Gold nanocrystals are dispersed uniformly in poly(dimethylsiloxane) to produce a plasmonic composite. The composite can be readily used to fabricate microfl uidic channels. An effi cient optical heating approach on the microfl uidic chips made of the composite is realized on the basis of plasmon- enabled photothermal conversion. A fl uid fl ow switch based on the plasmonic heating is also demonstrated.