Gallium-based liquid metals such as eutectic gallium–indium (EGaIn) have long been viewed as the most promising intrinsically deformable conductors. They combine metallic-level conductivity, on the order of a million siemens per meter, with liquid-like flow at room temperature, allowing them to endure extreme strain without fracturing. Yet their practical adoption has been hampered by two stubborn problems. In air, gallium rapidly forms a self-limiting oxide shell roughly three nanometers thick that stabilizes droplet shape but acts as an electrical insulator, blocking electron transport between neighboring particles. At the same time, the metal’s very high surface tension, near 600 millinewtons per meter, makes it difficult to wet and pattern uniformly on soft elastomeric substrates. As a result, most liquid metal inks are electrically dead when deposited and require a separate thermal, mechanical, laser, or chemical activation step to rupture the oxide and establish conductive pathways.

The new work tackles both obstacles at once by wrapping each liquid metal particle in an ultrathin polymer shell and then exploiting the physics of the spray process itself. Bulk EGaIn is fractured into microscale droplets by tip sonication in a 5 weight percent aqueous PVA solution, run at 20 percent amplitude in pulsed mode to prevent overheating. PVA chains hydrogen-bond to the freshly formed gallium oxide surface, lowering particle surface energy and improving wettability. A centrifugation step removes free, unbound polymer, leaving particles with a controlled PVA layer estimated at 7 to 10 nanometers thick atop the 3 to 5 nanometer native oxide. Transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed this layered structure, with the carbon signal of the polymer conformally wrapping the oxygen-rich oxide shell. The team emphasizes that the PVA is retained after deposition, where it serves as a fusion mediator and adhesive bridge rather than an insulating barrier.

Getting the shell thickness right proved decisive. Particles carrying an excessively thick PVA coating, produced before the centrifuge refinement, showed improved wettability but could not make direct particle-to-particle contact, yielding films roughly eightfold less conductive than the optimized formulation. The refined PmLMP films reached an electrical conductivity of approximately 1.5 × 10^6 siemens per meter immediately after spraying. Zeta potential measurements help explain why: pristine particles carry a strongly negative surface charge of about −70 millivolts, creating an electrostatic barrier that keeps neighbors apart, while PVA modification reduces this to roughly −38 millivolts, allowing hydrodynamic forces during printing to push particles into intimate contact. Density functional theory calculations, using isopropanol as a model for the PVA repeat unit and hydroxylated gallium oxide as a surface model, supported the feasibility of a moderate hydrogen bond at the interface, with a counterpoise-corrected interaction energy of −23.2 kilojoules per mole.

The heart of the innovation is a synergistic mechano-fluidic mechanism that unfolds in a single deposition event. First, high-velocity impact of aerosolized particles delivers enough mechanical stress to rupture the oxide–polymer shell, exposing fresh metallic surfaces that coalesce on contact. Atomic force microscopy nanoindentation measured a yield force of 266.08 nanonewtons per particle, only slightly above the 200 to 250 nanonewtons reported for bare oxide-shelled particles, confirming that the ultrathin PVA layer does not meaningfully suppress rupturability. X-ray photoelectron spectroscopy provided chemical corroboration: screen-printed control films showed only oxidized gallium signals, whereas spray-printed films revealed distinct indium peaks and metallic Ga^0 features, consistent with shell rupture exposing the metallic core. The researchers estimate a critical impact velocity of only about 4 meters per second, well below the particle speeds achieved at the optimized 30 psi spray pressure.

Second and third, the drying process itself consolidates the network. Because the ink uses a binary solvent of deionized water and ethanol in a 3:1 volume ratio, a surface-tension gradient arises within each deposited droplet, driving Marangoni convection. High-speed imaging of fluorescent tracer particles and microparticle image velocimetry showed flow velocities up to 50 times faster, averaging a 22.4-fold increase, compared with a single-solvent system. These vortical flows redistribute particles, counteract gravitational sedimentation, and wedge smaller particles into the voids between larger ones, creating nanoscale point contacts where capillary stress concentrates. The team’s capillary-bridge model predicts a lateral force of roughly 79 nanonewtons at each interparticle meniscus, and under an illustrative contact radius of about 11 nanometers this corresponds to local stresses near 200 megapascals, plausibly sufficient to rupture residual shells. Transmission electron microscopy captured metallic neck formation at particle contacts, and the binary-solvent formulation delivered a threefold conductivity enhancement over the water-only control.

Process optimization revealed how sensitively the mechanism depends on spray parameters. Ultrasonic amplitudes above 50 percent, despite producing smaller particles, introduced enough energy to generate gallium oxide and hydroxide byproducts that interfered with coalescence, so 20 percent amplitude proved optimal. Conductivity saturated at carrier-gas pressures above 30 psi, where kinetic energy reliably exceeds the rupture threshold. Working distance mattered too: at 6 centimeters, air resistance dissipated too much particle energy, while at 3 centimeters the balance of partial solvent evaporation and retained impact energy enabled efficient fusion. The resulting process patterned conductive traces with nominal linewidths down to 50 micrometers and coated areas larger than 20 by 20 square centimeters, and a batch-printed 4 by 4 array showed an average conductivity of 1.55 × 10^6 siemens per meter with limited pixel-to-pixel variation.

Electromechanical testing underscored the practical payoff. Under monotonic tension, PmLMP traces retained electrical continuity beyond 200 percent strain and up to 800 percent, with relative resistance rising only gradually to about 2.8, whereas unmodified particle films lost continuity through droplet beading and over-coated films fractured near 100 percent strain. Cyclic testing at 100 percent strain over 50,000 seconds, roughly 1,400 stretch-release cycles, showed reproducible resistance modulation with limited drift. Integrated light-emitting diodes stayed illuminated through twisting, 100 percent stretching, and bending, and star-shaped LED arrays printed on table-tennis balls, tennis balls, and basketballs remained operational, demonstrating conformability across curvatures. On nonpolar substrates such as PDMS and Ecoflex, an oxygen-plasma pretreatment improved trace uniformity by increasing surface polarity for hydrogen bonding.

The team then pushed the platform toward real devices. Because the printed interconnects are conductive on arrival, standard components, including a microcontroller, resistor, and LEDs, could be pick-and-placed directly onto as-printed flexible circuits that remained functional after folding. A flexible wound-healing patch carrying 640-nanometer red LEDs, driven at 10 hertz and encapsulated in Ecoflex, accelerated macroscopic wound closure relative to untreated controls over seven days in a murine full-thickness excisional wound model. Large-area conductive patterns were printed directly onto textile banners, and the same platform, paired with a LiCl-hydrogel skin interface, served as a wearable electromyography and electrocardiography system. Wireless EMG signals transmitted over Bluetooth Low Energy controlled a remote-controlled vehicle in real time, while custom software visualized ECG waveforms and computed heart rate. Together, these demonstrations sketch a manufacturing route in which liquid metal circuits emerge from an ordinary airbrush already alive with current, opening possibilities for wearable healthcare, bio-integrated electronics, and human-interactive devices that no longer wait for a sintering oven to switch them on.

Subject of Research: Post-treatment-free spray deposition of PVA-modified liquid metal particles for soft and wearable electronics

Article Title: Synergistic Mechano‐Fluidic Self‐Fusion of Poly(Vinyl Alcohol)‐Modified Liquid‐Metal Particles for Post‐Treatment‐Free Soft Electronics

Article References: Yook, K.-Y., Kim, S., Kim, C., Kang, M., Lee, Y., Kim, M., Park, K., Han, S. Y., Cho, S.-W., Lee, G.-H., Son, K., Jang, H., Kim, T. Y., & Seo, J. (2026). Synergistic Mechano‐Fluidic Self‐Fusion of Poly(Vinyl Alcohol)‐Modified Liquid‐Metal Particles for Post‐Treatment‐Free Soft Electronics. Advanced Science, Article e78062. https://doi.org/10.1002/advs.78062

Image Credits: AI Generated

DOI: 10.1002/advs.78062

Keywords: liquid metal, soft electronics, spray printing, EGaIn, poly(vinyl alcohol), self-fusion, wearable sensors, Marangoni convection, capillary forces, stretchable conductors, electromyography, wound healing

The device itself is deceptively simple in architecture. It consists of a vertical stack of silver, hexagonal boron nitride, and indium tin oxide, all deposited on a flexible polyethylene terephthalate substrate. Hexagonal boron nitride, often nicknamed white graphene, is a layered insulating crystal whose atomically flat sheets can be stacked like a deck of cards. In a conventional memristor, electrical pulses program the resistance state, and mechanical deformation is usually treated as a nuisance, a source of noise or failure to be engineered away. The Shiv Nadar team inverted that logic. In their device, bending is the programming signal. When the flexible substrate flexes, the hBN flakes within the stack slide laterally relative to one another, and that sliding perturbs the stacking arrangement and the inter-flake tunneling distance that governs how easily electrons can hop across the layered insulator.

The elegance of the mechanism lies in what does not happen. Because the programming arises from interlayer sliding rather than from stretching the crystal lattice itself, the hBN sheets are never strained at the atomic level. The covalent bonds within each flake remain intact, which means the process is non-destructive and, crucially, reversible. Straighten the device and the flakes can slide back, restoring the previous tunneling gap and the previous conductance state. This stands in sharp contrast to many flexible memristor designs, where repeated mechanical cycling gradually degrades the active material through crack formation, atomic displacement, or electromigration. Here, deformation is not damage; it is information. The researchers describe this as a mechanoelectronic design principle, one in which the physical interaction between device and environment becomes the write mechanism for synaptic plasticity.

What makes the comparison to the neuromuscular junction more than a metaphor is the way the device responds to bending. Biological mechanosensitive neurons transduce deformation into graded changes in synaptic strength, with both the amplitude and the dynamics of the response modulated by the magnitude and history of the mechanical stimulus. The hBN memristor reproduces this co-modulation quantitatively. Different bending conditions produce different families of conductance states, and the temporal evolution of those states mirrors the amplitude and dynamics seen in their biological counterparts. In other words, the device does not simply switch between on and off; it exhibits the continuous, history-dependent plasticity that neuroscientists associate with real synapses, where the same stimulus can produce different outcomes depending on what came before.

To demonstrate that these mechanically programmed states are more than a laboratory curiosity, the team put the device to work as an artificial synapse in a computational brain. The conductance values measured under varying bending conditions were used as analog synaptic weights in a fully connected neural network, the workhorse architecture of modern machine learning. The network was trained on MNIST, the classic benchmark of handwritten digit recognition that has served for decades as a proving ground for neuromorphic hardware. Across all bending conditions tested, the network achieved classification accuracy exceeding 91 percent. That figure matters because it shows that the mechanically induced conductance states are not random or noisy; they are stable, distinguishable, and useful as computational elements. A synapse that changes when you bend it, yet still supports high-accuracy inference, is a synapse that could live inside a prosthetic hand or a soft robot.

The implications for flexible and wearable neuromorphics are considerable. Current approaches to tactile sensing in soft electronics typically separate the sensing element from the computing element: a pressure sensor converts touch into an electrical signal, which is then routed to a processor that decides what it means. That separation costs power, latency, and wiring complexity, all of which are precious commodities in a wearable device. A memristor that programs itself through touch collapses that boundary. The sensing and the memory update are the same physical event, happening at the same place at the same time. For applications such as electronic skin, adaptive prosthetics, or soft robotic grippers that must learn from contact, this kind of co-located mechanosensation and plasticity could dramatically simplify the hardware stack.

The choice of materials is also strategically significant. Hexagonal boron nitride is chemically robust, thermally stable, and widely studied as a protective encapsulant and tunneling barrier in two-dimensional electronics. Its layered structure, with weak van der Waals forces between sheets and strong covalent bonds within them, is precisely what enables the sliding mechanism at the heart of the device. The silver and indium tin oxide electrodes provide the vertical conduction path, and the PET substrate supplies the flexibility that makes the whole concept possible. Because the active mechanism does not rely on electrochemical filament formation or oxygen vacancy migration, the usual culprits behind memristor variability and endurance limits, the device sidesteps several long-standing reliability problems in the field.

There are, of course, hurdles between a promising laboratory demonstration and a deployable technology. The reported work establishes the principle and the benchmark performance, but scaling from individual devices to the dense crossbar arrays needed for practical neuromorphic systems will require careful control of device-to-device uniformity, particularly for a mechanism that depends on the precise stacking of exfoliated or grown two-dimensional flakes. Integration with conventional readout circuitry, long-term cycling stability under millions of bending events, and compatibility with large-area manufacturing are all questions that the field will now press forward. The authors acknowledge support from the Science and Engineering Research Board and the Department of Science and Technology in India, reflecting the growing investment in flexible neuromorphic platforms worldwide.

Still, the conceptual shift is hard to overstate. For half a century, computing has treated memory and processing as separate functions and mechanical deformation as an enemy of reliability. This work suggests a future in which the shape of a device is part of its computational state, in which a bend is a bit, and in which soft machines learn the way our muscles do, through the very act of moving. The neuromuscular junction has been quietly optimizing that trick for hundreds of millions of years. With a few atomic layers of boron nitride and a flexible plastic backing, engineers have finally started to take notes.

Subject of Research: Mechanosensitive hexagonal boron nitride memristors for flexible neuromorphic computing

Article Title: Neuromuscular Junction Inspired Mechanosensitive hBN-based Memristors for Flexible Neuromorphics

Article References: Parida, T., Swain, S. K., Sengupta, D., & Kanjilal, A. (2026). Neuromuscular Junction Inspired Mechanosensitive hBN-based Memristors for Flexible Neuromorphics. npj Flexible Electronics. https://doi.org/10.1038/s41528-026-00647-0

Image Credits: AI Generated

DOI: 10.1038/s41528-026-00647-0

Keywords: memristor, hexagonal boron nitride, neuromorphic computing, flexible electronics, neuromuscular junction, synaptic plasticity, mechanosensitive, interlayer sliding, MNIST, wearable devices, two-dimensional materials, artificial synapse

The appeal of liquid metals begins with a basic physical paradox. Conventional stretchable conductors rely on rigid fillers, such as silver flakes or carbon particles, embedded in an elastic matrix. Increasing the filler loading improves conductivity but stiffens the composite and accelerates fatigue under repeated strain; reducing the loading preserves softness but degrades electrical performance. This conductivity–softness trade-off has constrained generations of wearable and implantable devices. Liquid metals, most notably eutectic gallium–indium alloys that remain molten at room temperature, sidestep the problem entirely because the conductive phase is itself a fluid. Droplets of the alloy can be suspended in elastomers, where they deform, elongate and reconfigure with the surrounding polymer rather than resisting it, maintaining metallic properties across large strains.

The review emphasizes that liquid metal composites deliver far more than stretchable wiring. When droplets are dispersed through a soft polymer, they enhance not only electrical conductivity but also dielectric and thermal properties. Elongated liquid metal inclusions, for example, have been shown to raise the thermal conductivity of elastomers dramatically, enabling soft materials that can dissipate heat, and liquid metal inclusions have been used to create high-permittivity dielectric elastomers for capacitive and actuating applications. In one striking demonstration highlighted in the review, an electrically insulating liquid metal silicone compound combined electromagnetic interference shielding with direct electronic potting and thermal management, showing that a single soft composite can perform multiple functions once reserved for rigid metal housings.

Yet the same fluidity that gives liquid metals their conformability creates their greatest engineering headaches. A liquid conductor can leak, smear, delaminate or migrate within a device, destroying pattern fidelity and reliability. The authors argue that the decisive design variable is not the liquid metal itself but the interfaces it forms, both between liquid metal and the surrounding polymer and between liquid metal inks and the substrates and components they must connect. Interface engineering, they contend, is essential for mitigating leakage, delamination and functional degradation under deformation, and tailored interfacial design is what converts a promising ink into a robust, integrated device.

A rich toolkit of surface chemistry has emerged to control these interfaces. Gallium-based alloys spontaneously form a thin native oxide skin that dramatically alters their interfacial energy, lowering surface tension enough to allow the metal to be shaped, printed and stabilized as droplets. Researchers have exploited this oxide, and chemical modifications of it, to stabilize particles, tune wettability and promote adhesion. Polyphenol-induced adhesives have produced liquid metal inks that write directly on nearly any substrate, while thiol coordination chemistry has been used to soften liquid metal particles and switch their conductivity on demand. Hydrogen-doped viscoplastic microparticles have enabled stretchable printed metal lines, and finite-gel strategies have produced highly concentrated inks suitable for direct writing.

Patterning at high resolution remains one of the field’s defining challenges, and the review surveys how recent advances in droplet stabilization and ink formulation are addressing it. Ultrasonic sintering has been used to assemble liquid metal particles within polymers into elastic printed circuit boards, in which pressing or sonicating the particles ruptures their oxide shells and merges them into continuous, leakage-resistant traces. Laser sintering of liquid metal nanoparticles offers a scalable route to soft, flexible electronics, and projection lithography has enabled rapid printing of highly stretchable circuits. Meniscus-guided printing has produced stable semi-solid microgranular particles for soft electronics, while high internal phase emulsion inks have allowed direct-ink-writing of three-dimensional liquid metal structures. One recent metalgel formulation maintained a conductivity of three million siemens per metre through a million stretching cycles, a durability benchmark that would have seemed unattainable for a fluid conductor only a decade ago.

The applications catalogued in the review span the full breadth of soft electronics. In wearable healthcare, liquid metal electrodes and sensors have been fashioned into electronic tattoos, electromyography patches for tendon localization and muscle injury prevention, and pressure sensors for health monitoring. In implantable and bioelectronic systems, liquid metal microelectrodes have been wafer-patterned for chronic biocompatibility, printed directly on the cranium for soft neural probes, and formed into three-dimensional microelectrode arrays integrated with ultrathin retinal prostheses for vision restoration; liquid metal neuro-interfaces have even been used to stimulate and record from human hippocampal organoids. Phase-transition behavior adds another dimension: temperature-responsive intravenous needles that irreversibly soften on insertion, and biphasic microfibers for minimally invasive implantable electronics, exploit alloys that are rigid at room temperature and compliant at body temperature.

Soft robotics and integrated systems feature prominently as well. Liquid metal–elastomer composites have demonstrated autonomous electrical self-healing, in which damaged circuits reconnect themselves as the liquid metal flows back together, and liquid metal inclusions have enabled shape-morphing elastomers that couple thermal transport with programmable actuation. Stretchable Arduinos embedded in soft robots, octopus-inspired sensorized arms, and stretchable core–shell cables that are patternable, recyclable and noise-resistant all illustrate how liquid metals can bridge soft and rigid electronic domains. Liquid crystal elastomer composites actuated by induction heating point toward untethered, programmable soft machines, while liquid metal antennas exploit fluidic deformability for reconfigurable radio-frequency devices.

The authors are candid about what stands between laboratory demonstrations and real-world deployment. Long-term interface durability and manufacturing precision remain the key translation challenges: devices must survive millions of deformation cycles in wet, biological environments without leaking, delaminating or drifting in performance, and patterning methods must reach the resolution and throughput that industrial electronics demand. Questions of biocompatibility are being actively studied, with gallium’s known antimicrobial activity offering intriguing therapeutic possibilities even as toxicity profiles continue to be mapped. The review’s central message is nonetheless one of momentum: by treating the liquid metal–material interface as the primary design object, rather than an afterthought, researchers now have a coherent strategy for building soft electronics that no longer force a choice between how well a device performs and how gracefully it bends. If that strategy matures, the circuits of the future may not merely sit on the body but move with it, heal with it and, in the case of implants, dissolve the boundary between machine and tissue altogether.

Subject of Research: Design strategies for liquid metal-based soft and stretchable electronics

Article Title: Design strategies for liquid metal-based soft electronics

Article References: Pan, C., Zhang, C., Wang, J., Han, M., CHIU, W. Y. P., Zhao, P., & Dickey, M. D. (2026). Design strategies for liquid metal-based soft electronics. Nature Reviews Electrical Engineering. https://doi.org/10.1038/s44287-026-00335-1

Image Credits: AI Generated

DOI: 10.1038/s44287-026-00335-1

Keywords: liquid metals, stretchable electronics, soft electronics, gallium alloys, interface engineering, wearable devices, implantable bioelectronics, soft robotics, elastomer composites, self-healing materials, printed electronics, dielectric elastomers