Table 4.

Overview of integrated systems for synthesis of microparticles (MPs.)

MPs Type	Enabling Technologies/Modules	Crucial Parameters	MP Size (μm)	Costs 1	Year	Reference
PEDOT/PSS-agarose hybrid MPs	Microfluidic droplet generator	Continuous oil flow rate	20–80	★★	2016	Lee [127]
Solid core enzyme-immobilised microcapsules	Flow focusing		580 ± 10	★★	2019	Varshney [132]
Magnetic droplets	Step emulsion device Magnetically driven microfluidic droplet generation technique	Dimensions of channels	85–125	★★	2016	Kahkeshani [130]
W/O emulsions W/O/W emulsions	Flow focusing Droplet-based microfluidics Commercially available self-setting rubber	Flow rate Nozzle diameter	100–500	★	2015	Lapierre [131]
Chitosan microspheres	512-microchannel geometrical passive breakup device T-junction	Flow rate	40.0 ± 2.2	★★	2019	Kim [133]
PLGA microspheres	512-channel geometric droplet-splitting microfluidic device 256 T-junction		6.56	★★	2020	Kim [136]
Cell-laden microgel	Flow-focusing platform On-chip	Cell concentration	~240–300	★★	2019	Mohamed [138]
Drops	Parallelised microfluidic device Millipede device	Device geometry	20–160	★★	2016	Amstad [135]
Free-floating polymer (PEGDA)	Contact flow lithography system	Microchannel dimensions	20–150	★★★	2015	Goff [139]
W/O and O/W emulsions	Glass microfluidic device Step emulsification		80.9 (CV = 2.8%)	★★	2017	Ofner [137]
Chitosan/TiO2 composite	Factory-on-chip Modularised microfluidic reactors		539.65	★★★	2017	Han [134]
Water-in-water (W/W) emulsions	Microneedle-assistance Microfluidics Flow focusing	Column pressure	5–65	★★★	2019	Jeyhani [128]
W/O emulsions	Electrical detection Microfluidics Closed-loop control	Flow rate	200	★★★★	2017	Fu [144]
Liquid metal	Microfluidic flow-focusing device	Electrical potential Flow rate	~80–160	★★★	2016	Tang [48]
W/O and oil-in water (O/W) emulsions	3D-printed droplet generator Plug-and-play	Liquid flow rate ratio Viscosity of the dispersed phase	~50	★★	2016	Zhang [146]
PEGDA	3D-printed generator Screw-and-nut	T-junction gap height Flow rates	34–1404	★★	2019	Nguyen [147]
W/O droplets	3D-printing technology Millifluidics Chimney-shaped void geometry	Flow rates Apex angle	36–616	★★	2019	Hwang [148]
Magnetic liquid metal	3D-printed coaxial microfluidic device	Orifice diameter Flow rate ratio	650–1900	★★★	2020	He [149]
EGaIn	Acoustic waves Electrochemistry Electrocapillary	Oxidative/reducing voltages Activating frequency	10–80	★★★	2016	Tang [48]
Water-in-oil (W/O) emulsions	Ultrasonic transducer	Vibrational velocity Pressure	62.5 ± 2.6	★★★	2018	Fujimoro [151]
Pure water, silicone oils	Ultrasonic torsional transducer	Pressure Resonance frequency Diameter of liquid column	~80–120	★★★	2015	Kishi [150]
W/O microdroplets	Glass-capillary-based microfluidic device Tabletop minicentrifuge	Diameter of inner and outer capillary orifice	~6.6–13.8	★★	2014	Yamashita [154]
W/O emulsions	Spinning micropipette liquid emulsion generator	Flow rate Motion velocity of the micropipette	25–230	★★	2016	Chen [49]
W/O emulsion	Centrifugal microchannel	Size of microchannels Centrifugal force	~52.5	★★	2017	Chen [156]
Calcium alginate	Centrifugal microfluidic technique	Centrifugal force Circumference of the channel outlet	~109–269	★★★	2015	Liu [162]
W/O picolitre droplets	Centrifuge-based step emulsification device	Level of oil phase Centrifugal force Height of microchannel	18–90	★★★	2019	Shin [155]
Gallium-based liquid metal	Submerged electrodispersion technique Spinning disk	Electric field Flow rate Rotation speed of the disk	~10–800	★★★	2019	Zhang [157]
Water, liquid metal, hydrogel, double emulsions	Spinning conical frustum	Rotational speed Applied voltage Flow rate	~200–550	★	2019	Tang [129]
Sodium alginate multicompartmental particles	Centrifuge-based droplet shooting device	Barrel configuration Diameter of capillary orifice	99 and 16	★★★	2012	Maeda [152]
Sodium alginate with complex shape	Centrifuge 3D nonequilibrium-induced microflows	Diffusional flow Marangoni microflows	~112.4–135.1 (various shapes)	★★★	2016	Hayakawa [153]
Janus MPs	Centrifugal gravity UV irradiation		282 (mean)	★★★	2020	Tsuchiya [163]
Solder (Sn63Pb37)	Piezoelectric membrane-piston-based jetting technology	Pulse length Voltage value Temperature	~85	★★★★	2019	Ma [160]
PDMS, UV-curing optical glue (high viscosity >2000 cps)	Tip-assisted electric field intensity enhancement effect High-resolution capability of EHD printing	Applied voltage Gap distance Nozzle inner diameter Deposition time	>2.3	★★★★	2019	Zou [164]
Al	Pneumatic drop-on-demand technology	The aspect ratio of the nozzle hole The distance between inlet hole and nozzle hole	359.9	★★★★	2017	Zhong [165]
Ink drops	Pneumatic valve Feedback control Ejection technology Machine vision	Solenoid valve “ON” time		★★★★★	2018	Wang [166]
Al alloys (AlSi12)	StarJet technology	Applied pressures	235 ± 15	★★★★	2017	Gerdes [126]
Alginate	Drop-on-demand jetting Piezoelectric print-head	Voltage waveform Microdroplet velocity Concentration of CaCl2 solution	~80–110	★★★★	2016	Gao [158]
Water drops	Piezo-actuated microdroplet generator Drop on demand	Deflection voltage Suction and compression time Nozzle diameter	450–1000	★★★★	2014	Sadeghian [167]
Chitosan aerogel	Jet cutting Supercritical drying of gel	Nozzle diameter Cutting disc velocity Number of wires of the cutting disc	700–900	★★★	2020	López-Iglesias [168]
Sodium alginate	Alternating viscous and inertial force jetting mechanism	Applied voltage Nozzle diameter Fluid viscosity	~30–80	★★★★	2017	Zhao [169]
Sodium alginate	Alternating viscous and inertial force jetting mechanism	Actuation signal waveforms Nozzle dimensional features Solution velocity	53–72	★★★★	2015	Zhao [159]
Al	Supersonic laser-induced jetting	Incubation time Droplet velocity	~3.9	★★★★	2015	Zenou [161]
High viscous microdroplets	Pneumatically driven inkjet printing system	Droplet volume Standoff distance frequency	~143–247 (12.2–63.5 nL)	★★★★	2016	Choi [50]

¹ The number of asterisks (★) represents the cost of synthesis system; 1 means relatively low cost, while 5 means expensive.