A green, fully recyclable and stretchable electronic sensor based on ionic conductive gelatin organohydrogels can operate at ultra-low temperature.

Underwater adhesion plays an essential role in soft electronics for the underwater interface. Although hydrogel-based electronics are of great interest, because of their versatility, water molecules prevent hydrogels from adhering to substrates, thus bottlenecking further applications. Herein, inspired by the barnacle proteins, MXene/PHMP hydrogels with strong repeatable underwater adhesion are developed through the random copolymerization of 2-phenoxyethyl acrylate, 2-methoxyethyl acrylate, and N-(2-hydroxyethyl) acrylamide with the presence of MXene nanosheets. The hydrogels are mechanically tough (elastic modulus of 32 kPa, fracture stress of 0.11 MPa), and 2-phenoxyethyl acrylate (PEA) with aromatic groups endows the hydrogel with nonswelling property and prevents water molecules from invading the adhesive interface, rendering the hydrogels an outstanding adhesive behavior toward various substrates (including glass, iron, polyethylene terephthalate (PET), porcine). Besides, dynamic physical interactions allow for instant and repeatable underwater adhesion. Furthermore, the MXene/PHMP hydrogels exhibit a high conductivity (0.016 S/m), fast responsiveness, and superior sensitivity as a strain sensor (gauge factor = 7.17 at 200%–500% strain) and pressure sensor (0.63 kPa–1 at 0–70 kPa). The underwater applications of bionic hydrogel-based sensors have been demonstrated, such as human motion, pressure sensing, and holding objects. It is anticipated that the instant and repeatable underwater adhesive hydrogel-based sensors extend the underwater applications of hydrogel electronics.

as electronic skins, [1][2][3] robotics, [4,5] energy storage devices, [6,7] wearable sensors, [8][9][10] and so forth. As one of the important flexible electronic devices, wearable sensors can convert external stimuli (e.g., human motions, [11,12] temperature, [13] and biochemical signals [14] ) into electrical signals (e.g., resistance, [15] voltage, [16] and capacitance changes [17] ). The wearable sensors have drawn progressively increasing attention due to their promising applications in motion detection, [18] health monitoring, [19] remote health management, [20] humanmachine interfaces, [21] etc. Recently, a large amount of strain-sensitive and pressure-sensitive skin-like sensors have been fabricated through embedding conductive components (e.g., metal nanowires, conductive nanomaterials, and conductive polymers) into flexible substrates. However, these wearable sensors show restrict stretchability and poor fatigue resistance, which is a challenge to achieve interface matching while coupling with human skins, resulting in limited sensing ranges (generally low than 200%) and poor sensing stability. [22,23] Therefore, it is necessary to develop flexible wearable sensors with high stretchability and anti-fatigue properties.As a kind of water-rich polymer material, hydrogels have high stretchability, flexibility, suitable modulus, and biocompatibility, rendering them attractive substances for the fabrication of wearable sensors. [24][25][26][27] The outstanding mechanical properties of hydrogels ensure mechanical matching to dynamic surfaces (such as human skin). For instance, Qin et al. prepared a recyclable strain sensor using ionic conductive gelatin organohydrogels with high stretchability (542%) and skin-like modulus (155 kPa). This hydrogel-based sensor exhibited stable sensing performance and a wide sensing range of strains, even at subzero temperatures. [28] Yang et al. developed a highly stretchable and anti-fatigue double-network hydrogel with high sensitivity and broad sensing ranges of strain and pressure. [2] However, hydrogels exhibit tremendous swelling behavior in underwater environments largely due to that water molecules, as hydrogen bond donors/acceptors, bind to most of the hydrogen bond sites and/or metal-ligand sites, thus greatly reducing their binding strength. This swelling behavior can lead to the destruction of sensing ability. In addition, most hydrogels have good biocompatibility and can support the adhesion of proteins and bacteria.Flexible wearable sensors are of interest for underwater applications such as aquatic robots and marine exploration. Non-swelling hydrogels would be a preferable candidate for underwater sensing with stable sensing performance. Herein, hydrogels comprised of MXene and polyhydroxyethyl methacrylate (PHEMA) are designed and manufactured. Owing to the synergistic effect of phase separation zones and hydrophilic/hydrophobic interaction, MXene/ PHEMA hydrogels exhibit non-swelling performance in various liquid media (e.g., water, seawater) and effectively a...

Fully-physically crosslinked hydrogels with strain sensitivity and anti-freezing properties for wireless sensing and low temperature sensing were prepared.

As a new member of the 2D material family, MXene integrates high metallic conductivity and hydrophilic property simultaneously. It shows tremendous potential in fields of energy storage, sensing, electromagnetic shielding, and so forth. Due to the abundant surface functional groups, the physical and chemical properties of MXene can be tuned by the formation of MXene-polymer composites. The introduction of polymers can expand the interlayer spacing, reduce the distance of ion/electron transport, improve the surface hydrophilicity, and thus guide the assembly of MXene-polymer structures. Herein, the preparation strategies of MXene-polymer composites including physical mixing, surface modification, such as anchoring through Ti-N and Ti-O-C bonds, bonding through esterification, grafting functional groups through Ti-O-Si/Ti-O-P bonds, photograft reaction, as well as in situ polymerization are highlighted. In addition, the possible mechanisms for each strategy are explained. Furthermore, the applications of MXene-polymer composites obtained by different preparation strategies are summarized. Finally, perspectives and challenges are presented for the designs of MXene-polymer composites.

No abstract

Prokaryotes possess CRISPR-Cas systems to exclude parasitic predators, such as phages and mobile genetic elements (MGEs). These predators, in turn, encode anti-CRISPR (Acr) proteins to evade the CRISPR-Cas immunity. Recently, AcrVA4, an Acr protein inhibiting the CRISPR-Cas12a system, was shown to diminish Lachnospiraceae bacterium Cas12a (LbCas12a)-mediated genome editing in human cells, but the underlying mechanisms remain elusive. Here we report the cryo-EM structures of AcrVA4 bound to CRISPR RNA (crRNA)-loaded LbCas12a and found AcrVA4 could inhibit LbCas12a at several stages of the CRISPR-Cas working pathway, different from other characterized type I/II Acr inhibitors which target only 1 stage. First, it locks the conformation of the LbCas12a-crRNA complex to prevent target DNA-crRNA hybridization. Second, it interacts with the LbCas12a-crRNA-dsDNA complex to release the bound DNA before cleavage. Third, AcrVA4 binds the postcleavage LbCas12a complex to possibly block enzyme recycling. These findings highlight the multifunctionality of AcrVA4 and provide clues for developing regulatory genome-editing tools.

To improve the therapeutic effect of hydrogel for damaged tissue, a series of hydroxybutyl chitosan (HBC) and poly (sulfobetaine methacrylate) (PSBMA) composite hydrogels (HBC-PSB) with thermosensitivity, self-healing, antibiofouling, and synergistic...