Gallium‐based alloys, which are virtually non‐toxic liquid metals at room temperature, are considered highly promising electrode materials for state‐of‐the‐art electronics with new form factors. Herein, a facile and rapid method to fabricate liquid metal electrodes with highly precise patterns via a one‐step coating is presented. For this work, polymeric stencil masks with dual structures, comprising upper and lower structures for injecting and molding the liquid metal, respectively, are used for direct patterning of the liquid metal via spray deposition for few seconds, enabling the formation of complex and minute patterns including long thin lines and hollow forms. This method can be adapted to 3D substrates of various materials without any surface treatment, owing to the intrinsic adhesive and flexible properties of the polymeric masks ensuring conformal contact with non‐flat surfaces, and is also expected to be applicable to sub‐micron patterns. In addition, a number of highly flexible/stretchable electronic applications, exhibiting no change in electrical conductivity upon consecutive structural deformations, are demonstrated on various substrates including human skin. It is anticipated that these results will not only spur the further development of flexible/stretchable electronics, but also significantly contribute to the innovative on‐site fabrication of wearable electronics with high durability.

We investigated characteristics of highly flexible and stretchable electrodes consisting of Galinstan (i.e., a gallium-based liquid metal alloy) under various conditions including sub-zero temperature (i.e., <0 °C) and demonstrated solar-blind photodetection via the spontaneous oxidation of Galinstan. For this work, a simple and rapid method was introduced to fabricate the Galinstan electrodes with precise patterns and to exfoliate their surface oxide layers. Thin conductive films possessing flexibility and stretchability can be easily prepared on flexible substrates with large areas through compression of a dried suspension of Galinstan microdroplets. Furthermore, a laser marking machine was employed to facilitate patterning of the Galinstan films at a high resolution of 20 μm. The patterned Galinstan films were used as flexible and stretchable electrodes. The electrical conductivity of these electrodes was measured to be ~1.3 × 106 S m−1, which were still electrically conductive even if the stretching ratio increased up to 130% below 0 °C. In addition, the surface oxide (i.e., Ga2O3) layers possessing photo-responsive properties were spontaneously formed on the Galinstan surfaces under ambient conditions, which could be solely exfoliated using elastomeric stamps. By combining Galinstan and its surface oxide layers, solar-blind photodetectors were successfully fabricated on flexible substrates, exhibiting a distinct increase of up to 14.7% in output current under deep ultraviolet irradiation (254 nm wavelength) with an extremely low light intensity of 0.1 mW cm−2, whereas no significant change was observed under visible light irradiation.

Device Miniaturization Intaglio contact printing enables the realization of highly precise carbon nanotube (CNT) network patterns exhibiting multi‐functionalities without restrictions on the substrate. In article number 2106174, Soonmin Seo, Yoon‐Kyu Song, Ju‐Hyung Kim, and co‐workers present this method for the fabrication and miniaturization of high‐performance devices, including flexible fringe‐effect capacitive sensors.

In last few decades, organic materials (or carbon-based materials in a broad sense) including polymers have received much attention for their potential applications in electronics, because they have outstanding advantages such as high processibility, mechanical flexibility, and low weight [...]

The production of energy has become a major issue in today’s world. Triboelectric nanogenerators (TENGs) are promising devices that can harvest mechanical energy and convert it into electrical energy. This study explored the use of Galinstan particles in the production of TENGs, which convert mechanical energy into electrical energy. During the curing process, the evaporation of the hexane solvent resulted in a film with varying concentrations of Galinstan particles. The addition of n-hexane during ultrasonication reduced the viscosity of the polydimethylsiloxane (PDMS) solution, allowing for the liquid metal (LM) particles to be physically pulverized into smaller pieces. The particle size distribution of the film with a Galinstan concentration of 23.08 wt.% was measured to be within a few micrometers through ultrasonic crushing. As the amount of LM particles in the PDMS film increased, the capacitance of the film also increased, with the LM/PDMS film with a 23.08% weight percentage exhibiting the highest capacitance value. TENGs were created using LM/PDMS films with different weight percentages and tested for open-circuit voltage, short-circuit current, and charge amount Q. The TENG with an LM/PDMS film with a 23.08% weight percentage had the highest relative permittivity, resulting in the greatest voltage, current, and charge amount. The use of Galinstan particles in PDMS films has potential applications in wearable devices, sensors, and biomedical fields.