In this work, degas-driven microfluidic deterministic lateral displacement devices were fabricated from poly(dimethylsiloxane). Two device configurations were considered: one with a single input for the enrichment of particles and the other one with sheath inputs for the separation of particles based on their sizes. Using the single-input device, the characteristics of the degas-driven fluid through micropillars were investigated, and then selective enrichment of fluorescent polymer particles with diameters of around 13 μm mixed with similar 7 μm particles was demonstrated. Using the sheath-input device, the separation of 13 and 7 μm beads was achieved (the corresponding purities exceeded 92.62% and 99.98%, respectively). In addition, clusters composed of 7 μm beads (including doublets, triplets, and quadruplets) were fractionated based on their equivalent sizes. Finally, white blood cells could be separated from red blood cells at a relatively high capture efficiency (95.57%) and purity (86.97%).