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MXene, which is known for its high electrical/thermal conductivity, surface hydrophilicity, excellent mechanical flexibility, and chemical stability, is a versatile and smart material for soft actuators. However, most MXene actuators are fabricated by combining MXene with other inert materials to form a bilayer or multilayer structure. Considering the strain mismatch at multimaterial interfaces under frequent deformation, MXene‐based actuators are generally associated with poor stability, which limits their practical applications. Herein, inspired by the natural quantum‐confined superfluidic (QSF) effect, a multiresponsive MXene actuator that can be driven by moisture, light, and electricity by engineering an asymmetric QSF structure on both sides of the MXene film is reported. The actuation mechanism of the MXene film can be attributed to nonuniform water adsorption, transport, and desorption within the asymmetric QSF channels under moisture, photothermal, and electrothermal stimuli. Interestingly, MXene actuators can be flexibly formed into various shapes under moisture‐assisted mechanical compression, which not only enhances their multiresponsive actuation, but also permits a more complex deformation. As proof‐of‐concept demonstrations, various intriguing applications including a dual‐role robot, a smart shielding curtain, and a dragonfly robot, are fabricated, revealing the potential of MXene actuators for soft robotics. [ABSTRACT FROM AUTHOR]

Fluorescent hydrogels have emerged as one of the most promising candidates for developing biomimetic materials and artificial intelligence owing to their unique fluorescence and responsive properties. However, it is still challenging to fabricate hydrogel that exhibits synergistic changes in fluorescence color and shape in response to multistimulus via a simple method. Herein, blue‐ and orange‐emitting fluorescent microgels (MGs) both are designed and synthesized with pH‐, thermal‐, and cationic‐sensitivity via one‐step polymerization, respectively. The two fluorescent MGs are incorporated into transparent doubly crosslinked microgel (DX MG) hydrogels with a preset ratio. The DX MG hydrogels can tune the fluorescent color accompanied by size variation via subjecting to external multistimulus. Thus, DX MG hydrogels can be exploited for multiresponsive fluorescent bilayer actuators. The actuators can undergo complex shape deformation and color changes. Inspired by natural organisms, an artificial morning glory with color and size changes are showcased in response to buffer solutions of different pH values. Besides, an intelligent skin hydrogel, imitating natural calotes versicolor, by assembling four layers of DX MG with different ratios of MGs, is tailored. This work serves as an inspiration for the design and fabrication of novel biomimetic smart materials with synergistic functions. [ABSTRACT FROM AUTHOR]

Abstract Fluorescent hydrogels have emerged as one of the most promising candidates for developing biomimetic materials and artificial intelligence owing to their unique fluorescence and responsive properties. However, it is still challenging to fabricate hydrogel that exhibits synergistic changes in fluorescence color and shape in response to multistimulus via a simple method. Herein, blue‐ and orange‐emitting fluorescent microgels (MGs) both are designed and synthesized with pH‐, thermal‐, and cationic‐sensitivity via one‐step polymerization, respectively. The two fluorescent MGs are incorporated into transparent doubly crosslinked microgel (DX MG) hydrogels with a preset ratio. The DX MG hydrogels can tune the fluorescent color accompanied by size variation via subjecting to external multistimulus. Thus, DX MG hydrogels can be exploited for multiresponsive fluorescent bilayer actuators. The actuators can undergo complex shape deformation and color changes. Inspired by natural organisms, an artificial morning glory with color and size changes are showcased in response to buffer solutions of different pH values. Besides, an intelligent skin hydrogel, imitating natural calotes versicolor, by assembling four layers of DX MG with different ratios of MGs, is tailored. This work serves as an inspiration for the design and fabrication of novel biomimetic smart materials with synergistic functions.

Light emission from CaZnOS:Nd3+ by high‐intensity ultrasound excitation is demonstrated. Acoustic power and duty ratio enable simultaneous control of the degree of (local) thermo‐acoustic heating in isothermal or nonisothermal conditions. The Nd‐related photoemission provides direct thermometric feedback at an absolute sensitivity on the order of 10−4 K−1, within the physiological temperature range. From the individual temperature dependence of persistent luminescence and mechanoluminescence, both effects are attributed to a heterologous de‐trapping mechanism. In addition to acoustic heating and optical thermometry, this enables optical information storage and smart labeling with optoacoustic read‐out. [ABSTRACT FROM AUTHOR]

Light emission from CaZnOS:Nd3+ by high‐intensity ultrasound excitation is demonstrated. Acoustic power and duty ratio enable simultaneous control of the degree of (local) thermo‐acoustic heating in isothermal or nonisothermal conditions. The Nd‐related photoemission provides direct thermometric feedback at an absolute sensitivity on the order of 10−4 K−1, within the physiological temperature range. From the individual temperature dependence of persistent luminescence and mechanoluminescence, both effects are attributed to a heterologous de‐trapping mechanism. In addition to acoustic heating and optical thermometry, this enables optical information storage and smart labeling with optoacoustic read‐out. [ABSTRACT FROM AUTHOR]

Supramacromolecular hydrogels (SMHGs) are attractive materials in various areas. Due to their excellent reversible photoisomerization ability, azobenzene derivatives have been widely applied to construct SMHGs. But the majority of these systems were realized only by transplanting azobenzene function groups into macromolecule chains, while low-molecular-weight (LMW) azobenzene derivatives are fairly rare. Therefore, it is highly desirable to develop facile and effective strategies for the construction of SMHG. Here, a new ABA-typed azobenzene derivative (AD) has been designed and synthesized, which can be applied as LMW crosslinkers to construct SMHGs through electrostatic interactions between AD and sodium alginate (SA). When AD is mixed with SA solution in acidic conditions, SMHGs can form at various concentrations of SA. In addition, the concentration of AD also has a large impact on the moduli values. Profiting from electrostatic interactions between AD and SA, as well as interchain hydrogen bonds of SA, SMHGs can experience sol-gel transitions under pH-, photo- or thermo-stimuli. This work contributes a simple but effective strategy for the construction of SMHGs using azobenzene derivatives as LMW crosslinkers.

The rapid development of wearable devices and soft robotics has an urgent demand for polymer conductors with a switchable adhesion property. Herein, we report a supramolecular ionogel (SIG) that can reversibly switch between adhesion and debonding to various substrates. The on/off switchable adhesion of SIG is attributed to phase separation induced by the aggregation of polymer chains and the formation of a lubricating layer, which impairs the contact between polymer chains and substrates, thus weakening interfacial interaction. The phase separation ionogel (PSIG) is highly sensitive to humidity, leading to the debonded PSIG instantly transforming into the adhesion-hydrated ionogel (HIG) owing to the disruption of phase structure. Based on the switchable adhesion property, this multiresponsive ionogel shows potential applications as a fire alarm and intelligent conductive tape. This work provides a simple method for developing a switchable adhesion ionic polymer conductor and broadens the application of the ionogel in flexible devices.

Whereas cotton as an abundant natural cellulose has been widely used for sustainable and skin-friendly textiles and clothes, developing cotton fabrics with smart functions that could respond to various stimuli is still eagerly desired while remaining a great challenge. Herein, smart multiresponsive cotton fabric with hierarchically copper nanowire interwoven MXene conductive networks that are seamlessly assembled along a 3D woven fabric template for efficient personal healthcare and thermal comfort regulation is successfully developed. The robust hierarchically interwoven conductive network was "glued" and protected by organic conductive polymer poly(3,4-ethylenedioxythiophene) along a 3D interconnected fabric template to enhance interfacial adherent and environmental stability. Benefiting from the robust multiresponsive hierarchically interwoven conductive network, smart cotton fabric exhibits real-time response to various external stimuli (light/electrical/heat/temperature/stress), and the details of human activities can be accurately recognized and monitored. Furthermore, the porous structure of 3D smart fabric induced strong capillary force and confinement to phase change materials PEG, which exhibits a wide range of phase transition temperatures for efficient thermal comfort regulation. After further encapsulation with transparent fluorosilicone resin, the smart cotton fabric exhibits excellent self-cleaning performance with water/oil repellent. The smart multiresponsive cotton fabrics hold great promise in next-generation wearable systems for efficient personal healthcare and thermal management.

Bilayer hydrogels, endowed with multiresponsive and switchable color-changing properties, have garnered significant attention for bioinspired artificial intelligent materials. However, the design and fabrication of such hydrogels that can fully mimic the adaptation of the live organism, i.e ., simultaneous changes in shape, fluorescent, and/or visible color, still remain significant challenges. Herein, a multiresponsive (e.g., temperature, salt, and pH) and multiadaptive (shape, fluorescent color, and visible color changes) hydrogel was fabricated by employing monomers featuring pH-responsive fluorescence 4-(2-(4-(dimethylamino) phenyl)-1-isocyanovinyl) phenol (DP) and switchable color-changing 4-(2-sulfethyl) -1-(4-vinylbenzyl) pyridinium betaine (VPES). The bilayer hydrogel comprises a temperature- and pH-responsive gel layer, poly( N -isopropylacrylamide- co -2-(dimethylamino) ethyl methacrylate), along with a pH-, temperature-, and salt-responsive gel layer, poly(acrylamide- co -2-(dimethylamino)ethyl methacrylate- co -VPES)@DP. Due to the opposite swelling/shrinking behavior between the two layers, the prepared hydrogel exhibits shape changes in response to thermal, salt, and pH stimuli, along with switchable fluorescent color and visible color change that originate from DP and polyVPES, respectively. Apart from multiresponsive behavior, this hydrogel also shows an excellent antifatigue property and high sensitivity, which makes it hold significant potential in many applications. We anticipate that this strategy to realize multiresponsive capability in this work can also inspire the design of the biomimetic smart materials.

Abstract Soft actuators exhibit activeness and flexibility and are widely used as next‐generation intelligent devices. However, their locomotion depends on friction with contact surfaces that restrict their movement. To overcome this limitation, a noncontact‐type multiresponsive soft actuator that levitates in a magnetic field is proposed. This soft actuator can respond to humidity, heat, and diamagnetic repulsion force stimuli, resulting in high degrees of freedom and multiple motions. The soft actuator is fabricated by coating a highly hygroscopic membrane onto a diamagnetic graphite film, which enables the actuator to levitate in the magnetic field. Bending actuation is induced by the swelling mismatch between the two layers via the hygrothermal response. The translational force driven by local concentrated heating of the actuator leads to the realization of high‐speed linear and curvilinear motions. Frictionless rotational motion is also realized remotely with broad heating of an asymmetrically bent soft actuator, generating nonzero torque acting on the floating soft actuator. The proposed levitating soft actuators are applied to a fast and reliable capsule‐delivery gripper and a remotely controllable levitated motor. The soft actuator exhibits the potential to be applied in a wide range of applications, such as soft robotics and smart mechanical devices.

Soft actuators exhibit activeness and flexibility and are widely used as next‐generation intelligent devices. However, their locomotion depends on friction with contact surfaces that restrict their movement. To overcome this limitation, a noncontact‐type multiresponsive soft actuator that levitates in a magnetic field is proposed. This soft actuator can respond to humidity, heat, and diamagnetic repulsion force stimuli, resulting in high degrees of freedom and multiple motions. The soft actuator is fabricated by coating a highly hygroscopic membrane onto a diamagnetic graphite film, which enables the actuator to levitate in the magnetic field. Bending actuation is induced by the swelling mismatch between the two layers via the hygrothermal response. The translational force driven by local concentrated heating of the actuator leads to the realization of high‐speed linear and curvilinear motions. Frictionless rotational motion is also realized remotely with broad heating of an asymmetrically bent soft actuator, generating nonzero torque acting on the floating soft actuator. The proposed levitating soft actuators are applied to a fast and reliable capsule‐delivery gripper and a remotely controllable levitated motor. The soft actuator exhibits the potential to be applied in a wide range of applications, such as soft robotics and smart mechanical devices. [ABSTRACT FROM AUTHOR]

Fabrication strategies for programmed hydrogels that provide precise spatial control with predetermined responses to external stimuli are highly desirable. In this study, a partially reversible light‐driven assembly (PRLDA) method is introduced to construct multiresponsive hydrogels utilizing microgel (MG) particle building blocks (swollen diameter of 107 nm). No other material is required to prepare the gels beyond the MGs themselves. Facile preparation of multiresponsive hydrogels that are reversibly responsive to light, pH, and temperature using phototriggered covalent interlinking of coumarin‐based MGs is demonstrated. The gels have phototuneable moduli and swelling ratios and show light‐assisted healing and reshaping. Remarkably, the intrinsic fluorescence of the gels undergoes a reversible light‐triggered wavelength‐shift. The emission peak blueshifted from 420 to 390 nm upon irradiation with 365 nm light. The PRLDA gels can be constructed using either positive or negative photopatterning. It is shown that the gels can be exploited for multiresponsive cytocompatible actuators, grippers, and ON/OFF circuit components as well as anticounterfeit gels. The PRLDA method provides new insight into programmed gel property control and has excellent potential for biomaterial and optoelectronic applications. [ABSTRACT FROM AUTHOR]

MXene, renowned for its natural "quantum-confined-superfluidic" (QSF) channels, demonstrates superior electrical/thermal conductivity, favorable hydrophilicity, and remarkable mechanical strength, rendering it an ideal candidate for multiresponsive actuators, which are promising for soft electronics and robots. Currently, most MXene-based actuators are mainly prepared by combining an active layer and an inner layer, with only a few utilizing regulated QSF channels. However, tailoring QSF channels for multiresponsive actuators is extremely challenging. Herein, we introduce a multiresponsive graphene oxide (GO)&Fe 3 O 4 /MXene actuator that can respond to humidity, light, heat, electricity, and magnetic fields by constructing asymmetric QSF channels. The asymmetric water adsorption, transportation, and desorption behaviors, controlled by the different QSF channels between the GO&Fe 3 O 4 layer and the MXene layer, enable the multiresponsiveness of the actuator. As proof-of-concept demonstrations, several smart devices, such as a bionic crab-like crawler, a transporting flower robot, and a smart gripper, are prepared, holding great potential for advancing future soft robotics.

The potential to improve mechanical, structural, and mechanochemical properties of charge‐functionalized poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA)‐based hybrid cryogels is investigated. The simple and versatile synthesis of hybrid cryogels with high strength and toughness using cationic DMAEMA and ionic comonomer 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid has been proposed via in situ free‐radical crosslinking (cryo)polymerization by which the properties of virgin polymer can be modulated to required applications by incorporation of inorganic filler kaolin (KLN). Two factors affecting swelling and elasticity of hybrid gels (referred as PDA/KLNm), KLN content and gel preparation temperature, are studied. The optimum KLN concentration for desired swelling and modulus of elasticity is determined as 0.80% (w/v). Effective crosslinking density of hybrid hydrogels increases with KLN addition and this dependence is expressed by a quadratic polynomial as a function of KLN concentration. The results show that obtained hybrid gels with multiresponsive properties could be regarded as "smart materials" in sensing and actuation applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1758–1778 [ABSTRACT FROM AUTHOR]

Increasing interest for the application of polypeptide-based smart systems in the biomedical field has developed due to the advantages given by the peptidic sequence. This is due to characteristics of these systems, which include: biocompatibility, potential control of degradation, capability to provide a rich repertoire of biologically specific interactions, feasibility to self-assemble, possibility to combine different functionalities, and capability to give an environmentally responsive behavior. Recently, applications concerning the development of these systems are receiving greater attention since a targeted and programmable release of drugs (e.g. anti-cancer agents) can be achieved. Block copolymers are discussed due to their capability to render differently assembled architectures. Hybrid systems based on silica nanoparticles are also discussed. In both cases, the selected systems must be able to undergo fast changes in properties like solubility, shape, and dissociation or swelling capabilities. This review is structured in different chapters which explain the most recent advances on smart systems depending on the stimuli to which they are sensitive. Amphiphilic block copolymers based on polyanionic or polycationic peptides are, for example, typically employed for obtaining pH-responsive systems. Elastin-like polypeptides are usually used as thermoresponsive polymers, but performance can be increased by using techniques which utilize layer-by-layer electrostatic self-assembly. This approach offers a great potential to create multilayered systems, including nanocapsules, with different functionality. Recent strategies developed to get redox-, magnetic-, ultrasound-, enzyme-, light- and electric-responsive systems are extensively discussed. Finally, some indications concerning the possibilities of multi-responsive systems are discussed.

Lanthanide organometallic complexes exhibit strong luminescence characteristics, owing to their antenna effects. The f-d energy level transition causes this phenomenon, which occurs when ligands and the external electrons of lanthanide metals coordinate. Based on this phenomenon, we used two lanthanide metals, europium (Eu) and terbium (Tb), in the present study as the metal center for iminodiacetic acid ligands. Further, we developed the resulting fluorescent organometallic complex as a smart material. The ligand-metal bond in the material functioned as a metal chelating agent and a cross-linking agent in a dynamically coordinated form, thereby prompting the material to self-heal. Temperature-sensitive poly- N -isopropylacrylamide was incorporated into the material as the polymer backbone. Afterward, we combined it with water-soluble poly(vinyl alcohol) and an additional ligand from poly(acrylic acid) to fabricate a high-performance hydrogel composite material. The shrinkage and expansion of the polymer form a grid between the materials. Because of the different coordination stabilities of Eu 3+ and Tb 3+ , the corresponding material exhibits environmental responses toward excitation wavelength, temperature, and pH, thus generating different colors. When used in fabrics, the cross-linking mechanism of the material effectively looped the material between fabric fibers; furthermore, the temperature sensitivity of the polymer adjusted the size of pores between fabric fibers. At relatively higher temperatures (>32 °C), the polymer structure shrank, fiber pores expanded, and air permeability improved. Thus, this material appears to be promising for use in smart textiles.

Abstract: 4D printing represents one of the most advanced fabrication techniques for prospective applications in tissue engineering, biomedical devices, and soft robotics, among others. In this study, a novel multiresponsive architecture is developed through stereolithography‐based 4D printing, where a universal concept of stress‐induced shape transformation is applied to achieve the 4D reprogramming. The light‐induced graded internal stress followed by a subsequent solvent‐induced relaxation, driving an autonomous and reversible change of the programmed configuration after printing, is employed and investigated in depth and details. Moreover, the fabricated construct possesses shape memory property, offering a characteristic of multiple shape change. Using this novel multiple responsive 4D technique, a proof‐of‐concept smart nerve guidance conduit is demonstrated on a graphene hybrid 4D construct providing outstanding multifunctional characteristics for nerve regeneration including physical guidance, chemical cues, dynamic self‐entubulation, and seamless integration. By employing this fabrication technique, creating multiresponsive smart architectures, as well as demonstrating application potential, this work paves the way for truly initiation of 4D printing in various high‐value research fields. [ABSTRACT FROM AUTHOR]

Abstract: An “off‐the‐shelf” hydrogel with high‐efficiency shape memory property is designed on the basis of the dynamic borax‐diol chemistry. The system is facilely prepared from only several unmodified commercially available components: acrylamide (AAm), bis‐acrylamide (Bis), poly(vinyl alcohol) (PVA), and borax. The chemically crosslinked poly(acrylamide) network works to fix the permanent shapes of the hydrogel, while the dynamic PVA–borax boronate ester bonds serve as the reversible crosslinks to memorize the deformed temporary shapes. Retreatment of the hydrogel in acid/glucose solutions dissipates the PVA–borax ester bonds to recover its permanent shape. Because of the highly invertible nature of borax‐diol chemistry, the developed hydrogel system is characterized by high shape memory/recovery ratios, continuously adjusted shape memory/recovery rates, thus having a wealth of potential applications. [ABSTRACT FROM AUTHOR]

In the present study, magnetic and thermo/pH-sensitive (multiresponsive) nanocomposites based on N-isopropylacrylamide (NIPAAM) were synthesized and characterized. Nanocomposites were synthesized by free radical emulsion polymerization of NIPAAM as thermosensitive monomer and N,N-dimethyl-aminoethyl methacrylate (DMAEMA) as pH-sensitive monomer in the presence of methylene-bis-acrylamide as cross-linking agent. Doxorubicin, an anti-cancer drug, was loaded into these nanocomposites via equilibrium swelling method. Thermo/pH-sensitive cross-linked poly (NIPAAM–DMAEMA)–Fe3O4nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The volume of the loaded drug and drug release amount was determined by UV measurements. The results showed that this thermo/pH-sensitive magnetic nanocomposite has a high drug-loading efficiency. Doxorubicin was released at 40 °C and pH 5.8 more than the 37 °C and pH 7.4. [ABSTRACT FROM AUTHOR]

In this paper, multiresponsive actuators based on asymmetric design of graphene-conjugated poly(3,4-ethylene dioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) gradient films have been developed by a simple drop casting method. The biomimetic actuation is attributed to the hygroscopic expansion property of PEDOT:PSS and the gradient distribution of graphene sheets within the film, which resembles the hierarchical swelling tissues of some plants in nature. Graphene-conjugated PEDOT:PSS (GCP) actuators exhibit reversible bending behavior under multistimuli such as moisture, organic vapor, electrothermal, and photothermal heating. Noticeably, the bending curvature reaches 2.15 cm -1 under applied voltage as low as 1.5 V owing to the high electrical conductivity of GCP actuator. To mimic the motions of nyctinastic plants, a GCP artificial flower that spreads its petals under sunlight illumination has been fabricated. GCP actuators have been also demonstrated as intelligent light-controlled switches for light-emitting diodes and smart curtains for thermal management. Not only do the GCP gradient films exhibit potential applications in flexible electronics and energy harvesting/storage devices but also the facile fabrication of multiresponsive GCP actuators may shed light on the development of soft robotics, artificial muscles, wearable electronics, and smart sensors.

Advancements in flexible electronics using piezoelectric materials have paved the way for numerous applications. In this study, we suggest a three-dimensional (3D) structured poly(vinylidene fluoride) (PVDF) film cube switch to maximize piezoelectric anisotropy and flexibility. Unlike piezoelectric material-based flexible electronics, PVDF cube switches have a simple design and easy fabrication process. Each side of the cube switch demonstrates independent voltage signals with pressing displacements and corresponding directions. With cutting angle variations and planar figure designs, derived cube switches respond with various combinations of voltage waveforms. PVDF switches can endure more than 1000 cycles of 70% vertical strain in terms of both electrical responses and mechanical operations. As an application, we establish a security system with multiresponsibility of a cube switch. This security system can protect users from potential threats owing to its multiresponsibility and user-dependent operability.

Untethered submillimeter microrobots have significant application prospects in environment monitoring, reconnaissance, and biomedicine. However, they are practically limited to their slow movement. Here, an electrical/optical-actuated microactuator is reported and developed into several untethered ultrafast submillimeter robots. Composed of multilayer nanofilms with exquisitely designed patterns and high surface-to-volume ratios, the microrobot exhibits flexible, precise, and rapid response under voltages and lasers, resulting in controllable and ultrafast inchworm-type movement. The proposed design and microfabrication approach allows various improved and distinctive 3D microrobots simultaneously. The motion speed is highly related to the laser frequency and reaches 2.96 mm/s (3.66 body length/s) on the polished wafer surface. Excellent movement adaptability of the robot is also verified on other rough substrates. Moreover, directional locomotion can be realized simply by the bias of the irradiation of the laser spot, and the maximum angular speed reaches 167.3°/s. Benefiting from the bimorph film structure and symmetrical configuration, the microrobot is able to maintain functionalized after being crashed by a payload 67 000 times heavier than its weight, or at the unexpectedly reversed state. These results provide a strategy for 3D microactuators with precise and rapid response, and microrobots with fast movement for delicate tasks in narrow and restrictive scenarios.

As one of the most promising smart materials, stimuli-responsive polymer hydrogels (SPHs) can reversibly change volume or shape in response to external stimuli. They thus have shown promising applications in many fields. While considerable progress of 2D deformation of SPHs has been achieved, the realization of 3D or even more complex deformation still remains a significant challenge. Here, a general strategy towards designing multiresponsive, macroscopically anisotropic SPHs (MA-SPHs) with the ability of 3D complex deformations is reported. Through a local UV-reduction of graphene oxide sheets (GOs) with a patterned fashion in the GO-poly( N-isopropylacrylamide) (GO-PNIPAM) composite hydrogel sheet, MA-SPHs can be achieved after the introduction of a second poly(methylacrylic acid) network in the unreduced part of GO-PNIPAM hydrogel sheet. The resulting 3D MA-SPHs can provide remote-controllable light-driven, as well as thermo-, pH-, and ionic strength-triggered multiresponsive 3D complex deformations. Approaches in this study may provide new insights in designing and fabricating intelligent soft materials for bioinspired applications. [ABSTRACT FROM AUTHOR]

Recently, actuating materials based on carbon nanotubes or graphene have been widely studied. However, present carbon-based actuating materials are mostly driven by a single stimulus (humidity, light, electricity, etc.), respectively, which means that the application conditions are limited. Here, a new kind of multiresponsive actuating material which can be driven by humidity, light, and electricity is proposed, so it can be used in various conditions. The fabrication is based on the simplest pencil-on-paper method, in which the pencil and paper are both low-cost and easily obtained daily materials. The actuation effect is more remarkable due to a dual-mode actuation mechanism, which leads to an ultralarge actuation (bending curvature up to 2.6 cm−1). Elaborately designed, the actuator can further exhibit a bidirectional bending actuation, which is a significant improvement compared with previous reported thermal actuators. What is more, a colorful biomimetic flower and a smart curtain are also fabricated, fully utilizing the printable characteristic of the paper and multiresponsive characteristic of the actuator. It is assumed that the newly designed actuating material has great potential in the fields of lab-on-paper devices, artificial muscles, robotics, biomimics, and smart household materials. [ABSTRACT FROM AUTHOR]

Increasing interest for the application of polypeptide-based smart systems in the biomedical field has developed due to the advantages given by the peptidic sequence. This is due to characteristics of these systems, which include: biocompatibility, potential control of degradation, capability to provide a rich repertoire of biologically specific interactions, feasibility to self-assemble, possibility to combine different functionalities, and capability to give an environmentally responsive behavior. Recently, applications concerning the development of these systems are receiving greater attention since a targeted and programmable release of drugs (e.g. anti-cancer agents) can be achieved. Block copolymers are discussed due to their capability to render differently assembled architectures. Hybrid systems based on silica nanoparticles are also discussed. In both cases, the selected systems must be able to undergo fast changes in properties like solubility, shape, and dissociation or swelling capabilities. This review is structured in different chapters which explain the most recent advances on smart systems depending on the stimuli to which they are sensitive. Amphiphilic block copolymers based on polyanionic or polycationic peptides are, for example, typically employed for obtaining pH-responsive systems. Elastin-like polypeptides are usually used as thermoresponsive polymers, but performance can be increased by using techniques which utilize layer-by-layer electrostatic self-assembly. This approach offers a great potential to create multilayered systems, including nanocapsules, with different functionality. Recent strategies developed to get redox-, magnetic-, ultrasound-, enzyme-, light- and electric-responsive systems are extensively discussed. Finally, some indications concerning the possibilities of multi-responsive systems are discussed. [ABSTRACT FROM AUTHOR]

A noncovalent bonding method was utilized for forming multiresponsive surface-active ionic liquids in mixed N-alkyl- N-methylpiperidinium bromide (CMDB) and potassium phthalic acid (PPA). Rheology, cryogenic-transmission electron microscopy, dynamic light scattering and nuclear magnetic resonance were used to investigate the aggregation property of surface-active ionic liquids in aqueous solution. The efficiency of the shielding effect in the form of hydrophobic effects and electrostatic attraction between PPA and the CMDB headgroup under diverse pH conditions is found to be the root cause of a shift in the aggregate's morphological transformation. In addition, the molecular motion of surfactant molecules becomes more active as the temperature increase provides the property of thermoresponsive to the surface-active ionic liquid system. [ABSTRACT FROM AUTHOR]

• Multi-responsive hydrophilic molecularly imprinted microspheres (HMIMs) were prepared. • HMIMs show pH/thermo-controlled uptake/release of gardenia yellow and magnetic separation. • SPE process for gardenia yellow from water extract use HMIMs as sorbent was optimized. • Gardenia yellow and geniposide were separated successfully by the developed approach. In this work, a robust method for the separation of gardenia yellow and geniposide from gardenia fruit was developed based on a molecularly imprinted solid phase extraction (MISPE) procedure. First, hydrophilic molecularly imprinted microspheres (HMIMs) were prepared using gardenia yellow as the template via reversible addition fragmentation chain transfer (RAFT) precipitation polymerization. The resultant HMIMs demonstrated the multiresponsiveness to pH, temperature, and magnetism, achieving controllable uptake and release of gardenia yellow and easy recovery by external magnets. Meanwhile, the HMIMs possessed high adsorption capacity, fast binding kinetics, specific recognition, and reusability. Finally, a MISPE approach using HMIMs as adsorbent was developed for extraction of gardenia yellow and purification of geniposide after optimization of the adsorption and elution conditions. Thus, efficient separation of gardenia yellow and geniposide with relative purities of 99.77 ± 0.05% (94.04 ± 0.10% recovered) and 94.50 ± 0.62% (95.40 ± 0.86% recovered), respectively, was achieved. [ABSTRACT FROM AUTHOR]

Highlights: [•] Macromonomers bearing BTP ligand units and UPy motifs are synthesized. [•] Gels are constructed by orthogonal metal–ligand coordination and hydrogen bonding. [•] Gelation is influenced by the length of polymer linker between terminal UPy motifs. [•] Gels exhibit multi-responsive properties. [Copyright &y& Elsevier]

ABSTRACT One-pot synthesis of thermoresponsive magnetic composite microspheres with a poly( N-isopropylacrylamide) (PNIPAM) shell and a Fe3O4 core is demonstrated. Temperature sensitivity of PNIPAM was adopted to design the novel synthesis pathway. The as-prepared composite microspheres have an obvious core-shell structure with a mean size of approximately 250 nm. The Fe3O4 core is approximately 5 nm and the thickness of the PNIPAM shell is approximately 10 nm. The content of Fe3O4 in the composite microspheres can be controlled by this method. The composite microspheres experience a swelling and shrinking process in water by adjusting the temperature below and above the lower critical solution temperature (LCST) around 32 °C. These microspheres also show fine response to an external magnetic field. This work presents a platform to synthesize organic/inorganic composite microspheres in a facile and efficient approach. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2702-2708 [ABSTRACT FROM AUTHOR]

Owing to the distinctive constituents of tumor tissue from those healthy organs, nanomedicine strategies show significant potentials in smart drug delivery. Nowadays, stimuli-responsive nanogels are playing increasingly important roles in the application of cancer therapy because of their sensitivity to various internal or external physicochemical stimuli, which exhibit site-specific and markedly enhanced drug release. Besides, nanogels are promising as drug carriers because of their porous structures, good biocompatibility, large surface area, and excellent capability with drugs. Taking advantage of multiresponsiveness, recent years have witnessed the rapid evolution of stimulus-responsive nanogels from monoresponsive to multiresponsive systems; however, there lacks a comprehensive review summarizing these reports. In this Review, we discuss the properties, synthesis, and characterization of nanogels. Moreover, tumor microenvironment and corresponding designing strategies for stimuli-response nanogels, both exogenous (temperature, magnetic field, light) and endogenous (pH, biomolecular, redox, ROS, pressure, hypoxia) are summarized on the basis of the recent advances in multistimuli-responsive nanogel systems. Nanogel and two-dimensional material composites show excellent performance in the field of constructing multistimulus-responsive nanoparticles and precise intelligent drug release integrated system for multimodal cancer diagnosis and therapy. Finally, potential progresses and suggestions are provided for the further design of hybrid nanogels based on emerging two-dimensional materials.

Multiresponsive Nanoparticles: Multiresponsive Elastic Colloidal Crystals for Reversible Structural Color Patterns (Adv. Funct. In article number 1902954, Cun Zhu, Zhongze Gu, and co-workers synthesize multiresponsive elastic copolymer nanoparticles that are utilized as building blocks for the construction of multiresponsive films. The resultant films can not only control the concealment or exhibition of encrypted color information, but also rapidly respond to external stimuli including solvent, strain, and pH in a reversible manner. [Extracted from the article]

Multiresponsive elastic poly(methyl methacrylate‐butyl acrylate) (P(MMA‐BA)) copolymer nanoparticles with controlled sizes are fabricated through a one‐step method, which further serve as building blocks for the construction of multiresponsive films via self‐assembly. Taking advantage of the relatively low glass transition temperature and the core–shell structure of the copolymer nanoparticles, they possess the capacity to partially deform and fuse at room temperature under dry status, eventually resulting in the enhancement of the mechanical properties as well as the control of optical properties in the assembled ordered structures. The generated elastic films not only can control the concealment or exhibition of the designed color information, but also can rapidly respond to external stimuli such as the solvent, pH, and tensile force in a reversible fashion. These functional elastic copolymer nanoparticles have potential applications in dynamic color display, optical sensing, and anticounterfeiting. [ABSTRACT FROM AUTHOR]

Smart photovoltaic windows (SPWs) are functional devices possessing the capabilities of electrical power output, energy saving, and privacy protection by managing sunlight under external stimuli and potentially applicable in the fields of energy‐saving buildings, automobiles, and switchable optoelectronics. However, long response time, low power conversion efficiency (PCE), poor stability and cycling performance, and monostimuli responsive behavior restrict their practical applications. To address these issues, high‐efficiency and reliable SPWs are demonstrated by coupling multiresponsive liquid crystal/polymer composite (LCPC) films and semi‐transparent perovskite solar cells (ST‐PSCs). In this design, fast and multiple stimuli‐responsive LCPC films are utilized as an inside layer to control the transparency of SPWs. The ST‐PSCs with competitive PCE and qualified transparency acting as an outside layer offer energy generation functionality. Benefiting from repeatable transparency transition modulated by external stimuli, a series of working modes are achieved in the SPWs providing distinguished and stable energy generation, energy saving, and privacy protection performances. [ABSTRACT FROM AUTHOR]

Smart Photovoltaic Windows: High-Efficiency and Reliable Smart Photovoltaic Windows Enabled by Multiresponsive Liquid Crystal Composite Films and Semi-Transparent Perovskite Solar Cells (Adv. Keywords: high-efficiency; liquid crystal composite films; multiresponsive; semi-transparent perovskite solar cells; smart photovoltaic windows High-efficiency, liquid crystal composite films, multiresponsive, semi-transparent perovskite solar cells, smart photovoltaic windows. [Extracted from the article]

Strong rigidity, low thermal conductivity, and short of multi-driven capabilities of form-stable phase change materials (FSPCMs) have limited their practical utilization. Herein, we report a shape-adaptable FSPCM with the coinstantaneous light/electro-driven shape memory properties and light/electro-to-thermal energy storage performance. The FSPCM is fabricated by incorporating the poly(ethylene glycol) (PEG) into the cellulose nanofiber/graphene nanoplatelet (GNP) hybrid-coated melamine foam (CG@MF). The CG@MF/PEG FSPCMs show a good encapsulation effect, enhanced thermal conductivity, and large melting enthalpy (178.9 J g -1 ). Due to the high elasticity of MF and the excellent photothermal conversion and electrical conductivity of the GNP network, the CG@MF/PEG FSPCMs exhibit a remarkable light/electro-driven shape memory effect by activating the phase change process of PEG. Meanwhile, the CG@MF/PEG FSPCMs can effectively convert light or electric energy into heat energy and reposit the converted energy during the phase change process. Furthermore, the CG@MF/PEG FSPCMs possess excellent multiresponsive self-adhesion properties. A light-sensitive, shape-adaptable, and thermal-insulating container is further explored. This study provides routes toward the development of multiresponsive shape-adaptable FSPCMs for energy storage applications.

Nanocomposite hydrogels with multiresponsiveness and self-healing property are attracting extensive interest due to their enhanced performance for a wide range of applications. In this work, we have successfully developed novel hydrogels based on interfacial polymer-nanogel benzoxaborolate cross-linking at physiological pH. Temperature-sensitive nanogels (NG-Gal) containing galactose residues on the nanosurface were prepared and subsequently used as macro-cross-linkers to form a hydrogel network through formation of dynamic adducts with benzoxaborole groups of a hydrophilic copolymer poly(DMA- st -MAABO). Benefiting from the low p K a value of benzoxaborole (∼7.2), hydrogels can be constructed rapidly at physiological pH, which is of great significance for biomedical applications. Changing the molar ratio between benzoxaborole and galactose was found to alter the mechanical properties of hydrogels as confirmed by rheological measurements. The dynamic nature of benzoxaborole esters endowed the hydrogel with moldability and self-healing ability after disruption. Moreover, the hydrogel showed multiresponsiveness toward pH, sugar, adenosine triphosphate (ATP), hydrogen peroxide (H 2 O 2 ), and temperature. Therefore, the novel nanocomposite hydrogel we demonstrated here exhibits great potential for biomedical applications such as tissue engineering and controlled drug delivery.

Dynamic micro-/nanowrinkle patterns with response to multienvironmental stimuli can offer a facile method for on-demand regulation of surface properties, thus allowing for generation of a smart surface. Here a practical yet robust strategy is described to fabricate redox, light and thermal responsive wrinkle by building dynamic double interpenetrating polymer network (IPN) as the top layer for a typical bilayer system. IPNs were constructed through the photochemical reaction of a mixture comprised of light-sensitive anthracene-containing polymer (PAN) and redox-sensitive disulfide-containing diacrylate monomer (DSDA). Thanks to the dynamic covalent reversible C-C bond in PAN and S-S bond in DSDA, the morphology of wrinkled surface not only can be reversibly and precisely (micrometer scale) tailored to all kinds of complicated hierarchical pattern permanently, but also can be controlled temporarily by irradiation of near-infrared light (NIR). A sine wave model is proposed to investigate the dynamics of real-time reversible wrinkle evolution. This general approach based on IPN allows independent multistimuli control over wettability and optical properties on the wrinkled surface, thus, presents a considerable alternative to implement a smart surface.

A phase change material (PCM) essentially making up hexadecyl acrylate-grafted graphene (HDA- g-GN) was fabricated via a solvent-free Diels-Alder (DA) reaction. The novel material exhibits multiresponsive, enhanced thermal and electrical conductivities and valid thermal enthalpy. In addition, the optimum DA reaction conditions were explored. A variety of characterization techniques were used to study the thermal, crystalline, and structural properties of HDA- g-GN. The melting and crystallizing enthalpies of HDA- g-GN were as high as 57 and 55 J/g, respectively. Furthermore, the melting and freezing points of HDA- g-GN were 29.5 and 32.7 °C, respectively. The thermal conductivity of HDA- g-GN reached 3.957 W/(m K), which is well above that of HDA itself and the previously reported PCMs. HDA- g-GN exhibited an excellent electric conductivity of 219 S/m. Compared to HDA, the crystalline activation energy of HDA- g-GN decreased from 397 to 278 kJ/mol (Kissinger model) and 373 to 259 kJ/mol (Ozawa model). Moreover, HDA- g-GN exhibited excellent thermal stability, shape stability, and thermal reliability. More importantly, HDA- g-GN can be employed to realize high-performance light-to-thermal and electron-to-thermal energy conversion and storage, which provides wide application prospects in energy-saving buildings, battery thermal management system, bioimaging, biomedical devices, as well as real-time and time-resolved applications.

Background: Nanoparticle technologies used for human administration must be designed to interact with a living host environment. The idea about bioinspired smart drug delivery carriers includes the development of biocompatible nanomaterials which can be further loaded with the drug for specific targeted drug delivery applications., Objective: Biosmart nanosystems are used for several applications in the delivery of drugs and pharmaceuticals for their therapeutic applications like biological markers, diagnostic purposes such as imaging applications and also for gene therapy. Thus, the bioinspired nanocarriers are capable of carrying biologically active molecules to the target sites. This bioinspired nanosystem constitutes of lipids, polymers and biomaterials which utilizes various responsive sensors for targeted drug delivery systems. However, external conditions such as heat, light, magnetic or electric field and ultrasounds, along with temperature, altered pH and ionic strength can affect the bioinspired smart nanosystem for drug delivery., Conclusion: The present review focuses on challenges for the development of bioinspired smart nanocarriers for the management of various disorders., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

A multiresponsive microcapsule has been synthesized by incorporating photoswitchable spiropyran units and the thermoresponsive monomer N-isopropylacrylamide into membrane lumens. By using functionalized light or thermoresponsive groups, this multifunctional microcapsule can modulate programmed release and interface reactions between lipase and fluorescein diacetate, alkaline phosphatase and fluorescein diphosphate, and others. Exposing this multifunctional microcapsule in a programmed controlled way allowed us to develop schematics to understand complicated interface interactions on protocells.

Designing a smart nanotheranostic system has recently attracted tremendous attention and is highly desirable for realizing targeted cancer therapy and early diagnosis. Herein we report the fabrication of smart nanotheranostic system using multiresponsive gatekeeping protocol of mesoporous silica nanoparticles (MSN). Acid, oxidative stress and redox sensitive manganese oxide (MnO x ) coated superparamagnetic iron oxide nanoparticle (SPION) were employed as nanolids to regulate the camptothecin drug release from the channels of mesoporous silica and achieve responsive dual-mode MRI contrast. The nonvehicle showed high magnetization and T2 contrast in magnetic resonance imaging (MRI) due to the significant density of SPION onto the surface of MSN, and at the same time the MnO x shell degradation release Mn 2+ which enhanced the T1MRI visualization. The efficacy of responsive drug delivery system was investigated on pancreatic cancer cells and tumor-bearing mice, and results reinforced that MnO x -SPION@MSN@CPT nonvehicle is efficacious against cancer cells. We envision that our unique and multiresponsive nanoplatform may find applications in effective delivering of imaging and therapeutic agents to wide range of diseases besides cancer.