Biomedical Engineering Reference
In-Depth Information
Pins:
123…n1 23
n
-phase bus
(a)
E
2
E
3
E
4
E
5
E
8
E
1
E
6
E
7
Pins:
12345123
n
-phase bus
(b)
Pins:
12 3… n1 23
n
-phase bus
(c)
Figure 4.35
The functional test on an
n
-phase-bus chip.
4.5.4.1 An n-Phase Chip
In the
n
-phase chip, every
n
th electrode is electrically connected and con-
trolled using a single control pin. Therefore, every
n
th electrode must be
activated/deactivated simultaneously, as shown in Figure 4.35. Due to this
constraint, the mixing and splitting test cannot be carried
out currently on
every other electrode following the six steps presented in Subsection 4.5.3.
In the example of Figure 4.35b, a linear array consisting of eight electrodes
is controlled using a 5-phase bus. To carry out the splitting test on every
other electrode, for example, E
1
, E
3
, and E
5
, the control pins 1, 3, and 5 need
to be activated currently to hold the test droplets on these three electrodes.
However, since electrode E
6
is connected to Pin 1, it is also activated. This
causes unintentional splitting of the test droplet on E
5
.
To avoid this problem, the proposed functional test procedure needs to be
modified. For an array controlled using an
n
-phase bus, current mixing and
splitting tests are only allowed on every
n
th electrode. Since these electrodes
are connected to the same control pins, carrying out the splitting or mix-
ing test on these electrodes requires the same pattern of pin activations. As
shown in Figure 4.35c, to execute a splitting test on both E
2
and E
7
requires
Pin 1 and Pin 3 to be activated and Pin 2 to be deactivated. Therefore, carry-
ing out the splitting-and-mixing test on these electrodes concurrently will
not lead to unintentional fluidic operations.
