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Dry liquid crystal marbles, thermotropic liquid crystal droplets encapsulated by cellulose nanocrystals, exhibit fast response to an external stimuli. [Display omitted] Dry liquid crystal marbles are structures that consist of cholesteric liquid crystal (CLC) droplets prepared by the mixture of chiral-doped thermotropic LCs encapsulated by cellulose nanocrystals (CNCs) that have been dried under ambient conditions. The characterizations revealed that CLC droplets were successfully encapsulated by self-standing CNC shells and responsive to the external gaseous stimulus. The dry LC marbles offer several advantages over previously reported LC-based gas sensors, such as fast response against minor external stimuli, and ease of handling, which make them particularly attractive for practical applications in sensing. We demonstrate the use of these marbles for detecting toluene vapor, a common industrial solvent and pollutant, which we also use to understand the response characteristics. The dry CLC marbles exhibit a significant response to toluene vapor with a detection limit below 500 ppm, attributed to the change of pitch size of the helical structure of CLC droplets induced by the toluene vapor. The CNC-capsulated CLC droplets were stable in emulsion for up to two weeks, and their dried form exhibited a sensitive response upon toluene exposure. The real-time experiments revealed that the LC marbles can be used multiple times without a significant loss of sensitivity, where 90 % of the maximum response was observed at 13.3 ± 4.7 s. These dry LC marbles can also be utilized in other areas, including drug delivery, optical devices, and biosensors. [ABSTRACT FROM AUTHOR]

Smart devices, such as soft robots, artificial organs, and soft actuators, require materials that adapt their morphologies and properties in response to their environment. These materials can be obtained through the composition of different types of materials that exhibit different responses to environmental stimuli, arranged in a rational spatial configuration. We achieved unique responsive materials by forming interfaces and surfaces of appropriate materials using the sol–gel method. In recent decades, we have proposed the use of wrinkles and nano-brushes on sol–gel-derived materials for various sophisticated applications, such as micropattern fabrication, wettability control, and linear actuators for size-selective transportation. This account introduces environment-responsive materials with rational interfaces via the sol–gel method, particularly those characterized by surface morphology. Highlights: Responsive and adaptive interfaces fabricated via the sol–gel method. Microrolls formed by self-scrolling of sol–gel hybrid films. Photofabrication of micropatterns and actuators on sol–gel hybrid films. Manipulation of water droplets on titanate nanotube brushes fabricated by the sol–gel method. [ABSTRACT FROM AUTHOR]

Phototherapy, also known as photobiological therapy, is a non-invasive and highly effective physical treatment method. Its broad use in clinics has led to significant therapeutic results. Phototherapy parameters, such as intensity, wavelength, and duration, can be adjusted to create specific therapeutic effects for various medical conditions. Meanwhile, Magnetic Resonance Imaging (MRI), with its diverse imaging sequences and excellent soft-tissue contrast, provides a valuable tool to understand the therapeutic effects and mechanisms of phototherapy. This review explores the clinical applications of commonly used phototherapy techniques, gives a brief overview of how phototherapy impacts different diseases, and examines MRI's role in various phototherapeutic scenarios. We argue that MRI is crucial for precise targeting, treatment monitoring, and prognosis assessment in phototherapy. Future research and applications will focus on personalized diagnosis and monitoring of phototherapy, expanding its applications in treatment and exploring multimodal imaging technology to enhance diagnostic and therapeutic precision and effectiveness. [ABSTRACT FROM AUTHOR]

Electrically triggered color‐changing materials, termed as electrochromic materials, offer precise and programmable color transistions through the manipulation of electric field frequency and amplitude. They are used as displays, sensors, military camouflage, wearable devices, and anticounterfeiting materials. Their future advancements depend on clear understanding of the color change mechanisms and pros/cons between different electrochromic materials. To this end, we starts by categorizing electrochromism into two classes according to color production mechanism: chemical color‐based and physical color‐based. Within the former, color emerges from chemical molecules selectively absorbing specific wavelengths of light and color changes stem from electrochemical redox reactions. The latter, meanwhile, hinges upon electrically induced alterations in the geometries, dimensions, or arrangements of nano/micro structures, such as photonic crystals and plasmonic nanostructures. The principles of color changes in both categories are detailed, and compare their differences in terms of response time, operating voltage, degree of color change, and stability. At the end, their applications will be discussed spanning from smart windows to color display, dynamic camouflage, energy storage, and thermal management. This critical review is aimed to provide multidisciplinary insights that will benefit both novices and seasoned experts engaged in fundamental exploration or practical investigations of electrochromic materials. [ABSTRACT FROM AUTHOR]

The employment of Microbially Induced Calcium Carbonate Precipitation (MICP) is of increasing interest as a technique for environmentally sustainable soil stabilisation. Recent advancements in synthetic biology have allowed for the conception of a pressure-responsive MICP process, wherein bacteria are engineered to sense environmental loads, thereby offering the potential to stabilise specific soil regions selectively. In this study, a 2D smart bio-geotechnical model is proposed based on a pressure-responsive MICP system. Experimentally obtained pressure-responsive genes and hypothetical genes with different pressure responses were applied in the model and two soil profiles were evaluated. The resulting model bridges scales from gene expression within bacteria cells to geotechnical simulations. The results show that both strata and gene expression–pressure relationships have a significant influence on the distribution pattern of calcium carbonate precipitation within the soil matrix. Among the evaluated experimental genes, Gene A demonstrates the best performance in both of the two soil profiles due to the effective stabilisation in the centre area beneath the load, while Genes B and C are more effective in reinforcing peripheral regions. Furthermore, when the hypothetical genes are utilised, there is an increasing stabilisation area with a decreased threshold value. The results show that the technique can be used for soil reinforcement in specific areas. [ABSTRACT FROM AUTHOR]

Abstract Advanced materials could perform functions in response to external stimuli. These are responsive materials. In order for us to develop advanced functional systems with a good responsive nature, we need to create a methodology that goes one step further. It is the artificial architecture of functional material systems based on the knowledge of nanotechnology. The task will be fulfilled by the new concept of nanoarchitectonics. Nanoarchitectonics integrates nanotechnology with various material sciences, basic chemistry, microfabrication techniques, and biological processes to architect functional material systems from atomic, molecular, and nanomaterial units. This review will deal with the nanoarchitectonics of responsive materials related with phenomena at interfaces. In order to demonstrate the effectiveness of responsive materials nanoarchitectonics at interfaces for functional systems of various sizes, this review article is organized by size for various functional systems. Specifically, this review has grouped them into (i) molecular level response, (ii) nanodevice level response, (iii) material level response, and (iv) living cell level response. If the social demand for these materials is fully recognized, such development is expected to efficiently progress. This review article would play a role in stimulating such development.

Abstract Stimuli‐responsive fluorescent hydrogels are three‐dimensional networked polymeric materials with tunable luminescence and dynamic properties, which play an important role as a water‐rich soft material in the fields of information encryption, bionic actuation, bioimaging, environmental monitoring, and luminescent materials. Compared with conventional hydrogels, their unique luminescent properties allow the visualization of microscopic dynamics within the polymer network. By rational inclusion of dynamic motifs, such as photoswitches, AIEgens, lanthanide complexes, and host–guest complexes, these materials are endowed with tunability of emission, shape, and phase in time and space in response to environmental effectors. In this review, we summarize the fabrication strategies that are mainly used by recently reported stimuli‐responsive fluorescent hydrogels and the applications of these materials.

Abstract Compared with traditional rigid actuators, soft actuators exhibit a large number of advantages, including enhanced flexibility, reconfigurability, and adaptability, which motivate us to develop artificial soft actuators with widespread applications. Soft actuators with MXene nanomaterials are regarded as highly promising candidates for advancing the development of bioinspired soft robotics as a consequence of their unprecedented physicochemical characteristics, such as high electronic conductivity, thermal conductivity, photothermal conversion capability, and abundant surface functional groups. Herein, a comprehensive overview of the recent advancement of soft actuators with MXene nanomaterials and their extensive applications from the perspective of bioinspiration is provided. First, synthetic methods of MXene and their properties are briefly summarized. Subsequently, soft actuators with MXene nanomaterials (including photoresponsive soft actuators, electroresponsive soft actuators, and chemoresponsive soft actuators) are sequentially investigated with a focus on the fabrication approaches, actuation properties, underlying mechanisms, and promising applications. At the end, the future challenges and opportunities for the rapid development of soft actuators with MXene nanomaterials are discussed.

Chemically responsive liquid crystal (LC) based polymers can change their mechanical or optical properties when exposed to chemical triggers. The anisotropy inherent in LC materials allows the programming and control of predictable changes in shape, stiffness, and/or color. By further incorporating ionizable moieties into the polymer formulation, these materials may exhibit a response to chemical stimuli such as pH, solvents, or specific analytes. This mini‐review highlights seminal papers and recent advances in the use of chemoresponsive LC polymers for sensing and actuation. We also discuss how these materials can respond to biochemical stimuli through the immobilization of enzymes into the network, and provide examples of different types of responses (e.g., shape reconfigurations and color transitions). Multiple ways of modulating the response, such as chemical gating and enzyme patterning, are also reviewed. Finally, we illuminate some of the challenges and opportunities in the use of these materials for state‐of‐the‐art applications, including shape‐controllable medical implants and real‐time field‐deployable sensors. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The field of biosensor development is fueled by innovations in new functional transduction materials and technologies. Material innovations promise to extend current sensor hardware limitations, reduce analysis costs, and ensure broad application of sensor methods. Optical sensors are particularly attractive because they enable sensitive and noninvasive analyte detection in near real-time. Optical transducers convert physical, chemical, or biological events into detectable changes in fluorescence, refractive index, or spectroscopic shifts. Thus, in addition to sophisticated biochemical selector designs, smart transducers can improve signal transmission and amplification, thereby greatly facilitating the practical applicability of biosensors, which, to date, is often hampered by complications such as difficult replication of reproducible selector-analyte interactions within a uniform and consistent sensing area. In this context, stimuli-responsive and optically active Janus emulsions, which are dispersions of kinetically stabilized biphasic fluid droplets, have emerged as a novel triggerable material platform that provides as a versatile and cost-effective alternative for the generation of reproducible, highly sensitive, and modular optical sensing layers. The intrinsic and unprecedented chemical-morphological-optical coupling inside Janus droplets has facilitated optical signal transduction and amplification in various chemo- and biosensor paradigms, which include examples for the rapid and cost-effective detection of major foodborne pathogens. These initial demonstrations resulted in detection limits that rival the capabilities of current commercial platforms. This trend article aims to present a conceptual summary of these initial efforts and to provide a concise and comprehensive overview of the pivotal kinetic and thermodynamic principles that govern the ability of Janus droplets to sensitively and selectively respond to and interact with bacteria. [ABSTRACT FROM AUTHOR]

In pH‐responsive drug carriers, the distribution of charges has been proven to affect delivery efficiency but is difficult to control and verify. Herein, we fabricate polyampholyte nanogel‐in‐microgel colloids (NiM−C) and show that the arrangement of the nanogels (NG) can easily be manipulated by adapting synthesis conditions. Positively and negatively charged pH‐responsive NG are synthesized by precipitation polymerization and labelled with different fluorescent dyes. The obtained NG are integrated into microgel (MG) networks by subsequent inverse emulsion polymerization in droplet‐based microfluidics. By confocal laser scanning microscopy (CLSM), we verify that depending on NG concentration, pH value and ionic strength, NiM−C with different NG arrangements are obtained, including Janus‐like phase‐separation of NG, statistical distribution of NG, and core–shell arrangements. Our approach is a major step towards uptake and release of oppositely charged (drug) molecules. [ABSTRACT FROM AUTHOR]

The transport of liquid droplets plays an essential role in various applications. Modulating the wettability of the material surface is crucial in transporting droplets without external energy, adhesion loss, or intense controllability requirements. Although several studies have investigated droplet manipulation, its design principles have not been categorized considering the mechanical perspective. This review categorizes liquid droplet transport strategies based on wettability modulation into those involving (i) application of driving force to a droplet on non-sticking surfaces, (ii) formation of gradient surface chemistry/structure, and (iii) formation of anisotropic surface chemistry/structure. Accordingly, reported biological and artificial examples, cutting-edge applications, and future perspectives are summarized.

Smart materials respond to environmental signals by changing their microstructure and physical properties. Programming multiple behaviors and functions into a single material could increase its utility and adaptability to ever‐changing environmental conditions. A swellable and stretchable metamaterial hydrogel or "metasponge" engineered to morph into customized sizes and shapes that dynamically tune its physical properties and functions is reported. Multiple case studies that take advantage of the morphing properties of the metasponge, including robotic actuation, light guidance, optical and sonic invisibility ("cloaking"), adaptation of propulsion mode, sampling, and multiple biomedical applications, are illustrated. Developing multifunctional smart materials in which logic is programmed into the materials rather than electronic components could pave a new path to autonomy and dynamic responses in soft robots, sensors, and actuators. [ABSTRACT FROM AUTHOR]

Within the framework of a circular economy, we aim to efficiently use raw materials and reduce waste generation. In this context, the longevity of biomimetic material systems can significantly contribute by providing robustness and resilience of system functionality inspired by biological models. The aim of this review is to outline various principles that can lead to an increase in robustness (e.g., safety factor, gradients, reactions to environmental changes) and resilience (e.g., redundancy, self-repair) and to illustrate the principles with meaningful examples. The study focuses on plant material systems with a high potential for transfer to biomimetic applications and on existing biomimetic material systems. Our fundamental concept is based on the functionality of the entire system as a function of time. We use functionality as a dimensionless measure of robustness and resilience to quantify the system function, allowing comparison within biological material systems and biomimetic material systems, but also between them. Together with the enclosed glossary of key terms, the review provides a comprehensive toolbox for interdisciplinary teams. Thus, allowing teams to communicate unambiguously and to draw inspiration from plant models when developing biomimetic material systems with great longevity potential. [ABSTRACT FROM AUTHOR]

We report a liquid material based on a pyromellitic diimide (PMDI) framework with branched alkyl chains for the first time. An electron‐accepting PMDI‐based liquid can dissolve electron‐donating solid naphthalene. This liquid demonstrates green photoluminescence (PL) originating from exciplex formation, the properties of which are different from those of the PMDI‐based liquid and naphthalene. The photophysical behavior was investigated by measuring PL spectra and undertaking excited‐state decay measurements. [ABSTRACT FROM AUTHOR]

The employment of Microbially Induced Calcium Carbonate Precipitation (MICP) is of increasing interest as a technique for environmentally sustainable soil stabilisation. Recent advancements in synthetic biology have allowed for the conception of a pressure-responsive MICP process, wherein bacteria are engineered to sense environmental loads, thereby offering the potential to stabilise specific soil regions selectively. In this study, a 2D smart bio-geotechnical model is proposed based on a pressure-responsive MICP system. Experimentally obtained pressure-responsive genes and hypothetical genes with different pressure responses were applied in the model and two soil profiles were evaluated. The resulting model bridges scales from gene expression within bacteria cells to geotechnical simulations. The results show that both strata and gene expression–pressure relationships have a significant influence on the distribution pattern of calcium carbonate precipitation within the soil matrix. Among the evaluated experimental genes, Gene A demonstrates the best performance in both of the two soil profiles due to the effective stabilisation in the centre area beneath the load, while Genes B and C are more effective in reinforcing peripheral regions. Furthermore, when the hypothetical genes are utilised, there is an increasing stabilisation area with a decreased threshold value. The results show that the technique can be used for soil reinforcement in specific areas.

Smart materials respond to environmental signals by changing their microstructure and physical properties. Programming multiple behaviors and functions into a single material could increase its utility and adaptability to ever‐changing environmental conditions. A swellable and stretchable metamaterial hydrogel or “metasponge” engineered to morph into customized sizes and shapes that dynamically tune its physical properties and functions is reported. Multiple case studies that take advantage of the morphing properties of the metasponge, including robotic actuation, light guidance, optical and sonic invisibility (“cloaking”), adaptation of propulsion mode, sampling, and multiple biomedical applications, are illustrated. Developing multifunctional smart materials in which logic is programmed into the materials rather than electronic components could pave a new path to autonomy and dynamic responses in soft robots, sensors, and actuators.

Despite education campaigns linking sun overexposure and skin cancer, it remains one of the leading preventable cancer diagnoses. Skin cancer risk is correlated with overexposure to UV light in sunlight and can be prevented by avoiding exposure. While sun protection can be achieved using sunscreen and clothing, people must be made aware of their risk to facilitate behavior change. Herein, new rewearable UV sensors which overcome the single‐use limitations of other products are presented. These sensors utilize diarylethene photoswitches, which develop a colored appearance upon exposure to UV and are reset to colorless by green light (<10 min). These photoswitches are incorporated into a range of materials, enabling the use of advanced manufacturing to develop highly desirable consumer products. 3D stereolithographic printing is used to prototype sensors, with complex geometries and appealing aesthetics, that can be worn by users. The UV sensitivity of these devices is tuned by incorporating chromophores, meeting the needs of diverse skin types. The colorimetric response allows for direct visual feedback to the user, or quantification using photography, allowing for dosimetry of UV exposure. These new reusable devices aim to reduce people's exposure to UV, while reducing the waste generated by single‐use devices. [ABSTRACT FROM AUTHOR]

In recent years, significant advances have been made in the field of functionalized membranes. With the functionalization using various materials, such as polymers and enzymes, membranes can exhibit property changes in response to an environmental stimulation, such as heat, light, ionic strength, or pH. The resulting responsive nature allows for an increased breadth of membrane uses, due to the developed functionalization properties, such as smart-gating filtration for size-selective water contaminant removal, self-cleaning antifouling surfaces, increased scalability options, and highly sensitive molecular detection. In this review, new advances in both fabrication and applications of functionalized membranes are reported and summarized, including temperature-responsive, pH-responsive, light-responsive, enzyme-functionalized, and two-dimensional material-functionalized membranes. Specific emphasis was given to the most recent technological improvements, current limitations, advances in characterization techniques, and future directions for the field of functionalized membranes. [ABSTRACT FROM AUTHOR]

Smart materials that respond to external stimuli are the top choice as actuators. Herein, inspired by the natural plants, a smart dual-response actuator with Janus structure was fabricated from natural cellulose. Two cellulose derivatives with controllable chemical structure acted as the responsive elements, including ethanol-responsive cellulose 3,5-di-tert-butyl-4-hydroxybenzoate (CBH) and water-responsive carboxymethyl cellulose (CMC). Via changing the degree of substitution of 3,5-di-tert-butyl-4-hydroxybenzoate, the solubility, swellable property and swellable ratio of CBH in ethanol were precisely adjusted. After transforming the partial carboxylate group into the carboxylic acid, water-swellable CMC was obtained. Combining the ethanol-swellable CBH with water-swellable CMC by two-step blade-coating process, a Janus film was fabricated with dual-driven motility and complete biodegradability. This eco-friendly dual-responsive film can predict the concentration of ethanol/water mixture according to the different deformation angle. Moreover, it can be acted as a dual-responsive single-pole double-throw switch, indicating a huge potential in practical eco-friendly actuator. [ABSTRACT FROM AUTHOR]

Buildings must adapt and respond dynamically to their environment to reduce their energy loads and mitigate environmental impacts. Several approaches have addressed responsive behavior in buildings, such as adaptive and biomimetic envelopes. However, biomimetic approaches lack sustainability consideration, as conducted in biomimicry approaches. This study provides a comprehensive review of biomimicry approaches to develop responsive envelopes, aiming to understand the connection between material selection and manufacturing. This review of the last five years of building construction and architecture-related studies consisted of a two-phase search query, including keywords that answered three research questions relating to the biomimicry and biomimetic-based building envelopes and their materials and manufacturing and excluding other non-related industrial sectors. The first phase focused on understanding biomimicry approaches implemented in building envelopes by reviewing the mechanisms, species, functions, strategies, materials, and morphology. The second concerned the case studies relating to biomimicry approaches and envelopes. Results highlighted that most of the existing responsive envelope characteristics are achievable with complex materials requiring manufacturing processes with no environmentally friendly techniques. Additive and controlled subtractive manufacturing processes may improve sustainability, but there is still some challenge to developing materials that fully adapt to large-scale and sustainability needs, leaving a significant gap in this field. [ABSTRACT FROM AUTHOR]

Water-responsive materials alter their volumes in response to relative humidity changes. Recent progress in water-responsive materials demonstrates that this novel category of materials can perform better than natural muscles and conventional actuators by utilizing sustainable and renewable water energy. Textile fibers make excellent candidates for viable water-responsive actuators due to their scalability. However, the lack of a fundamental understanding of water responsiveness impedes their real-world applications. In this research, we selected seven different types of commercially available sewing threads: natural cellulose (cotton, flax). natural protein (wool, silk). regenerated cellulose (rayon), and synthetic (nylon, polyester) to systematically investigate their water-responsive behavior. All the sewing threads, without any chemical nor physical modification, except for polyester, repeatedly lifted a weight in response to humidity changes and generated higher specific energy density (15–210 J/kg) than mammalian muscles (8 J/kg). While the maximum water sorption by a sewing thread does not directly correlate to its mechanical actuation, the disruption of intermolecular hydrogen bonding between polymer chains by sorbed water seems critical for WR tensile actuation. In addition, the twisting of fibers to the right degree could direct the WR actuation in the desired direction. Our research with common threads sheds light on the water-responsive mechanisms and provides design guidelines for a large-scale water-responsive actuator applicable in various engineering systems, including energy harvesting, soft robotics, and protective gears that can help expand the applicability of natural fibers.

The development of photoinduced luminescent radicals with dynamic emission color is still challenging. Herein we report a novel molecular radical system (TBIQ) that shows photo‐controllable luminescence, leading to a wide range of ratiometric color changes via light excitation. The conjugated skeleton of TBIQ is decorated with steric‐demanding tertiary butyl groups that enable appropriate intermolecular interaction to make dynamic intermolecular coupling possible for controllable behaviors. We reveal that the helicenic pseudo‐planar conformation of TBIQ experiences a planarization process after light excitation, leading to more compactly stacked supermolecules and thus generating radicals via intermolecular charge transfer. The photo‐controllable luminescent radical system is employed for a high‐level information encryption application. This study may offer unique insight into molecular dynamic motion for optical manufacturing and broaden the scope of smart‐responsive materials for advanced applications. [ABSTRACT FROM AUTHOR]

Microfluidic valves based on chemically responsive materials have gained considerable attention in recent years. Herein, a wireless enantio‐responsive valve triggered by bipolar electrochemistry combined with chiral recognition is reported. A conducting polymer actuator functionalized with the enantiomers of an inherently chiral oligomer was used as bipolar valve to cover a tube loaded with a dye and immersed in a solution containing chiral analytes. When an electric field is applied, the designed actuator shows a reversible cantilever‐type deflection, allowing the release of the dye from the reservoir. The tube can be opened and closed by simply switching the polarity of the system. Qualitative results show the successful release of the colorant, driven by chirality and redox reactions occurring at the bipolar valve. The device works well even in the presence of chemically different chiral analytes in the same solution. These systems open up new possibilities in the field of microfluidics, including also controlled drug delivery applications. [ABSTRACT FROM AUTHOR]

Despite noteworthy technological progress and promising preclinical trials, brain disorders are still the leading causes of death globally. Extracellular vesicles (EVs), nano-/micro-sized membrane vesicles carrying bioactive molecules, are involved in cellular communication. Based on their unique properties, including superior biocompatibility, non-immunogenicity, and blood-brain barrier (BBB) penetration, EVs can shield their cargos from immune clearance and transport them to specific site, which have attracted increasing interests as novel nanocarriers for brain disorders. However, considering the limitations of native EVs, such as poor encapsulation efficiency, inadequate targeting capability, uncontrolled drug release, and limited production, researchers bioengineer EVs to fully exploit the clinical potential. Herein, this review initially describes the basic properties, biogenesis, and uptake process of EVs from different subtypes. Then, we highlight the application of EVs derived from different sources for personalized therapy and novel strategies to construct bioengineered EVs for enhanced diagnosis and treatment of brain disorders. Besides, it also presents a systematic comparison between EVs and other brain-targeted nanocarriers. Finally, existing challenges and future perspectives of EVs have been discussed, hoping to bolster the research from benchtop to bedside. [ABSTRACT FROM AUTHOR]

We study the role of temperature on the structure of pure polymer brushes and their mixture with attractive nanoparticles in flat and cylindrical geometries. It has previously been established that the addition of such nanoparticles causes the polymer brush to collapse and the intensity of the collapse depends on the attraction strength, the nanoparticle diameter, and the grafting density. In this work, we carry out molecular dynamics simulation under good solvent conditions to show how the collapse transition is affected by the temperature, for both plane grafted and inside-cylinder grafted brushes. We first examine the pure brush morphology and verify that the brush height is insensitive to temperature changes in both planar and cylindrical geometries, as expected for a polymer brush in a good solvent. On the other hand, for both system geometries, the brush structure in the presence of attractive nanoparticles is quite responsive to temperature changes. Generally speaking, for a given nanoparticle concentration, increasing the temperature causes the brush height to increase. A brush which contracts when nanoparticles are added eventually swells beyond its pure brush height as the system temperature is increased. The combination of two easily controlled external parameters, namely, concentration of nanoparticles in solution and temperature, allows for sensitive and reversible adjustment of the polymer brush height, a feature which could be exploited in designing smart polymer devices. [ABSTRACT FROM AUTHOR]

Thermoresponsive hydrogels such as poly(N‐isopropylacrylamide) (pNIPAM) are highly interesting materials for generating soft actuator systems. Whereas the material has so far mostly been used in macroscopic systems, here it is demonstrated that pNIPAM is an excellent material for generating actuator systems at the micrometer scale. Two‐photon direct laser writing is used to precisely structure thermoresponsive pNIPAM hydrogels at the micrometer scale based on a photosensitive resist. This study systematically shows that the surface‐to‐volume ratio of the microactuators is decisive to their actuation efficiency. The phase transition of the pNIPAM is also demonstrated by nanoindentation experiments. It is observed that the mechanical properties of the material can easily be adjusted by the writing process. Finally, it is found that not only the total size and surface structure of the microactuator play an important role, but also the crosslinking of the polymer itself. The results demonstrate for the first time a systematic study of pNIPAM‐based microactuators, which can easily be extended to systems of microactuators that act cooperatively, e.g., in microvalves. [ABSTRACT FROM AUTHOR]

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Dynamic bonds introduce unique properties such as self‐healing, recyclability, shape memory, and malleability to polymers. Significant efforts have been made to synthesize a variety of dynamic linkers, creating a diverse library of materials. In addition to the development of new dynamic chemistries, fine‐tuning of dynamic bonds has emerged as a technique to modulate dynamic properties. This Review highlights approaches for controlling the timescales of dynamic bonds in polymers. Particularly, eight dynamic bonds are considered, including urea/urethanes, boronic esters, Thiol–Michael exchange, Diels–Alder adducts, transesterification, imine bonds, coordination bonds, and hydrogen bonding. This Review emphasizes how structural modifications and external factors have been used as tools to tune the dynamic character of materials. Finally, this Review proposes strategies for tailoring the timescales of dynamic bonds in polymer materials through both kinetic effects and modulating bond thermodynamics. [ABSTRACT FROM AUTHOR]

Covalent molecular functionalization allows the physicochemical properties of 2D materials to be precisely tuned and modulated on-demand. Nonetheless, research on the molecular functionalization of 2D monoelemental graphene-like materials─known as Xenes─remains scarce, being mainly restricted to a specific type of solid-state chemical reaction based on the topotactic transformation of bulkier Zintl phases. Herein, a robust and general chemical approach is reported for the direct functionalization of commercially available H-terminated 2D germanene ( 2D-GeH ) with thiolated molecules ( R-SH ) via Ge-S bond formation. While the material characterization data provide direct experimental evidence of the Ge-S chemical bonding, density functional theory (DFT) calculations also predict its existence. Remarkably, the anchored thiolated molecules also favor the passivation of the 2D Xene against air oxidation, enlarging its benefits for real implementation. As a proof-of-principle, a redox-responsive molecular moiety such as 6-(ferrocenyl)hexanethiol ( Fc 6 -SH ) has been exploited to induce changes in the optoelectronic properties of the resulting 2D-GeFc 6 heterostructure by simply modulating the external bias potential, making it possible to optically and electrically read out a molecular switch on 2D Xene via implanting molecular responsiveness. Remarkably, the ON/OFF ratio has been shown to be dependent on the distance between the redox-responsive Fc moiety and the 2D Xene surface through the alkyl chain length. Overall, the reported a-la-carte molecular engineering approach provides the basis toward the rapid development of stable 2D-GeR derivatives exhibiting molecule-programmable properties.

This mini-review summarizes the seminal exploration of aqueous supramolecular chemistry of crown ether macrocycles. In history, most research of crown ethers were focusing on their supramolecular chemistry in organic phase or in gas phase. In sharp contrast, the recent research evidently reveal that crown ethers are very suitable for studying abroad range of the properties and applications of water interactions, from: high water-solubility, control of Hofmeister series, “structural water”, and supramolecular adhesives. Key studies revealing more details about the properties of water and aqueous solutions are highlighted.

A glycan-stimulated and poly(3,4-ethylene-dioxythiophene)s (PEDOT)-based nanomaterial platform is fabricated to purify circulating tumor cells (CTCs) from blood samples of prostate cancer (PCa) patients. This new platform, phenylboronic acid (PBA)-grafted PEDOT NanoVelcro, combines the 3D PEDOT nanosubstrate, which greatly enhances CTC capturing efficiency, with a poly(EDOT-PBA-co-EDOT-EG3) interfacial layer, which not only provides high specificity for CTC capture upon antibody conjugation but also enables competitive binding of sorbitol to gently release the captured cells. CTCs purified by this PEDOT NanoVelcro chip provide well-preserved RNA transcripts for the analysis of the expression level of several PCa-specific RNA biomarkers, which may provide clinical insights into the disease.

Injectable delivery systems that respond to biologically relevant stimuli present an attractive strategy for tailorable drug release. Here, the design and synthesis of unique polymers are reported for the creation of hydrogels that are formed in situ and degrade in response to clinically relevant endogenous and exogenous stimuli, specifically reducing microenvironments and externally applied light. Hydrogels are formed with polyethylene glycol and heparin-based polymers using a Michael-type addition reaction. The resulting hydrogels are investigated for the local controlled release of low molecular weight proteins (e.g., growth factors and cytokines), which are of interest for regulating various cellular functions and fates in vivo yet remain difficult to deliver. Incorporation of reduction-sensitive linkages and light-degradable linkages affords significant changes in the release profiles of fibroblast growth factor-2 (FGF-2) in the presence of the reducing agent glutathione or light, respectively. The bioactivity of the released FGF-2 is comparable to pristine FGF-2, indicating the ability of these hydrogels to retain the bioactivity of cargo molecules during encapsulation and release. Further, in vivo studies demonstrate degradation-mediated release of FGF-2. Overall, our studies demonstrate the potential of these unique stimuli-responsive chemistries for controlling the local release of low molecular weight proteins in response to clinically relevant stimuli.

Laboratory on-chip (LOC) technology facilitates numerous developments across diverse disciplines, such as medicine, tissue engineering, materials science, biomedical engineering, and biotechnology. Moreover, the potential applications appear boundless when LOC is integrated with intelligent hydrogels. In the literature, however, there are few accounts of the vast array of developments and applications that this combination has spawned. These new systems, which integrate smart hydrogels and LOC and thus significantly advance cutting-edge technology, have been thoroughly examined in this review. The functions of smart hydrogels in LOC applications were described and subsequently the developed intelligent hydrogels were classified as multi-responsive, thermo-responsive, pH-responsive, and stimuli-responsive (light, magnetic, and electric). Following this, details regarding tunable properties for LOC functions were provided, followed by a discussion of the fabrication processes and integration of these intelligent hydrogels into LOC systems, including their benefits and drawbacks. Following that, current literature examples of LOC systems utilizing these intelligent hydrogels for biosensing, 3D culture, tissue engineering, controlled release, personalized medicine, drug delivery, analyte enrichment, and organ-on-a-chip applications were presented. Following the presentation of state-of-the-art information regarding smart hydrogel characterization techniques, present challenges and prospective prospects were discussed. [Display omitted] • The functions of smart hydrogels in LOC applications were described and following this the developed intelligent hydrogels were classified as multi-responsive, thermo-responsive, pH-responsive, and stimuli-responsive (light, magnetic, and electric). • Tunable properties of LOC functions were provided, followed by a discussion of the fabrication processes and integration of these intelligent hydrogels into LOC systems. • Current literature examples of LOC systems utilizing these intelligent hydrogels for biosensing, 3D culture, tissue engineering, controlled release, personalized medicine, drug delivery, analyte enrichment, and organ-on-a-chip applications were presented. [ABSTRACT FROM AUTHOR]

The development of robust bioanalytical devices and biosensors for infectious pathogens is progressing well with the advent of new materials, concepts, and technology. The progress is also stepping towards developing high throughput screening technologies that can quickly identify, differentiate, and determine the concentration of harmful pathogens, facilitating the decision-making process for their elimination and therapeutic interventions in large-scale operations. Recently, much effort has been focused on upgrading these analytical devices to an intelligent technological platform by integrating them with modern communication systems, such as the internet of things (IoT) and machine learning (ML), to expand their application horizon. This review outlines the recent development and applications of bioanalytical devices and biosensors to detect pathogenic microbes in environmental samples. First, the nature of the recent outbreaks of pathogenic microbes such as foodborne, waterborne, and airborne pathogens and microbial toxins are discussed to understand the severity of the problems. Next, the discussion focuses on the detection systems chronologically, starting with the conventional methods, advanced techniques, and emerging technologies, such as biosensors and other portable devices and detection platforms for pathogens. Finally, the progress on multiplex assays, wearable devices, and integration of smartphone technologies to facilitate pathogen detection systems for wider applications are highlighted. [ABSTRACT FROM AUTHOR]

A new family of C2-symmetric pseudopeptides with a high functional density for supramolecular interactions has been synthetized through the attachment of four amino acid subunits to a diamino aliphatic spacer. The resulting open-chain compounds present remarkable properties as low-molecular-weight hydrogelators. The self-assembled 3D networks were characterized by SEM analyses, observing regular nanofibres with 80–100 nm diameters. Spectroscopic and molecular modelling experiments revealed the presence of strong synergic effects between the H-bonding and π–π interactions, with the best results obtained for the homoleptic tetra-pseudopeptide derived from l-Phe. In addition, these bioinspired hydrogels possessed pH- and CO2-responsive sol–gel transitions. The formation of ammonium carbamate derivatives in the presence of carbon dioxide led to a detrimental change in its adequate self-assembly. CO2 desorption temperatures of ca. 70 °C were assigned to the thermodynamically favoured recovery of the supramolecular gel. [ABSTRACT FROM AUTHOR]

The high‐pressure behaviour of flexible zeolitic imidazolate frameworks (ZIFs) of the ZIF‐62 family with the chemical composition M(im)2−x(bim)x is presented (M2+=Zn2+, Co2+; im−=imidazolate; bim−=benzimidazolate, 0.02≤x≤0.37). High‐pressure powder X‐ray diffraction shows that the materials contract reversibly from an open pore (op) to a closed pore (cp) phase under a hydrostatic pressure of up to 4000 bar. Sequentially increasing the bim− fraction (x) reinforces the framework, leading to an increased threshold pressure for the op‐to‐cp phase transition, while the total volume contraction across the transition decreases. Most importantly, the typical discontinuous op‐to‐cp transition (first order) changes to an unusual continuous transition (second order) for x≥0.35. This allows finetuning of the void volume and the pore size of the material continuously by adjusting the pressure, thus opening new possibilities for MOFs in pressure‐switchable devices, membranes, and actuators. [ABSTRACT FROM AUTHOR]

Carefully designed geometries and materials can program desired shapes. In this review, we introduce shape-transformable materials and their recent applications in electronic devices and robots. Strain-guiding shape transformation can be achieved by geometry design or materials design, which can program the magnitude and direction of strain to develop desired shapes. For the geometry design, we discuss origami and kirigami, which transform 2D sheet materials into desired 3D shapes via local deformations caused by fold creases and cut openings. The desired shape can be programmed by controlling the length and alignment of folds or cuts. For the material design, heterogeneities in materials can develop strain driven shape transformation. Heterogeneities in materials include those in anisotropic materials, graded materials, or mixtures of different materials. Shape-transformable materials can be prepared by introducing heterogeneities into stimuli-responsive materials, including inflatable materials, shape memory polymers, liquid crystal elastomers, and hydrogels. The development of shape-transformable materials has led to innovations in energy storage devices, displays, sensors, epidermal electronics, actuators, and robots. [ABSTRACT FROM AUTHOR]

With recent advances in both responsive materials and fabrication techniques, it is now possible to construct integrated functional structures, composed of both structural and active materials. We investigate the robust design of such structures through topology optimization. By applying a typical interpolation scheme and filtering technique, we prove existence of an optimal design to a class of objective functions which depend on the compliances of the stimulated and unstimulated states. In particular, we consider the actuation work and the blocking load as objectives, both of which may be written in terms of compliances. We study numerical results for the design of a 2D rectangular lifting actuator for both of these objectives, and discuss some intuition behind the features of the converged designs. We formulate the optimal design of these integrated responsive structures with the introduction of voids or holes in the domain, and show that our existence result holds in this setting. We again consider the design of the 2D lifting actuator now with voids. Finally, we investigate the optimal design of an integrated 3D torsional actuator for maximum blocking torque. [ABSTRACT FROM AUTHOR]

Stimuli−responsive hydrogels are important in soft actuators research, as they change volume in response to environmental factors. Thermoresponsive hydrogels, such as poly(N‐isopropylacrylamide) (pNIPAM), typically have slow response rates and exert comparably weak forces, which usually limit their use as artificial muscles. Herein, it is shown that the incorporation of interconnected microchannels into the pNIPAM hydrogel by a template‐assisted approach leads to a significant increase in both the response rate and the volume change. For a microchannel density of only 5 vol%, a volume reduction of 90% is achieved, compared with only 12% for the bulk material, while material stiffness of the swollen hydrogels remains unchanged. By tailoring the channel density and the stiffness of the material, it is further possible to adjust the response rate and the exerted stroke force in an actuation setting. It is shown in a demonstrator gripper setup driven by the pNIPAM‐based artificial muscle that the performance of the gripper is strongly improved by the microengineered material compared with conventional bulk pNIPAM. The strategy of incorporating microchannels into the pNIPAM hydrogel provides a practical approach for the future use of volume phase transition‐based responsive materials in soft robotic applications. [ABSTRACT FROM AUTHOR]