Novel Microfluidic Jet Deflection: Significant Modeling Challenge with Great Application Potential

A novel method is described for deflecting a liquid jet emanating from an orifice having a diameter of approximately ten microns. While awkward mechanical valves or unwieldy electrodes can be used to deflect a jet, the new method relies on asymmetrically heating a portion of the orifice producing the jet. Embedded in the orifice structure, the orifice and heater are fabricated employing precise techniques used in the manufacture of silicon-based microelectronic components. The jet deflection phenomenon is probed experimentally and investigated theoretically using a computational fluid dynamics approach. It is shown that the jet deflection phenomena stem from three highly coupled competing effects. Two of these are related to the variation of liquid surface tension with temperature and the third to that of viscosity variation [1]. The former manifest themselves as stresses that act normal as well as being tangent to the fluid interface, the tangential component being Marongoni stress that often plays a role in small scale thermocapillary flows [2]