Biomedical Engineering Reference
In-Depth Information
Figure 2.33
Schematicviewofthedrugdispenseneedle.
The active molecules transit through the needle tip into the cells extracellular space
(ECS) and finally inside the cells.
Let us focus now on the injection device. The rapidity of dispense and its ef-
ficiency can be increased by a microneedle, which has many exits uniformly dis-
tributed on the sides (Figures 2.33 and 2.34). The advantage of this type of needle
is that drug delivery starts from all side exits disposed along the needle. For the
best possible efficiency of the microneedle, all side exits should have the same flow
rate.
Eventually, the needle may be used as an electrode to increase the uptake rate.
It has been observed that an electric field increases the uptake rate [42], so the
needle can be electrically actuated. However, we discuss here only the microfluidic
aspects.
2.2.9.2
LumpedModel
The statement of the problem is: What should be the dimensions of the differ-
ent side exits if we want them to deliver the same flow rate? Intuitively, it is clear
Figure 2.34
Schematicviewofthecentralchannelandthesideexits.Allsidechannelsmustdeliver
thesamelowrate.
