The principle advantages offered by the MRDI process are: (1) a sturdy mold,
(2) repeated use of the mold for replication of polymer, (3) an overall inexpensive
process as compared to other photolithography-driven processes,(4) A reusable
mold, and (5) the use of laser ablation or other micromachining techniques for
mold making.
PDMS replica mold is widely used for channel making in microfluidic applica-
tions although when we talk of embedded channels and features there are some very
serious limitations of replication and moulding processes [ 24 ]. For example if the
structure that is to be realized is a long micro-channel which is embedded within a
chunk of the polymer PDMS both replication and moulding process done in the way
as explained and also the MRDI may prove out to be failures and if done as a
sandwiching between two replicated surface may impose limitations in terms of
accurate alignment. In order to address these issues a replication and moulding
technique has been developed with wires where the features and structures are
replicated as embedded features within polymeric domains [ 25 ].
2.5 Embedded Structures with Replication and Moulding
Processes
An easy fabrication procedure has been developed for three dimensional structures
with soft materials like PDMS [ 26 ]. This has been used to develop micro-channel
arrays within PDMS matrices which in a separate module as described below been
tested for micro vibration control. An array of upto six rows of micro-channels with
20 numbers of micro-channels in each row have been fabricated using this proce-
dure and in a very innovative manner The process was initiated with a micro
drilling exercise wherein 200μm diameter holes (20 in numbers) were drilled
using MIKROTOOLS (DT 100, Singapore) machine tool in a simple plastic mold
box using a CAD package on the side walls of this mold box. The centre to centre
distance between these holes in x and y direction were taken as 2 mm. In order to
Fig. 2.6 Schematic representation of MRDI process
42 G. Bhatt et al.