|
| Platform | Manipulation principles | Targets | Functions and applications | Light sources | References |
|
| Pure optics | Optical levitation | Balance of an optical scattering force and droplet gravity | Aerosol droplets (about tens of μm in diameter) | Droplet levitation, atmospheric physics, chemistry, and hygroscope | Ar+ laser (488 nm, 1.2 W)
Nd:YVO4 laser (532 nm, 150 mW) | Jordanov and Zellner [37]
Kohira et al. [36] |
| Optical tweezers | Optical gradient force | Aerosol droplets ( μm in diameter) | Droplet trap, atmospheric chemistry and physics (Brownian dynamics), combustion science, and drug delivery | Nd:YAG laser (1064 nm, 5 mW)
Nd:YAG laser (532 nm, 2 W) | Magome et al. [40], McGloin et al.[21]
Leonardo et al. [43] |
| Optical vortex traps | Optical cage at the dark core induced by the ring of laser intensity | Aqueous droplets in oil ( μm in diameter) | Droplet trap, transport, fusion, dynamic control of concentration | Nd:YAG laser to create Laguerre-Gaussian beam | Gahagan and Swartzlander [47], Lorenz et al. [49] |
|
| Optothermal | Photothermocapillary in microfluidic channels | Optically induced Marangoni effect | Aqueous droplets in oil (pL ~ μL) | Droplet transport, trapping, high-speed sorting, and protein assay | Holographic laser (532 nm, 4 W)
Argon-ion laser (514.5 nm in vacuum, 159 mW) Projector | Cordero et al. [52]
Vincent et al. [53],
Kotz et al. [54]
Hu and Ohta [55] |
| Photothermal cavitations in microfluidic channels | Optical breakdown of liquid molecules | Picoliter aqueous droplets in oil | High-speed droplet generation, and fast droplet merging | Q-switched Nd:YVO4 pulse laser (532 nm, 15 ns width, 100 μJ)
Nd:YAG pulse laser (532 nm, 6 ns width, 100 μJ) | Park et al. [56]
Li et al. [57] |
|
| Optoelectronic | Optoelectrowetting (OEW)
Open-OEW
COEW
SCOEW | Optically induced electrowetting | Aqueous droplets in air or oil (pL ~ μL) | Droplet transport, mixing, splitting, dispensing, and integration with an external reservoir | Laser (532 nm, 636 mW/cm2)
Laser (760 nm, 15 mW/cm2)
Laser (632 nm, 254 W/cm2)
Projector, or LCD | Chiou et al. [58, 59]
Chuang et al. [60]
Chiou et al. [61]
Park et al. [62] |
OET
FEOET | Optically induced dielectrophoresis (DEP) | Aqueous droplets in oil (nL ~ μL) | Droplet transport, mixing, integration with microfluidic channel, and microwell structures | LCD
Laser (532 nm, 400 μW/cm2) or projector | Lee et al. [63]
Park et al. [23, 64] |
| Combination of OET and COEW | EWOD for droplet and DEP for microscopic particle manipulation | Nanoliter aqueous droplets in air | Droplet splitting for enhancing particle concentration, and single-cell encapsulation | Projector | Valley et al. [22] |
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