Molecular-Sized Outward-Swinging Gate: Experiment and Theoretical Analysis of a Locally Nonchaotic Barrier

TL;DR

This paper introduces a molecular-sized outward-swinging gate that can decrease entropy locally, demonstrated through experiments and simulations, challenging traditional thermodynamic principles and suggesting new ways to produce work from a single reservoir.

Contribution

It presents the concept and experimental validation of a locally nonchaotic gate that asymmetrically controls particle flow, offering a novel mechanism for entropy manipulation.

Findings

Gas flows from low to high pressure through the membrane.

The gate imposes constraints that maximize entropy in a nonequilibrium state.

The mechanism differs from Maxwell's demon and Feynman's ratchet.

Abstract

We investigate the concept of molecular-sized outward-swinging gate, which allows for entropy decrease in an isolated system. The theoretical analysis, the Monte Carlo simulation, and the direct solution of governing equations all suggest that under the condition of local nonchaoticity, the probability of particle crossing is asymmetric. It is demonstrated by an experiment on a nanoporous membrane one-sidedly surface-grafted with bendable organic chains. Remarkably, through the membrane, gas spontaneously and repeatedly flows from the low-pressure side to the high-pressure side. While this phenomenon seems counterintuitive, it is compatible with the principle of maximum entropy. The locally nonchaotic gate interrupts the probability distribution of the local microstates, and imposes additional constraints on the global microstates, so that entropy reaches a nonequilibrium maximum. Such a mechanism is fundamentally different from Maxwell's demon and Feynman's ratchet, and is consistent with microscopic reversibility. It implies that useful work may be produced in a cycle from a single thermal reservoir. A generalized form of the second law of thermodynamics is proposed.