Fabricating millifluidic reaction-diffusion devices: Droplet-in-oil networks structured by laser cutting

Abstract

All known forms of life utilise information processing to maintain their complex organisation. In contrast to conventional information technology built on solid-state semiconductor devices, biological information processing is built on transformations through chemical reactions and interactions mediated by diffusion. The theoretical understanding of reaction-diffusion computing as well as prototype implementations have progressed in parallel over the past decades. We report here on a technique for studying spatially structured networks in which chemicals are compartmentalised as droplets-in-oil and laser-cut topologies impose spatial structure. Experiments with halogen displacement reactions demonstrate that the feature size achievable with laser cutting is well suited to practical diffusion time scales. Further advantages of the technique are the optical accessibility, enabling readout from bromine and iodine production, diffusion and indicator reactions, and the good chemical compatibility between the compartmentalisation medium (oil) and the structuring medium (PMMA), while the fast turn-around times enable rapid topology optimisation.