Maximizing power and velocity of an information engine

Abstract

Information-driven engines that rectify thermal fluctuations are a modern realization of the Maxwell-demon thought experiment. We introduce a simple design based on a heavy colloidal particle, held by an optical trap and immersed in water. Using a carefully designed feedback loop, our experimental realization of an “information ratchet” takes advantage of favorable “up” fluctuations to lift a weight against gravity, storing potential energy without doing external work. By optimizing the ratchet design for performance via a simple theory, we find that the rate of work storage and velocity of directed motion are limited only by the physical parameters of the engine: the size of the particle, stiffness of the ratchet spring, friction produced by the motion, and temperature of the surrounding medium. Notably, because performance saturates with increasing frequency of observations, the measurement process is not a limiting factor. The extracted power and velocity are at least an order of magnitude higher than in previously reported engines.

Maximal fluctuation exploitation in Gaussian information engines

“…As a model for an information engine, we use the setup from our previous work [15], where a particle with effective mass m immersed in a fluid medium diffuses while under the influence of gravity and a harmonic potential (Fig. 1), henceforth the trap potential.…”

“…Although the unconstrained feedback scheme does not present a conceptual challenge, there are practical experimental difficulties in storing work via the trap (i.e., negative trap work). Information engines have so far been able to extract and store energy via a flow field [8] or gravity [15]. However, all other energy flows not directly linked to either an increase in the system's internal energy via the trap or an increase in system free energy System Thermal reservoir…”

“…Recently, we experimentally realized an information engine based on a colloidal particle, which successfully extracts energy from a thermal reservoir and stores this energy by raising a weight against gravity [15]. We systematically optimized this information engine under the constraint that no external work be done on the particle, finding that there is an optimal particle mass that maximizes the energy-storage rate (the output power).…”

Hidden Dissipation and Irreversibility in Maxwell’s Demon

“…For most of the century and a half since Maxwell first proposed the thought experiment an entity that could sort molecules on the molecular scale was beyond the reach of technology, and Maxwell’s demon stood primarily as an abstract conceptual tool for understanding the statistical foundations of thermodynamics. In recent years, though, advances in nanotechnology have brought molecular machines into the realm of possibility, and devices approximating the function of Maxwell’s demon have now been made [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Biochemical analogs of Maxwell’s demon are under development for molecular synthesis [ 31 , 32 ].…”

Spectroscopic characterization of rare events in colloidal particle stochastic thermodynamics

“…Conversely, by treating these systems as the Brownian particle in a Langevin equation description of the underlying dynamics, experimental results have been used to verify theoretical predictions of stochastic thermodynamics, such as fluctuation theorems, the Jarzynski equality, and trajectory entropy (Seifert, 2012). Considering that nowadays it is possible to prepare colloidal particles with varying size, shape, chemical composition, and spectroscopic properties (Chen, 2014;Hueckel et al, 2021), it is interesting to explore such systems in connection with stochastic thermodynamics (Ciliberto, 2017;Bonança and Deffner, 2018;Saha et al, 2021). For example, large, thermal fluctuations can play an important role in individual stochastic realizations of a thermodynamic process, thus motivating the development of experimental methods for enhanced sampling of such rare events.…”