The liquid flow will be held in a hydrophilic channel when the cross section suddenly becomes large, while the flow will be held when the cross section of hydrophobic channel suddenly shrinks. The siphon valve is simply based upon the siphon phenomenon. When the cross section of the channel is small enough, the liquid in the chamber is able to flow along the channel due to surface tension. Unlike hydrophilic or hydrophobic valves, surface tension acts as a pump in this model while centrifugal force acts as resistance instead. The sacrificial valve is a new technique that is controlled by laser irradiation. These sacrificial valves are composed of iron oxide nanoparticles dispersed in paraffin wax. Upon excitation with a laser diode, iron oxide nanoparticles within the wax act as integrated nanoheaters, causing the wax to quickly melt at relatively low intensities of laser diode excitation. The valve operation is independent of the spin speed or the location of the valves and therefore allows for more complex biological assays integrated on the disk. Volume metering Volume metering is a typical function of centrifugal fluidics to reach a certain amount of liquid reagent. It can be achieved by simply connecting an overflow channel to the chamber. Once the liquid is at the level of the overflow channel, the rest of the liquid will be routed into the waste chamber connected to the overflow channel. Mixing Mixing is an important function in microfluidics, which combines various reagents for downstream analysis. As the fluid is confined in the microscale domain, mixing becomes difficult due to the low Reynolds number with laminar flow. That indicates that there is no convective mixing but diffusion, which limits the mixing process. This problem can be solved using several methods. A typical way is to rotating the disk in different directions, namely clockwise and counter clockwise rotation. Flow switching Flow switching is necessary when routing reagents into different chambers. A common method for flow switching in a centrifugal device is to utilize the Coriolis force within a Y-shaped structure. When the rotating speed is too low, the liquid flow will follow the original path; when the rotating speed is high enough, which is at almost the same level as centrifugal force, the liquid flow will be routed into another chamber. Others Other functions such as sedimentation are also used in microfluidic platforms when necessary. Due to the different mass