Pathogen Detection Using Magnetoelastic Biosentinels - Biomedical Engineering Systems and Technologies - page 51

1
1 Δ

(2)

The addition of a small mass results in a shift in resonant frequency ∆f such that ∆ f =
f - f 0 < 0 . The mass load on the ME resonator can easily be obtained by simply mea-
suring the resonant frequency shift.
The mass sensitivity ( S m ) can be obtained from a truncated Maclauren series ex-
pansion of (2), giving:

1

(3)

2

The sensitivity of the ME biosentinel is compared with microcantilevers in Figure 5.
For ME biosentinels and cantilevers fabricated from the same material and of the
same size, the ME sensor exhibits an S m about 100 times better than the cantilever.
Advanced microfabrication processes will enable the optimization of the resonance
performance of the ME sentinels which will lead to improved pathogen detection
capabilities.

1x10 4

Sentinels

1x10 2

1x10 0

1x10 -2

1x10 -4

Cantilevers

1x10 -6

1x10 2 1x10 3 1x10 4

Length (um)

Fig. 5. Sensitivity vs. length for cantilever and biosentinels. Biosentinels are 100 times more
sensitive.

Many ME biosentinels may be simultaneously deployed but remain individually
distinguishable [19, 20]. Different types of ME biosentinels can be made by changing
dimensions, microstructures, heat treatments and/or compositions of the resonators
and the different biorecognition elements may be employed to detect different patho-
gens. Each type of resonator will have its own characteristic resonant frequency. Dep-
loying a large number of ME sensors greatly increases the probability that the sensors
will react with the targeted pathogen, thereby reducing detection time. When multiple
sensors are employed, the apparent sensitivity can be significantly higher than that of
a single sensor.

2.2 Biosentinel Motion

An external magnetic field may also be used to impart motion to the biosentinels,
propelling them through a media to gain greater exposure to potential biological targets