Materials with a temperature‐controlled reversible electrical transition between insulator and conductor are attracting huge attention due to their promising applications in many fields. However, most of them are intrinsically rigid and require complicated fabrication processes. Here, a highly stretchable (680% strain) liquid metal polymer composite as a reversible transitional insulator and conductor (TIC), which is accompanied with huge resistivity changes (more than 4 × 109 times) reversibly through a tuning temperature in a few seconds is introduced. When frozen, the insulated TIC becomes conductive and recovers after warming. Both the phase change of the liquid metal droplets and the rigidity change of the polymer contribute directly to transition between insulator and conductor. A simplified model is established to predict the expansion and connection of liquid metal droplets. Along with high stretchability, straightforward fabrication methods, rapid triggering time, large switching ratio, good repeatability, the TIC offers tremendous possibilities for numerous applications, like stretchable switches, semiconductors, temperature sensors, and resistive random‐access memory. Accordingly, a system that can display numbers and letters via converting alternative TIC temperature to a binary signal on a computer is conceived and demonstrated. The present discovery suggests a general strategy for fabricating and stimulating a stretchable transitional insulator and conductor based on liquid metal and allied polymers.

wireless power transfer, [6] stretchable electromagnetic actuator, [7] and stretchable loudspeaker. [8] To date, various fabrication techniques have been applied to pattern the liquid metals on flexible substrates, such as microchannel injection, [9] atomized spraying deposition, [10] imprinting, [11] microcontact printing, [12] direct writing, [13] masked deposition, [14] direct laser patterning, [15] Cu transfer-printing, [16] phase transition dual-trans printing, [17] and liquid metal droplet printing. [18][19][20] Although the currently available current printing techniques can achieve good control to some extent, it is worth noting that the printed substrates are usually limited to polymer-based materials because of the extremely large surface tension of EGaIn. With the explosive research and application of liquid metal electronics, developing a universal printing method to resolve the challenging tough wettability issues was put to an ever higher level from both academic aspect and industrial demand.To improve the wettability and adhesion between LMs and substrate, one strategy is to develop functional LM materials. For example, Tang et al. introduced liquid metal alloys with Cu particles to significantly enhance its electroconductivity and adhesion for directly writing soft electronics on papers and polyvinyl chloride (PVC) substrates. [21] Chang et al. developed GaIn-Ni amalgams to improve affinity of LMs with various substrates, such as paper, polydimethylsiloxane (PDMS), and polyethylene terephthalate (PET). [22] However, all these functional LM materials exhibit low liquidity and high viscosity, which may limit their direct printing capability with high resolution and rapid manufacture. Clearly, the underlying mechanism is rooted As soft conductive materials with high liquid fluidity, the room-temperature liquid metal alloys (LMs) offer a superior alternative to the fabrication of flexible electronics. So far, techniques aiming at patterning LMs are seriously limited by the alloy's high surface tension and poor wettability with many substrates. Additionally, LMs based mass production with fast and efficient printing on desired target still encounters tremendous unsolved challenges. Here, a one-step liquid metal transfer printing method with wide range substrate adaptability, comprising of polymer-based adhesive glue, its printing machine, the LMs ink, and the soft substrate is presented. It is demonstrated that even on those substrates with weak wettability to LMs, the liquid metal transfer printing still works well to create complex conductive geometries, multilayer circuits, and large-area conductive patterns with excellent transfer efficiency, facile fabrication process, and remarkable electrical stability, which is beneficial to quickly construct wearable electronics, 3D folding conductive structures, flexible actuators, soft robots, etc. Moreover, its advantages of self-healing and recyclable ability make the strategy possible to prepare reconfigurable circuits and further reduce the cost of fabri...

Quasi‐2D β‐Ga2O3 is a rediscovered metal‐oxide semiconductor with the advantage of an ultrawide bandgap of 4.6–4.9 eV. It is reported to be a promising material for next‐generation power and radio‐frequency electronics. However, realizing macroelectronics based on β‐Ga2O3 film is challenging due to the nonuniformity and improper thickness of the film. Herein, a straightforward and rapid impact fabrication method for depositing high‐quality β‐Ga2O3 films is introduced. Structural and film properties of the deposited β‐Ga2O3 are characterized using scanning electron microscopy, X‐ray diffraction, and atomic force microscopy. To illustrate the applicability of the deposited β‐Ga2O3 in constructing electronic devices, β‐Ga2O3‐based field‐effect transistors (FETs) are fabricated with a source–drain spacing of 400 μm. Films of β‐Ga2O3 exhibit a good performance with carrier mobilities as high as 21.3 cm2 V–1 s–1, transconductances of 1.4 μS, and on/off current ratios of 104. The device performances indicate a big potential of β‐Ga2O3 for future power device applications. The method paves the way for future application of β‐Ga2O3 in electronics. It also provides a scalable approach for the integration of 2D morphologies of industrially important semiconductors into emerging electronics and optical devices.

In article number https://doi.org/10.1002/admt.201800265, Rui Gao, Jing Liu, Wei Rao, and co‐workers demonstrate a new kind of one‐step liquid metal transfer printing method with rather wide range substrate adaptability. As illustrated here, a classical Chinese ancient painting (Riverside Scene on Pure Brightness Festival) was thus printed on a picture scroll. With preprinted glue, liquid metal can be selectively patterned on target substrate such as paper to compose various flexible functional electronics.

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