We reported herein a facile method that utilized surface-initiated Polymerization (SIP) alone to produce superhydrophobic poly(dimethylsiloxane) (PDMS) Surfaces, either flat or as the wall of microfluidic channels. In this so-called relayed SIP strategy, the first SIP was conducted from the initiator integrated PDMS (iPDMS) of varied initiator density, i.e., from 0.5iPDMS to 10(-6)iPDMS, corresponding to surface density of 3.7 x 10(-2) and 1.0 x 10(-9) chains nm(-2), respectively, an estimation based on uniform distribution of feed initiator molecules. The monomer in use was oligo(ethylene glycol) methacrylate, resulting in poly(OEGMA) chains with terminal hydroxyl groups. The iPDMS Substrates were then treated with bromoisobutyryl bromide as the initiation moiety, followed by the second SIP using monomer 1H,1H,2H,2H-perfluorodecyl methacrylate (FMA). The resulting surface was covered with polymeric trees that had poly(FMA) Lis the branches and poly(OEGMA) as the central trunk. Only the iPDMS of ultralow initiator density, i.e., 10(-3)iPDMS (1.0 x 10(-5) chains nm(-2)), produced a superhydrophobic surface with a contact angle of water at 155 degrees. The impact of SIP duration and monomer in use was also studied. The results demonstrated that SIP from Substrates of ultralow initiator density could also produce functional surfaces. Furthermore, because this method is compatible with the in situ modification of microfluidic channels, it also provides new opportunities for the field of microfluidics.