Biomedical Engineering Reference
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Figure 4.11
Online parallel scan-like test for a 6 × 6 microfluidic array. Shaded cells correspond to modules
in use for bioassay operations.
operation scheduling and module placement results [15] are used to calculate
the waiting time for test droplets. Once arrival times are determined, online
fault diagnosis can be carried out using the same procedure presented earlier
for off-line diagnosis.
4.2 Diagnosis of Multiple Defects
The proposed parallel scan-test method efficiently tests the target biochip and
locates defects. However, it is not able to always unambiguously and accu-
rately locate multiple defect sites. In this section, we integrate a redundant test
method into the parallel scan-like test technique to address this problem.
4.2.1 incorrectly Classified Defects
When multiple defects exist in the array, multiple columns and multiple rows
might fail during the parallel scan-like test method. However, unlike the case
of a single defect, we cannot identify the multiple defect locations by simply
examining the failing columns and rows. This is because the failing columns
and rows intersect not only at the defect site but also at some defect-free elec-
trodes, which are referred to
as incorrectly classified defect sites
. This problem
is illustrated in Figure 4.12.
The preceding problem can be solved by carrying out a binary search for
each column/row that fails the test, as shown in Figure 4.13. This method
eliminates the likelihood of incorrectly classified defect sites as false and
helps us to precisely locate the actual defect sites. However, it suffers from
the drawback that precise defect localization is not possible when there are
“untestable sites” in the array, a problem that is described next.
