Miniaturized Detection Systems - Waterborne Pathogens: Detection Methods and Applications - page 318

properties of the cell, or resort to extrinsic “labels” for cellular differen-
tiation. Additionally, separation can be performed by a variety of means
including optical, electric, and magnetic forces, or hydrodynamic forces, and
examples of such techniques are shown in Fig. 10.3 .
Despite the proliferation of papers dealing with cell sorting, much less
work has focused on sample processing of waterborne pathogens, though
this has been increasing in recent years. However, sample volumes remain
small and many devices have been demonstrated only with purified water.
Centrifugation on-chip has also been demonstrated, 57 though not yet
applied to waterborne pathogens. Several approaches combine some form
of microfluidic enrichment with detection. Some examples of flow cytom-
etry are covered later under optical detection.
In 2010, Dharmasiri et al. described a cell purification platform for
the isolation and washing of Escherichia coli in antibody-coated high aspect
ratio curved microchannels. 58 Prefiltered lake water was employed in the
study with the microfluidic device processing 1 mL at a flow rate of around
5 µL min −1 . A 10 2 concentration factor was achieved with a 71% recovery
rate. Microfluidic chips with antibody-coated microbeads inside the micro-
channels overcome the potential limitations of the low surface area of planar
microchannels, and have been applied for the immunoseparation of E. coli . 59
A flow-through immunomagnetic separation (IMS) for Cryptosporidium and

Microparticle continuous
separation

General
separation
types

Magnetic
separation
[21-31]

Electrical
separation
[34-58]

Fluidic-only
separation
[59-71]

Optical separation
[9-19]

Other separation
[72-77]

Optical
fractionation

Hydrodynamic
separation

Thermal
fractionation

Magnetophoresis Stop-flow

Use of
ferromagnetic
strips

Deterministic
lateral
displacement

Dielectrophoretic
fractionation

Accustic
fractionation

Detailed
separation
techniques

Dielectrophoretic
barriers

Liquid-liquid
extraction

Tranveling-wave
dielectrophoresis

Particles
properties
involved

- refractive index
- size

- magnetic susceptibility
- size

- dielectric properties
- size

- size
- diffusion coefficient

- size
- thermal susceptibility

Figure 10.3 Figure illustrating different methods of cellular separation in microfluidic
systems. Source: Reproduced from Ref. 56 .