Building Reconfigurable Devices Using Complex Liquid–Fluid Interfaces

Liquid–fluid interfaces provide a platform both for structuring liquids into complex shapes and assembling dimensionally confined, functional nanomaterials. Historically, attention in this area has focused on simple emulsions and foams, in which surface‐active materials such as surfactants or colloids stabilize structures against coalescence and alter the mechanical properties of the interface. In recent decades, however, a growing body of work has begun to demonstrate the full potential of the assembly of nanomaterials at liquid–fluid interfaces to generate functionally advanced, biomimetic systems. Here, a broad overview is given, from fundamentals to applications, of the use of liquid–fluid interfaces to generate complex, all‐liquid devices with a myriad of potential applications. Surface‐active materials at liquid–liquid interfaces can be used to generate functional, reconfigurable materials. Harnessing this capability may enable the development of new devices with applications in chemical separations and synthesis, drug delivery, and reconfigurable electronics and microfluidics. Recent progress and open questions in this field, from nanoscale to macroscopic and from fundamentals to applications, are summarized.