Thermally Driven Sol-Gel Transition of Gelatin in a 3D-Printed Microfluidic Chip

Here we show a facile microfluidic technique to cover an inner wall of microchannel with a thin film of gelatin hydrogel. This was implemented by embedding a temperature-controlling unit in a flow focusing microchannel device, which was fabricated using a 3D-printing method. By tuning the ratio of flow rates between water (gelatin) and oil, in situ sol-to-gel transition of gelatin flow in the locally cooled chip enabled us to selectively achieve symmetric or asymmetric gel coating of a rectangular channel surface in an efficient way.