FIG. 1: Schematic illustration of a possible control mechanism for vesicle shape-change and swimming: Axisymmetric bilayer vesicle with embedded reactive polymers and polymers grafted to its surface. ( a ) → ( b ): Short frequency light impinges on the vesicle, catalyzing a de-polymerization reaction amidst the particle chains, and increasing the fluid volume available to the vesicle. ( b ) → ( c ): A second frequency of light induces the grafted polymers to coil up, inducing an entropic repulsion from the membrane and changing the macroscopic morphology. ( c ) → ( d ): The dispersed particles begin to polymerize back to their initial configuration, deflating the vesicle. ( d ) → ( a ): A third frequency of light is used to uncoil the polymers, relaxing the entropically induced curvature and returning the vesicle to its initial state. By combining two shape-changing mechanisms, it would in theory be possible to achieve a periodic shape cycle which is not time-reversible, yielding a net locomotion. One of many possible configurations that could produce a cycle in shape space is displayed schematically in Fig. 1, where we consider a bilayer vesicle with embedded reactive polymers and with polymers grafted to its surface. In the first step (Fig. 1a → b), a photo-chemical polymerization reaction is catalyzed by green (short wavelength) light, and the polymer chains in the interior of the vesicle disperse into a solution of particles, thus increasing the available volume within the vesicle. At a later time, another frequency of light (red, or longer wavelength) impinges on the vesicle, and the grafted polymers change from a distended to a coiled conformation, inducing an entropic repulsion and changing the curvature of the membrane (Fig. 1b → c). Over time the dispersed particles will polymerize and return the vesicle to its original volume (Fig. 1c → d), and finally a third frequency of light (blue or very short wavelength) can be used to change the conformation of the polymers to distended once more, returning the vesicle to its original state (Fig. 1d → a). While osmotic volume change or chemical-induced composition alteration are two possible ex- 5