We rationally synthesized the thermoplastic and hydrophilic poly(urethane-acrylate) (HPUA) binder for a type of printable and stretchable Ag flakes–HPUA (Ag-HPUA) electrodes in which the conductivity can be enhanced by human sweat. In the presence of human sweat, the synergistic effect of Cl− and lactic acid enables the partial removal of insulating surfactant on silver flakes and facilitates sintering of the exposed silver flakes, thus the resistance of Ag-HPUA electrodes can be notably reduced in both relaxed and stretched state. The on-body data show that the resistance of one electrode has been decreased from 3.02 to 0.62 ohm during the subject’s 27-min sweating activity. A stretchable textile sweat-activated battery using Ag-HPUA electrodes as current collectors and human sweat as the electrolyte was constructed for wearable electronics. The enhanced conductivity of the wearable wiring electrode from the reaction with sweat would provide meritorious insight into the design of wearable devices.

In the era of big data, with the development and application of 5G technology, artificial intelligence technology, and wearable electronics, the acquisition, storage, search, sharing, analysis, and even visual presentation require huge amounts of data in storage and processing at any time. This propounds a strong demand for the stretchable and wearable memory devices with ultrafast switching, high density, and high energy efficiency. Herein, an overview of the advanced progresses made on developing stretchable resistive switching random‐access memory (RRAM) is presented, concentrating on the fundamental components, materials selection principles, and configuration design strategies. The basic electrical and mechanical properties of stretchable components to meet the functionality of memory storage are summarized. Novel materials with the intrinsically stretchable features toward the realization of stretchable RRAM are discussed. Ingenious configuration design strategies to obtain stretchable RRAM are evaluated. Finally, the challenges and perspectives for the practical applications of stretchable RRAM are also addressed. Some helpful guidelines are provided in promoting the development on stretchable and wearable RRAM for making deployable and portable artificial intelligence and smart devices.

Highlights A stable laminated Al 2 O 3 /HfO 2 insulator is developed by atomic layer deposition at a relatively lower temperature of 150 °C. The flexible thin-film transistors (TFTs) with bottom-gate top-contacted configuration are fabricated on a flexible substrate with the Al 2 O 3 /HfO 2 insulator. The flexible TFTs present the carrier mobilities of 9.7 cm 2 V −1 s −1 , ON/OFF ratio of ~ 1.3 × 10 6 , subthreshold voltage of 0.1 V, saturated current up to 0.83 mA, and subthreshold swing of 0.256 V dec −1 . Abstract Flexible thin-film transistors (TFTs) have attracted wide interest in the development of flexible and wearable displays or sensors. However, the conventional high processing temperatures hinder the preparation of stable and reliable dielectric materials on flexible substrates. Here, we develop a stable laminated Al 2 O 3 /HfO 2 insulator by atomic layer deposition at a relatively lower temperature of 150 °C. A sputtered amorphous indium-gallium-zinc oxide (IGZO) with the stoichiometry of In 0.37 Ga 0.20 Zn 0.18 O 0.25 is used as the active channel material. The flexible TFTs with bottom-gate top-contacted configuration are further fabricated on a flexible polyimide substrate with the Al 2 O 3 /HfO 2 nanolaminates. Benefited from the unique structural and compositional configuration in the nanolaminates consisting of amorphous Al 2 O 3 , crystallized HfO 2 , and the aluminate Al–Hf–O phase, the as-prepared TFTs present the carrier mobilities of 9.7 cm 2 V −1 s −1 , ON/OFF ratio of ~ 1.3 × 10 6 , subthreshold voltage of 0.1 V, saturated current up to 0.83 mA, and subthreshold swing of 0.256 V dec −1 , signifying a high-performance flexible TFT, which simultaneously able to withstand the bending radius of 40 mm. The TFTs with nanolaminate insulator possess satisfactory humidity stability and hysteresis behavior in a relative humidity of 60–70%, a temperature of 25–30 °C environment. The yield of IGZO-based TFTs with the nanolaminate insulator reaches 95%. Supplementary Information ...

Magnetically directed localized polymerization is of immense interest for its extensive impacts and applications in numerous fields. The use of means untethered from an external magnetic field to localize initiation of polymerization to develop a curing system is a novel concept, with a sustainable, efficient, and eco-friendly approach and a wide range of potential in both science and engineering. However, the conventional means for the initiation of polymerization cannot define the desirable location of polymerization, which is often exacerbated by the poor temporal control in the curing system. Herein, the copper-immobilized dendrimer-based magnetic iron oxide silica (MNPs-G2@Cu2+) co-nanoinitiators are rationally designed as initiators for redox radical polymerization. The nanoinitiators are magnetically responsive and therefore enable localized polymerization using an external magnetic field. In this work, anaerobic polymerization of an adhesive composed of triethylene glycol dimethacrylate, tert-butyl peroxybenzoate, and MNPs-G2@Cu2+ as the magnetic co-nanoinitiators has been investigated. The use of a magnet locates and promotes redox free radical polymerization through the synergistic functions between peroxide and MNPs-G2@Cu2+ co-nanoinitiators. The mechanical properties of the resulting polymer are considerably reinforced because the MNPs-G2@Cu2+ co-nanoinitiators concurrently play another crucial role as nanofillers. This strategy provides a novel approach for magnetically tunable localized polymerization, which allows new opportunities to govern the formulation of advanced adhesives through polymerization under hazard-free conditions for various promising applications.

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