Colloidal materials are a platform for studying self-assembly as well as the bottom-up creation of next generation hierarchical materials, and controllably perturbing their collective dynamics is an important step towards directing their assembly. In a liquid droplet, silica nanoparticles collect on the surface and organize to form an ordered 2D lattice. A STROBE research team led by Naomi Ginsberg (UC Berkeley) investigated these monolayers on a low vapor pressure ionic liquid, allowing experiments to be performed under the vacuum environment of a scanning electron microscope. Alongside imaging the particles, the electron beam serves as a perturbative tool for controllably charging the colloidal lattice. As particles charge, they sink into the droplet reducing the monolayer’s density and driving a melting transition. These findings will provide new insights for understanding phase transitions in soft materials and analogous atomic crystals.
