Rapid microfluidic mixers
PI: Juan G. Santiago
Collaborator:
Prof. Kenneth Goodson of the Mechanical Engineering Department at Stanford
Collaborator:
Prof. James W. Palko of the Mechanical Engineering Department at UC Merced
We have developed novel methods of cooling of electronics which require dissipation of extreme heat fluxes exceeding 1 kW/cm2
over areas of a single centimeter squared. Our approach uses a combination of heat spreading using laser micromachined diamond heat sinks;
evaporation/boiling in fine featured (5 microns) conformal porous copper coatings; microfluidic liquid routing for uniform coolant supply over
the surface of the heat sink; and phase separation to control distribution of liquid and vapor phases.
Figure 1: Boiling experiment using volumetrically Joule heated porous copper structures with passive capillary feeding of water. (a) Schematic of heat transfer
experiment cross section A-A' showing liquid feed from stagnant pool and condensate removal. (b) Image of actual patterned porous copper layer sample,
shown here without supply or condensate removal wicks. Labels indicate current delivery to and voltage measurement across active region. (c) Scanning electron
micrograph of templated electrodeposited porous copper. (d) Length-averaged cross-sections of active regions for three porous copper samples used in
heat transfer experiments.
We have designed and demonstrated the performance of these technologies independently and integrated into functional devices. For example, we have reported two-phase heat transfer performance of diamond/porous copper heat sinks with microfluidic manifolding at full device scales (0.7 cm2) with heat fluxes exceeding 1300 W/cm2 using water working fluid. We further show application of hydrophobic phase separation membranes for phase management with heat dissipation exceeding 450 W/cm2 at the scale of a single extended surface (~300 microns).
Reference
Zhang, C., Palko, J.W., Barako, M.T., Asheghi, M., Santiago, J.G., and Goodson, K.E., "Enhanced Capillary-Fed Boiling in Copper Inverse
Opals via Template Sintering," Advanced functional materials, 2018.
Palko, J.W., Zhang, C., Wilbur, J.D., Dusseault, T.J., Asheghi, M., Santiago, J.G., and Goodson, K.E., "Approaching the limits of two-phase boiling heat transfer: High heat flux and low
superheat," Appl. Phys. Lett., 2015.