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There is growing demand for multiresponsive soft actuators for the realization of natural, safe, and complex motions in robotic interactions. In particular, soft actuators simultaneously stimulated by electrical and magnetic fields are always under development owing to their simple controllability and reliability during operation. Herein, magnetically and electrically driven dual-responsive soft actuators (MESAs) derived from novel nickel-based metal–organic frameworks (Ni-MOFs-700C), are reported. Nanoscale Ni-MOFs-700C has excellent electrochemical and magnetic properties that allow it to be used as a multifunctional material under both magnetoactive and electro-ionic actuations. The dual-responsive MESA exhibits a bending displacement of 30 mm and an ultrafast rising time of 1.5 s under a very low input voltage of 1 V and also exerts a bending deflection of 12.5 mm at 50 mT under a high excitation frequency of 5 Hz. By utilizing a dual-responsive MESA, the hovering motion of a hummingbird robot is demonstrated under magnetic and electrical stimuli.

The application of biodegradable and biocompatible materials to triboelectric nanogenerators (TENGs) for harvesting energy from motions of the human body has been attracting significant research interest. Herein, we report diatom bio-silica as a biomaterial additive to enhance the output performance of cellulose nanofibril (CNF)-based TENGs. Diatom frustules (DFs), which are tribopositive bio-silica having hierarchically porous three-dimensional structures and high surface area, have hydrogen bonds with CNFs, resulting in enhanced electron-donating capability and a more roughened surface of the DF-CNF composite film. Hence, DFs were applied to form a tribopositive composite film with CNFs. The DF-CNF biocomposite film is mechanically strong, electron-rich, low-cost, and frictionally rough. The DF-CNF TENG showed an output voltage of 388 V and time-averaged power of 85.5 mW/m2 in the contact-separation mode with an efficient contact area of 4.9 cm2, and the generated power was sufficient for instantaneous illumination of 102 light-emitting diodes. In addition, a cytotoxicity study and biocompatibility tests on rabbit skin suggested that the DF-CNF composite was biologically safe. Moreover, a practical application of the DF-CNF TENG was examined with a self-powered smart mask for human breathing monitoring. This study not only suggests high output performance of biomaterial-based TENGs but also presents the diverse advantages of the DFs in human body-related applications such as self-powered health monitoring masks, skin-attachable power generators, and tactile feedback systems.

In the field of bioinspired soft robotics, to accomplish sophisticated tasks in human fingers, electroactive artificial muscles are under development. However, most existing actuators show a lack of high bending displacement and irregular response characteristics under low input voltages. Here, based on metal free covalent triazine frameworks (CTFs), we report an electro-ionic soft actuator that shows high bending deformation under ultralow input voltages that can be implemented as a soft robotic touch finger on fragile displays. The as-synthesized CTFs, derived from a polymer of intrinsic microporosity (PIM-1), were combined with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) to make a flexible electrode for a high-performance electro-ionic soft actuator. The proposed soft touch finger showed high peak-to-peak displacement of 17.0 mm under ultralow square voltage of ±0.5 V, with 0.1 Hz frequency and 4 times reduced phase delay in harmonic response compared with that of a pure PEDOT-PSS-based actuator. The significant actuation performance is mainly due to the unique physical and chemical configurations of CTFs electrode with highly porous and electrically conjugated networks. On a fragile display, the developed soft robotic touch finger array was successfully used to perform soft touching, similar to that of a real human finger; device was used to accomplish a precise task, playing electronic piano., Actuators often show a lack of high bending displacement with back relaxation and irregular response characteristics under low input voltages. Here, the authors demonstrate a covalent triazine framework-based electroionic soft actuator that shows controllable high bending deformation under low input voltages.

Triboelectric nanogenerators (TENGs) can be utilized as power sources of wearable devices because of flexibility, light weight and cost effective devices. However, materials utilized in the wearable devices should be carefully selected to avoid side effects to the human body. In this work, we developed a chitosan-diatom (CD) composite film for triboelectric nanogenerators(TENGs) and fabricated a skin-attachable motion sensor. The CD film was composed of the chitosan and diatom silica. All of materials are biomaterials which cannot cause side effects. The biocompatible diatom silica embedded in the chitosan film enhanced the positive charge density of the chitosan film. The CD film was assembled with the fluorinated ethylene propylene (FEP) film for a contact and separation TENG. The maximum instantaneous power density was 468 mW/m2, which was 3.5 times higher than the chitosan film. Furthermore, the skin-attachable motion sensor was developed base on the CD TENG. We believe this work can provide the simple and safe way to increase the performance of biocompatible TENGs for wearable devices.

Electroactive artificial muscles has drawn special attention for potential engineering applications, such as biomedical active devices, haptic-feedback systems, wearable soft electronics, and soft micro-robotics. However in the field of bioinspired soft robotics, to accomplish sophisticated tasks as human fingers, electroactive artificial muscles are under development. Because, most of the exiting soft actuators show lack of high bending displacements with irregular response characteristics under low input voltages due to instabilities of active electrode materials under operation. This situation necessitates for the development of totally brand new functional electrode materials with enormous stability under prolonged electro-chemical exposures. The developed electrode materials based on pre-designed functional covalent organic frameworks and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) show promising actuation characteristics under low electric stimuli towards real-field soft robotics. The proposed artificial muscles can readily be operated on fragile display to make a soft touch similar to real human finger and can successfully accomplishes precise sophisticated tasks such as controlling personal folders and swiping pages of online books, and playing music apps.

Thin oxide coatings are attractive both for research and application as they possess good thermal and electrical resistance properties. In the recent time these coatings are commercially exploited because of good oxidation, wear, erosion resistance than metals even in high-temperature environments. Incorporation of different ceramic particles in organic coating is well studied and even commercialized as it incorporates the advantages of both inorganic and organic coating. Even nanosized silica was reported to be an alternative to chromate conversion coating. There are different techniques used to have ceramic coating on different surfaces including sol–gel, thermal spray, slurry, chemical vapor deposition, etc. Use of nano-SiO2 and TiO2-based coatings for superhydrophilicity and self-cleaning properties were also studied in recent years. Light-mediated antifungal and antibacterial properties of semiconductor oxides namely TiO2, ZnO also attracted the attention of researchers. In particular sol–gel based oxide (Al2O3, TiO2, ZrO2, and SiO2) coatings are of interest to develop different functional protective properties. Sol–gel-based coating attracted much attention in recent years as it can be used to formulate self-healing coating thus increasing the life of the material. In general sol–gel coating can have thickness from nanometer to micron level with high corrosion and erosion resistance. With this technique one can create transparent layer thus preserving the luster and aesthetic of the material with high corrosion protection. Hydrophobicity and self-cleaning properties are added advantages to corrosion protection and hence quite useful for outdoor applications like buildings, infrastructures, and solar cell. Sometime mixed oxide ceramic coatings serve much better than the single oxide coating. Inhibitor loaded oxide container-based self-healing coating inspired by the nature also discussed because of growing number of articles in this subject. Due to the growing interest in this subject area this chapter is compiled focusing on the oxide-based coatings in the specific light of corrosion protection, hydrophobic, superhydrophilic, and self-cleaning properties.

Pyrazole‐linked covalent organic polymer is synthesized using an asynchronous double Schiff base from readily available monomers. The one‐pot reaction features no metals as a building block or reagent, hence facilitating the structural purity and industrial scalability of the design. Through a single‐crystal study on a model compound, the double Schiff base formation is found to follow syn addition, a kinetically favored product, suggesting that reactivity of the amine and carbonyls dictate the order and geometry of the framework building. The highly porous pyrazole polymer COP‐214 is chemically resistant in reactive conditions for over two weeks and thermally stable up to 425 °C in air. COP‐214 shows well‐pronounced gas capture and selectivities, and a high CO2/N2 selectivity of 102. The strongly coordinating pyrazole sites show rapid uptake and quantitative selectivity of Pd (II) over several coordinating metals (especially Pt (II)) at all pH points that are tested, a remarkably rare feature that is best explained by detailed analysis as the size‐selective strong coordination of Pd onto pyrazoles. Density functional theory (DFT) calculations show energetically favorable Pd binding between the metal and N‐sites of COP‐214. The polymer is reusable multiple times without loss of activity, providing great incentives for an industrial prospect., One step, consequential imine linking produced the first pyrazole network polymers with an unusual selectivity for the syn addition. Proven by single‐crystal studies, a kinetic controlled product provides tailor‐made pockets for rapid, pH independent, reversible Pd binding and an exceptional selectivity over other strongly coordinating precious metals like platinum.

Herein, we report a straigthforward procedure to prepare an excellent intertwined nanosponge solid-state polymer electrolyte (INSPE) for highly bendable, rollable, and foldable lithium-ion batteries (LIBs). The mechanically reliable and electrochemically superior INSPE is conjugated with intertwined nanosponge (IN) poly(vinylidene fluoride

Electro-active ionic polymer actuators are an attractive type of soft actuators that bend due to the ion migration in the polymer electrolyte membrane under the electrical field. However, further explorations are required to enhance their performance, which, in turn, demands for strong and flexible polymer electrolytes with continuous conducting phases, facilitating ion movement. Here, we report a facile methodology to generate continuous ion-conducting channels in polymer electrolytes using two-phase evaporation technique. Immersing the corresponding porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) membrane into an ionic liquid converted it into an electrolyte membrane with continuous conducting phases. In such electrolyte membrane, while the PVDF-co-HFP skeletal frame provided high mechanical strength and flexibility, the continuous conducting phases facilitated the ion movement. This enhanced actuation performance. The prepared actuator showed 1.5 times higher performance in comparison with those made of conventional PVDF-co-HFP electrolyte membranes. The as-prepared actuator exhibited a large tip displacement of 25 mm at low voltage of 0.5 V and 0.1 Hz, fast rise time of 2.5 s without back relaxation, good stability with retrieving of 95% of the original performance after 20,000 actuation cycles. This high performance actuator could potentially be used in future technologies such as soft robotics and healthcare devices.

Emerging technologies such as soft robotics, active biomedical devices, wearable electronics, haptic feedback systems, and healthcare systems require high‐fidelity soft actuators showing reliable responses under multi‐stimuli. In this study, the authors report an electro‐active and photo‐active soft actuator based on a vanadium oxide nanowire (VONW) hybrid film with greatly improved actuation performances. The VONWs directly grown on a cellulose fiber network increase the surface area up to 30‐fold and boost the hydrophilicity owing to the presence of oxygen‐rich functional groups in the nanowire surfaces. Taking advantage of the high surface area and hydrophilicity of VONWs, a soft thermo‐hygroscopic VONW actuator capable of being controlled by both light and electric sources shows greatly enhanced actuation deformation by almost 70% and increased actuation speed over 3 times during natural convection cooling. Most importantly, the proposed VONW actuator exhibits a remarkably improved blocking force of up to 200% compared with a bare paper actuator under light stimulation, allowing them to realize a complex kirigami pop‐up and to accomplish repeatable shape transformation from a 2D planar surface to a 3D configuration., An electro‐active and photo‐active soft actuator based on a vanadium oxide nanowire (VONW) hybrid film is developed with greatly improved actuation performances. The VONWs directly grown on a cellulose fiber network increase the surface area up to 30‐fold and boost the hydrophilicity owing to the presence of oxygen‐rich functional groups in the nanowire surfaces, resulting in superior thermo‐hygroscopic soft actuation.

Here, inspired by mechanoreceptors in the human body, a self‐sensing ionic soft actuator is developed that precisely senses the bending motions during actuating utilizing a 3D graphene mesh electrode. The graphene mesh electrode has the permeability of mobile ions inside the ionic exchangeable polymer and shows low electrical resistance of 6.25 Ω Sq−1, maintaining high electrical conductivity in large bending deformations of 180°. In this sensing system, the graphene woven mesh is embedded inside ionic polymer membrane to interact with mobile ions and to trace their movements. The migration of mobile ions inside the membrane induces an electrical signal on the mesh and provides the information regarding ion distribution, which is proven to be highly correlated with the bending deformation of the actuator. Using this integrated self‐sensing system, the responses of an ionic actuator to various input stimulations are precisely estimated for both direct current and alternating current inputs. Even though the generated displacement is extremely small around 300 µm at very low driving voltage of 0.1 V, high level accuracy (96%) of estimated deformations could be achieved using the self‐sensing actuator system., A graphene mesh electrode having high ion permeability and electrical conductivity is adopted as a self‐sensing ionic soft actuator inspired by mechanoreceptors in the human body. The graphene mesh electrode provides electrical signals sensitive to ion migration inside the polymer electrolyte without blocking their movements and is used to predict the bending deflection of the actuator.

Conductive polymers in the form of pellet and coating on a suitable substrate have been extensively used in recent years as sensor materials for the vapor phase sensing of aliphatic alcohols. But due to lack of mechanical stability and reversible adsorption/desorption of alcohol molecules the use of conducting polymers in the above forms suffers from limited repeatability of sensing response. Here, we have developed some mechanically stable free standing doped polyaniline-poly (vinyl alcohol) (PVA-PANI) composite membranes as efficient materials for sensing of aliphatic alcohols in vapor phase. Camphor sulphonic acid (CSA), L-aspartic acid (ASP) and p -toluene sulphonic acid (PTSA) were used as dopants at the time of synthesis of polyaniline in presence of sodium dodecyl sulfate (SDS) by oxidative polymerization of aniline using 1 (M) ferric chloride solution at 0 °C under nitrogen atmosphere. Membranes of thickness 0.15–0.18 mm were prepared with PVA in dimethyl sulphoxide (DMSO) by solution casting. Doped polymer membranes were spectroscopically characterized. It has been observed that dopant has significant effect on the formation of polyaniline morphology in presence of SDS as seen in SEM images. Conductivities of doped membranes, viz., CSA-PANI-PVA, PTSA-PANI-PVA and ASP-PANI-PVA, are 9.30 × 10 −3 , 3.86 × 10 −4 and 4.83 × 10 −4 S/cm respectively. Membranes have shown good sensing responses and repeatability of response patterns towards aliphatic alcohols with lower response time.

Skin-attachable wearable devices including triboelectric nanogerators (TENGs) and self-powered sensors will have biofriendly and biocompatible issues, because they can directly interact with the human body. Based on the diatom frustule and chitosan, known as biocompatible ocean biomaterials, we developed a chitosan-diatom TENG for biofriendly and skin-attachable wearable devices. The highly porous diatom frustule, which is naturally abundant and mass-producible from mega-scale ocean environments, can be used as a biocompatible additive to greatly change electro-positivity and surface properties of chitosan films, showing bio-affinity and much higher output power. The time averaged power density of the chitosan-diatom triboelectric nanogenerator is measured as 15.7 mW/m2, which is 3.7 times higher than that of the pure chitosan TENG. For practical applications, the electrode-encapsulated chitosan-diatom film is successfully applied for a self-powered watch and a skin-attachable motion sensor. We believe that the diatom bio-silica can be used to make a synergy with other biomaterials for achieving the high power of TENGs for the skin-attachable wearable devices.

In article number https://doi.org/10.1002/advs.201901711, Il‐Kwon Oh and co‐workers propose a new sensing mechanism for measuring the actuation displacement of ionic actuators using a graphene mesh. Inspired by the mechanoreceptor in the human body, a graphene mesh is embedded inside the actuator membrane to record the change of electrical potential due to ion movement during actuation. This signal is then correlated with the movement of the actuator which also caused by ion migration inside the membrane.

Graphical abstract: Cerium doped titania having optimum 5 wt% of cerium can decompose methylene blue and reduce selenium (IV) efficiently under visible light. Highlights: Black-Right-Pointing-Pointer Effect of cerium doping on the surface properties and visible light mediated photocatalytic reaction is studied. Black-Right-Pointing-Pointer Cerium doping increases the anatase phase stability, surface area (up to 137 m{sup 2}/g) and visible light absorption. Black-Right-Pointing-Pointer Importance of Ce{sup 3+}/Ce{sup 4+}, oxygen vacancy, surface area and crystallinity is correlated with improved catalytic activity. Black-Right-Pointing-Pointer Material with 5 wt% Ce is found to be most active photocatalyst for methylene blue decomposition and Se (IV) reduction. -- Abstract: Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N{sub 2} adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 Degree-Sign C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 Degree-Sign C shows better activity than that calcined at 400more » Degree-Sign C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce{sup 4+}/Ce{sup 3+} rather than only visible light absorption.« less

Novel polymer membranes, viz., hexadecyl trimethyl ammonium chloride (HDTC) modified poly (vinyl alcohol) (PVA)-poly (acrylic acid) (PAA), PVA-co-ethylene (EVOH), crosslinked and phosphorylated PVA with active ionic functional sites have been developed for sensing of five basic tastes, viz., sourness, saltiness, bitterness, sweetness, etc. as well as of tea and mineral water with good stability and reproducibility.

Tea is one of the most widely consumed beverages all over the world due to its delicate taste. It is, therefore, essential to establish a simple and reliable analytical tool for determination (or, discrimination) of tea quality. We have taken an attempt to discriminate the black tea of different qualities/grades by means of polymer membrane electrode based potentiometric taste sensor. Different types of phosphorylated and crosslinked polymer membranes were used to discriminate different grades of black tea by measuring the tastes in terms of membrane potential.

There are reports of taste sensor fabrication by incorporating lipids in PVC matrix. We have taken an attempt to prepare taste sensor material by using functionalized polymer. Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) have been modified to fabricate the sensor material. The research work covers polymer membrane preparation, morphology study, and structural characterization of membrane and study of the taste sensing characteristics. The membrane was prepared by cross-linking polyvinyl alcohol and polyacrylic acid in aqueous-organic medium by using hexadecyltrimethylammonium chloride (HDTC) with proper heat treatment. The cross-linked PVA-PAA was phosphorylated with POCl 3• PVA-PAA membranes of suitable thickness were thus prepared with good threshold sensing value and less swelling in water. FTIR spectroscopic analysis, XRD analysis and optical microscopy were done to get an idea about the structure and morphology of the polymer membrane. Sensor device prepared with this membrane has shown distinct response patterns for different taste substances in terms of membrane potential. The sensor characteristics like temporal stability, response stability, response to different taste substances, and reproducibility of sensing performance were studied. Membranes also showed characteristic response patterns for organic acids like acetic acid, citric acid, formic acid, etc., mineral acids like HCI, H 2 S0 4 and HN0 3 , etc., salt, bitter substance, sweet substance, umami substance and different grades of tea. Sensor device prepared with this membrane has excellent shelf life.

Functionalized polymer membrane based potentiometric taste sensors with efficient selectivity and sensitivity was developed to mimic the mammalian tongue for measurement of basic tastes like saltiness, sourness, bitterness, sweetness and umami or savory. It may solve the real-world analytical problems arising out of inspection judgment of human sensory organ in wide area of application ranging from foodstuff recognition to environmental monitoring and pharmaceutical application. The membrane was developed using poly (vinyl alcohol) as base polymers (containing -OH as active group); glutaraldehyde (as cross linking reagent); POCl 3 (for functionalization as phosphorylation). The investigation covers polymer membrane preparation, its characterization and study of taste sensing characteristics like temporal stability, response stability, response to different taste substances, and reproducibility of sensing performance. Membrane electrode based on the polymer showed distinct response patterns in terms of electric potentials for different taste substances and their sensing ability of basic tastes is highlighted in this work.

This manuscript deals with the increased and selective nitrate reduction under visible light over a WN co-doped titania photocatalyst. A series of WN co-doped titania nanomaterials were synthesized with varying tungsten content and were characterized by TEM, XRD, UV-vis and nitrogen adsorption–desorption studies. Tungsten doped materials are found to be noodle shaped and mesoporous with a stable anatase phase after 500 °C calcination. Peak shifting in the XRD pattern indicates the tungsten doping in the crystal lattice. Visible light absorption increases with the increasing tungsten amount. Among the studied hole scavengers, formic acid was found to be the best for nitrate reduction with more than 94% nitrogen gas selectivity. The amount of hole scavenger also controls the reaction efficiency and product selectivity. Both nitrate reduction and nitrogen gas selectivity increases with WN co-doping in comparison to only N doped titania. High nitrate reduction with formic acid is attributed to the formation of CO2˙− species having high reduction potential. The material with 2% tungsten shows the highest surface area and the best photocatalytic activity under visible light. Presence of anion like chloride increases the nitrate photoreduction. Overall high nitrate reduction can be attributed to the synergistic effect of tungsten and nitrogen co-doping, optimum surface hydroxyl group, mesoporosity and appreciable visible light absorption of the materials.