Discrete chemical release from a microfluidic chip

We demonstrate a discrete chemical release method, capable of delivering picoliter volumes of chemical solutions with 100 mu m of spatial resolution and 20 mu s of response time. The releasing mechanism is based on the transfer of pulsed liquid plugs through a hydrophobic air chamber. A microfluidic chip consisting of such a releasing array (2 x 10) is designed and fabricated. Numerical simulation and experimental testing are performed to verify the working principle. Advantages of this release-on-demand technology include leakage-free, fast response and versatile control of release profile. This new method could be a key enabling technology for precisely controlled release of biochemicals for modern pharmacological and biological research.