Systems that are intelligent have the ability to sense their surroundings, analyze, and respond accordingly. In nature, many biological systems are considered intelligent (e.g., humans, animals, and cells). For man‐made systems, artificial intelligence is achieved by massively sophisticated electronic machines (e.g., computers and robots operated by advanced algorithms). On the other hand, freestanding materials (i.e., not tethered to a power supply) are usually passive and static. Hence, herein, the question is asked: can materials be fabricated so that they are intelligent? One promising approach is to use stimuli‐responsive materials; these “smart” materials use the energy supplied by a stimulus available from the surrounding for performing a corresponding action. After decades of research, many interesting stimuli‐responsive materials that can sense and perform smart functions have been developed. Classes of functions discussed include practical functions (e.g., targeting and motion), regulatory functions (e.g., self‐regulation and amplification), and analytical processing functions (e.g., memory and computing). The pathway toward creating truly intelligent materials can involve incorporating a combination of these different types of functions into a single integrated system by using stimuli‐responsive materials as the basic building blocks.

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The Wells-Dawson-derived sandwich-type polyoxometalates (POMs) are a versatile and robust group of compounds with applications in catalysis, 1-5 molecular magnetism, 6,7 and other areas. These compounds (formula [M 4 (H 2 O) 2 (P 2 W 15 O 56 )] n-where M ) Co II , Mn II , Cu II , Zn II , and Fe III ) are isostructural with a central planar tetrameric M 4 unit bound to two trivacant R-[P 2 W 15 O 56 ] 12-units. 8-13 We report here a new type of synthesis which results in a new type of sandwich POM. This complex, H 2 Na 14 [Fe III 2 -(NaOH 2 ) 2 (P 2 W 15 O 56 ) 2 ] (Na1), is a structural isomer of the conventional Wells-Dawson and B-Keggin-derived sandwich POMs. It differs in the way the two R-[P 2 W 15 O 56 ] 12-units are bound to the central unit in a manner analogous to Baker-Figgis (cap rotation) isomers (e.g., R-versus -[XM 12 O 40 ] n-and Rversus -[P 2 W 18 O 62 ] 6-), and it contains only two central d-electron metals. This structurally novel diiron POM, unlike previously reported Fe III -containing sandwiches 1,8,14 and [FePW 11 O 39 ], 15 is an effective catalyst for H 2 O 2 -based epoxidation, exhibiting selectivity and rates that approach the Neumann/Khenkin systems. Reaction of R-[P 2 W 15 O 56 ] 12-with 2.0 equiv of Fe(II) in aqueous NaCl followed by air oxidation produces Na1. 16 The synthesis of 1 requires Fe(II), H 2 O, and Na + . Use of Fe(III) in place of Fe(II) produces only the conventional Wells-Dawson sandwich POM, [(Fe III OH 2 ) 2 (Fe III ) 2 (P 2 W 15 O 56 ) 2 ] 12-(2). If the Fe(II)/R-[P 2 W 15 O 56 ) 2 ] 12-mixture is phase transferred from H 2 O to CH 2 Cl 2 using tetra-n-butylammonium chloride (TBACl) prior to air oxidation, only TBA2 is formed. In the preparation of 1, the new dark green air-sensitive complex, [Fe II 4 (P 2 W 15 O 56 ) 2 ] 16-, forms initially (the Fe/P/W ratios are 2/2/15, and the IR spectrum is virtually identical to that of [Zn II 4 (P 2 W 15 O 56 ) 2 ] 16-). 13 During the O 2 oxidation process, the iron atoms with terminal aqua ligands exchange with the sodium atoms in solution. While 2 is stable over the pH range in which Na1 is prepared (pH 4.5-5), 2 is not observed as an intermediate in the synthesis of 1.The X-ray structure 17 reveals that only two d-electron metals reside in the central unit. The other positions in this central unit are occupied by two weakly bound seven-coordinate Na + ions. 18 Each sodium ion is ligated by three of the oxygens from each of the trivacant R-[P 2 W 15 O 56 ] 12-units and by a weakly bound terminal water molecule. In contrast, four d-block metals (and/or Zn) reside in the central tetrameric unit in all published WellsDawson and B-Keggin-derived sandwich POMs.

Polymers that prevent the generation of static charge by contact electrification can be fabricated by copolymerizing an appropriate proportion of a molecule that has the tendency to charge positively, and a molecule that has the tendency to charge negatively, against a reference material. These non-conductive polymers resist charging by contact or rubbing, and prevent the adhesion of microscopic particles.

Conductive hydrogels are promising multifunctional materials for wearable sensors, but their practical applications require combined properties that are difficult to achieve. Herein, we developed a flexible wearable sensor with double-layer structure based on conductive composite hydrogel, which included the outer layer of silicone elastomer (Ecoflex)/ silica microparticle composite film and the inner layer of P(AAmco-HEMA)-MXene-AgNPs hydrogel. Through covalently crosslinking silicone elastomer on the surface of the hydrogel polymer, we bonded a thin Ecoflex film (100 μm) on the P(AAm-co-HEMA)-MXene-AgNPs hydrogel with robust interface, which can easily adhere to the Ecoflex/SiO 2 microparticle composite film by silicone glue. The Ecoflex/SiO 2 microparticle composite film endows the strain wearable sensor with superhydrophobic function that could maintain the stability under stretching or bending. Moreover, it can effectively resist the interference of water droplets and water flow. The P(AAm-co-HEMA)-MXene-AgNPs hydrogel exhibits outstanding antibacterial activity to inhibit Staphylococcus aureus, Escherichia coli, and even drug-resistant Escherichia coli. In addition, the flexible wearable sensor exhibited good self-adhesive performance by changing the reaction temperature of hydrogel and can adhere strongly onto various materials. The conductive composite hydrogel reported in this work contributes an innovative strategy for the preparation of multifunctional flexible wearable sensor.

Novel chitosan-supported cinchona alkaloids have been developed as heterogeneous catalysts for enantioselective Michael reaction. As-synthesized products as organocatalysts for asymmetric Michael reaction have a high efficiency, providing highly functionalized products (containing adjacent quaternary and tertiary stereocenters) with good stereoselectivity (up to 93% enantiomeric excess) in high yields and recyclability (up to five runs).

Chemical logic gates can be fabricated by synthesizing molecules that have the ability to detect external stimuli (e.g., temperature or pH) and provide logical outputs. It is, however, challenging to fabricate a system that consists of many logic gates using this method: complex molecules can be difficult to synthesize and these logic gates typically cannot be integrated together. Here, we fabricated different types of logic gates by assembling a combination of different types of stimuli-responsive hydrogels that change their size under the influence of one type of stimulus. Importantly, the preparation of these stimuli-responsive hydrogels is widely reported and technically simple. Through designing the geometry of the systems, we fabricated the YES, NOT, OR, AND, NOR, and NAND gates. Although the hydrogels respond to different types of stimuli, their outputs are the same: a change in size of the hydrogel. Hence, we show that the logic gates can be integrated easily (e.g., by connecting an AND gate to an OR gate). In addition, we fabricated a standalone system with the size of a normal drug tablet (i.e., a "smart tablet") that can analyze (or diagnose) different stimuli and control the release of a chemical (or drug) via the logic gates.

A general class of stimuli-responsive grippers and actuators (e.g., temperature- and pH-responsive) with surprisingly high gripping strengths is introduced.