Liquid crystal elastomers (LCEs) are responsive materials that can undergo large reversible deformations upon exposure to external stimuli, such as electrical and thermal fields. Controlling the alignment of their liquid crystals mesogens to achieve desired shape changes unlocks a new design paradigm that is unavailable when using traditional materials. While experimental measurements can provide valuable insights into their behavior, computational analysis is essential to exploit their full potential. Accurate simulation is not, however, the end goal; rather, it is the means to achieve their optimal design. Such design optimization problems are best solved with algorithms that require gradients, i.e., sensitivities, of the cost and constraint functions with respect to the design parameters, to efficiently traverse the design space. In this work, a nonlinear LCE model and adjoint sensitivity analysis are implemented in a scalable and flexible finite element-based open source framework and integrated into a gradient-based design optimization tool. To display the versatility of the computational framework, LCE design problems that optimize both the material, i.e., liquid crystal orientation, and structural shape to reach a target actuated shapes or maximize energy absorption are solved. Multiple parameterizations, customized to address fabrication limitations, are investigated in both 2D and 3D. The case studies are followed by a discussion on the simulation and design optimization hurdles, as well as potential avenues for improving the robustness of similar computational frameworks for applications of interest.

Responsive organic luminescent aggregates have a wide range of application fields, but currently there is still a lack of reasonable molecular design strategies. Introducing ion-π interactions into molecules can effectively alter their luminescent properties. However, current research typically focuses on ion localization at luminescent conjugated groups with the strong interaction forces. In this work, we introduce the flexible alkoxy chain spacers between fluorescent conjugated groups and ion-π interaction sites, and then adjust the fluorescence performance of the molecule by changing the strength of ion-π interactions. Bromine ion-based molecules with strong ion-π interactions exhibit high and stable fluorescence quantum yields in crystals and amorphous powders under the external stimuli. Hexafluorophosphate ion-based molecules with weak ion-π interactions have the high fluorescence quantum yield in crystals and very low fluorescence quantum yield in amorphous powders, showing variable fluorescence intensities under external stimuli. This demonstrates a new class of responsive organic luminescent solid-state materials.

Controlled modulation of electronic and magnetic properties in stimuli-responsive materials provides valuable insights for the design of magnetoelectric or multiferroic devices. This paper demonstrates the modulation of electrical and magnetic properties of a semiconductive, paramagnetic metal-organic framework (MOF) Cu3(C6O6)2 with small gaseous molecules, NH3, H2S, and NO. This study merges chemiresistive and magnetic tests to reveal that the MOF undergoes simultaneous changes in electrical conductance and magnetization that are uniquely modulated by each gas. The features of response, including direction, magnitude, and kinetics, are modulated by the physicochemical properties of the gaseous molecules. This study advances the design of multifunctional materials capable of undergoing simultaneous changes in electrical and magnetic properties in response to chemical stimuli.

Stimuli-responsive materials have recently gained significant attention in the field of soft robotics, sensors, and biomimetic devices. The most facile way for the fabrication of such materials remains to endow bilayer structures which are fabricated with the combination of active and passive layers. Although, easily fabricated, these structures suffer from the generation of stress points between connection areas. In this work we develop a method to create a thin film with controlled cross-link variation across its thickness. The cross-link gradient is achieved through polymerization induced diffusion of dithiol molecules in thiol-ene network. As a result, the film exhibits bending deformation upon illumination with light or exposure to a chemical solvent, thereby demonstrating dual responsiveness. Light actuation of the film is achieved via photothermal effects due to the incorporation of dye into the system which can absorb UV light and heat the network. While solvent induced actuation is due to anisotropic swelling. Furthermore, the straightforward fabrication procedure allows for the creation of more complex deformations by patterning the film using a photomask during photopolymerization.

Microgels are commonly applied as solute carriers, where the size, density, and functionality of the microgels depend on solute binding. As representatives for ionic solutes with high affinity for the microgel, we study here the effect of superchaotropic Keggin polyoxometalates (POMs) PW12O403- (PW) and SiW12O404- (SiW) on the aqueous swelling and internal structure of nonionic poly(N-isopropylacrylamide) (pNiPAM) microgels by light scattering techniques and small-angle X-ray scattering. Due to their weak hydration, these POMs bind spontaneously to the microgels at millimolar concentrations. The microgels thus become charged and swell at low POM concentration, surprisingly without strongly increasing the volume phase transition temperature, and deswell at higher POM concentration. The swelling arises because of the osmotic pressure of dissociated counterions of the POMs, while the deswelling is due to POMs acting as physical cross-links in the microgels under screened electrostatics in NaCl or excess POM solution. This swelling/deswelling transition is sharper for PW than for SiW related to the lower charge density, weaker hydration, and stronger binding of PW. The POMs elicit qualitatively and quantitatively different swelling effects from ionic surfactants and classical salts. Moreover, the network softness and topology govern the swelling response upon POM binding. The softer the microgel, the stronger is the swelling response, while, inside the microgel, regions of high polymer density swell/contract more upon electric charging/cross-linking than regions with low polymer density. POM binding thus enables fine-tuning of microgel properties and highlights the role of network topology in microgel swelling. Because POMs decompose at an alkaline pH, these POM/microgel systems also exhibit pH-responsive swelling in addition to the typical temperature responsiveness of pNiPAM microgels.

Multifunctional flexible sensors are the development trend of wearable electronic devices in the future. As the core of flexible sensors, the key is to construct a stable multifunctional integrated conductive elastomer. Here, ionic conductive elastomers (ICEs) with self-wrinkling microstructures are designed and prepared by in situ phase separation induced by a one-step polymerization reaction. The ICEs are composed of ionic liquids as ionic conductors doped into liquid crystal elastomers. The doped ionic liquids cluster into small droplets and in situ induce the formation of wrinkle structures on the upper surface of the films. The prepared ICEs exhibit mechanochromism, conductivity, large tensile strain, low hysteresis, high cycle stability, and sensitivity during the tension-release process, which achieve dual-mode outputs of optical and electrical signals for information transmission and sensors.

In this work, we present core-shell microgels with tailor-made architecture and properties for the incorporation of palladium nanoparticles. The microgel core consists of poly-N-isopropylacrylamide (PNIPAM) copolymerized with methacrylic acid (MAc) as anchor point for the incorporation of palladium nanoparticles. The microgel shell is prepared by copolymerization of NIPAM and the UV-sensitive comonomer 2-hydroxy-4-(methacryloyloxy)-benzophenone (HMABP). The obtained core-shell architecture was analyzed by means of photon correlation spectroscopy, while the incorporated amount of HMABP was further confirmed via Fourier transform infrared spectroscopy. Subsequently, the microgel system was used for loading with palladium nanoparticles and their size and localization were investigated by transmission electron microscopy. The catalytic activity of the monodisperse palladium nanoparticles was tested by reduction of 4-nitrophenol to 4-aminophenol. The obtained reaction rate constants for the core-shell system showed enhanced activity compared to the Pd-loaded bare core system. Furthermore, it was possible to recycle the catalyst several times. Analysis via transmission electron microscopy revealed, that the incorporated palladium nanoparticles emerged undamaged after the reaction and subsequent purification process since no aggregation or loss in size was observed.

Amyloids are self-assembled protein aggregates that take cross-β fibrillar morphology. Although some amyloid proteins are best known for their association with Alzheimer\'s and Parkinson\'s disease, many other amyloids are found across diverse organisms, from bacteria to humans, and they play vital functional roles. The rigidity, chemical stability, high aspect ratio, and sequence programmability of amyloid fibrils have made them attractive candidates for functional materials with applications in environmental sciences, material engineering, and translational medicines. This review focuses on recent advances in fabricating various types of macroscopic functional amyloid materials. We discuss different design strategies for the fabrication of amyloid hydrogels, high-strength materials, composite materials, responsive materials, extracellular matrix mimics, conductive materials, and catalytic materials.

The preparation of thermoresponsive mannose functionalized monolayers of poly(N-isopropylacrylamide) microgels and the analysis of the specific binding of concanavalin A (ConA) and E. coli above and below the lower critical solution temperature (LCST) are shown. Via inhibition and direct binding assays it is found that ConA binding is time-dependent, where at short incubation times binding is stronger above the LCST. Given larger incubation times, the interaction of ConA to the microgel network is increased below the LCST when compared to temperatures above the LCST, possibly due to increased ConA diffusion and multivalent binding in the more open microgel network below the LCST. For E. coli, which presents only monovalent lectins and is too large to diffuse into the network, binding is always enhanced above the LCST. This is due to the larger mannose density of the microgel layer above the LCST increasing the interaction to E. coli. Once bound to the microgel layer above the LCST, E. coli cannot be released by cooling down below the LCST. Overall, this suggests that the carbohydrate presenting microgel layers enable specific binding where the temperature-induced transition between swollen and collapsed microgels may increase or decrease binding depending on the receptor size.

Biosensing is a rising analytical field for detection of biological indicators using transducing systems. Smart materials can response to external stimuli, and translate the stimuli from biological domains into signals that are readable and quantifiable. Smart materials, such as nanomaterials, photonic crystals and hydrogels have been widely used for biosensing purpose. In this review, we illustrate the incorporation of smart materials in biosensing systems, including the design of responsive materials, their responsive mechanism of biosensing, and their applications in detection of four types of common biomolecules (including glucose, nucleic acids, proteins, and enzymes). In the end, we also illustrate the current challenges and prospective of using smart materials in biosensing research fields.