P.O. Box 90291
130 Hudson Hall, Science Drive
Duke University, Durham, NC 27708

(work) 919.660.5294
(e-mail) pyp@ee.duke.edu
Electrical and Computer Engineering (ECE)



Current research involves the development of a droplet-based cooling platform for integrated circuits (ICs) using digital microfluidics platform developed by Pollack, et al. Decreasing feature sizes, increasing speeds, and increasing package densities in ICs are contributing to increased power consumption and elevated die temperatures, which is detrimental to circuit behavior and reliability. Furthermore, hot-spots due to spatially non-uniform heat flux in integrated circuits can cause physical stress and further reduce reliability. Current methods methods in IC cooling are ill-equipped to address the uneven thermal profiles and hotspots generated in high performance ICs.

The aim of my research is to develop a droplet-based digital microfluidic cooling system that can adaptively perform thermal management to dynamically cool these hotspots through real-time reprogrammable flow. Cooling droplets are independently moved in user-defined patterns over an array of discrete electrodes, using a process known as electrowetting. These patterns can be redefined on-the-fly, depending on the thermal profile of the IC.

Studies [4] on the thermal effects of droplet transport in digital microfluidics have shown that using droplets to adaptively cool hotspots. Droplet transport is facilitated by way of reduced voltage requirements necessary to transport droplets at higher temperatures. In other words, droplets move at higher velocities at a given actuation voltage at higher temperatures. This allows for real-time feedback of droplet speeds with respect to temperature (i.e. the hotter the chip, the faster the flow).

Publications and Presentations during my Ph.D. track:

  1. Phil Paik, Vamsee K. Pamula, and K. Chakrabarty, "Adaptive Hot-Spot Cooling of Integrated Circuits Using Digital Microfluidics ," ASME International Mechanical Engineering Congress and Exposition (IMECE), accepted talk, 2005.
  2. Phil Paik, Vamsee K. Pamula, Michael G Pollack, and K. Chakrabarty, "Coplanar Digital Microfluidics Using Standard Printed Circuit Board Processes," 9th International Conference on Miniaturized Systems for Chemistry and Life Sciences (microTAS) , accepted poster, 2005.
  3. Phil Paik, Vamsee K. Pamula, and K. Chakrabarty, "Droplet-Based Hot Spot Cooling Using Topless Digital Microfluidics on a Printed Circuit Board ," International Workshops on Thermal Inestigations of ICs and Systems (THERMINICs), accepted talk, 2005.
  4. Phil Paik, Vamsee K. Pamula, and K. Chakrabarty, "Thermal effects on Droplet Transport in Digital Microfluidics with Applications to Chip Cooling Processing for Integrated Microfluidics," International Conference on Thermal, Mechanics, and Thermomechanical Phenomena in Electronic Systems (ITherm), pp.649-654, 2004.
  5. R. B. Fair, V. Srinivasan, H. Ren, P. Paik, V.K. Pamula, M.G. Pollack, "Electrowetting-based On-Chip Sample Processing for Integrated Microfluidics," IEEE Inter. Electron Devices Meeting (IEDM) 2003.

 


In May 2003, I completed my M.S. thesis which focused on droplet-based mixing on the digital microfluidics platform developed by Pollack, et al. Droplet volumes are of micro- and nanoliter scale, with reduced volume flow rates and low Reynolds numbers making rapid mixing (milliseconds) difficult to achieve. Rapid mixing in microfluidic devices is crucial in realising lab-on-a-chip applications. The basic electrowetting-based system used is shown below:


(electrode pitch size is 1.5 mm and smaller)

Videos demonstrating microfluidic functions are available below (from our group research page). Except where otherwise noted the droplets are approximately 700 nl in volume (about 1.5 mm diameter) and are surrounded by silicone oil.

  • Side-view of a moving droplet (1.2 MB MPEG)
  • Flow of a droplet on a 2-D array (1.6 MB MPEG)
  • Rotary flow of a droplet (2.3 MB MPEG)
  • Dispensing of droplets from a continuous source (1.8 MB MPEG)

Videos demonstrating microdroplet mixing are shown below. Fluorescent and non-fluorescent droplets are merged and shuttled across several electrodes. The volume of each droplet is 1.32 uL (about 1.5 mm diameter with 600 um height), and are surrounded by silicone oil.

Publications and Presentations during my M.S. track:

  1. Phil Paik , Vamsee K. Pamula , Michael G. Pollack and Richard B. Fair, "Rapid droplet mixers for digital microfluidic systems", Lab on a Chip, advance article, 2003.
  2. M.G. Pollack, P.Y. Paik, A.D. Shenderov, V.K. Pamula, F.S. Dietrich and R.B. Fair, "Investigation of electrowetting-based microfluidics for real-time PCR applications", 7th Int'l Conference on Micro Total Analysis Systems (uTAS), 2003.
  3. Phil Paik , Vamsee K. Pamula , Michael G. Pollack and Richard B. Fair, "Electrowetting-based droplet mixers for microfluidic systems", Lab on a Chip, vol 3, pp. 28-33, 2003.
  4. Vamsee K. Pamula, Phil Paik, Jai Venkatraman, Michael G. Pollack, and Richard B. Fair, “Microfluidic electrowetting-based droplet mixing”, (Presented at MEMS Conference 2001, Berkeley).

 


Previous research (B.S. work, BME) was focused on examining the effects of physical stimuli on extra cellular matrix synthesis in porcine inverterbral discs. In one study, isolated disc cells suspended in alginate (gel) beads were subjected to altered osmolarity environments (hypo, iso, and hyper). Another study subjected disc cells suspended in alginate discs to static compression. Changes in gene expression of aggrecan, collagen I, and collagen II were studied using quantative real-time RT-PCR techniques. Please refer here for continued research.

Publications and Presentations during my Undergraduate track:

  1. Jun Chen, Phil Y. Paik, Anthony E. Baer and Lori A. Setton, "Static Compression Effects on Cytoskeletal Gene Expression for Cells of the Intervertebral Disc", Proceedings of the 2001 Annual Meeting of the Biomedical Engineering Society: 3.9.6.
  2. Phil Y. Paik, Jun Chen, Anthony E. Baer, Wei Yan and Lori A. Setton, "Extracellular Matrix Gene Expression in Intervertebral Disc Cells Subjected to Altered Osmolarity", In: Proceedings of the 2001 Annual Meeting of the Biomedical Engineering Society, P3.59.

 


Toward the beginning 2004, I got myself an Pentax K-1000 SLR camera with a 50mm f/2.0 lens as my foray into serious photography. After learning to develop my own black and whites, I invested in a film scanner to digitize my results. I've created a photoblog (short for photo web-log), which can be found below:


(link to photo-blog )


(link to personal blog)

 

 


  • Edmund T. Pratt, Jr. Dean's Graduate Fellowship, 2001 - present
  • Cisco Systems John Chambers Fellowship (2002-2003)
  • Charles R. Vale Award for outstanding research for Duke undergraduates continuing on in graduate studies, Duke University, 2001-2002.

 

 

Last Updated: March 2005