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Metal micro/nanoparticle ink-based printed circuits have shown promise for promoting the scalable application of flexible electronics due to enabling superhigh metallic conductivity with cost-effective mass production. However, it is challenging to activate printed metal-particle patterns to approach the intrinsic conductivity without damaging the flexible substrate, especially for high melting-point metals. Here, we report a pressure-constrained sonication activation (PCSA) method of the printed flexible circuits for more than dozens of metal (covering melting points from room temperature to 3422 °C) and even nonmetallic inks, which is integrated with the large-scale roll-to-roll process. The PCSA-induced synergistic heat-softening and vibration-bonding effect of particles can enable multilayer circuit interconnection and join electronic components onto printed circuits without solder within 1 s at room temperature. We demonstrate PCSA-based applications of 3D flexible origami electronics, erasable and foldable double-sided electroluminescent displays, and custom-designed and large-area electronic textiles, thus indicating its potential for universality in flexible electronics. It is challenging to activate the flexible printed metal circuit to approach the intrinsic conductivity with minimal damage to the substrate. Here, the authors report a large-scale pressure-constrained sonication activation method for various metals and non-metallic inks. [ABSTRACT FROM AUTHOR]

The active-cooling elastomer concept, originating from vascular thermoregulation for soft biological tissue, is expected to develop an effective heat dissipation method for human skin, flexible electronics, and soft robots due to the desired interface mechanical compliance. However, its low thermal conduction and poor adaptation limit its cooling effects. Inspired by the bone structure, this work reports a simple yet versatile method of fabricating arbitrary-geometry liquid metal skeleton-based elastomer with bicontinuous Gyroid-shaped phases, exhibiting high thermal conductivity (up to 27.1 W/mK) and stretchability (strain limit >600%). Enlightened by the vasodilation principle for blood flow regulation, we also establish a hydraulic-driven conformal morphing strategy for better thermoregulation by modulating the hydraulic pressure of channels to adapt the complicated shape with large surface roughness (even a concave body). The liquid metal active-cooling elastomer, integrated with the flexible thermoelectric device, is demonstrated with various applications in the soft gripper, thermal-energy harvesting, and head thermoregulation. Low thermal conduction and conformability of traditional rigid heat sinks limit their adoption in flexible electronics and soft robotics. Here, authors report a liquid metal skeleton-based active-cooling elastomer with high thermal conductivity, stretchability, and hydraulic-driven adaptable morphing. [ABSTRACT FROM AUTHOR]

Flexible plant sensors, as a noninvasive and real-time monitoring method for plant physiology, are becoming crucial for precision agriculture. However, integrating flexible devices with plants are challenging due to their fragility and complex surfaces. In this study, we introduce a liquid metal-based plant electronic tattoo (LM-PET) that can harmlessly and continuously monitor the loss of water content and plant electrical signals, which are critical parameters for analyzing plant physiological status. The LM-PET achieves double-sided conductivity through soluble electrostatic spinning films and transferring technology, effectively addressing the issue of mismatch between the rigid interface of electronic devices and the surface of delicate plants. The fabricated tattoo electrode can adhere tightly to the leaf surface for a long time and can significantly broaden the scope of moisture monitoring, even in cases of severe wrinkling caused by water loss. At the optimum operating frequency of 100 kHz, the sensitivity of LM-PET can reach 25.4 kΩ%−1. Thus, LM-PETs can record the electrical signals generated when abiotic stresses threaten plants. They are also significant in providing a deeper understanding of the drought adaptation mechanisms of plants and developing drought-resistant varieties. They offer data-driven crop management and decision-making guidance, which is imperative for advancing precision agriculture. Overall, our findings provide valuable insights into the performance of agricultural inputs and facilitate real-time monitoring of plant growth and development. [ABSTRACT FROM AUTHOR]

Phase change materials have attracted significant attention due to their promising applications in many fields like solar energy and chip cooling. However, they suffer leakage during the phase transition process and have relatively low thermal conductivity. Here, through introducing hard magnetic particles, we synthesize a kind of magnetically tightened form-stable phase change materials. They achieve multifunctions such as leakage-proof, dynamic assembly, and morphological reconfiguration, presenting superior high thermal (increasing of 1400–1600%) and electrical (>104 S/m) conductivity, and prominent compressive strength, respectively. Furthermore, free-standing temperature control and high-performance thermal and electric conversion systems based on these materials are developed. This work suggests an efficient way toward exploiting a smart phase change material for thermal management of electronics and low-grade waste heat utilization. Despite phase change materials' promising properties for thermal management, their application can be hindered by challenges regarding leakage and low thermal conduction. Here, authors report PCMs with embedded magnetic particles displaying zero leakage and morphological reconfiguration. [ABSTRACT FROM AUTHOR]

In this paper, a novel liquid metal-based minichannel heat dissipation method was developed for cooling electric devices with high heat flux. A high-performance electromagnetic induction pump driven by rotating permanent magnets is designed to achieve a pressure head of 160 kPa and a flow rate of 3.24 L/min, which could enable the liquid metal to remove the waste heat quickly. The liquid metal-based minichannel thermal management system was established and tested experimentally to investigate the pumping capacity and cooling performance. The results show that the liquid metal cooling system can dissipate heat flux up to 242 W/cm2 with keeping the temperature rise of the heat source below 50°C. It could remarkably enhance the cooling performance by increasing the rotating speed of permanent magnets. Moreover, thermal contact resistance has a critical importance for the heat dissipation capacity. The liquid metal thermal grease is introduced to efficiently reduce the thermal contact resistance (a decrease of about 7.77 × 10−3 °C/W). This paper provides a powerful cooling strategy for thermal management of electric devices with large heat power and high heat flux. [ABSTRACT FROM AUTHOR]

Phase change materials have attracted significant attention due to their promising applications in many fields like solar energy and chip cooling. However, they suffer leakage during the phase transition process and have relatively low thermal conductivity. Here, through introducing hard magnetic particles, we synthesize a kind of magnetically tightened form-stable phase change materials. They achieve multifunctions such as leakage-proof, dynamic assembly, and morphological reconfiguration, presenting superior high thermal (increasing of 1400–1600%) and electrical (>104 S/m) conductivity, and prominent compressive strength, respectively. Furthermore, free-standing temperature control and high-performance thermal and electric conversion systems based on these materials are developed. This work suggests an efficient way toward exploiting a smart phase change material for thermal management of electronics and low-grade waste heat utilization. Despite phase change materials' promising properties for thermal management, their application can be hindered by challenges regarding leakage and low thermal conduction. Here, authors report PCMs with embedded magnetic particles displaying zero leakage and morphological reconfiguration. [ABSTRACT FROM AUTHOR]

In this article, room temperature gallium-based fluids (RTGFs) with unique thermal and conductive properties are proposed as a transmission fluid for the force carrying medium of hydraulics, which rectify the lack of the multi-functional hydraulic roles of liquid metal (LM). The typical physical properties of RTGFs and comparative conventional hydraulic fluids (commercial hydraulic oil and deionized water), such as thermal stability and rheological characteristics, are evaluated. Experimental and numerical methods, then, were adopted to clarify the force transmission performance of RTGFs and commercial hydraulic oils, as well as the influence of temperature fields on the viscosity of fluids. The results disclosed that the advantages of inherent flame resistance, wide liquid temperature range, and the viscosity changing slightly with temperature made RTGFs potential in finding efficient application in the hydraulics as new working fluids. Finally, for illustration, the rigid and flexible actuators driven by RTGFs were designed as hydraulic fluid and demonstrated their capabilities in grasping objects with various shapes and weights, respectively. And the tunable stiffness of such a flexible actuator was enabled via the solid-liquid phase change of LM. Additionally, a frequency-adjustable antenna was manufactured and showcased owing to the introduced transformable electromagnetic behaviors of LM. Overall, the gallium-based LM fluids with thermoelectrical and mechanical multimodal signal medium would serve as a potential candidate for future complex multifunctional signal transmission systems. [ABSTRACT FROM AUTHOR]

This paper reported a study on a flexible liquid metal coil (LMC) for electromagnetic collection from the transmission line for self-powered sensor and electromagnetic generation for wireless charging of cellular telephone. The room temperature liquid metal of Galinstan was perfused to elastic silicone tube, which is then terminated with gallium-plated copper wire. The as-prepared liquid metal wire can sustain stretching, twisting, and bending with large deformation, and has a good electrical contact stability with the external circuit. The LMC based magnetic energy harvester was then designed and demonstrated to collect the magnetic field energy induced by a wire carrying alternating current. The power of 260 mW was obtained for the wire carrying current of 10 A. The flexible toroidal inductor was fabricated and tested for magnetic energy harvesting. The flexible spiral-shaped LMC was also designed and demonstrated to power cellular telephone through wireless charging. The present study opens the way for further applications of elastic LMC in electromagnetic energy harvesting and charging. [ABSTRACT FROM AUTHOR]