Two-stage optical trapping and assembling of protein at air/solution interface

Optical trapping at interfaces has recently gained relevance due to the expansion of optical potential far away from the focus, especially for proteins where submillimeter structures have been described. Initially, lysozyme clusters are trapped as a shallow layer at the surface, becoming thicker with irradiation time. Nonetheless, overcoming a concentration threshold, lysozyme clusters inside the solution are collected and transported toward the focus, invading the lysozyme layer, which results in a border between them, although no concentration jump is detected. This two-stage optical trapping occurs due to the long-range interaction originating from the focus.