Biomedical Engineering Reference
In-Depth Information
(a)
(b)
400
Horizontal
displacement
Vertical
displacement
300
200
X
100
Y
θ
2
θ
1
0
−100
−200
0035 15 kV ×65 100 µm
−300
10
30
50
70
90
110
Temperature (
º
C)
FIGURE 9.66
A TiNiCu bending-up microcage structure and examples of capturing of (a) an ant and (b) an aphid. (From Fu et
al., 2007, reproduced with permission from IOP Publisher, UK.) Vertical and horizontal displacement of TiNiCu
fingers in microcage as a function of substrate temperature where negative displacements denote a downward
displacement. (From Fu et al,
Smart. Mater. Struct
. 16, 2651-2657, 2007.)
application of very high powers (>20 mW) resulted in visible changes in the color of the
TiNiCu—an indication of overheating and surface oxidation. The microcage can be used
to capture microscale objects (Fu et al., 2007). Figure 9.67b shows the measured tip dis-
placement produced by passing a current through the metallic layers as a function of the
voltage amplitude and frequency of the square wave signal applied (Fu et al., 2007). For
frequencies below ~100 Hz, the tip displacement increases with applied voltage. However,
above ~100 Hz, the displacement decreases with increasing frequency for all applied volt-
ages, indicating that about 10 ms is required to cool the microstructure due to the thermal
capacity of the system. This places a maximum operating frequency of about 100 Hz for this
microcage design. The realization of high-frequency microactuators utilizing TiNi-based
250
200
150
100
50
0
0
2
4
6
8
10
Power (mW)
FIGURE 9.67
(a) Horizontal displacement of fingers of microcage as a function of input power applied; (b) horizontal dis-
placement of fingers of microcage as a function of voltage and frequency of the applied actuation square wave.
(From Fu et al,
Smart. Mater. Struct.
16, 2651-2657, 2007. Reproduced with permission from IOP Publisher, UK.)
