Hardware Reference
In-Depth Information
7. A scheduling algorithm that can be applied to biochips with pin-constraints
(Sect.
6.6
).
8. Results for commercial biochips and experimental prototypes (Sect.
6.7
).
6.2
Analysis of Pin-Assignment
In this section, we first discuss the relationship between droplet movement and
voltages applied to the electrodes. Next, the concept of pin-actuation conflict is
introduced. Finally, in order to determine the conditions that guarantee conflict-free
pin-assignment, several pin-assignment configurations are analyzed.
6.2.1
Pin-Actuation Conflicts
Appropriate control voltages must be applied to a group of electrodes to manipulate
a droplet that currently resides on an electrode
. According to the working prin-
ciple of electrowetting-on-dielectric (EWOD)-based microfluidic biochips, move-
ments of a droplet are determined by the group of electrodes that are directly in
contact with the droplet. Suppose a droplet of unit volume (referred to as a “1
”
droplet) is held on electrode
E
. Then the electrode group that can determine the
movement of the 1
droplet consists of the central electrode
E
and all its non-
diagonally adjacent electrodes. Each non-diagonally adjacent electrode is a possible
destination for the droplet. An example is presented in Fig.
6.1
a. Each square in
Fig.
6.1
a presents an electrode on the microfluidic biochip; letters (such as “A”, “B”
and “C”) stand for the names of control pins that are connected to the corresponding
electrodes. The control voltages applied to the control pins are either “High”, “Low”
or “don't-care”. Here we introduce two definitions:
E
a
b
c
d
Droplet
D
1
Control electrode
group
Shared
Pin A
Shared
Pin A
Droplet
D
2
Fig. 6.1
(
a
) A central electrode and its non-diagonally adjacent electrodes comprising an electrode
group; (
b
) an example of pin-actuation conflicts; (
c
) an example where two diagonally adjacent
electrodes in the same CEG share one pin (Pin A); (
d
) an example where two non-adjacent
electrodes in the same CEG share one pin (Pin A)
