Three unique methods for laptop cooling using MEMS devices are discussed: impingement using microscale jets, heat exchangers and sinks using microchannel liquid cooling, and an integrated liquid cooling method using electric fields to control wettability. Impingement can achieve high heat transfer rates but has issues with pressure losses. Microchannel liquid cooling in heat exchangers and sinks can also achieve high rates but requires a bulky closed-loop system. The integrated electric field method has lower rates but is self-contained and controllable. Other promising technologies discussed include corona-driven air flow and micro-thermoelectric coolers.

1. Methods of Heat Dissipation for
Laptops using MEMS Devices
Tyler Baker
May 31, 2016 ME 141A

2. Agenda
● Background
● Three Unique Methods
○ Impingement
○ Heat Exchangers and Sinks
○ Liquid Cooling
● Other Promising Technologies
● Conclusions

3. Background
● As the demand for more,
and more powerful laptop
computers increases, so
does the problem of heat
Experimental Investigation of the Thermal Performance of Piezoelectric Fans S. M. Wait, et al.
Heat Transfer Engineering 2004
● Devices need to cool
quickly, efficiently, and
quietly...
● ...but most importantly, a
cooling device needs to be
small

4. Impingement
● Investigated the effects of different flow regimes
determined by height, h
● Stagnation - Needs to be avoided (for large jets)
● Laminar - Ideal
● Transition
● Turbulent
● High heat transfer rates depended on diameter, spacing of
jets, and location of jets
● heat transfer rate of 420 W/cm2
● Problem of high pressure loss
● Bifurcation
3-D visualization of flow in microscale jet impingement systems E. N.
Wang, et al. International Journal of Thermal Sciences 2010
Direct Liquid Jet-Impingement Cooling with Micronsized Nozzle Array
and Distributed Return Architecture T. Brunschwiler, et al. IEEE 2006

5. Heat Exchangers and Sinks
● Cooligy’s closed loop Liquid Cooling System
● Microheat exchangers with high surface to
volume ratio microstructures (HSVRM)
significantly enhance heat transfer
● Heat is sinked into the HSVRM
● Closed loop system attained a heat transfer
rate of 420 W/cm2
● High pumping requirements for microchannels
● Hydraulic diameters between 318 and 564 μm
tested
● Analytical models derived for microchannel heat
exchangers
● Pressure and flowrate dominated by channel
width, wc
Liquid Cooling
System for
Advanced
Microelectronics
M. Datta, et al.
ECS 2007
Single-Phase flow and
Heat Transport and
Pumping
Considerations in
Microchannel Heat
Sinks S. V. Garimella, et
al. Heat Transfer
Engineering 2004

6. Liquid Cooling
● control electrodes regulates
wettability through use of an
electric field (Pamula et al.)
● Three mechanisms for flow
control
● thermal sensor feedback
control
● Flow-rate feedback control
● Electrothermocapillary
control
Development of a chip-integrated micro cooling device J. Darabi, et al. Microelectrics Journal 2003
● Device using electrohydrodynamics to pump a thin film
over a heated surface
● Self-contained design
● Opening should be approximately 50 μm and have a
length of 10 mm when HFE-7100 (C4
F9
OCH3
) is used as
the fluid (best results)
● 35 W/cm2

7. Other Promising Technologies
● Gas molecules are ionized; forms a flow of air
● Corona-driven flow ensures greater flow
closer to the walls
● Effective for cooling
● Requires high voltages
● Not ideal for laptops
● Bridge-type micro-thermoelectric coolers (μ-
TECs)
● Bridge-type shown to have better heat
transfer characteristics compared to
column-type
● Peltier Effect
● Transfers heat from center of the device
outwards at the cost of electrical energy
Corona Driven air propulsion for cooling of electronics F. Yang, et al. Millpress 2003
Development of low-cost
micro-thermoelectric
coolers utilizing MEMS
technology I. Huang, et al.
Elsevier 2008

8. Conclusions● Impingement
● Requires source of fluid
● High heat transfer rates (420 W/cm2
)
● not self-contained
● Avoids high pressure losses with bifurcation, but pressure is still a problem
● Heat Exchangers and Sinks
● High heat transfer rates (500 W/cm2
)
● Requires entire system (Cooligy)
● Large pressure drops
● Pumping requirements
● Liquid Cooling Using Electric Fields
● Low heat transfer rates (35 W/cm2
)
● Highly controllable
● Can be attached to an existing device
● Self-contained
● Other Technologies
● Corona driven flow optimizes flow profile, but requires high voltage (kV range)
● μ-TECs are well understood and already have a place in cooling technologies
● Bridge-type is better option

9. References1. 3-D visualization of flow in microscale jet impingement systems E. N. Wang, et al. International Journal of Thermal Sciences 2010
2. Direct Liquid Jet-Impingement Cooling with Micronsized Nozzle Array and Distributed Return Architecture T. Brunschwiler, et al. IEEE 2006
3. Development of a chip-integrated micro cooling device J. Darabi, et al. Microelectrics Journal 2003
4. MEMS-enabled thermal management of high-heat-flux devices EDIFICE: embedded droplet impingement for integrated cooling of electronics C. H. Amon, et al.
Experimental Thermal and Fluid Science 2001
5. Liquid Cooling System for Advanced Microelectronics M. Datta, et al. ECS 2007
6. Corona Driven air propulsion for cooling of electronics F. Yang, et al. Millpress 2003
7. Closed-Loop Cooling Technologies for Microprocessors C. Upadhya, et al. (Cooligy, Inc.) IEEE 2003
8. Cooling of Integrated Circuits Using Droplet-Based Microfluidics V. K. Pamula, et al. ACM 2003
9. Single-Phase flow and Heat Transport and Pumping Considerations in Microchannel Heat Sinks S. V. Garimella, et al. Heat Transfer Engineering 2004
10. Development of low-cost micro-thermoelectric coolers utilizing MEMS technology I. Huang, et al. Elsevier 2008
11. Experimental Investigation of the Thermal Performance of Piezoelectric Fans S. M. Wait, et al. Heat Transfer Engineering 2004