Biomedical Engineering Reference
In-Depth Information
0.5
Independently controlled chip
Pin-constrained chip
0.4
0.3
0.2
0.1
0
0
0.01
0.05
Defect Occurence Probability p
0.075
0.1
Figure 6.18
Evaluation of the failure rates for a pin-constrained chip and an independently controlled chip.
to one or more wells, and these wells cannot be loaded. In this case, a failure
occurs on the chip.
Next, we define a parameter referred to as “failure rate.” Let N t be the total
number of biochips in a representative sample, and let N f be the number of
defective chips that suffers from a failure. Then the failure rate f is defined by
the equation f = N f / N t .
We run the simulations with difference defect occurrence probabilities for
the pin-constrained chip and record the failure rates. As a baseline, we also
carry out a defect injection for a direct-access chip. The results are shown in
Figure 6.18. Note that if we do not set any upper limit on the well-loading
time, any defect that can be bypassed in the direct-access chip can also be
bypassed in the pin-constrained chip. This is because we can manipulate only
one droplet to load only one well in any iteration of the shuttle-passenger-like
routing, which allows the same degree of freedom as in the direct-access chip.
However, this scheme results in a significant increase in the well-loading
time. Therefore, in our evaluation, we use a restricted definition of failure
for the pin-constrained design; it refers to the case that the injected defects
cannot be bypassed using the “cross-loading” method.
Figure 6.18 shows that, as expected, the introduction of pin constraints
leads to a slightly higher failure rate compared to the direct-access chip.
However, this increase is acceptable in practice due to the significant reduc-
tion in the number of control pins for the proposed design.
6.2 Automated Solution Preparation
A critical step in protein crystallization is to generate various mixed crys-
tallizing solutions with desired concentration levels using a fixed volume
Search WWH ::




Custom Search