Active thermal management of on-chip hot spots using EWOD-driven droplet microfluidics


In response to the rapid advances in microelectronics, novel cooling technologies are needed to meet increasing cooling requirements. As a paradigm-shifting technique, electrowetting-on-dielectric (EWOD) uses electric potential to control the movement of a liquid droplet on a dielectric surface. In this work, we developed an EWOD-based microfluidic technique for active and adaptive thermal management of on-chip hot spots. A two-dimensional array of control electrodes was patterned on the chip surface for EWOD operations. By applying DC or AC voltages with appropriate sequence and timing to the electrode units, we were able to transport microdroplets of tens of μL along a programmable path. Without the need of external pumps and valves, the droplets were precisely delivered to cooling targets. With the driving voltage as low as 40 VAC, we demonstrate high heat flux (7.6 W/cm2) cooling on a hot spot. The EWOD-induced internal circulation within the droplets led to a time-averaged Nusselt number of ~45.

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  1. Baird E, Mohseni K (2008) Digitized heat transfer: a new paradigm for thermal management of compact micro systems. IEEE Trans on Compon and Packag Technol 31(1):143–151

  2. Bell LE (2008) Cooling, heating, generating power, and recovering waste heat with thermoelectric systems. Science 321:1457–1461

  3. Chatterjee D, Shepherd H, Garrell RL (2009) Electromechanical model for actuating liquids in a two-plate droplet microfluidic device. Lab Chip 9:1219–1229

  4. Cheng JT and Chen CL (2008) Adaptive chip cooling using electrowetting. Proceedings of the ECI international conference on heat transfer and fluid flow in microscale, Whistler, Canada, September 21–26

  5. Garimella SV et al (2008) Thermal challenges in next-generation electronic systems. IEEE Trans on Compon and Packag Technol 31(4):801–815

  6. Gong J, Kim CJ (2008) Direct-referencing two-dimensional-array digital microfluidics using multilayer printed circuit board. J Microelectromech Syst 17(2):257–264

  7. Jones TB, Wang KL, Yao DJ (2004) Frequency-dependent electromechanics of aqueous liquids: electrowetting and dielectrophoresis. Langmuir 20:2813–2818

  8. Kumari N, Bahadur V, Garimella SV (2008) Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages. J Micromech Microeng 18:105015

  9. Mugele F, Baret JC (2005) Electrowetting: from basics to applications. J Phys Condens Matter 17:R705–R774

  10. Paik P, Pamula VK, Fair RB (2003) Rapid droplet mixers for digital microfluidic systems. Lab Chip 3:253–259

  11. Tuckerman DB, Pease RFW (1981) High-performance heat sinking for VLSI. IEEE Electron Device Lett 2(5):126–129

  12. Yi UC, Kim CJ (2006) Characterization of electrowetting actuation on addressable single-side coplanar electrodes. J Micromech Microeng 16:2053–2059

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This work was supported by Rockwell Automation, Inc. The authors thank L. Lin, D. Taber and B. Wen for EWOD device fabrication, technical assistances, and helpful discussion.

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Correspondence to J.-T. Cheng.

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Cheng, J., Chen, C. Active thermal management of on-chip hot spots using EWOD-driven droplet microfluidics. Exp Fluids 49, 1349–1357 (2010).

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