Biomedical Engineering Reference
In-Depth Information
L
F
L
FF
H
1
2
F
Unintentional
splitting
Destination
cells
F
F
F
Figure 3.14
An example of electrode interference within the same row.
here we only focus on the implementation of a set of multiple droplet manip-
ulations that can be carried out concurrently (in a single-routing step) on a
direct-addressing-based chip, without violating any fluidic constraints. We
refer to such a set of droplet manipulations as a
droplet-manipulation snapshot
.
We present a solution based on destination-cell categorization. Note that
the problem highlighted in Figure 3.13 can be avoided if the destination cells
of the droplets being moved simultaneously reside on the same column or
row. However, electrode interference may still occur within the same column
or row, as shown in Figure 3.14. Suppose Droplet 1 and Droplet 2 are both
moved one cell to the left at the same time. Even though no additional cells
are activated unintentionally, Droplet 1 undergoes unintentional splitting
in this situation. Fortunately, further scrutiny reveals that the situation in
Figure 3.14 is only a false alarm. The intended multiple droplet manipulation
violates the constraint |
P
i
(
t
+ 1) −
P
j
(
t
)| ≥ 2. Such manipulations cannot be
carried out concurrently even on a direct-addressing-based chip. Thus, they
will never appear in a single droplet-manipulation snapshot. Therefore, it is
safe to carry out concurrent manipulation of multiple droplets whose desti-
nation cells are accessed by the same column or row.
On the basis of the preceding observations, we consider the droplets that
can be moved simultaneously as part of the bioassay and place them in dif-
ferent groups. A group consists of droplets whose destination cells share
the same column or row. An example is shown in Figure 3.15. A total of
nine droplets are needed to be moved on a 10 × 10 array. As discussed ear-
lier, we group the droplet movements according to their destination cells.
For example, Droplets 4 and 9 form a group since the destination cells in
both cases reside on Row 2. Similarly, Droplets 1, 2, and 3 are placed in the
same group since they are all moving to Column 3. Following this group-
ing process, we finally get four groups of droplets, that is, {4,9}, {1,2,3}, {5,6},
and {7,8}. In this way, the manipulation of multiple droplets is ordered in
time; droplets in the same group can be moved simultaneously without
electrode interference, but the movements for the different groups must
