So such a fluid having molecular loop components will gradually accumulate to higher pressure on one side of the film. Then this pressure difference between the two sides can be nicely exploited to keep some tiny electric generator turning.
Or make a submicroscopic hole in a thin film just big enough for a gas molecule to get through. At both ends of the hole hinge a thin short low mass molecule, slightly longer than the hole diameter, so it can open up out right to 90deg from the hole, or can slam shut left obstructing the hole. Then a gas molecule striking this from the left can often get through the hole by knocking the hinged thin light molecule out of its way.
One striking from the right usually gets bounced back right, away from the hinged thin molecule there which is often too much obstructing its path. But sometimes one coming from the right will get through while the hinged thin molecule had gotten bounced briefly open enough by some of the other kinetic heat random motion blows. But when the gas molecule reaches the inner hinged left end of the hole, often it will fail to also pass through there, and thus may often get bounced back right, through and back out of the hole's right end.
Fill the surface of a thin film full of such holes. Gas then tends to collect on the right side to higher pressure, (lower on the left). Use this pressure difference to turn an electric generator. Stretch many such thin films up & down air tight in parallel, all inside some average temperature sealed gas volume box. Then such films cumulatively gain ever higher pressures at their right sides, allowing all this to drive an electric generator.
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