Application: Thermodynamic Engine Powered by Anisotropic Fluctuations

Mechanisms of energy generation are ubiquitous in living systems. Common examples are the F0/F1 ATP synthase and the bacterial flagellar motor. In most cases, it is a gradient of ion (or other chemical) concentration that provides the fuel for these biological engines. Inspired by nature’s ability to harvest energy, we introduce an engine that autonomously extracts work from anisotropic fluctuations. Our embodiment consists of a simple electrical network composed of two resistors and three capacitors. We postulate variable capacitors with moveable dielectric material coupled to a flywheel, which provides both dissipation that absorbs generated power and inertia. We explore the coupling between (fast) thermal fluctuations and a (slow) mechanical component in a way that allows generation of mechanical power. A proof-of-concept is established via stability analysis to ensure the existence of a stable periodic orbit generating sustained power output. The envisioned embodiment requires inertia to maintain rotary motion and average out the generated fluctuating torque. We show that one can dispense with this inertia, often uncharacteristic of biological systems, by coupling multiple subsystems, while still ensuring stability of limit cycles. It is postulated that a similar principle may be at work in biomolecular engines such as flagellar motors or ATPases, where several torque-generating subunits engage to produce energy.