Biomedical Engineering Reference
In-Depth Information
Te st
outcomes
Source
Defect
Odd column
1
2
3
4
5
6
Sink
Even column
Even row
123456
Pseudo
source/sink
Source
Source
Defect site
Sink
Figure 4.10
Diagnosis of an electrode-short defect using a parallel scan-like test.
A binary-search method can next be used to locate the shorted electrode pair
by iteratively partitioning the column/row and carrying out the single-line
parallel scan-like test, as shown in Figure 4.10.
Compared to the Euler-circuit-based method, the 2-D array partitioning
of [36] is simplified to 1-D. As a result, both the number of test iterations
and the complexity of each iteration are reduced, which leads to a significant
decrease in diagnosis time.
The preceding discussion on diagnosis assumes a single faulty cell. The
procedure can also be used to locate multiple faulty cells, but it does not guar-
antee that only faulty cells are placed in the set of candidate defect sites.
4.1.2 Online Parallel Scan-like Test
The proposed parallel scan-like test method can also be used for online test-
ing with a few modifications. First, note that some test droplets are stalled,
while the target cells are occupied by the sample and reagent droplets
needed for the bioassay. Therefore, some test droplets may be out of step
with each other, as shown in Figure 4.11. The three droplets arrive at the
pseudosinks at different times. Second, test droplets are routed to the sink
only after all the test droplets arrive at the boundary. While this procedure
leads to an increase in testing time, it guarantees a regular output at the
detection sensor that is easy to read; therefore, the capacitive sensing circuit
can be kept simple. Online fault diagnosis, although based on the same idea
as off-line diagnosis, is more complicated since test droplets are moving out
of step with each other. To determine the arrival time for droplet detection,
