Biomedical Engineering Reference
In-Depth Information
is also shown in Fig. 9.41. The frequency shift and insertion loss
change upon vapor exposure of a 10 min pulse have been measured
relative to dry air by retrieving the minimum point at steady state
in the S
transfer curve. Dry air is used as carrier gas. Reversibility
of TFBAR response was also observed upon dry air exposure when
the test vapor is switched of. An advantage of this TFBAR sensor is
its ability to detect acetone vapors over a wide concentration range
without saturating the response, as reported by calibration curves
of frequency shift and insertion loss change in the Fig. 9.41. The
limit of detection (LOD) achieved by this developed TFBAR sensor
was measured as 12.5 and 8.7 ppm for acetone and ethylacetate,
respectively. The sensitivity, intended as frequency shift per unit
concentration, to acetone of this 1.045 GHz TFBAR coated by
28 nm thick 75 wt.% SWCNT-nanocomposite LB film was as high as
12 kHz/ppm in the range of concentration from 165 to 500 ppm.
21
Figure 9.41
(
) (a) Schematic view of TFBAR gas sensor with
SWCNTs-CdA nanocomposite LB film; (b) SEM image of Si
substrate back side etched by KOH solution. (
Top-left
) Real
and imaginary part of the impedance of unloaded TFBAR
device. (
Down-left
parameter LogMag room temperature
response to acetone 10-minutes pulses of TFBAR sensor
coated by a 28-nm thick 75 wt.% LB nanocomposite film of
SWCNTs. (b) Calibration curves of the frequency shift and
insertion loss change in the S
Right
) (a) S
21
parameter of TFBAR. This
figure is adapted as referenced by Penza
21
et al.
[292].
