Microfluidics for Biologists Fundamentals and Applications

damping. The channel array is embedded in blocks of viscoelastic materials in an
oil filled and hermetically sealed manner [ 27 ]. In this work, the passive response of
a replicated array of oil-filled micro-channels, structured within a block of PDMS is
reported. Constrained and unconstrained vibration-damping experiments are
performed on this block, by applying an excitation signal transversely at the
geometric centre of the lower face of the block; its vibration suppression ability
is detected. Figure2.11shows the constrained and unconstrained configurations
schematically and the respective loss factor data with no. of embedded channel
layers.

1.0

0.8

0.6

0.4

0.2

0.0

0 5000 10000 15000 20000 25000 30000

channel length (microns)

Re = 1

Plain Channel

SHM

ABHM

AsyBHM

SymBHM

OrSHM

Relative Fluorescence Intensity (AU)

ab

c

Fig. 2.10 PDMS Replica obtained after soft lithography and herringbone structures ((a), (b)); (c)
Mixing performance by dilution of a fluorescence dye in a plain channel, symmetric Herringbone
structure, alternate bilayer Herringbone mixer, Asymmetric bilayer herringbone mixer, symmetric
bilayer herringbone mixer and oblique ridges and staggered herringbone mixer (Reproduced from
Choudhary et al. [ 27 ] with permission from the Springer)

2 Microfluidics Overview 47