A “nano-windmill” driven by a flux of water vapour: a comparison to the rotating ATPase

Abstract

We measure the frequency of collective molecular precession as a function of temperature in the ferroelectric liquid crystalline monolayer at the water-air interface. This movement is driven by the unidirectional flux of evaporating water molecules. The collective rotation in the monolayer with angular velocities ω ~ 1 s(-1) (at T = 312 K) to 10(-2) s(-1) (at T = 285.8 K) is 9 to 14 orders of magnitude slower than rotation of a single molecule (typically ω ~ 10(9) to 10(12) s(-1)). The angular velocity reaches 0 upon approach to the two dimensional liquid-to-solid transition in the monolayer at T = 285.8 K. We estimate the rotational viscosity, γ1, in the monolayer and the torque, Γ, driving this rotation. The torque per molecule equals Γ = 5.7 × 10(-8) pN nm at 310 K (γ1 = 0.081 Pa s, ω = 0.87 s(-1)). The energy generated during one turn of the molecule at the same temperature is W = 3.5 × 10(-28) J. Surprisingly, although this energy is 7 orders of magnitude smaller than the thermal energy, kBT (310 K) = 4.3 × 10(-21) J, the rotation is very stable. The potential of the studied effect lies in the collective motion of many (>10(12)) "nano-windmills" acting "in concerto" at the scale of millimetres. Therefore, such systems are candidates for construction of artificial molecular engines, despite the small energy density per molecular volume (5 orders of magnitude smaller than for a single ATPase).

Optimum Particle Size for Gold-Catalyzed CO Oxidation

“…For nonactivated molecular adsorption, the rate of adsorption is determined by the rate of surface impingement of gas-phase molecules. The flux of incident molecules is given by the Hertz–Knudsen equation 67 Therefore, the molecular adsorption rate constant can be written as with P the partial pressure of the adsorbate in the gas phase, A ′ the surface area of the adsorption site, m the mass of the adsorbate, and S the sticking coefficient. The sticking coefficient used here is 1 for CO and O 2 adsorptions.…”

Chemical Leslie effect in Langmuir monolayers: a complete experimental characterization

“…This is 10 to 50 times larger than the area of the target patterns previously achieved in the literature. 5, [19][20][21] . It is important to note that a free rotation of the molecules can only be observed on domains at least this wide.…”

“…Although targets had been previously observed in Langmuir monolayers of chiral compounds [10][11][12] , it was in the seminal work of Tabe and Yokoyama 5 that such patterns were first attributed to a molecular rotation driven by the evaporation of water in the subphase. This work prompted additional theoretical [13][14][15][16][17] and experimental [18][19][20] studies that featured both evolving target patterns and spirals when the rotation started with defects of strength +1 17,18 . In their publication, Tabe and Yokoyama claimed to have observed the rotation in all of the 14 chiral compounds they tested.…”

“…In their publication, Tabe and Yokoyama claimed to have observed the rotation in all of the 14 chiral compounds they tested. In later experiments, however, Nitoń and co-workers [19][20][21] reported that they could only find molecular rotation in two of the four tested amphiphilic compounds, in particular in those where the chiral center was away from the polar group in the molecules i.e., away from the water/air interface.…”

Deformable active nematic particles and emerging edge currents in circular confinements

“…These results are similar to the edge currents in our simulations and their propagation towards the centre with increasing packing fraction. These similarities with other systems range from collective rotation of chiral molecules of a liquid crystal [ 50 ], to sperm cells [ 51 , 52 ], colloidal and millimetre scale magnetes [ 53 , 54 ] and rotating robots [ 55 ]. An interesting biological example is provided by Chlamydomonas reinhardtii (C. reinhardtii).…”