Fabrication of metallic heat exchangers using sacrificial polymer mandrils

This paper demonstrates the use of poly(dimethylsiloxane) (PDMS), polyureth ane (PU), epoxy, and poly(methyl methacrylate) (PMMA) as mandrils to fabric ate metallic heat exchangers having 300-700 mum internal channels. The mand rils were prepared using two soft lithographic techniques-replica molding, and microembossing. To fabricate the heat exchangers, the polymeric mandril s were coated with a thin layer of metal by thermal evaporation or sputteri ng; this layer acted as the cathode for electrodeposition of a shell of nic kel or copper that was 100 mum thick. The polymers were removed by burning them out at 400 degreesC in air, or by dissolving them with a tetrahydrofur an solution of tetrabutylammonium fluoride. Studies of heat dissipation sho wed that the nickel heat exchangers with features that range in size from 1 50-750 mum have thermal resistances ranging from 0.07 to 0.12 degrees C-2 W -1 cm at flow rates of water of similar to 20 L h(-1) and pressures of 8.6- 83 x 10(3) N m(-2).