T-type or Y-type micromixers and also parallel and sequential Lamination
mixer [ 34 ].
Nanoparticle synthesis using microscale controlled mixing is a new essence that
is being carried out in micromixers and microreactors. The nanoparticles so syn-
thesized have a much skewed distribution and can be custom-made in regards to the
average size of the distribution and also the standard deviation on the particle
diameters [ 35 ].
Many materials which are either amenable to microfabrication such as Silicon
and glass or to laser micromachining such as PDMS and PMMA as discussed in
previous sections can be employed for the fabrication of the flow channels which
constitute the path in a micromixer. Sometimes when the requirement of fabrication
is extremely complex precision orientated techniques like micro-stereolithography
[ 36 ], two photon processes [ 37 ] etc. are deployed to realized complex 3-D flow
paths.
3.2 Bilayer Staggered Herringbone Micromixers (BSHM)
A novel modification of passive micro-mixers has been attempted by Choudhary
et al. [ 38 ] wherein a method is developed to fabricate micro fluidic devices using
MRDI technique as described above onto soft polymeric material PDMS [ 38 ]. It has
been observed that the novel fabrication method—MRDI was able to produce
excellent replication results. The limitation that the process faced however came
from the lack of control on speed and power in the laser ablation step which had to
be iterated with design of experiments (DOE) strategy. The dimensions used for
fabrication were simulated and arrived at in this work (channel width¼ 100 μm;
channel depth¼ 100 μm; herringbone¼ 30 μm deep and 50μm wide). Well shaped
herringbone structures were created on the path of flow and mixing was thoroughly
evaluated as a function of the overlapping herringbones arm. It was found that as
the overall ratio of the herringbone arms on the top and bottom sides of the flow
path was reduced the flow length reduced. The image of fabricated herringbone
micromixer has been shown in Fig.2.10a,band a snap shot of the experimental
mixing data evaluated through dilution of a fluorescence marker dye is provide in
Fig.2.10c.
3.3 Long Microchannel Arrays as Vibration Pads
Long microchannels arrays have been also found to be suitable for custom made
vibration damping characteristics and can passively reduce mechanical vibrations
at a range of low frequencies and as such can be used for passive micro-vibration
46 G. Bhatt et al.