Particle-sorting devices

Fig. 13 Particle-sorting devices using negative ODEP force [47], (a) Principle of negative ODEP. (b) Principle of two-outlet particle-sorting device, (c) Particle sorting with ODEP guide patterns. Reprinted with kind permission from [47] Copyright 2008 Chemical Biochemical Microsystems Society...

Sorting can be seen as a preliminary assembly step. Particle sorting has been known as a common application for microfluidic devices and could be integrated into a microfluidic assembly system. While most sorting methods utilize spherical components, railed microfluidic chaimels have been created to sort and control orientation of non-geometric components [6]. Furthermore, concept of space confinement within a microfluidic channel has been applied to the assembly of microscale components into structures that resemble polymer chains [7]. 

Lab-on-a-Chip devices for particle and ceU separation are used to either remove particles of interest, sort a mixed population of particles into subpopulations of like particles, or concentrate (enrich) particles for downstream processing within microdevices. Methods for particle or cell separations exploit specific physical properties which include fluorescence-based, magnetic-based, affinity-based, and cell density gradient-based separations depending on the properties of the particles of interest. Particle separation devices are often geared toward biomedical research and diagnostics particularly in blood cell separation and blood diagnostics. 

Spiral Inertial Microfluidk Devices for Cell Separations, Fig. 5 (a) Image of the spiral sorting device [11, 12]. (b) Bright-field image of the outlet system, (c) At 1.8 mL/min flow rate (FI), two focused streams are observed, the narrow stream in the middle of the channel is formed by 7.32 pm particles, and the broad stream near the iimer channel wall is the composite of three streams of 10, 15, and 20 pm particles. Particles in the range of 10-20 pm are obtained out of the first outlet, and the 7.32 pm particles are obtained from the second and third outlets [11]. (d) Fluorescent image of the focused streams of all three particles, 10,15, and 20 pm in diameter, at the flow rate of 2.2 mL/min (F2) [11]. (e) Normalized... 

As mentioned above, the electronic properties of SWCNTs depend on their chirality and may be semiconducting or metallic. There is still no satisfying way to produce just one sort of SWCNTs, which would require the exact control of catalyst particle size at elevated temperature. Hence, the separation of semiconducting from metallic SWCNTs is of paramount importance for their application in, for example, electric devices, field emission and photovoltaics etc. 

This is not the only kind of cell sorter which is possible. Basically there are three different types. Firstly, there are those which utilise electrical forces only. The travelling wave device is an example of this. Since the electrical forces scale with particle volume, this kind will sort according to the passive electrical properties of the cells [51-53]. Secondly, there are those which use an electrical and another force in combination. Flow is the most promising candidate. As the... 

The ejection system must be capable of physically removing unwanted product items from the main accept stream. The ejection process typically takes place while the product is in free fall accept particles are allowed to continue along their normal trajectory, and rejects are deflected into a receptacle. Deflection is usually achieved by emitting short bnrsts of compressed air through nozzles aimed directly at the rejects, althongh large or heavy objects (e.g., whole potatoes) may reqnire some sort of piston-operated device to mechanically deflect the rejects. 

SORTING CLASSIFIERS. Devices that separate particles of differing densities are known as sorting classifiers. They use one or the other of two principal separation methods—sink-and-float and differential settling. 

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