Nanomedicine - Bionanoelectronics: Bioinquiring and Bioinspired Devices - page 142

Fig. 4.20 Schematic view of
an electrostatic micropump

counterelectrode

electrostatic driven
diaphragm

l

inlet outlet

Fig. 4.21 The continuous
electrowetting effect

Hg

electrolyte

V

is moved due to the protonation effect on the mercury surface. At the application of
a voltage V between the two ends of the electrolyte/mercury system, a potential
difference between the two sides of the mercury droplet is produced, modifying
the surface tension which pushes the mercury drop in the direction of the negative
electrode, as shown in Fig. 4.21 . Using the continuous electrowetting effect, a
micropump could have a flow rate of 40-100lmin 1 , a very low driving voltage
of 2.3 V at 25 Hz, and a power consumption of 0.15 mW while attaining a pressure
of 800 Pa ( Yun et al. 2002 ).
Micro/nanotechnologies do not only influence the concept of drug delivery but
also the way in which they are administrated. For example, micro/nanoneedles are
dedicated to an enhanced transdermal delivery during which the pain felt by the
patient is significantly reduced. A comprehensive review on microneedles is found
in Prausnitz ( 2004 ). In principle, microneedles are made by etching Si or other
materials, such as stainless steel. A typical microneedle array, as that shown in
Fig. 4.22 , contains 400-500 microneedles with a length of 300-500m, the entire
array having an area of 2 cm 2 . There are various ways in which these microneedle