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This paper describes for the first time the use of alginate hydrogels as miniaturised microvalves in microfluidic devices. These biocompatible and biodegradable microvalves are in situ generated, on demand, allowing for microfluidic flow control. The microfluidic devices were fabricated using the origami technique with a single sheet of cyclic olefin polymer folded into several layers followed by thermocompression bonding. The hydrogels can be dehydrated at mild temperatures, 37 ºC, to slightly open the microvalve and chemically erased using an ethylenediaminetetraacetic acid disodium salt dehydrated (EDTA) solution, to completely open the channel, ensuring the reusability of the whole device.

and replaceable from the external electronic and pneumatic actuators box. Functionality of the LFCS is tested by connecting it to a microfluidic droplet generator, rendering highly stable flow rates and allowing generation of monodisperse droplets over a wide range of flow rates. The results indicate the successful performance of the LFCS with significant improvements over existing LFCS devices, facing the possibility of using the system for biological applications such as generating distinct perfusion modes in cell culture, novel digital microfluidics. Moreover, the integration capabilities and the reproducible fabrication method enable straightforward transition from prototype to product in a way that is lean, cost-effective and with reduced risk.

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