Page 208 - Optofluidics Fundamentals, Devices, and Applications

Adaptive Optofluidic Devices 183

promises of the suggested design is a low-complexity N × N switch-
ing. For example, only two of these components are required to con-
struct a 4 × 4 switch, which would otherwise consist of five 2 × 2
crossbar or sixteen 1 × 2 switches [47]. The device is fabricated in
PDMS, which also suggests easy integration into lab-on-a-chip
devices.

8-1-3 Deflectors and Beam Scanners
In many applications it is crucial to have the capability of a continu-
ous scanning of an optical beam. Beam deflectors in which fluids are
used as the major functional element were recently demonstrated.
Fluid actuation techniques employed for continuous beam scanning
are essentially the same as those used for discrete beam switching.
Examples include mechanically driven fluidic lens [48], electrowetting-
based prism [49], and thermally actuated mirrors [50].
Optical deflector for continuous beam scanning based on elec-
trowetting microprism is shown in Fig. 8-2a. Beam scanning in the

~1 mm

0 V 0 V 80 V 30 V 60 V 60 V 50 V 70 V

(a)
Metallization
Mirrorchip Hinge
PDMS

Cavity
Channel

2 mm
Glass
(b) (c)

FIGURE 8-2 Tunable optical defl ectors: (a) electrowetting-based optical defl ector—
prism with a variable angle is used to defl ect an optical beam. (N.R. Smith, D.C.
Abeysinghe, J.W. Haus, and J. Heikenfeld, “Agile wide-angle beam steering with
electrowetting microprisms,” Opt. Express, 14 (14), 6557–6563, 2006.) Tunable
micro-mirror; (b) a mirror is embedded into PDMS membrane. (A. Werber and
H. Zappe, “Thermo-pneumatically actuated, membrane-based micro-mirror devices,”
J. Micromech. Microeng., 16, 2524–2531, 2006. Institute of Physics and IOP
Publishing.) (c) The membrane forms a cavity. When a pressure is applied to infl ate
the cavity the membrane tilts the mirror. (A. Werber and H. Zappe, “Thermo-
pneumatically actuated, membrane-based micro-mirror devices,” J. Micromech.
Microeng., 16, 2524–2531, 2006. Institute of Physics and IOP Publishing.)