Hardware Reference
In-Depth Information
Routing cell
Interference
region cell
External heater
Module cell
External detector
Fig. 1.13
Constraints for module placement on a digital microfluidic biochip [
45
]
above is simplified. Researchers divide the biochips into different regions with
specific usages. Figure
1.13
shows an example of the layout of a biochip. On the
biochip, four 3
3 electrode arrays are reserved as “basic modules”. Fluidic
operations, including the mixing, splitting, and storage of droplets, are performed
by these modules. If there is an external detector or heater inside a basic module,
that module also can perform detecting and heating operations.
The white cells in Fig.
1.13
represent the electrodes preserved for transporting
droplets between modules and I/O ports. By using these dedicated routing cells,
it is ensured that a valid path always exists between any source-destination pair.
Surrounding each basic module, there are interference region (IR) electrodes, which
are not used to perform any fluidic operation. Hence, the droplets inside the basic
modules are isolated with the droplets in the routing paths, and interference-free
droplet routes can be computed online easily.
When running the online synthesis procedure, the control software only deter-
mines the priority of the fluidic operations and then restricts the operations to the
resources that are available on the biochip.
1.2.2
Testing Techniques
Many testing and diagnosis techniques have been proposed in recent years for use
in detecting and locating catastrophic and parametric faults on biochips. In the test
method proposed by [
46
], test stimuli droplets are dispensed into the biochip and
then transported following the designed testing scheme.
In the testing scheme, the test stimuli droplets traverse every electrode on the
biochip, after which they are moved to the droplet sink on the biochip. As discussed
in Sect.
1.1.4
, if an electrode has a catastrophic fault, droplets will stick to the
electrode. Thus, if a digital microfluidic biochip has electrodes with catastrophic
