Biophotonics_Concepts_to_Applications

(Dana P.) #1

11.2.2 Lab-on-Fiber Concept.


Thelab-on-fiberconcept arose from the joining of nanotechnology and opticalfiber
disciplines [ 20 – 22 ]. One activity in this evolving technology is the deposition of
patterned layers of nanoparticles either on the tip of afiber or as an external coating
over a Bragg grating written inside of a photonic crystal opticalfiber. By depositing
a pattern of nanoparticles on the tip of a standard opticalfiber, localized surface
plasmon resonances (LSPRs) can be excited on the tip surface when an illuminating
optical wave exits thefiber. This condition arises because of a phase matching
between the light waves scattered at the surface and the resonance modes supported
by the nanostructure. The LSPRs are very sensitive to the refractive index value of
the analyte material that surrounds thefiber tip. For example, the blue curve in
Fig.11.4shows a surface plasmon resonance wave for the condition when no
analyte is covering the nanoparticle pattern on the end of afiber. Analyses of
particles in afluid then can be made by inserting thefiber tip into an analyte liquid,
so that now the liquid covers the nanoparticle pattern. This action changes the
refractive index of the interface between the nanoparticle layer and thefluid. The


Table 11.2 Selected examples of microfluidic chips and associated devices [ 15 ]


Chip or device Key elements Chip/device function
Sample
preparation
chip

Reaction chambers of various
volumes

Extracts target molecules out of a given
sample in preparative quantities

Plasma/serum
generation
chip

4 membranes for plasma/serum
generation out of full blood

Each membrane can generate about 12μl
of plasma/serum out of 25μl of full blood

Particle and
cell sorting
chip

Spiraled channels used to
separate particles and cells
according to their size

Can separate cells, analyze them, and
optionally sort and collect desired cells;
particles of different sizes can be received
at different outlet ports.
Droplet
generator chip

Contains 8 droplet channels with
different channel dimensions

Creates 50– 80 μm sized droplets at
various droplet generation frequencies, to
generate droplets with different volumes
Micro mixer
chip

Applies either passive or active
mixing principles

Passive elongated channels enable
diffusion mixing; active integrated stir
bars enable a wide range of mixing ratios
Fluidic
interface

Uses lab-on-a-chip device
technology

Miniaturized connectors and tubing
enable connection to pumps, valves, or
waste reservoirs
Liquid storage
device

Uses miniature tanks with a 500
μl volume

Enables off-chip storage of liquids

Syringe
pumps

Uses high-end syringe pump
technology

Enable extremely precise dosing and
pumping offluids

11.2 Miniaturized Analyses Tools 331

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