Search

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, are 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, make RTGFs potential to efficiently apply 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 is 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.

Real-time monitoring of tire deformation is crucial in achieving vehicle safety, fuel economy, and intervention control before emergencies. It is challenging to integrate sensors for long-term continuous information collection inside high-speed rotating and deforming tires. In this study, we innovatively developed a flexible liquid metal (LM)-based sensing and wireless charging system and applied it for the first time to smart tire strain monitoring. The LM sensors and coils manufactured using microfluidic technology have remarkable stretchability (over 400% tensile strain) and durability, effectively resolving the mismatch between the rigid electronic interface and the complex inner surface of the tire during long-term use. The sensor comprises multiple LM microfluidic sensing layers that provide high linear fit and simultaneously monitor circumferential and axial microstrain in the tire. The system delivers power to the sensors through wireless charging and transmits the sensing signals to the developed mobile application through Bluetooth. We integrated this system into the tires, successfully achieving wireless charging of the lithium battery and real-time monitoring of sensor waveform changes while the vehicle is moving. This work provides valuable insights for the development of next-generation intelligent tires.

It is a crucial point to monitor real-time plantar pressure for application in physical condition assessment and sports injury diagnosis. In this work, we report a high-resolution (sensitive points number of 187) plantar pressure sensor (PPS) array based on the piezoresistive principle. It consists of a force-sensitive film (FSF) and a network of orthogonal conductive threads on both sides. The PPS could achieve a sensitivity of 0.124 kPa−1, a measurement range of up to 50 kPa, and excellent stability. An intelligent insole system consisting of a centimeter-level resolution PPS array, wireless Bluetooth transmitter data acquisition system, and wireless receiving terminal intelligent system is established to monitor and map the plantar pressure in real time. This intelligent insole system can identify various standing and sports positions, which is a terrific way to monitor health, avoid injuries, and train athletes.

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.