Biomedical Engineering Reference
In-Depth Information
10 10
10 9
10 8
10 7
10 6
10 5
10 4
10 3
0
30
60
90
120
150
t
/ h
Figure 3. Time course of the membrane resistance R m obtained by EIS analysis of a
nano-BLM in a frequency range of 10 -2 -10 6 Hz. The membrane resistance was ex-
tracted from the impedance data by fitting the parameters of the equivalent circuit
shown in the inset of Fig. 2A to the data. 24
and scanning ion conductance microscopy (SICM). 29 Monitoring
this process by EIS results in a decreasing membrane resistance R m
over time as shown in Fig. 3 .
In the first 48 hours after membrane formation, R m drops from
7 Gȍ to 1 Gȍ. During this time period, the membrane is well suit-
ed for single channel measurements. Then, the membrane re-
sistance decreases further leading to membrane resistances of
around 150 Mȍ after 72 hours and 2 Mȍ after 120 hours. After
132 hours, the membrane resistance has reached 1 Mȍ. From a
statistical analysis, the lifetime of the nano-BLM with membrane
resistances larger than 1 Gȍ was calculated to be (1.5 ± 0.5) days
( n > 30). These data prove that the long-term stability of nano-
BLMs is by far greater than the one of classical BLMs. Notably, in
some cases it happened during the time course of the experiment
that the membrane resistance increased again, which indicates that
a self-healing process might occur within the membrane. This im-
plies that nano-BLMs underlie permanent fluctuations affecting
the resistance and capacitance of the membrane.
 
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