Biomedical Engineering Reference
In-Depth Information
Figure 2.36
Calculatedwidthofsidechannelsasafunctionofthechannelnumber.Thewidth
increasesfromtheentrancetothetipoftheneedle.
(
)
2
8
η
L
+
9 sin
a
α
V
( )
D =
P
g
λ
(2.85)
2
a
For
α
= 90°, formula (2.85) is the same as (2.77). Figure 2.36 shows that the
distribution of the
a
i
in the case of 2 ´ 10 side channels, for a value of
a
10
, equals
30
m
m.
We now can use a direct model to verify the accuracy of the algorithm. Here,
the direct model is the SABER code from the COVENTOR package [43]. Calcu-
lated widths are used as inputs in the SABER calculation. If the algorithm is correct,
the results should agree. It is checked in Figure 2.37 that the SABER results agree
well with the lumped model results.
Microneedles based on the results of the dimensioning algorithm have been re-
alized in silicon using microtechnologies for silicon etching and assembling (Figure
2.38). Needles of different sizes (from 500
m
m to 300
m
m) and with different side
channel angles have been fabricated (Figures 2.39 and 2.40).
Using methyl blue colored water and disposing the needle on a flat blotter, it is
checked that all the flows at all exits are identical (Figure 2.41).
Figure 2.37
Comparisonofsideexitvelocities.Continuousline:presentalgorithm,anddots:SA-
BERresults.
