Shape and size-dependent surface plasmonic resonances of liquid metal alloy (EGaIn) nanoparticles.

Liquid metals (LM) are emerging plasmonic nanomaterials with transformable surface plasmon resonances (SPR) due to their liquid-like deformability. This study delves into the plasmonic properties of LM nanoparticles, with a focus on EGaIn (eutectic gallium-indium)-based materials. Leveraging Finite-Difference Time-Domain (FDTD) simulations, we explored the localized SPR (LSPR) effects of EGaIn nanoparticles with various shapes, including nanospheres, dimers, nanorods, nanodisks, nanoellipses, nanocubes, and nanocuboids, in the broad range of the ultraviolet (UV)-visible-near infrared (NIR) spectrum.

Design and characterization of a self-powered microneedle microfluidic system for interstitial fluid sampling.

Dermal interstitial fluid (ISF) is a promising source of biomarkers for point-of-care (PoC) diagnostics, yet noninvasive and reliable extraction remains a significant challenge. In this study, we present a fully passive microneedle (MN) platform that integrates hydrogel-forming MNs, a hydrogel-based osmotic pump, and paper microfluidics to enable zero-power ISF extraction and analyte transport from skin models. The system's performance was evaluated using paper microfluidic designs optimized for both bulk fluid uptake and lateral flow-based detection.

Phase-change metal ink with pH-controlled chemical sintering for versatile and scalable fabrication of variable stiffness electronics.

Variable stiffness electronics represent the forefront of adaptive technology, integrating rigid and soft electronics in a single system through dynamic mechanical modulation. While gallium's high modulus tuning ratio and rapid phase transitions make it ideal for transformative electronic systems (TES), its liquid-state instability, high surface tension, and unintended phase transitions during processing pose substantial challenges. Here, we introduce STiffness-Adjustable temperature-Responsive ink (STAR ink), a chemically sinterable gallium composite electronic ink designed to overcome these obstacles.

pH-Switchable Multi-Enzyme-Mimicking via Liquid Metal Nanozyme.

Liquid metal (LM), with unique reversible morphology and tunable electronic properties, has become a promising platform for designing advanced nanozymes. The catalytic activity in nanozymes is typically highly dependent on the environmental pH value. Here a magnetic LM-buffered iron oxide nanozyme (FeO@EGaIn) is designed with pH-switchable enzymatic activities, in which LM serves as an electron transport substrate effectively promoting the catalytic efficiency.

DendriPep Nanocoats: Substrate-Agnostic, Self-Assembling Constructs with Shear-Controlled Thickness and Permeability.

This study investigates the self-assembly of hybrid poly(amidoamine)-peptide dendrimers (DendriPeps) into shear-responsive vesicle-like structures with nanometric thickness, called "Nanocoats", that are capable of encapsulating nano- and microscale particles. To assess the material-agnostic coating power of DendriPeps, we tested the formation of Nanocoats on a variety of synthetic and biological substrates, including polystyrene nanoparticles, poly(-isopropylacrylamide) microgels, gallium-indium liquid metal nanodroplets, and bacteriophages and lentiviruses. Specifically, we utilized spectroscopic and microscopic techniques to monitor the reversible assembly of Nanocoats on the surface of the particles upon controlling the shear stress of the surrounding aqueous phase.

Soft Variable Resistance Material for Pressure Sensing Platform.

Herein, we present the mechanical response of two porous and conductive foams made of polydimethylsiloxane (PDMS) and polyurethane (PU). A coating of carbon nanotubes (CNTs) renders the foams with positive piezo-conductivity, which is useful for sensing mechanical loads. Such materials are useful as sensors to improve the fitting process of a prosthetic socket for lower limb amputees, PDMS and PU are used commonly in prosthetic liners; here, we modify them with CNTs to convert these soft foams to sensor elements.

Connecting the Dots: Sintering of Liquid Metal Particles for Soft and Stretchable Conductors.

This review focuses on the sintering of liquid metal particles (LMPs). Here, sintering means the partial merging or connecting of particles (or droplets) to form a network of percolated and, thus, conductive electrical pathways. LMPs are attractive materials because they can be suspended in a carrier fluid to create printable inks or distributed in an elastomer to create soft, stretchable composites.

Impact of rheology on formation of oil-in-liquid metal emulsions.

To quantify how the viscosities of silicone oil (SO) and liquid metal (LM) relate to emulsion-formation (LM-in-SO SO-in-LM), a process was developed to produce LM pastes with adjustable viscosity and minimal oxide and bubbles. Increased LM viscosity allows greater silicone oil intake and/or intake of higher-viscosity silicone oils.

Ultrahigh Electrical Conductivity in p-Type CsPbIBr Perovskite Thin Films by Modulation Doping.

The widespread adoption of halide perovskites for application in thermoelectric devices, DC power generators, and lasers is hindered by their low charge carrier concentration. In particular, increasing their charge carrier concentration is considered the main challenge to serve as a promising room-temperature thermoelectric material. Efforts have been devoted to enhancing the charge carrier concentration by doping and composition engineering.

The Liquid Metal Age: A Transition From Hg to Ga.

This review offers an illuminating journey through the historical evolution and modern-day applications of liquid metals, presenting a comprehensive view of their significance in diverse fields. Tracing the trajectory from mercury applications to contemporary innovations, the paper explores their pivotal role in industry and research. The analysis spans electrical switches, mechanical applications, electrodes, chemical synthesis, energy storage, thermal transport, electronics, and biomedicine.

Ambient printing of native oxides for ultrathin transparent flexible circuit boards.

Metal oxide films are essential in most electronic devices, yet they are typically deposited at elevated temperatures by using slow, vacuum-based processes. We printed native oxide films over large areas at ambient conditions by moving a molten metal meniscus across a target substrate. The oxide gently separates from the metal through fluid instabilities that occur in the meniscus, leading to uniform films free of liquid residue.

Highly Stretchable, Tissue-like Ag Nanowire-Enhanced Ionogel Nanocomposites as an Ionogel-Based Wearable Sensor for Body Motion Monitoring.

The development of wearable electronic devices for human health monitoring requires materials with high mechanical performance and sensitivity. In this study, we present a novel transparent tissue-like ionogel-based wearable sensor based on silver nanowire-reinforced ionogel nanocomposites, P(AAm--AA) ionogel-Ag NWs composite. The composite exhibits a high stretchability of 605% strain and a moderate fracture stress of about 377 kPa.

Particle-assisted formation of oil-in-liquid metal emulsions.

Gallium-based liquid metals (LMs) have surface tension an order of magnitude higher than water and break up into micro-droplets when mixed with other liquids. In contrast, silicone oil readily mixes into LM foams to create oil-in-LM emulsions with oil inclusions. Previously, the LM was foamed through rapid mixing in air for an extended duration (over 2 h).

Glassy gels toughened by solvent.

Glassy polymers are generally stiff and strong yet have limited extensibility. By swelling with solvent, glassy polymers can become gels that are soft and weak yet have enhanced extensibility. The marked changes in properties arise from the solvent increasing free volume between chains while weakening polymer-polymer interactions.

3D-Printing of Hierarchical Porous Copper-Based Metal-Organic-Framework Structures for Efficient Fixed-Bed Catalysts.

Metallic structures with hierarchical open pores that span several orders of magnitude are ideal candidates for various catalyst applications. However, porous metal materials prepared using alloy/dealloy methods still struggle to achieve continuous pore distribution across a broad size range. Herein, we report a printable copper (Cu)/iron (Fe) composite ink that produces a hierarchical porous Cu material with pores spanning over 4 orders of magnitude.

Surface Embedded Metal Nanowire-Liquid Metal-Elastomer Hybrid Composites for Stretchable Electronics.

Both liquid metal (LM) and metallic filler-based conductive composites are promising stretchable conductors. LM alloys exhibit intrinsically high deformability but present challenges for patterning on polymeric substrates due to high surface tension. On the other hand, conductive composites comprising metallic fillers undergo considerable decrease in electrical conductivity under mechanical deformation.

Liquid Metal Nanoparticles Physically Hybridized with Cellulose Nanocrystals Initiate and Toughen Hydrogels with Piezoionic Properties.

Liquid metal (LM) particles can serve as initiators, functional fillers, and cross-linkers for hydrogels. Herein, we show that cellulose nanocrystals (CNCs) stabilize LM particles in aqueous solutions, such as those used to produce hydrogels. The CNC-coated LM particles initiate free-radical polymerization to form poly(acrylic acid) (PAA) hydrogel with exceptional properties─stretchability ∼2000%, excellent toughness ∼1.

Injection Molding of Liquid Metal by Harnessing Nonstick Molds.

The fluid nature of liquid metals combined with their ability to form a solid native oxide skin enables them to be patterned in ways that would be challenging for solid metals. The present work shows a unique way of patterning liquid metals by injecting liquid metals into a mold. The mold contains a nonstick coating that enables the removal of the mold, thereby leaving just the liquid metal on the target substrate.

A Guide to Printed Stretchable Conductors.

Printing of stretchable conductors enables the fabrication and rapid prototyping of stretchable electronic devices. For such applications, there are often specific process and material requirements such as print resolution, maximum strain, and electrical/ionic conductivity. This review highlights common printing methods and compatible inks that produce stretchable conductors.

Printable Liquid Metal Foams That Grow When Watered.

Pastes and "foams" containing liquid metal (LM) as the continuous phase (liquid metal foams, LMFs) exhibit metallic properties while displaying paste or putty-like rheological behavior. These properties enable LMFs to be patterned into soft and stretchable electrical and thermal conductors through processes conducted at room temperature, such as printing. The simplest LMFs, featured in this work, are made by stirring LM in air, thereby entraining oxide-lined air "pockets" into the LM.