Major Areas of Opportunity - Implications of Emerging Micro-and Nanotechnologies - page 74

signal-conditioning circuitry on a flexible belt. Installed on an aircraft's wing, the
pressure belt provides data during the aerostructure's design stage.
While the MEMS pressure belt described above is intended for measuring
the pressure distribution on a wing in flight, nanoscience has provided an alterna-
tive solution for wind tunnel measurements. When fluorescent dye molecules are
applied as paint they act as tiny oxygen probes, reacting by altering the fluores-
cent intensity in response to the local oxygen concentration. This pressure-sensi-
tive paint (PSP) is illuminated with light to excite the fluorescence. As the pres-
sure of the airflow across the surface changes, the intensity of the light generated
is monitored, as shown in Figure 3-12, clearly indicating pressure gradients. The
temperature sensitivity of the thin-film coating is corrected using infrared mea-
surement.
Condition-Based and Prognostic Health Monitoring
Status sensing is done for both routine operation of systems—for example,
as part of control loops—and for determining when routine or critical mainte-
FIGURE 3-12 A typical pressure-sensitive paint result for a wind tunnel model of a
transonic transport airplane. Courtesy of Boeing.