Hardware Reference
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b
R 2
a
D 2
R 6
R
D
R
R 5
D 1
H
R
D
H
R 7
R
R
R 3
R 4
R
R 1
R
Fig. 5.13 ( a ) Device placement obtained by the proposed algorithm. R represents the output port
of the reservoir, D represents the DE, and H represents the heater. All the reservoirs are treated as
identical devices and all the PDs are treated as identical devices; ( b ) Reservoir allocation with the
minimum droplet routing cost. R 1 7 are reservoirs assigned to inputs x 1 7 in Fig. 3.10 , D 1 and
D 2 are DEs, and H is the heater
In addition, the degree of parallelism for fluid-handling operation is high since
the conflicts of resource-sharing and droplet routing on the biochip can be avoided.
Here we assume that the completion time of mixing on a 1 4 mixer is 5 s, and the
time of moving the droplet from electrode to another electrode is t m s(t m usually
varies from 0.01 to 1 [ 33 ]). Then the execution time of the whole bioassay on the
layout shown in Fig. 5.13 b will be calculated as (35+36t m ) seconds.
Here we design another device placement as the baseline algorithm. In the
baseline method, all the devices (including the output ports of reservoirs, PDs, and
the heater) are placed at the boundary of the layout one by one. The distance between
any two devices is set as L max D max{L RR , L DD , L RD , L RH , L DH }, as shown in
Fig. 5.14 . A circular path, which consists of all the boundary electrodes, connects
all these devices.
The size of the electrode array derived by baseline algorithm is 20 15,and
the number of electrodes required for this design is 68. The execution time of the
complete bioassay is .80 C 115t m / seconds.
Compared with the baseline algorithm, the proposed design method can thus
reduce the chip area by 59.7 %, the number of electrodes by 35.3 %, and the
execution time by 57.8 % (when the value of t m is set as 0:1).
Next, we study a protocol which represents a real-life PCR mixing ratio [ 34 ].
This bioassay is referred to as Bioassay 2. The mixing ratio of the eight components
is written as [ 34 ]:
{Reaction buffer: Mag_Sulf: dNTPs: Forward primer: Reverse Primer: Opti-
mase: Water: DNA} Df 10 % W 10 % W 8 % W 0:8 % W 0:8 % W 1 % W 68:4 % W 1 % g .
This ratio can be approximately as {51 W 51 W 41 W 4 W 4 W 5 W 351 W 5} on 512-scale;
the corresponding mixing tree can be derived using the ratioed+ mixing algorithm
(RMA) [ 27 ]. The simulation results of the PCR biochip designed for Bioassay 2 are
shown in Table 5.2 .
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