ATRP is a reversible-deactivation radical polymerization (RDRP, also called controlled radical polymerization) system in which the equilibrium between propagating and dormant chain ends is mediated by transfer of a halide to a transition metal catalyst (usually copper) . The mechanism by which oxygen interferes with ATRP is by oxidising the Cu(I)-ligand complex (the activator species) to Cu(II), as well as by quenching the propagating radicals, although the former mechanism dominates over the latter at ATRP equilibrium because of the low concentration of propagating chain ends. Activator regeneration methods are based on continuously regenerating the activator species by steadily reducing Cu(II) back to Cu(I). In activators regenerated by electron transfer (ARGET), this is achieved using an excess of a slowlyreacting non-radical forming reducing agent. In this way, the system formed by the Cu catalyst and reducing agent act as a kind of oxygen scavenger. The same mechanism also allows for a tremendous reduction of catalyst concentrations, to (sub-)100 ppm levels (relative to monomer): although in principle only the ratio of Cu(I) to Cu(II) affects the polymerization kinetics, in reality with normal ATRP a rather large absolute quantity of catalyst is required as a buffer, since inevitable chain termination reactions irreversibly convert Cu(I) to Cu(II). With ARGET, the accumulated Cu(II) is continuously reduced back to Cu(I). Note that activator regeneration methods only render ATRP oxygen tolerant to a limited extent, since the rate of oxygen diffusion into the system should not exceed the activator regeneration rate. This unfortunately means conducting ATRP wholly open to air is still not feasible, since in that case the rate of oxygen diffusion typically exceeds the activator regeneration rate. However, these methods do enable conducting ATRP without the need to deoxygenate the solution, as long as measures are taken to limit fresh air exchange during the polymerization, for example by using sealed vessels like capped vials or jars. Instead of using milliliters of solution in sealed vessels, the reaction volume can be reduced by conducting the reaction in a fluid film between the substrate and a coverslip employed as an oxygen barrier . This significantly reduces the amount of wasted monomer and other reagents, and facilitates scalability. Recently, Flejszar et. al. reported a procedure for polymerising 2-(dimethylamino)ethyl methacrylate (DMAEMA) using SI-ARGET-ATRP under a coverslip to limit oxygen exposure . DMAEMA is special as a monomer for ARGET-ATRP because it itself acts as a reducing agent , eliminating the need for a dedicated one.