Separation of a binary gas mixture by thermal diffusion in a two-dimensional cascade of many small cavities

•A new clean method for separating a binary gas such as H2 and CO2 is proposed.•A two-dimensional cascade consisting of over 19,000 micro-cavities is fabricated.•Tiny separations of a cavity via thermal diffusion is amplified by the cascade.•Pressure-driven flow spontaneously separates components without active units.•Using a large enough cascade, an almost complete separation is predicted in theory. A new method for separating a binary gas mixture, such as hydrogen and carbon dioxide, is proposed and investigated numerically and experimentally. As a pressure driven flow of the mixture goes through a two-dimensional Burgers cascade, the components are separated due to thermal diffusion and the amplifying effect of the cascade. Unlike traditional cascades in isotope separation, active elements like pumps are absent. The device is made thin enough so that the flow and the concentration distribution reaches an equilibrium within each cell. We have observed separation of up to about 9% in hydrogen concentration in our prototype array consisting of over 19,000 cavities placed under a 160-degree temperature difference.