Microfluidic flow control using selective hydrophobic patterning

We have developed a method to pattern Self Assembled Monolayer (SAM) films of n-octadecyltrichlorosilane (OTS) on silicon and glass substrates using a simple lift-off procedure. By defining hydrophobic regions at definite locations in microchannels and using an external pressure source, we can split off precise nanoliter volume liquid drops and control the motion of those drops through the microchannels. We have also constructed an on-chip pressure source for drop splitting and motion by heating air trapped in a micromachined chamber. Both techniques can produce and move drops on the order of 50 nl.