De-Sheng Meng

University of California, Los Angeles

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Chang‐Jin Kim

University of California, Los Angeles

Y. Sungtaek Ju

University of California, Los Angeles

Joonwon Kim

Cooperative Institutions

University of California, Los Angeles

California NanoSystems Institute

Bioengineering Center

University of Washington

Al-Farabi Kazakh National University

Sungkonghoe University

Seattle University

Samueli Institute

Soonchunhyang University

SUNY Downstate Health Sciences University

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A comparative study of electrolysis and boiling for bubble-driven microactuations

De-Sheng Meng Y. Sungtaek Ju Chang‐Jin Kim

Thermal generation (i.e., boiling) has been the most common bubble-generation method for bubble-driven microactuation, followed by the recent interests in electrochemical generation (i.e., electrolysis). This paper studies energy consumption of the two approaches through systematic experiments and simple thermal models. The objective is to start building a design guideline for the bubble-driven microactuators in microfluidic systems. The results indicate the power consumption of electrolysis microactuation is several orders of magnitude lower than that of boiling. Analysis of controllability, biocompatibility and scaling effect also shows the advantages of electrolysis. However, removal of bubbles is more problematic for electrolysis than that for thermal bubbles.

10.1109/sensor.2005.1497309

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Micropumping by directional growth and hydrophobic venting of bubbles

De-Sheng Meng Chang‐Jin Kim

This paper reports a new micropumping mechanism that combines directional bubble growth and symmetric bubble removal for a net liquid flow. By employing the recent hydrophobic venting technique, the problem of slow bubble collapse is solved and the removal of insoluble gas bubble is enabled. An electrochemical (i.e., electrolysis) bubble pump is built and tested to prove the concept. An open-loop pump produces the maximum flow rate of 65nL/s and the maximum static pumping pressure of 195 Pa, using 14 mW of input power, about an order lower than most reported micro pumps using thermal bubbles. A closed-loop pump circulates at the flow rate of 4.5-13.5 nL/s with input power of 2-85 mW. Variable flow rate is demonstrated by adjusting the input power.

10.1109/memsys.2005.1453957

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A Distributed Gas Breather for Micro Direct Methanol Fuel Cell (micrometer-DMFC)

De-Sheng Meng Joonwon Kim Chang‐Jin Kim

Abstract : This paper introduces a gas breather to remove the gas byproduct (CO2) from the micro direct methanol fuel cell (microDMFC). The concept and device configuration of distributed aim to improve the performance of the mDMFC by (1) decreasing flow resistance, (2) increasing the active electrode area, and (3) reducing or possibly eliminating the discrete gas separator. Experimental verification is provided by a prototype breather with microscale hydrophobic breathing holes, which successfully removed CO2 bubbles from a mixture of weak sulfuric acid and sodium bicarbonate aqueous solution. The techniques to fabricate sub-micron hydrophobic breathing holes with good stability, which would enable integration of the breather into the eventual mDMFC system, are discussed.

Microscale chemistry

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Separator (oil production)

Sodium bicarbonate

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Self-Aligned Micro Bubble Arrays by Using Surface Tension

De-Sheng Meng Chang‐Jin Kim

This paper describes the theory and experiments involve in the capture of bubbles onto a patterned surface. Guided by surface free energy, bubbles can automatically attach to the energetically favorable locations (bubble-traps) and align into bubble arrays. Bubble capturing potential φbc is proposed as the quantity to evaluate the surface’s “affinity” for bubbles. A bubble-trap can therefore be viewed as an area with locally maximum positive φbc. Two types of bubble-traps are proposed and evaluated. Type I bubble-traps are hydrophobic patterns on a hydrophilic flat surface. Type II bubble-traps are concave conic pits surrounded by a hydrophilic flat surface. Simulation of bubble capturing potential φbc explains the bubble-capturing behavior for both cases and predicts a better performance for type II bubble-traps. Experiments agree well with the theoretical prediction and suggest promising applications.

Conic section

10.1115/imece2004-62182

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Citations (9)