many of the properties of bilayer membranes composed of simple single - chain amphiphiles seem to be well - suited for a potential role as primitive cell membranes . however , the spontaneous formation of membranes from such amphiphiles is a concentration - dependent process in which a significant critical aggregate concentration ( cac ) must be reached . since most scenarios for 
 the prebiotic synthesis of fatty acids and related amphiphiles would result in dilute solutions well below the cac , the identification of mechanisms that would lead to increased local amphiphile concentrations is an important aspect of defining reasonable conditions for the origin of cellular life . 
 narrow , vertically oriented channels within the mineral precipitates of hydrothermal vent towers have previously been proposed to act as natural clusiusdickel thermal diffusion columns , in which a strong transverse thermal gradient concentrates dilute molecules through the coupling of thermophoresis and convection . here 
 we experimentally demonstrate that a microcapillary acting as a thermal diffusion column can concentrate a solution of oleic acid . upon concentration , 
 self - assembly of large vesicles occurs in regions where the cac is exceeded . 
 we detected vesicle formation by fluorescence microscopy of encapsulated dye cargoes , which simultaneously concentrated in our channels . 
 our findings suggest a novel means by which simple physical processes could have led to the spontaneous formation of cell - like structures from a dilute prebiotic reservoir .