Microfluidic devices as used, e.g., in lab‐on‐a‐chip and micro‐total‐analysis systems, are frequently fabricated using silicon or polydimethylsiloxane (PDMS)‐based technologies, both with their known disadvantages. Here, we design a fully polymeric, multifunctional microfluidic reactor device, using an alternative fabrication method, the two‐component co‐injection moulding technology, in which different polymer combinations—generally a flexible and a rigid thermoplastic polymer—can be applied. The prototype device is based on an ambi‐symmetrical design, combining two identical shells, that are each folded to occupy a 160 × 90 mm2 space and subsequently stacked into a 4 (double) layer system. One microfluidic reactor unit includes six different in‐ and output connections, six peristaltic pumps (built up from three membranes each), eighteen volume‐neutral, recoverable control valves, two fluid storages, and two efficient, flow splitting, rotating and recombining, serpentine mixers. The mixers realize an almost perfect baker's transformation and possess ten elements that create 2 × 410 layers with an individual striation thickness of 0.5 nm in 10 s. The total reactor volume amounts 7 mL. The capacity of the peristaltic pumps, with their stroke of 0.5 mm, equals about 35 µL · s?1 at an actuation frequency of 5 Hz. Actuation occurs by air pressure. One microfluidic device can be endlessly connected to its replicas.
