A Fundamental Review of the Relationships between Nanotechnology and Lignocellulosic Biomass - The Nanoscience and Technology of Renewable Biomaterials - page 31

requirement to bleach pulp to make white paper. The color gamut in the final printed
image could be greatly improved by allowing for 'pure' pastel shades.
Currently the Kubelka-Munk approach of deriving apparent light scatter and absorp-
tion coefficients is useful for characterizing materials (Jones 2004). In addition, Mie
theory uses fundamental Maxwell equations to describe the way light is scattered from
particles and is useful for predictions of optimal sizes for light scattering units. Regular
arrangement of these units can give rise to reinforcement of light interactions and is
called a 'photonic effect'. For example, photonic band-gaps are structures that prevent
the passage of light. Photonic properties have been shown to be possible using 'standard'
materials and producing structures with regularities that provide photonic effects. Natu-
ral materials such as butterfly wings, seashells (abalone) and insect cuticles demonstrate
effective optical barriers with minimal materials (Vukusic, Hallam and Noyes 2007).
These are effects different from those described by Kubelka-Munk, Mie or Raleigh
scattering.
It has been demonstrated that it is possible to make photonic structures that stop narrow
wavelength band (e.g. latexes, Stober Silica - Synthetic Opals, and block co-polymers).
The challenge is to make a structure with a range of sizes that has an effect over a
very broad bandwidth and therefore, appears white. We are looking for high (close to
100%) opacity with high whiteness/brightness with minimal amounts of materials. More
efficient optical performance with minimal weight is required at all grade levels but
especially at the ultra-light grade where opacity decreases rapidly with weight. If we
can make coated paper in the same weight range as tissue paper we can gain the benefits
of high distribution costs and consequently limit competition from far afield. This will
revitalize production units serving local areas. As a subgoal we expect to achieve:
1. a range of colors through unique structures (permanently stable unlike dyes);
2. improved gloss and appearance through control of unique structures;
3. pearlescent/iridescent effects;
4. control of ink interactions;
5. applications for security/ticket stock;
6. brightness unachievable today without using optical brightening agents (OBA) for
enhanced image quality.
Electromechanical coupling effects in wood date back to 1950 when Bazhenov reported a
piezoelectric response in wood (Bazhenov 1961). In 1955, Fukada also showed how the
piezoelectric coefficients of wood were related to oriented cellulose crystallites (Fukada
2000). Piezoelectricity, a linear coupling between electrical and mechanical properties,
is displayed by crystal structures that lack a center of symmetry (noncentric symmetric).
Cellulose in wood is piezoelectric due to the internal rotation of polar atomic groups
associated with asymmetric carbon atoms providing the noncentric symmetry. Shear
piezoelectricity in wood varies depending on the type of wood, orientation of wood
samples, moisture, and temperature and is comparable to that of quartz. Despite these
early studies the potential of cellulose as smart lightweight material that can be used as
a sensor and an actuator has not been investigated. Kim et al . have shown that it is
possible to take advantage of this noncentric symmetry feature of cellulose to develop
electro-active devices (Kim 2006). It is envisaged that, as we develop self-assembling