2.4 Micro-Scale Replication by Double Inversion (MRDI)
Process
Biological and chemical applications require micro-fluidic devices with micro/
nanoscale mechanical structures. Present fabrication techniques suffer from a low
pattern transfer quality particularly if the feature sizes are in the nanoscale during
the simultaneous embossing of the microscale and nanoscale patterns into a ther-
moplastic polymeric substrate since the polymer flow becomes insufficient. Fabri-
cation of 3-D micro and nano-structures require expensive and time-consuming
lithography assisted techniques and in some cases very high cost is involved in
realizing these mechanical structures through the use of processes like electron or
ion beam writing or nanolithography etc. [ 23 ]. In order to address the problems of
lithography driven processes we have developed a low cost and high throughput
replication based process called micro replication by double inversion (MRDI).
Figure2.5shows schematic of a standard replication process. The various steps
involved in such a process are (a) pouring the liquid monomer onto the master
(b) master and replica separation after photo-polymerisation by exposure to
UV-light (c) The use of the replica (with some surface pre-treatment) as a new
master for a further duplication of the features into another polymeric substrate.
After polymerisation and separation the second replica contains the same structures
as the initial one. (Represented in Fig.2.5a–d). The master in MRDI process can
also be made using laser micromachining as shown in Fig.2.6.
Fig. 2.5 Schematic
representation of replication
process
2 Microfluidics Overview 41