Colloidal membrane thickness sets critical surface area for vesicle formation*

The malleable size and shape of biological membranes allow them to act in a wide range of cellular functions. Vesicles in particular have different uses, from transport to compartmentalization, depending on their size and shape. However, the rapidity with which bio-membranes bend and change structure on the nanoscale makes studying the physics that drive these changes difficult. We use colloidal membranes as experimental models to study the forces governing vesicle formation. Due to the larger length and time scales present in our colloidal system, we directly observe membranes undergoing lateral growth and then bending into vesicles. Both theory and experiment indicate that the size of the final vesicle structure depends on the thickness of the membrane. By tuning the thickness of our colloidal membranes, we can set the critical surface area at which a flat sheet will transition into a vesicle. Our system therefore allows for direct probing of vesicle formation physics, measurement of physical properties, and control over membrane curvature and structure size.