Table 1.
Summary of typical geometric designs in passive label-free separation microfluidic systems
| Schemes | Geometry design types | Geometry design description | Particles to separate | Purity | Recovery | Throughput | Other promotions | Ref. |
|---|---|---|---|---|---|---|---|---|
| DLD | Pillar gap and size | Pillar gap variation | PS beads/RBCs | - | >95%(RBCs) | - | Increased throughput | 63 |
| Pillar size variation | Fluorescent beads | - | - | - | New DLD displacement theory | 64 | ||
| Pillar shape | Triangular pillar | Fluorescent beads | - | - | - | Reduced clogging increased throughput | 65 | |
| - | - | - | - | - | ||||
| I-shape/L-shape pillar | - | - | - | - | Increased lateral displacement | 15 | ||
| I-shape | PS beads/RBCs/E. coli | 100%(RBCs) | - | - | - | 73 | ||
| L-shape | RBCs | >99.7%(RBCs) | - | - | - | 74 | ||
| Protrusion-curvature structure | CTCs | - | 99%(CTC clusters) | - | - | 208 | ||
| Notched pillar | RSCs | - | 80% | 20 μL/min | - | 77 | ||
| Airfoil pillar | 10-μm beads | - | 75% | - | High throughput (Re = 51) | 80 | ||
| 15-μm beads | - | 83% | - | |||||
| 20-μm beads | - | 100% | - | |||||
| Sieve-based pillar | Visualization beads | - | - | - | High throughput (100 < Re < 600) | 82 | ||
| Sieve-based pillar | PS beads | - | - | 120 μL/min | Reduced clogging | 81 | ||
| WBCs | 78 ± 14% | 95% | ||||||
| Filter pillar | CTCs | 99.995% | - | 1 mL/min | Reduced clogging | 68 | ||
| Topology-optimized pillar | 2-6.5-μm beads | - | 92.2% | - | Reduced clogging | 67 | ||
| Combination of DLD arrays | Parallel mirrored device | Extracellular vesicles | - | 50% | 900 μL/h | Increased throughput | 84 | |
| Parallel mirrored device | Water-in-oil droplets | 100% | 100% | 0.2 mL/h | Increased throughput | 86 | ||
| Cascaded device | CTCs | >50% | >90% | 12 mL/h | Multiple stage separation | 8 | ||
| Parallel segmented device | 0.6-1-μm beads | - | - | - | Increased dynamic separation range | 87 | ||
| 3D DLD | Gravity-driven 3D device | Nylon beads | ≥89% | ≥95% | - | - | 99 | |
| Sieve-based 3D device | 785 µm beads | - | 95% | 2 mL/min | Increased throughput | 100 | ||
| Revolved 3D device | 60-μm beads | 99.8 ± 0.5% | - | - | Increased throughput | 53 | ||
| 100-μm beads | 98.7 ± 1.2% | - | - | |||||
| 150-μm beads | 99.1 ± 0.4% | - | - | |||||
| Simplified DLD | Single bumping column | 4.8- and 9.9-μm beads | 99% | 99% | 54 μL/min | Simplified structure/increased throughput | 102 | |
| PFF | Drainage channel | Asymmetric outflow drainage channel | 1.0-5.0-μm beads/RBCs | - | 80% (RBCs) | - | Increased resolution | 153 |
| Duplication | Duplicated focusing channel | 0.5- and 1.5-μm PS beads | - | - | - | 70% separation enhancement | 151 | |
| Focusing channel cross section | Parallelogram cross section | 3-, 6-, and 10-μm PS beads | 100%(10-μm beads) | - | - | - | 177 | |
| IMF | Straight channel | two-stage straight channel | 10- and 20-μm beads/CTCs | >90% | >99% | ≥100 μL/min | - | 114 |
| Straight channel with buffer inlets | 19-μm beads | - | 100% | - | - | 118 | ||
| HeLa cells | 98.5% | 81.4% | - | |||||
| Spiral channel | Triplet parallelizing spiral channel | MCF-7 cells | - | 80–90% | 80 ml/h | - | 131 | |
| Obstacle-based spiral channel | PS beads | - | 99.8% | - | - | 128 | ||
| MCF-7 cells | - | 97.5% | - | |||||
| HeLa cells | - | 92.3% | - | |||||
| Serpentine channel | Asymmetric serpentine channel | Fluorescent PS beads/RBCs | - | - | 15,000 cells/s | - | 139 | |
| Serpentine channel with 3 outlets | 2-m cyanobacteria | - | 96.3 ± 0.3% | - | - | 142 | ||
| Side chamber | Straight channel with chambers | RBCs | 99.6% | - | - | - | 209 | |
| WBCs | 91.0% | - | - | |||||
| Combination | Serpentine channel after spiral channel | CTCs/WBCs/RBCs | 93.60% (CTCs) | 93.84%(CTCs) | - | 99.992% blood cell removal rate | 158 | |
| VEM | Straight channel | Sample-sheath flow channel | 4.8-μm PS beads | - | - | 20 μl/min | 15-μm lateral displacement | 169 |
| Newtonian and viscoelastic fluids | Staphylococcus aureus | >98% | 97% | 3.0 mL/h | - | 170 | ||
| Platelets | - | 100% | - | |||||
| Straight channel | Shear-induced diffusion | Sandwiched straight channel | PS beads | - | 94.4% | 6.75 mL/h | - | 180 |
| Hep G2 cells | - | 89.1% | - | |||||
| Cross-flow microfiltration | Cross-flow membrane filtration | B. polymyxa | - | - | - | Extremely high throughput (Re >4000) | 181 | |
| Combination | DLD/IMF | DLD array after IMF spiral channel | CTCs | 92 ± 3% | - | 5 mL WB/3 h | - | 98 |
| Serpentine IMF channel after DLD array | CTCs | - | 98.6 ± 4.3% | 107 cells/s | - | 192 | ||
| DLD/VEM | DLD array with viscoelastic fluid | 8- and 12-μm beads | - | - | - | Dynamic control of critical size | 196 | |
| IMF/CFF | Three-stage spiral focusing device | 20-μm beads | - | 99.99% | 5 mL/h | - | 197 | |
| MCF-7 cells | - | 90.4% | ||||||
| WBCs | - | 97.97% | ||||||
| PFF/BFF | BFF after PFF | Beads/spores/eukaryotic cells | - | >90%(spores) | - | Large range of sample flow rates | 17 |
DLD deterministic lateral displacement, PS polystyrene, RBC red blood cells, CTC circulating tumor cell, RSC retinal stem cell, WBC white blood cell, PFF pinched flow fractionation, IMF inertial microfluidics, VEM viscoelastic microfluidics, CFF cross-flow filtration, BFF branch flow fractionation.