Biomedical Engineering Reference
In-Depth Information
Table 7.1
Typical substrate materials and technologies to fabricate
microluidic chips
SiO
2
-based
materials
(glass; quartz)
Thermoplastics*
(PMMA; PC; COC)
Elastomers**
(PDMS)
Chemical etching
×
Powder blasting
×
×
Template embossing
×
Ablation
×
Injection molding
Micro-milling
×
×
Mold casting
*PMMA, polymethylmethacrylate; PC, polycarbonate; COC, cycloolein copolymer.
**PDMS, polydimethylsiloxane.
After microchannel fabrication, the fabricated chip surface is
treated with acidic reagents to slightly melt in a furnace and then
bonded with another chip under pressure. This other chip is drilled
with inlet and electrode holes prior to the fusion bonding step.
Polymeric substrates, including thermoplastics and elastomers,
can also be used to fabricate microluidic devices.
8
Polymeric
substrates and related fabrication tools are less expensive than glass
materials and their tools. In addition, the physical and chemical
properties of polymeric substrates are easier to control. As a result,
polymeric chips make it easier to realize complex conduit layouts.
Common thermoplastic materials used to make microchannels
include polymethylmethacrylate (PMMA), polycarbonate (PC),
cycloolein copolymer (COC), and co-polyester. Plastic fabrication
techniques, such as template embossing and laser ablation, have
been implemented to craft microchannels on these substrates.
Structured master molds, which are typically made of metallic alloys
or silicon wafers, are pressed against plastic chips in an oven at
a temperature a little higher than the melting point of the plastic
for a few minutes to imprint channels. Ablation marker lasers
using various types of light sources have also been employed to
directly write microchannels on thermoplastic substrates.
9
These
light sources include carbon dioxide lasers, solid state lasers, and
argon-ion lasers. Higher-energy light sources, such as femto-second
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