A microfluidic droplet generator (MFDG) normally produces satellite droplets through break-off from the main droplet because of the Plateau–Rayleigh instability, resulting in contamination and/or poor size distribution of the products. Thus, we herein demonstrate the continuous, passive, and size-based separation of main and satellite droplets using the deterministic lateral displacement (DLD) array method. For the purpose of this study, we designed and employed microfluidic devices comprised of an upstream symmetric flow-focusing MFDG and a downstream DLD array composed of polydimethylsiloxane (PDMS). Initially, we produced water-in-oil (W/O) droplets containing main droplets of ∼61.1 μm diameter in addition to satellite droplets of 1–30 μm diameter in a hydrophobic MFDG, and we report the successful separation of the main and satellite droplets through a single-step DLD array with a critical diameter (D_c) of 37.1 μm. Furthermore, we demonstrated the generation and separation of single-phase or biphasic (i.e. Janus or core–shell) oil-in-water (O/W) main and satellite droplets using a hydrophilic MFDG and a DLD array. Finally, in addition to the removal of main and satellite W/O droplets, we also fractionated satellite droplets of different sizes into three groups (i.e., 21.4, 10.1, and 4.9 μm average diameter) using a device with three-step DLD arrays each having different D_c values (i.e., 37.1, 11.6, and 7.0 μm).

We propose sheath-free microfluidic deterministic lateral displacement devices with inertially focused single straight input.

Here, we present a deterministic lateral displacement (DLD) microfluidic device that may be used for label-free, passive, and continuous separation of viable and nonviable mammalian cells. Cells undergoing apoptosis (programmed cell death) become smaller than normal viable cells due to shrinkage and fragmentation. We used this distinct difference in size to selectively isolate viable Jurkat cells from nonviable apoptotic cells and their remnants through a DLD array that is capable of size-based fractionation of microparticles. First, we calibrated our DLD devices by separating a mixture of larger (∼15-μm) and smaller (∼8- or ∼10-μm) polystyrene beads that emulated viable and nonviable Jurkat cells, respectively. We then demonstrated the separation of viable and nonviable Jurkat cells by introducing their heterogeneous suspensions into two DLD devices with different design parameters. In a DLD device with a 20-μm gap, we collected viable cells at 100 ± 0% capture efficiency (n = 3), at a capture purity of 23.1 ± 4.8%, with 57.8 ± 8.1% removal efficiency of nonviable apoptotic cells and their remnants from the initial mixture solution. On a DLD device with a 23-μm gap, the capture purity of viable cells increased to 50.2 ± 15.0%, with 89.0 ± 3.5% removal efficiency of nonviable cells, and a lower capture efficiency of 48.2 ± 2.0% (n = 3). This first demonstration of label-free and passive separation of viable and nonviable cells by DLD illustrates its potential for, e.g., regenerative medicine and discovery of anti-cancer drugs.