Table 2.

Summary of closed microfluidics.

Manipulation mode		Principle	Existing problem	Application	Ref.
Active methods	Electroosmosis	Solution generates electroosmotic flow under an electric field	Complicated devices	Cell transport	[157,162]
				Gene analysis	[218]
	Dielectrophoresis	The translational motion of neutral particles in non-uniform electric fields due to dielectric polarization	Complicated devices	Nanoparticle sorting	[164,165,169,170]
				Cell enrichment	[167,168]
	Acoustic waves	Sound waves cause pressure fluctuations and disturbances in fluids	External equipment (signal generation and amplifiers); low throughput	Single cell analysis	[171,172]
				Cell enrichment	[173]
	Centrifugal force	Fluid control by adjusting the speed or direction of the centrifuge	Centrifugal driven mechanism; bulky systems	Molecular diagnosis	[176]
				Enrichment of immune targets	[174,211]
				Perfusion cell cultures	[11]
	Heat methods	Thermosensitive materials undergo deformation when temperature changes	Limitation for temperature-sensitive biological samples	ELISA	[181]
				NA amplification	[178,219]
	Chemical methods	Convert chemical energy to fluid propulsion	Difficulty in precise control; byproduct generation	Small molecule detection	[188]
				Particles manipulation	[154,191]
				Heavy metal detection	[190]
	Optical methods	Photo-sensitive materials	Complex processing of optical materials	Liquid manipulation	[195]
				High-speed flows generation	[155,196]
Passive methods	Gravity methods	Gravitational potential energy	Inability for dynamic or pulsatile flow generation	Immunoassays	[197]
				NA detection	[198]
	Capillary methods	The capillary force that naturally rises or falls with liquids that are wetted or non-wetted with the pipe wall	Difficulty in precise control; long liquid filling time	Biomarkers detection	[134,200,201,204]
				ELISA	[199,200,202]