Isolating the effects of surface roughness versus wall shape in numerically optimized, additively manufactured micro cooling channels

•A shape optimization method was applied to four designs of microchannels.•The optimized designs were 3D-printed using a Stereolithography (SLA) process.•The SLA process accurately reproduced the optimized channels.•Experiments on the SLA test coupons were directly comparable to the numerical results.•In previous work, the same optimized designs were additively manufactured using metal.•The metal microchannel surfaces were very rough and deviated from the intended design.•Comparing experiments between the SLA and metal microchannels shows roughness effects.•The influence of the surface roughness was dependent on the optimized shape changes.