3D printed reactor-in-a-centrifuge (RIAC): Making flow-synthesis of nanoparticles pump-free and cost-effective

It is widely recognised that flow-reactors offer greater control over the stoichiometry of chemical reactions when compared to batch methods, since they provide finer and more predictable regulation over the transport of fluids and chemical species. These characteristics are of critical importance in the context of nanoparticle production, since the physical and chemical properties of the fluidic environment within a reactor strongly influence the size and/or shape of the end-product. In the past decade, replica moulding techniques (e.g., based on soft-lithography) have been developed to manufacture flow-reactors in a relatively cost-effective and efficient fashion. However, devices are often operated using multiple syringe pumps, and several of these techniques require laborious and multi-step procedures. In this study, we developed rapidly prototyped reactors embedded within a cylindrical structure that are designed for actuation using a laboratory centrifuge (herein referred to as reactor-in-a-centrifuge, or RIAC). Using RIACs of different architecture, we demonstrated production of nanoscale liposomes of therapeutically relevant size (in the diameter range 80 - 300 nm) under varying operating conditions. We also demonstrated production of silver nanospheres (with UV-vis absorption maxima of 404 nm) at selected operating conditions. The novel concept proposed in this study has the potential to significantly simplify the synthesis of nanomaterials over more commonly used microfluidic techniques, as it relies on a costeffective and single-step reactor manufacturing process (using a desktop 3D printer) and employs widely available laboratory centrifuges to drive reagents through the reactor. In this paper we describe RIAC's design, manufacturing, and actuation protocols, and demonstrate its applicability to the flow synthesis of nanoparticles without relying on highly specialised instrumentation or costly procedures.