Autonomous microfluidics realized with active hydrophobic valves

Sophisticated microfluidic systems were realized using simple valves based on switching from a hydrophobic state to a hydrophilic state. The valve consisted of a hydrophobic self-assembled monolayer (SAM) formed on a platinum electrode in a poly (dimethylsiloxane) (PDMS) flow channel. The valve could stop a solution moving by capillary action. The solution passed through the valve following reductive desorption of the SAM when an appropriate potential was applied to the electrode. The same switching could also be implemented by changing the mixed potential by wetting a zinc electrode in a controlling flow channel connected to the valve electrode.