Complex Nucleic Acid Hybridization Reactions inside Capillary‐Driven Microfluidic Chips

Abstract Nucleic acid hybridization reactions play an important role in many (bio)chemical fields, for example, for the development of portable point‐of‐care diagnostics, and often such applications require nucleic acid‐based reaction systems that ideally run without enzymes under isothermal conditions. The use of novel capillary‐driven microfluidic chips to perform two isothermal nucleic acid hybridization reactions, the simple opening of molecular beacon structures and the complex reaction cascade of a clamped‐hybridization chain reaction (C‐HCR), is reported here. For this purpose, reagents are arranged in a self‐coalescence module (SCM) of a passive silicon microfluidic chip using inkjet spotting. The SCM occupies a footprint of ≈7 mm² of a ≈0.4 × 2 cm² microfluidic chip. By means of fluorophore‐labeled DNA probes, the hybridization reactions can be analyzed in just ≈2 min and using only ≈3 µL of the sample. Furthermore, the SCM chip offers a variety of reagent delivery options, allowing, for example, the influence of the initiator concentration on the kinetics of C‐HCR to be investigated systematically with minimal sample and time requirements. These results suggest that self‐powered microfluidic chips equipped with a SCM provide a powerful platform for performing and investigating complex reaction systems.