Hardware Reference
In-Depth Information
Chapter 7
Pin-Limited Cyberphysical Microfluidic Biochip
7.1
Introduction
On a digital microfluidic biochip, the number of control pins used to drive electrodes
is a major contributor to the fabrication cost [
1
]. The layout of a typical biochip is
shown in Fig.
7.1
a, it has three regions:
1.
Active region
, where the biochemistry assays are executed; electrodes and
on-chip reservoirs are fabricated in this region.
2.
Contact region
, where the contact pads of the input pins are fabricated. Here
each contact pad corresponds to one input pin of the biochip. In order to reduce
the contact resistance, the area of each pad is usually larger than an electrode [
1
].
3.
Wire routing region
, where metal wires are fabricated. The wires connect
electrodes to the contact pads of the input pins.
From Fig.
7.1
a, it is evident that most area of the biochip is occupied by the
connection wires and contact pads. Therefore, the area and the fabrication cost of a
biochip will increase when the number of the input pins increases.
In order to reduce the number of input pins in biochips, several design methods
for pin-limited biochips have been presented in the literature. These design methods
map a larger number of electrodes to a small number of control pins according to:
(1) the specific synthesis result of a bioassay (i.e., bioassay-specific design for pin-
assignment configurations) [
2
], or (2) the arrangement of electrodes on the biochip
(i.e., application-independent design for pin-assignment configurations) [
3
-
5
].
In particulary, the design method proposed in [
3
,
4
] generates an application-
independent pin-assignment configuration with a minimum number of control pins.
Compared with the bioassay-specific pin-assignment algorithms [
2
], the method
in [
3
,
4
] can reduce the number of control pins and facilitate the “general-purpose”
use of digital microfluidic biochips for a wider range of applications; each general-
purpose pin-limited biochip can be used to perform various target bioassays.
