Synthesis of 2D micro-assemblies using the interface of immiscible liquids: boundary control of self-assembled structures

We present a novel technique for the fabrication of multi-function microstructures which is a more efficient and economical alternative in the range 10–200 μm to current fabrication methods (e.g., photolithography and standard ink-jet printing). It is a modification of the classical drop-drying technique in which the material content and evaporation of water droplets are controlled by a toluene/water interface. This allows for sequential introduction of materials inside the droplets, with the possibility of in-drop controlled chemical reactions while keeping the form and a pinned contact line for each micro-droplet. It also makes the technique fully compatible with ink-jet printing methods, rendering it amenable to the fabrication of large-scale multi-function micro-arrays. As an illustration of its versatility, the technique is applied to the fabrication of microstructures from colloidal suspensions of nanoparticles, deposition of biological materials, in-drop fabrication of single crystals from water soluble materials, and fabrication of supported and free-standing polymer-based microstructure films.