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The ability to control interfacial tension electrochemically is uniquely available for liquid metals (LMs), in particular gallium‐based LM alloys. This imparts them with excellent locomotion and deformation capabilities and enables diverse applications. However, electrochemical oxidation of LM is a highly dynamic process, which often induces Marangoni instabilities that make it almost impossible to elongate LM and manipulate its morphology directly and precisely on a 2D plane without the assistance of other patterning methods. To overcome these limitations, this study investigates the use of an LM–iron (Fe) particle mixture that is capable of suppressing instabilities during the electrochemical oxidation process, thereby allowing for superelongation of the LM core of the mixture to form a thin wire that is tens of times of its original length. More importantly, the elongated LM core can be manipulated freely on a 2D plane to form complex patterns. Eliminating Marangoni instabilities also allows for the effective spreading and filling of the LM–Fe mixture into molds with complex structures and small features. Harnessing these excellent abilities, a channel‐less patterning method for fabricating elastomeric wearable sensors is demonstrated to detect motions. This study shows the potential for developing functional and flexible structures of LM with superior performance. [ABSTRACT FROM AUTHOR]

Unlike conventional microelectromechanical systems (MEMS), machines based on gallium liquid metal alloys rely on Marangoni flows to induce motion without mechanical moving parts. Despite this advantage, currently developed liquid metal enabled robotic systems still need the locomotion of liquid metal droplets, thereby generating weak actuating forces and limiting their manoeuvrability. Here, a liquid metal engine (LME) is created to work as a jet thruster to continuously power a robot boat without the need of locomotion. In addition, the engine is electrically driven by surface tension without any mechanical moving parts. The structural design and the parameters of operation of the LME are investigated and optimized. Finally, the manipulation of the LME using a motor control unit is demonstrated for driving an untethered robot boat to realize complex locomotion with the precise control over the direction and speed. Thus, this LME could offer new opportunities for developing high‐performance liquid metal machines to power robotic systems. [ABSTRACT FROM AUTHOR]

Patterning customized arrays of microscale Galinstan or EGaIn liquid metals enables the creation of a variety of microfabricated systems. Current techniques for creating microsized 3D structures of liquid metals are limited by the large dimension or low aspect ratio of such structures, and time-consuming processes. Here, a novel technique for creating 3D microstructures of Galinstan using dielectrophoresis is introduced. The presented technique enables the rapid creation of Galinstan microstructures with various dimensions and aspect ratios. Two series of proof-of-concept experiments are conducted to demonstrate the capabilities of this technique. First, the 3D Galinstan microstructures are utilized as 3D microelectrodes to enhance the trapping of tungsten trioxide (WO3) nanoparticles flowing through a microfluidic channel. Second, the patterned Galinstan microstructures are utilized as microfins to improve the dissipation of heat within a microfluidic channel that is located onto a hot spot. The presented technique can be readily used for creating customized arrays of 3D Galinstan microstructures for a wide range of applications. [ABSTRACT FROM AUTHOR]

Chaotic advection plays an important role in microplatforms for a variety of applications. Currently used mechanisms for inducing chaotic advection in small scale, however, are limited by their complicated fabrication processes and relatively high power consumption. Here, a soft actuator is reported which utilizes a droplet of Galinstan liquid metal to induce harmonic Marangoni flow at the surface of liquid metal when activated by a sinusoidal signal. This liquid metal actuator has no rigid parts and employs continuous electrowetting effect to induce chaotic advection with exceptionally low power consumption. The theory behind the operation of this actuator is developed and validated via a series of experiments. The presented actuator can be readily integrated into other microfluidic components for a wide range of applications. [ABSTRACT FROM AUTHOR]

A new platform described as the liquid metal/metal oxide (LM/MO) framework is introduced. The constituent spherical structures of these frameworks are made of micro- to nanosized liquid metal spheres and nanosized metal oxides, combining the advantages of both materials. It is shown that the diameters of the spheres and the stoichiometry of the structures can be actively controlled. Additionally, the liquid suspension of these spheres demonstrates tuneable plasmon resonances. These spherical structures are assembled to form LM/MO frameworks which are capable of demonstrating high sensitivity towards low concentrations of heavy metal ions, and enhanced solar light driven photocalalytic activities. These demonstrations imply that the LM/MO frameworks are a suitable candidate for the development of future high performance electronic and optical devices. [ABSTRACT FROM AUTHOR]

This review is focused on the basic properties, production, functionalization, cytotoxicity, and biomedical applications of liquid metal nanoparticles (LMNPs), with a focus on particles of the size ranging from tens to hundreds of nanometers. Applications, including cancer therapy, medical imaging, and pathogen treatment are discussed. LMNPs share similar properties to other metals, such as photothermal conversion ability and a propensity to form surface oxides. Compared to many other metals, especially mercury, the cytotoxicity of gallium is low and is considered by many reports to be safe when applied in vivo. Recent advances in exploring different grafting molecules are reported herein, as surface functionalization is essential to enhance photothermal therapeutic effects of LMNPs or to facilitate drug delivery. This review also outlines properties of LMNPs that can be exploited in making medical imaging contrast agents, ion channel regulators, and anti-pathogenic agents. Finally, a foresight is offered, exemplifying underexplored knowledge and highlighting the research challenges faced by LMNP science and technology in expanding into applications potentially yielding clinical advances. [ABSTRACT FROM AUTHOR]

Gallium‐based room temperature liquid metal alloys have recently been explored to be an emerging functional material. They have attracted particular attentions in a variety of applications due to their unique properties. Many of the applications are based on the precise control over the motion of liquid metal, and yet, the fact that currently lacking the advanced and reliable controlling methods greatly hinders the potential of liquid metal to be applied in a wider range of fields. In this study, an innovative approach is developed to obtain functional liquid metal (FLM) by modifying it with copper–iron magnetic nanoparticles (Cu–Fe NPs). The magnetic modification process enables the Cu–Fe NPs to be suspended within the liquid metal and form the FLM. The FLM exhibits similar appearance, actuating behaviors, and deformability in alkaline solutions to those of pure liquid metal alloys. Meanwhile, the magnetic modification enables the precise and rapid manipulation of the liquid metal using a magnetic field. Most importantly, for the first time, the precise control and climbing locomotion of the FLM is demonstrated with the interworking of both electric and magnetic fields simultaneously. The remarkable features of the FLM may represent vast potentials toward the development of future intelligent soft robots. An innovative electrochemistry‐assisted method for obtaining functional liquid metal (FLM) by modifying Galinstan with copper–iron magnetic nanoparticles is proposed. The FLM exhibits similar appearance, fluidity, and deformability as liquid metal without modification. Most importantly, the magnetic modification allows the precise control and climbing locomotion of the FLM with the interworking of both electric and magnetic fields simultaneously. [ABSTRACT FROM AUTHOR]