Autonomous Motion of Vesicle via Ion Exchange

Abstract

The autonomous motion of vesicle is observed in a simple chemical system. A vesicle composed of didodecyldimethylammonium bromide DDAB breaks down by ion exchange from Br(-) to I(-). When an electrolyte is supplied to vesicles, some of them begin to move after an induction period. They continue to move, leaving behind the reaction products on the trail. The ion exchange decreases the vesicle size, and smaller vesicles remain after the motion. We examine the characteristics of this motion. The surface tension of the DDAB-containing aqueous phase depends on the KI concentration. Considering this result carefully, we conclude that vesicles can move when the ion exchange from Br(-) to I(-) proceeds irreversibly. Then, inhomogeneity in the vesicle membrane develops because of the coagulating nature of the product, didodecyldimethylammonium iodide (DDAI), which is sparingly soluble in water. Inhomogeneous properties of vesicle membranes are then generated, which induce surface transport of the reaction product and flow in the water pool. As a result, a couple of convection rolls appear in the water pool of the vesicle. The convection rolls drive vesicle motion. A simple model for the semiquantitative description is proposed.

Orientational order in concentrated suspensions of spherical microswimmers

“…We impose u θ (θ) = B 1 P 1 (cos θ) + B 2 P 2 (cos θ), where P n is the n th Legendre polynomial, and θ = 0 defines the direction ē in which the squirmer swims, with speed (for a solitary squirmer) U ∼ B 1 (U is set to 1). Fluid disturbances in the far field are governed by the "stresslet" (or force-dipole) of the organisms, ≈ 0 for Volvox and artificially created squirmers [17,24,27], to ≈ +1 for Chlamydomonas [19].…”

Chemical robotics — chemotactic drug carriers

“…There are several autonomously moving chemical objects from nano-to millimeter scale [29][30][31][32], e.g., nanorods powered by redox reaction on their surface [33], self-powered vesicles [34] and microscopic oil droplet suspended in water based on asymmetric chemical reaction at their interfaces [35,36].…”

“…This can contain either drug or other drug carriers like nanoparticles, and the membrane of this small compartment will protect the drug from leakage. Autonomous motion can be governed by either asymmetrical chemical reaction at the leading and ending edges of the cell's membrane [34] or Marangoni effect (in a chemical gradient the protonation rate of fatty acid molecules in a membrane can be different, which can induce a surface tension gradient in the membrane and this can maintain an autonomous and tactic motion of fatty acid stabilized compartments) [35,36] rather than using "molecular" rotors or engines, and this motion can be controlled by taxis of the artificial cell.…”

Autonomously Moving Colloidal Objects that Resemble Living Matter

“…Recently, the authors' group studied an autonomously moving vesicle composed of didodecyldimethylammonium bromide (DDAB) with ion-exchange [58]. When iodide anions diffuse into the vesicular phase, ion-exchange occurs.…”