Table 2.

An overview of active and passive sorting devices and main advantages.

Device feature(s)	Active or passive	Advantage(s)	Reference
Single-layer PDMS
Arrays of geometrically optimized square columns	Active	Directed sorting with high efficiency (>96%), accuracy (>95%), and throughput (∼120 worms/min) and screening for size mutants	[48]
Optical fiber detection and laminar flow switching	Active	High throughput (60 worms/min), sorting accuracy (96.6%), and switching accuracy, gentle for worms	[112]
Arrays of chambers and clamps	Active	Longitudinal measurement of size and locomotion	[131]
Partially closed valves	Active	Highly reliable quantitative adaptive algorithm for high-throughput (~83.33 worms/min) sorting	[92]
A serpentine channel and an array of circular chambers	Passive	Parallelization, without costly and active off-chip components, longitudinal behavioral tracking	[132]
Local electric field traps and semicontinuous flow	Passive	Effective and automatic sorting using electrotaxis based on locomotion first (78 worms/min)	[20]
The electric field, hexagonally arrayed microstructures	Passive	Maximize worm motility for directed self-sorting under the electric field	[22]
Visual aid and electrophoresis box	Passive	Simple and quantitative measurement for self-sorting	[24]
Microchannels with electrodes	Passive	Cost-effective and sensitive sorting using electrotaxis	[25]
Geometrically optimized pillars	Passive	High-throughput (129 ± 31 worms/min) and purity (~96.8%) sorting with an average efficiency of 95%	[51]
Interconnecting channels (Smart mazes)	Passive	Repeated passive sorting to avoid clogging and efficiently separate adult and larval worms	[54]
Special angled symmetrical channels with electric field	Passive	Efficient, economic, and harmless stage-specific deflecting electrotactic responses sorting	[55]
Spiral channels with a trapezoidal cross-section	Passive	High-throughput (4200 worms/min) and high-accuracy (>95%) sorting without chemical	[93]
Microchannels applied dc and ac electric fields	Passive	Effective worm immobilization and high-throughput automated analysis	[133]
Inclined surface with conduit	Passive	High-throughput sorting using the surface following	[124]
Two-layer PDMS
Vision-assisted sorting valves	Active	High-throughput (>3.67 worms/min) quantitative phenotypic sorting of mutants	[134]
Pneumatic microvalves, micropillars, and microelectrodes	Active	Individual worms can be nondestructively recovered after electrophysiological phenotype-based sorting	[74]
Pneumatic microvalves and distributary channels	Active	High-throughput (30 worms/min) sorting based on label-free electrical impedance spectroscopy	[110]
Algorithm-assisted valves	Active	Anticlogging, gentle, high-accuracy (>95%) and high-throughput (15 worms/min) sorting	[50]
Algorithm-assisted, pressure-controlled valves	Active	Robust, real-time worm size measurement and high-throughput (∼10.34 worms/min) sorting	[61]
Circular arranged micropillars and multiple control valves	Active	High-speed (<100 ms per frame) image acquisition for sorting, anticlogging flow at high concentrations	[73]
Specific shape diode arrays	Passive	Directed high-throughput (97±4 worms/min) sorting	[47]
Adjustable filter structures	Passive	High-efficiency (~100%), high-purity (~100%), and high-throughput (210 worms/min) sorting	[49]
Curved channels and valves	Passive	Lateral positioning and efficient (85%) mutant sorting	[135]
Multiple-layer PDMS
Aspiration channels	Active	Reusable, stable, and noninvasive fixation for sorting	[56]
Adjustable filter structures	Passive	Reusable, high-purity (73%–100%) and high-throughput (160–240 worms/min) sorting and eggs extraction	[46]