Page 127 - Optofluidics Fundamentals, Devices, and Applications

CHAPTER 6

Optofluidic Colloidal

Photonic Crystals

Seung-Man Yang, Shin-Hyun Kim, and
Seung-Kon Lee

National Creative Research Initiative Center for Integrated Optofluidic Systems
and Department of Chemical and Biomolecular Engineering, KAIST, Daejeon,
Republic of Korea

olloidal crystals have been extensively studied during the last
two decades because their spatial regularity at the half-wavelength
Cscale of interacting light induces a photonic bandgap. The
bandgap properties appear as iridescent colors that are useful for
many applications, such as optical waveguides, lasing resonators,
and structural color pigments. However, tailoring colloidal crystals
into structures of desired shape (with good physical and chemical
resistance) is difficult, and controlling the bandgap position of the
crystal in real time requires complicated fabrication processes. In
spite of these limitations, there has been a recent breakthrough in
colloidal-crystal research as such crystals can now be incorporated
into optofluidic systems. Colloidal crystals embedded in microfluidic
channels show tunable bandgaps that depend on the type of fluid
flowing through the crystal interstices and may have important appli-
cations as sensing devices for biomolecules or chemicals. In addition,
the optofluidic system allows the colloids to assemble into discrete
and separated colloidal photonic crystals with desired shapes. In this
chapter, we will discuss two main categories of colloidal-crystal-
based optofluidic systems. The first is related to the integration of
colloidal photonic crystals into microfluidic devices for optofluidic
applications whereas the second involves the optofluidic synthesis of
colloidal photonic crystals.

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