Nanotransport controlled by means of the ratchet effect

Abstract

The directional motion of micro- and nanoparticles can be induced not only directly due to the effect of forces with a nonzero average value, which set the direction of the motion, but also, in the absence of such forces in systems with broken mirror symmetry, under the effect of nonequilibrium fluctuations of various natures (the motor or ratchet effect). Unlike other reviews on nanoparticle transport, we focus on the principles of nanotransport control by means of the ratchet effect, which has numerous practical applications and, in particular, is a promising mechanism for targeted delivery of drugs in living organisms. We explain in detail various techniques to arrange directional motion in asymmetric media by means of rectification of the nonequilibrium fluctuations that supply energy to the system and feature a zero average value of applied forces, whether actual or generalized. We consider in depth the properties and characteristics of ratchet systems, their dependences on temperature, load forces, and features of the periodic potential profile in which nanoparticles move, such as the frequency of fluctuations of this profile and its spatial and time asymmetry. A systematic description of factors that determine the direction of motion of ratchet systems is presented.

Temperature-Frequency Controlling the Characteristics of a Pulsating Brownian Ratchet with Slightly Fluctuating Potential Energy

“…Controlling of nanoscaled processes is possible through turning various parameters, among which temperature plays a special role. The currently well-known nonlinear systems, called Brownian motors or ratchets [1][2][3][4][5][6] are not an exception here: temperature changes can lead to changes in the hierarchies of both characteristic times and energies of ratchet systems and thus transfer them to a fundamentally different operating mode up to the elimination of the effect [7][8][9][10]. The same result can arise from changes in the frequency of the potential energy of a Brownian motor [1][2][3][9][10][11].…”

“…Thought the term "Brownian motor" (or "Brownian ratchet") was first invented to illustrate the impossibility of spontaneous emergence of directed motion from equilibrium fluctuations, later it has already been adapted or even reinvented to predict the possibility and explain the mechanism of the appearance of directed motion as a result of rectification of unbiased nonequilibrium fluctuations in nanoscaled nonlinear systems, natural or artificial [1,4], under the broken spatial and/or temporal symmetry [12][13][14][15][16]. At present, the controlled ratchet effect widens the set of new methods for controlling the nanoparticle transport which are both already successfully competing [17][18][19][20] and will compete or be combined with traditional methods [6]. For that reason, the following problems seem to be actual not only in theoretical, but firstly in an applied context: (i) finding the complete set of control parameters of ratchet systems, (ii) structuring the ranges of their values, operation modes, and responses of ratchets to changes in these values [1,3,5,6,21], (iii) methods for obtaining analytical results and recommendations for using them.…”

“…At present, the controlled ratchet effect widens the set of new methods for controlling the nanoparticle transport which are both already successfully competing [17][18][19][20] and will compete or be combined with traditional methods [6]. For that reason, the following problems seem to be actual not only in theoretical, but firstly in an applied context: (i) finding the complete set of control parameters of ratchet systems, (ii) structuring the ranges of their values, operation modes, and responses of ratchets to changes in these values [1,3,5,6,21], (iii) methods for obtaining analytical results and recommendations for using them. As one of the applications of the ratchet theory, we can mention biological protein motors [22].…”

Ratchet effect in frequency-modulated waveguide-coupled emitter arrays

“…Ratchets are periodic systems that generate a directed particle flow under an action of a time-oscillating force with zero mean. Ratchets are known in different fields of physics, chemistry and biology including Brownian motors, temperature ratchets as well as rocking and pulsating ratchets [1][2][3][4]. Ratchets can be realized in semiconductor, cold atom, superconducting and active matter systems [5].…”

Ratcheting charged polymers through symmetric nanopores using pulsed fields: Designing a low pass filter for concentrating DNA

“…Two elements are required to build a ratchet that can rectify otherwise random motion: keeping the system out of equilibrium and symmetry breaking. The first condition can be achieved using either a stochastic or a deterministic external perturbation [23][24][25], such as a pulsed field. The symmetry can be spatially [25][26][27][28][29] and/or temporally broken [26,30].…”