Liquid metal is being regarded as a promising material for soft electronics owing to its distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state. However, the applicability of liquid metal is still limited due to the difficulty in simultaneously achieving its mechanical stability and initial conductivity. Furthermore, reliable and rapid patterning of stable liquid metal directly on various soft substrates at high-resolution remains a formidable challenge. In this work, meniscus-guided printing of ink containing polyelectrolyte-attached liquid metal microgranular-particle in an aqueous solvent to generate semi-solid-state liquid metal is presented. Liquid metal microgranular-particle printed in the evaporative regime is mechanically stable, initially conductive, and patternable down to 50 μm on various substrates. Demonstrations of the ultrastretchable (~500% strain) electrical circuit, customized e-skin, and zero-waste ECG sensor validate the simplicity, versatility, and reliability of this manufacturing strategy, enabling broad utility in the development of advanced soft electronics.

High internal phase emulsions have been widely used as templates for various porous materials, but special strategies are required to form, in particular, particle-covered ones that have been more difficult to obtain. Here, we report a versatile strategy to produce a stable high internal phase Pickering emulsion by exploiting a depletion interaction between an emulsion droplet and a particle using water-soluble polymers as a depletant. This attractive interaction facilitating the adsorption of particles onto the droplet interface and simultaneously suppressing desorption once adsorbed. This technique can be universally applied to nearly any kind of particle to stabilize an interface with the help of various non- or weakly adsorbing polymers as a depletant, which can be solidified to provide porous materials for many applications.

Two-dimensional films of surface-active agents-from phospholipids and proteins to nanoparticles and colloids-stabilize fluid interfaces, which are essential to the science, technology and engineering of everyday life. The 2D nature of interfaces present unique challenges and opportunities: coupling between the 2D films and the bulk fluids complicates the measurement of surface dynamic properties, but allows the interfacial microstructure to be directly visualized during deformation. Here we present a novel technique that combines active microrheology with fluorescence microscopy to visualize fluid interfaces as they deform under applied stress, allowing structure and rheology to be correlated on the micron-scale in monolayer films. We show that even simple, single-component lipid monolayers can exhibit viscoelasticity, history dependence, a yield stress and hours-long time scales for elastic recoil and aging. Simultaneous visualization of the monolayer under stress shows that the rich dynamical response results from the cooperative dynamics and deformation of liquid-crystalline domains and their boundaries.

We present systematic measurements of the surface rheology of monolayers of liquid-condensed (LC) dipalmitoylphosphatidylcholine (DPPC) at the air–water interface. Using microfabricated, ferromagnetic ‘microbuttons’ as new microrheological probes, we measure the linear viscoelastic moduli of LC DPPC monolayers as both surface pressure and frequency are varied. Visualization of this interface reveals that the interlocked liquid crystalline domains that comprise an LC-DPPC monolayer give rise to a viscoelastic solid response. Two distinct behaviors arise as surface pressure is increased: for low surface pressures (8 mN m⁻¹ ≤ Π ≤ 12–14 mN m⁻¹), the monolayer behaves like a two-dimensional emulsion, with a surface elastic modulus G ^′ _s that is relatively constant, as would be expected from a line tension-mediated elasticity. The surface viscosity increases exponentially with Π, as would be expected for a condensed liquid monolayer. Above 12–14 mN m⁻¹, however, both moduli increase exponentially with Π, albeit with a weaker slope—a response that would not be expected from line-tension-mediated elasticity. This transition would be consistent with a second-order phase transition between the LC and solid-condensed phase, as has been observed in other phospholipid monolayers. Finally, we employ a controlled-stress (creep) mode to find a stress-dependent viscosity bifurcation, and thus the yield stress of this monolayer.

Conductive metal-organic framework (C-MOF) thin-films have a wide variety of potential applications in the field of electronics, sensors, and energy devices. The immobilization of various functional species within the pores of C-MOFs can further improve the performance and extend the potential applications of C-MOFs thin films. However, developing facile and scalable synthesis of high quality ultra-thin C-MOFs while simultaneously immobilizing functional species within the MOF pores remains challenging. Here, we develop microfluidic channel-embedded solution-shearing (MiCS) for ultra-fast (≤5 mm/s) and large-area synthesis of high quality nanocatalyst-embedded C-MOF thin films with thickness controllability down to tens of nanometers. The MiCS method synthesizes nanoscopic catalyst-embedded C-MOF particles within the microfluidic channels, and simultaneously grows catalyst-embedded C-MOF thin-film uniformly over a large area using solution shearing. The thin film displays high nitrogen dioxide (NO₂) sensing properties at room temperature in air amongst two-dimensional materials, owing to the high surface area and porosity of the ultra-thin C-MOFs, and the catalytic activity of the nanoscopic catalysts embedded in the C-MOFs. Therefore, our method, i.e. MiCS, can provide an efficient way to fabricate highly active and conductive porous materials for various applications.