Self-Powered Multifunctional Organic Hydrogel Based on Poly(acrylic acid‑<i>N</i>‑isopropylacrylamide) for Flexible Sensing Devices

Human–machine interactions, medical monitoring, and flexible robots stimulate interest in hydrogel sensing devices. However, developing hydrogel sensors with multifunctions such as good mechanics, electroconductivity, resistance to solvent volatility as well as freezing, self-adhesion, and independence on external power supply remains a challenge. In the work, a poly(acrylic acid-N-isopropylacrylamide) P(AA-NIPAm) organic hydrogel loading LiCl is prepared by ultraviolet cross-linking in ethylene glycol/H2O. The organic hydrogel exhibits favorable mechanical properties such as an elongation of break at 700% and a breaking strength of 20 KPa, can adhere to various substrates, and resists frost and solvent volatility. Especially, it possesses an excellent conductivity of 8.51 S/m. The organic hydrogel shows wide strain sensitivity based on resistance change, and the gauge factor reaches 5.84 in the range of 300–700%. It has short responsive and recuperative time and is still stable within 1000 rounds. Moreover, the organic hydrogel is also assembled into a self-powered device in which the open-circuit voltage is 0.74 V. The device can transform external stimuli such as stretching or compressing into the output current change, so it detects human motion effectively in real time. The work provides a perspective for electrical sensing engineering

Self-Powered Multifunctional Organic Hydrogel Based on Poly(acrylic acid‑<i>N</i>‑isopropylacrylamide) for Flexible Sensing Devices

Human–machine interactions, medical monitoring, and flexible robots stimulate interest in hydrogel sensing devices. However, developing hydrogel sensors with multifunctions such as good mechanics, electroconductivity, resistance to solvent volatility as well as freezing, self-adhesion, and independence on external power supply remains a challenge. In the work, a poly(acrylic acid-N-isopropylacrylamide) P(AA-NIPAm) organic hydrogel loading LiCl is prepared by ultraviolet cross-linking in ethylene glycol/H2O. The organic hydrogel exhibits favorable mechanical properties such as an elongation of break at 700% and a breaking strength of 20 KPa, can adhere to various substrates, and resists frost and solvent volatility. Especially, it possesses an excellent conductivity of 8.51 S/m. The organic hydrogel shows wide strain sensitivity based on resistance change, and the gauge factor reaches 5.84 in the range of 300–700%. It has short responsive and recuperative time and is still stable within 1000 rounds. Moreover, the organic hydrogel is also assembled into a self-powered device in which the open-circuit voltage is 0.74 V. The device can transform external stimuli such as stretching or compressing into the output current change, so it detects human motion effectively in real time. The work provides a perspective for electrical sensing engineering

Self-Powered Multifunctional Organic Hydrogel Based on Poly(acrylic acid‑<i>N</i>‑isopropylacrylamide) for Flexible Sensing Devices

Human–machine interactions, medical monitoring, and flexible robots stimulate interest in hydrogel sensing devices. However, developing hydrogel sensors with multifunctions such as good mechanics, electroconductivity, resistance to solvent volatility as well as freezing, self-adhesion, and independence on external power supply remains a challenge. In the work, a poly(acrylic acid-N-isopropylacrylamide) P(AA-NIPAm) organic hydrogel loading LiCl is prepared by ultraviolet cross-linking in ethylene glycol/H2O. The organic hydrogel exhibits favorable mechanical properties such as an elongation of break at 700% and a breaking strength of 20 KPa, can adhere to various substrates, and resists frost and solvent volatility. Especially, it possesses an excellent conductivity of 8.51 S/m. The organic hydrogel shows wide strain sensitivity based on resistance change, and the gauge factor reaches 5.84 in the range of 300–700%. It has short responsive and recuperative time and is still stable within 1000 rounds. Moreover, the organic hydrogel is also assembled into a self-powered device in which the open-circuit voltage is 0.74 V. The device can transform external stimuli such as stretching or compressing into the output current change, so it detects human motion effectively in real time. The work provides a perspective for electrical sensing engineering

Artificial Peroxidase/Oxidase Multiple Enzyme System Based on Supramolecular Hydrogel and Its Application as a Biocatalyst for Cascade Reactions

Inspired by delicate structures and multiple functions of natural multiple enzyme architectures such as peroxisomes, we constructed an artificial multiple enzyme system by coencapsulation of glucose oxidases (GOx) and artificial peroxidases in a supramolecular hydrogel. The artificial peroxidase was a functional complex micelle, which was prepared by the self-assembly of diblock copolymer and hemin. Compared with catalase or horseradish peroxidase (HRP), the functional micelle exhibited comparable activity and better stability, which provided more advantages in constructing a multienzyme with a proper oxidase. The hydrogel containing the two catalytic centers was further used as a catalyst for green oxidation of glucose, which was a typical cascade reaction. Glucose was oxidized by oxygen (O₂) via the GOx-mediated reaction, producing toxic intermediate hydrogen peroxide (H₂O₂). The produced H₂O₂ further oxidized peroxidase substrates catalyzed by hemin-micelles. By regulating the diffusion modes of the enzymes and substrates, the artificial multienzyme based on hydrogel could successfully activate the cascade reaction, which the soluble enzyme mixture could not achieve. The hydrogel, just like a protective covering, protected oxidases and micelles from inactivation via toxic intermediates and environmental changes. The artificial multienzyme could efficiently achieve the oxidation task along with effectively eliminating the toxic intermediates. In this way, this system possesses great potentials for glucose detection and green oxidation of a series of substrates related to biological processes

Furfural-Based Polyamides with Tunable Fluorescence Properties via Ugi Multicomponent Polymerization

Polyamides (PAs) are regarded as attractive fluorescent polymer materials due to their nontraditional intrinsic luminescence. In this work, a series of photoluminescence active PAs were prepared from renewable furfural derivatives via the Ugi four-component polymerization. Moreover, the fluorescence of dilute PA solutions can be accurately controlled by the intramolecular hydrogen bonding interactions using the furfural module as a switch, which was finally confirmed by DFT theory. As a probe, PAs can selectively recognize Fe2+ and Fe3+ among various metal ions by the fluorescence quenching effect. This protocol provides an efficient and moderate strategy for synthesizing biobased functional polymer materials with fluorescence properties, demonstrating high synthetic efficiency and high selectivity to Fe2+ and Fe3+

Hemin-Block Copolymer Micelle as an Artificial Peroxidase and Its Applications in Chromogenic Detection and Biocatalysis

Following an inspiration from the fine structure of natural peroxidases, such as horseradish peroxidase (HRP), an artificial peroxidase was constructed through the self-assembly of diblock copolymers and hemin, which formed a functional micelle with peroxidase-like activity. The pyridine moiety in block copolymer poly­(ethylene glycol)-<i>block</i>-poly­(4-vinylpyridine) (PEG-<i>b</i>-P4VP) can coordinate with hemin, and thus hemin is present in a five-coordinate complex with an open site for binding substrates, which mimics the microenvironment of heme in natural peroxidases. The amphiphilic core–shell structure of the micelle and the coordination interaction of the polymer to the hemin inhibit the formation of hemin μ-oxo dimers, and thereby enhance the stability of hemin in the water phase. Hemin-micelles exhibited excellent catalytic performance in the oxidation of phenolic and azo compounds by H₂O₂. In comparison with natural peroxidases, hemin-micelles have higher catalytic activity and better stability over wide temperature and pH ranges. Hemin-micelles can be used as a detection system for H₂O₂ with chromogenic substrates, and they anticipate the possibility of constructing new biocatalysts tailored to specific functions