Photoactive integrated microfluidic valves for on-chip fluid control

In microfluidics, on-chip fluid control is crucial for applications where programmable and automated fluid handling with low dead volume and limited auxiliary equipment is desired. This is, for instance, the case for point-of-care (POC) devices, especially in low resource settings. The integration of photoactive valves into a disposable microfluidic chip is one method of attaining low-power and non-contact fluid control in the blink of an LED. A liquid crystal network (LCN) based micro-valve was developed, which enables rapid fluid transfer on-chip by opening a venting channel upon illumination at 80 mW cm^-2 with a 455 nm wavelength LED. We show in two proof-of-principle devices that multiple valves can be integrated into a 3D-printed microfluidic chip. Their individual actuation leads to directed sequential filling as well as draining of a reaction chamber, providing the prerequisite for intricate on-chip processes. Thus, our photoactive valves show the potential of facilitating programmable lab-on-a-chip experiments, for instance, for sample preparation such as for bind-wash-elute protocols, for immunoassay, or for amplification-based detection methods.