Atomic Force Microscopy of Emulsions and Their Interfacial Nanoparticles

ABSTRACT Liquid–liquid interfaces and interfacially entrapped nanoparticles are ubiquitous in nature and technology. Their importance in the industry is rising because nanoparticle‐stabilized emulsions can be designed to be more stable, ecological, and safe for human health than conventional emulsions stabilized by molecular surfactants. The properties of these “Pickering emulsions” depend on the particle sizes and shapes, droplet coverage, and particle behavior in the interface, among other factors, some of which are yet to be understood better or even identified. Here, we present the first workflow for analyzing real Pickering emulsions in the nanoscale. Two case materials were chosen for the nanoparticles: silica and lignin to represent hard inorganic and soft biobased materials, respectively. The particle movements, deformation of interfacial particles, droplet movement, and droplet coalescence were inflicted and measured simultaneously at high forces. Our method opens a new analytical pathway to analyze and manipulate real‐world 3D nanostructures with fluid components, which are under intense research for self‐assembly, interfacial nanoarchitectonics, and functional devices. Furthermore, our results show that the interfacial behavior of a soft biomatter can be distinguished from that of a rigid inorganic particle, which is relevant for the green shift across multiple materials‐related industries. Summary AFM workflow is introduced to measure the topography, adhesion, and stiffness of emulsion droplets and their interfacial nanoparticles under liquid. The droplets and interfacial nanoparticles can be mechanically manipulated at high interaction forces. Lignin particles do not keep their size and shape in the emulsion interface.