Fabrication of metallic heat exchangers using sacrificial polymer mandrils

Abstract

This paper demonstrates the use of poly(dimethyl-siloxane) (PDMS), polyurethane (PU), epoxy, and poly(methyl methacrylate) (PMMA) as mandrils to fabricate metallic heat exchangers having 300-700 μm internal channels. The mandrils were prepared using two soft lithographic techniques-replica molding, and microembossing. To fabricate the heat exchangers, the polymeric mandrils were coated with a thin layer of metal by thermal evaporation or sputtering; this layer acted as the cathode for electrodeposition of a shell of nickel or copper that was 100 μm thick. The polymers were removed by burning them out at 400 °C in air, or by dissolving them with a tetrahydrofuran solution of tetrabutylammonium fluoride. Studies of heat dissipation showed that the nickel heat exchangers with features that range in size from 150-750 μm have thermal resistances ranging from 0.07 to 0.12° -2C W-1 cm at flow rates of water of ∼ 20 L h-1 and pressures of 8.6-83 x 103 N m-2.