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rules, surface tension and quantum mechanics are emerging as the operating
principle for the micro- and nanoscale devices [1]. Nanoscale structures have
materialized phenomena otherwise undiscovered, such as Coulomb blockade (or
single-electron tunneling) and quantized or ballistic conductance to metal in-
sulator transition. Quantum confinement of electrons by the potential wells at the
nanoscale structures has provided a basis for the electrical, optical, magnetic and
thermoelectric properties of a solid-state functional material. The advent of
microelectromechanical systems (MEMS) and nanoelectromechanical systems
(NEMS) has enabled researchers to interface physical phenomena with biochem-
ical and molecular interactions, thereby challenging the existing engineering and
biomedical paradigms.
The last decade has attested a paradigm shift in research activities from that of
the individualized endeavor to cross-disciplinary efforts. In 330 B.C., Aristotle
recognized cross-fertilization as a means to ''search for truth ''and he wrote:
The search for truth is one way hard another easy, for no one can master it
fully nor miss it fully, each adds a little knowledge to our nature, and from
all things assembled there arises a certain grandeur.
In this chapter, readers will embark on a journey to cross boundaries in search
of the bioinspired heterogeneous structures.
16.2. MICROSCALE COMPONENTS
16.2.1. Nature-Inspired Surface Tension Force
Nature reveals surface tension force at its best. Inspiring phenomena are the water
striders walking on the surface of water, a raindrop forming a spherical shape, and
blood flow in the capillary bed. The common property of these three examples lies
in the enormous surface to volume ratio. Surface tension
s
is defined as the ratio
of the magnitude of force F tangentially applied to the surface of a liquid to the
length L along which the force exerts as follows:
s ¼
F
=
L
ð
16
:
1
Þ
Using the jointed stilt-like legs, water striders flit to and fro across the unflustered
surfaces of water up to 1.5m/s [2] (Fig. 16.1). Stationary water striders rest their
weight on all six legs. The minimal requirement for static stability on the surface is
defined as [3]
Mg
s
P
¼
1
M
c
¼
;
ð
16
:
2
Þ
where M denotes mass, g force of gravity,
s
surface tension, and P the curvature
parameter. When M
c
=1, the body force Mg is equal to surface tension
s
P.
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