Biomedical Engineering Reference
In-Depth Information
Fig. 14
Fabrication process flow for the development of a flexible pressure sensor with aligned-
CNT/PDMS nanocomposites
A suitable candidate is the technology proposed by Sep ulveda [
28
], in which
aligned carbon nanotubes (CNTs) are used to implement the conductive elements
in a flexible substrate of polydimethylsiloxane (PDMS), a transparent, nontoxic and
biocompatible silicone elastomer.
The technology process flow enabling the fabrication of a flexible pressure sensor
is schematically presented in Fig.
14
. Acrylic moulds are produced by CNC milling
(Fig.
14
a) for posterior fabrication of the PDMS membranes. This technique has
low costs and fast production times, but it is associated with poor dimensional
control (dimensions less than 50 m are difficult to achieve) and more traditional
micromachining may achieve the required tolerances.
The electrical components are based on aligned CNTs, as shown in Fig.
14
b.
Chemical vapor deposition (CVD) is used to grow forests or “carpets” of vertically-
aligned CNTs [
29
]. A silicon substrate with patterned Fe/Al
2
O
3
catalyst is placed on
a horizontal quartz tube furnace at atmospheric pressure at 750
ı
C[
29
]fortheCNT
growth. This method has the advantage of allowing the growth of high purity, high
yield and vertically aligned CNTs. Next, the CNTs are embedded into the polymer
matrix (PDMS). This step is schematically represented in Fig.
14
c. The substrate is
