BACKGROUND:  Droplet-based microfluidic systems using two-phase immiscible flow have demonstrated potential in high speed diagnosis or chemical synthesis. However, in this kind of system, droplets immersed in oil are usually guided by physical microfluidic channels and active control of individual droplets as desired is extremely difficult. Using physically patterned metal electrodes to manipulate individual droplets is one approach, but complex wiring and interconnect issues have to be solved by an active addressing circuit matrix using CMOS techniques, dramatically increasing the fabrication costs.

INNOVATION:  The FEOET device utilizes a photosensitive layer such that when a spot is illuminated by a light source, a virtual electrode is created in the oil medium that can move aqueous droplets around via an induced dielectrophoretic force. Using a light projector and a computer, massively parallel manipulation of droplets can easily be controlled by programming the light output of a low power light projector, such as a DMD micromirror projector or LCD projector.

POTENTIAL APPLICATIONS:  The FEOET platform will open up numerous potential areas in the field of microfluidics or lab-on-a-chip systems, especially in systems requiring large scale, multiplexed, dynamic, biological, and chemical analysis and synthesis. The FEOET platform is extremely attractive for companies in drug and cell screening.

ADVANTAGES

• Optical manipulation is possible in an insulating medium like oil.
• FEOET utilizes a unique mechanism to actuate light-patterned virtual electrodes, which requires 10 orders of magnitude less optical power than conventional optical tweezers resulting in a larger optical manipulation area - a critical component of massively parallel chemical processing.
• The low cost of fabrication enables disposable platforms that prevent cross contamination in biological applications, especially compared to current metal-electrode based technologies and the high fabrication costs associated with complex wiring and interconnects.
• Using a million-pixel spatial light modulator, the FEOET platform has the capability of parallel manipulations of millions of droplets with a single light emitting diode or halogen lamp.
• High throughput, large scale, multiplexed screening of drugs and cells under a variety of physiological and non-physiologic conditions, in addition to non-biological uses.
• Compatible with PDMS microfluidic devices fabricated by soft lithography techniques
• FEOET can easily be integrated with mainstream lab-on-a-chip systems

DEVELOPMENT-TO-DATE:  The device has been simulated, fabricated, and experimentally demonstrated. A video demonstrating the actuation of a single aqueous droplet using a green laser can be seen here: http://www.seas.ucla.edu/~pychiou/Croped_no%20filter%20doplet%20motion%202.wmv

Reference: UCLA Case No. 2007-664