Binary colloidal mixture with maximum packing density*

Evaporative deposition of colloidal nanoparticles or nanoinks is a versatile process for inkjet printing. Typically, using monodisperse colloids, formation of empty spaces and pores between colloidal particles is inevitable in colloidal deposits. Such vacancies act as defects because they degrade physical properties of deposits. To eliminate pores, a polydisperse mixture that consists of large and small colloids is appropriate from theoretical predictions. Here, we examine binary colloidal mixtures to find a condition for maximum packing density in random packing and crystal structures. Particularly, we look into colloidal deposits of binary mixtures with X-ray nanotomography and light holographic microscopy to identify geometric information. Particle size segregation may occurs during evaporation because of Brazil nut effect or osmotic pressure. We show a method to achieve maximized packing density with polydisperse binary mixtures for applications into advanced colloidal nanoinks.

Keyword: droplet evaporation, binary colloidal mixture, packing density, X-ray nanotomography