology applications of GVs.
Programmable Anisotropic Transformations
In article number 2105024, Joanna Aizenberg, Katia Bertoldi, and co‐workers report that by programming independently anisotropy at the molecular and ...structural levels, unprecedented director‐determined symmetry breaking can be realized in microcellular structures made of liquid crystalline elastomers (LCEs). These can be exploited to achieve switchable and direction‐dependent frictional properties as well as to modulate light.
Vibrationally resonant sum-frequency generation (VR-SFG) and spectroscopic ellipsometry (SE) have been used to characterize self-assembled monolayer films of unsubstituted and mononitro-substituted ...oligo(phenylene−ethynylene) molecules on vapor-deposited Au substrates. When combined with quantum chemical calculations of the relevant transition moment directions, orientation distributions and electronic excitation spectra are obtained. The orientation distribution from VR-SFG is in good agreement with previous IR reflection studies, indicating both molecules are tilted from the surface normal by ∼30°. The calculated resonant hyperpolarizabilities are in good agreement with experimental spectra. The optical polarizability extracted from SE suggests strong intermolecular interactions, consistent with molecular exciton theory.
We have observed nitro-functionalized oligo(phenylene−ethynylene) molecules exhibiting motion up and down Au{111} substrate monatomic step edges within host self-assembled monolayers of ...n-alkanethiols, independent of previously observed conductance switching. Single molecules have been imaged with scanning tunneling microscopy to place-exchange reversibly between the top and bottom of monatomic substrate step edges.
Flexible and stretchable microscale fluidic devices have a broad range of potential applications, ranging from electronic wearable devices for convenient digital lifestyle to biomedical devices. ...However, simple ways to achieve stable flexible and stretchable fluidic microchannels with dynamic liquid transport have been challenging because every application for elastomeric microchannels is restricted by their complex fabrication process and limited material selection. Here, a universal strategy for building microfluidic devices that possess exceptionally stable and stretching properties is shown. The devices exhibit superior mechanical deformability, including high strain (967%) and recovery ability, where applications as both strain sensor and pressure‐flow regulating device are demonstrated. Various microchannels are combined with organic, inorganic, and metallic materials as stable composite microfluidics. Furthermore, with surface chemical modification these stretchable microfluidic devices can also obtain antifouling property to suit for a broad range of industrial and biomedical applications.
A simple and universal strategy is demonstrated for building a flexible microchannel which is inspired by blood vessels. The device exhibits superior mechanical deformability, with applications as both strain sensor and pressure‐flow regulating device. Furthermore, with chemical surface modification, the device can also obtain antifouling properties to suit for a broad range of industrial and biomedical applications.
Nanotechnology offers significant advantages for medical imaging and therapy, including enhanced contrast and precision targeting. However, integrating these benefits into ultrasonography is ...challenging due to the size and stability constraints of conventional bubble-based agents. Here bicones, truly tiny acoustic contrast agents based on gas vesicles (GVs), a unique class of air-filled protein nanostructures naturally produced in buoyant microbes, are described. It is shown that these sub-80 nm particles can be effectively detected both in vitro and in vivo, infiltrate tumors via leaky vasculature, deliver potent mechanical effects through ultrasound-induced inertial cavitation, and are easily engineered for molecular targeting, prolonged circulation time, and payload conjugation.
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