Biomedical Engineering Reference
In-Depth Information
The point of fracture is visually captured by the camera with the data acquisition system dis-
playing a sharp peak in force-time graph, interpreted as “needle failure point.”
10.9.2
Microelectrode Testing
Most of the mechanical constraints tested for microneedles also apply to microelectrodes.
However, as is obvious from the nature of application, testing of electrical parameters is of
prime importance here. There may be various methodologies to test a microelectrode
array depending on its design. One of them is highlighted here as an example.
Microelectrode testing is performed at the University of South Florida using a precision
Impedance Analyzer in conjunction with a Probe Station. The microelectrode array
(Figure 10.10) is placed on the probe station, and the impedance analyzer provides a
small voltage potential while measuring the resultant radio frequency current. Four ter-
minal sources are configured to create a bipolar measurement analysis. The most impor-
tant step is the calibration of the instrument to eliminate/null any parasitic capacitance
and resistance from additional cables attached to the probe tips. Phase compensations are
also done to allow signal stability over the specified frequency range. A vital considera-
tion is to avoid tissue heating during testing. The oscillating voltage should be chosen
such that the maximum current output is
2
A.
10.10
Conclusion
Skin interaction systems containing bioengineered interfaces will revolutionize the bio-
medical industry in the coming decades. They promise exceptional capabilities in diverse
transdermal diagnostic and therapeutic applications. Development of customized instru-
mentation will enable real-time electrical, mechanical, and electrochemical measurements
on the skin surface and also provide novel methods of drug delivery.
125
µ
m diameter
250
µ
m diameter
(a)
(b)
500
m diameter
µ
FIGURE 10.10
Microelectrode arrays with electroplated tips,
(a) 125-diameter configuration, (b) 250-diam-
eter configuration, (c) 500-diameter configu-
ration, and (d) exposed bonding pads.
(d)
(c)
