Biophotonics_Concepts_to_Applications

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