BACKGROUND:  Micropumps are a critical element of microfluidics, as they are required to move small volumes of liquid in a controlled, energy-efficient manner. Several categories of micropumps have been reported, such as mechanical micropumps, electrohydrodynamic pumps, and valve-less bubble-driven micropumps. The valve-less pumps are attractive for microfluidics because of its simplicity in fabrication over mechanical pumps and its flexibility in working liquids over electrohydrodynamic pumps. The preferred method to date of generating bubbles in the valve-less pump, however, is by thermal generation (boiling),which leads to several problems. First, boiling is energy inefficient due to dramatic heat loss. Secondly, liquids condense more slowly than boiling, which limits the actuation frequency of the pumping action and therefore limits control. Finally, overheating can occur which can damage or denature biological materials, making it incompatible for biomedical devices. Other bubble generation methods, such as electrolysis, fail for sealed devices, such as fuel cells, because of the inability to remove bubbles.

INNOVATION:  The invention herein involves a means to generate, move and remove gas bubbles from the microfluidic system quickly and with low power. The invention pumps liquids by taking advantage of surface energy differences to move bubbles through a channel. With current technology, bubble-driven pumps are made open so that bubbles are expelled with the liquid, but the invention described here vents the bubbles through a nano-porous membrane making closed-loop fluidic devices possible.

POTENTIAL APPLICATIONS:  The micro pump described here, with a much simpler and more efficient design over existing technologies, has great potential in fuel cell applications, chromatography, biological and chemical sensors, lab-on-a-chip, and drug delivery systems such as insulin pumps.

ADVANTAGES 

• more efficient in terms of energy consumption (an advantage for portable devices)
• bio-compatibility (biomedical applications)
• control of pumping rate (precision)
• innovative venting system makes closed-loop fluidic systems possible, a critical component for micro fuel cells and lab-on-a-chip applications.
• works with virtually any kind of bubbles, including thermal, electrolysis, injection, chemical reaction, and cavitation.

DEVELOPMENT-TO-DATE:  A device has been fabricated, tested, and characterized in both closed-loop and open-loop configurations.

ABOUT THE LAB:  This innovation is generated by the UCLA Micromanufacturing Laboratory at UCLA. Current research projects in the lab include digital microfluidics, nanoengineered surfaces, microdroplet-dispensing systems, RF liquid switches, micro fuel cells, 3-D microbatteries, and on-chip encapsulation of microdevices.

The web site for the lab is http://cjmems.seas.ucla.edu/

Reference: UCLA Case No. 2005-408

PCT Publication Number: PCT/US05/02212