Hardware Reference
In-Depth Information
As introduced in Sect.
4.2
, in the D/M phase, the biochip will stop an operation
when the feedback from sensors indicates the operation has been finished. Then the
output droplet will be stalled inside the modules, and will wait to be used as the
input of the following operation in the next D/M phase. In each T phase, all the
dilution/mixing operations executed in the last D/M phase have already finished,
and their output droplets of operations are stalled in their modules. The electrodes
where these droplets stay, as well as their neighboring electrodes, are considered
as “obstacles” for droplet transportation. The droplet transportation paths cannot
overlap with the obstacles, otherwise the interference between droplets may occur.
The transportation of droplets during a bioassay consists of three parts: moving
droplets from one module to another module; moving droplets from on-chip
reservoirs to the modules; and moving the “extra product droplets” to waste
reservoirs. For some bioassays, it is important to note that not all of the intermediate
product droplets are used for subsequent operations. Those product droplets that are
not used in the bioassay are defined as extra product droplets, and must be collected
in the waste reservoir.
As introduced in Sect.
4.3
, the placements of modules for dilution/mixing
operations are determined based on their input/output interdependencies. For any
droplet that contains an intermediate product of the bioassay, the module where
the droplet is generated and the module where it will participate during the next
operation, are overlapped. The output droplets for each module only need to “wait”
at the original position; they will be directly “fed” into the module of the following
operation. Therefore, the transportation of droplets from modules to modules can
be eliminated. Only droplet transportations from reservoirs to modules and from
modules to the waste reservoir need to be considered in the T phase.
In this section, first we consider the routability for the result derived by the
operation-interdependency-aware synthesis approach. Then the method of online
decision-making on the transportation paths of droplets is introduced.
4.4.1
Routability Analysis
If we randomly select an operation O
N
from the sequencing graph, and the
immediate predecessor operations of O
N
are written as O
L
and O
R
,thenwehave
the following lemma:
Lemma 4.2.
Transportation paths from a reservoir
R
to the module of
O
N
exist
if there are transportation paths from the reservoir to the modules of immediate
predecessor operations
O
L
and
O
R
.
Proof.
The existence of transportation paths from the reservoir R to the modules of
operations O
L
and O
R
indicates that paths from the reservoir to the modules can be
found when there are obstacles R
LR
on the biochip. Here, the set of storage units and
