Biomedical Engineering Reference
In-Depth Information
CHAPTER
3
Enabling Technologies
In addition to energy generators that have been presented previously in
the literature (Beeby et al., 2006; Cook-Chennault et al., 2008; Paulo
and Gaspar, 2010; Romero et al., 2009), there are novel approaches that
encompasses chemical (e.g. direct glucose fuel cells), thermal, and nano-
generators. An updated review of the latest research development for
biomedical applications is discussed. Thermal generators require a ther-
mal gradient to operate. This makes them impractical for deep implants
where thermal gradients can be as high as 0.2
C but when placed at the
skin surface they can have temperature differences from 1
Cto5
C.
For example, 1
C of temperature gradient can be enough to produce up
to 100
W of power on average, which should be enough for powering
a cardiac pacemaker. New advances in nanotechnology promises even
smaller devices for implantable applications. Nanowires made of zinc
oxide (a nontoxic piezoelectric material) can be manufactured into a
flexible implantable material that can harness the veins pulsations inside
the body to power heart beat and blood pressure monitors (Yang et al.,
2009). Biological fuel cells, or direct glucose fuel cells, using glucose
rather than nitrogen can be a possibility. Nishizawa et al. (2005) pre-
sented this approach fabricating a coin-sized biofuel cell that generated
up to 140
μ
μ
Wofpower.
3.1 CHEMICAL ENERGY
Direct glucose fuel cells, also known as biofuel cells, can use glucose as
a fuel. The main advantage is that when using blood glucose for energy
generation, it produces water as byproduct. A biofuel cell prototype
capable of producing up to 140
W of power was presented by
Nishizawa et al. (2005). However, these types of biofuel cells (enzymatic
type) are challenged by the short lifetimes, in the order of several weeks,
and by inefficient fuel oxidation (Barton et al., 2004; Minteer et al.,
2007). Biological batteries, using biological fluids, have also been
reported. Lee (2005) developed a low-cost paper laminated battery
(dimensions of 60 mm
μ
30 mm) using copper and magnesium as the
electrodes and a chloride-doped filter paper. This battery is activated
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