A Fundamental Review of the Relationships between Nanotechnology and Lignocellulosic Biomass - The Nanoscience and Technology of Renewable Biomaterials - page 32

cellulosic materials, we will be able to take advantage of these piezoelectric properties
to build in greater functional performance.
Smart paper and packaging materials including radio frequency identification (RFID)
and integrated moisture, impact and biological/chemical sensors, require paper substrates
with new physical and chemical specifications. Moreover, advanced devices may require
the ability to print much smaller and more uniform features onto paper substrates. How-
ever, several areas of advancement are needed. For example, printed electronics on
paper will place new constraints on paper substrate frequency response and conductiv-
ity. The complex dielectric constant and dielectric loss tangent performance will need
to be addressed to accommodate different frequency regimes. Radio frequency identi-
fication (RFID), for example, operates in the 1-50 MHz range, but development of

systems operating in the 300-500 MHz range is also underway. The specific applica-
tion will drive the final specifications, but process, material and coating technologies
capable of supporting device operation in the 1-50 MHz and 50-500 MHz should be
explored.
Electronic devices such as printed interconnects, resistors, reactive components and
even active electronic and optoelectronic devices operating at high frequencies will
require small printed feature dimensions and film thicknesses produced with better unifor-
mity and reproducibility than is currently achievable, thus placing an additional constraint
on the surface morphology of the paper substrate. Printed features, such as interconnect
lines, may exhibit feature dimensions ranging from < 10 to 100 microns in width and
from < 1 to 10 microns in thickness. The roughness and porosity of the paper sub-
strate may be limiting in these applications, creating opportunities for new fillers, fiber
materials, and fiber assembly or coatings to improve the structure of the substrate. We
expect to improve the particle size and shape distributions of selected building blocks.
This may be the extension of the engineered mineral pigments emerging currently or the
development of new synthetic materials from wood fiber.
In order to achieve the most benefit from the opportunities to modify optical and elec-
trical properties, we need to be able to select with precision the needed building blocks
and then control their assembly into useful structures. This is probably the most challeng-
ing area. Paper coatings currently use additives and components that are applied in shear
fields and dried under precise conditions to control the migration and positioning of the
components to best advantage. Much of this has been derived empirically with informa-
tion inferred from bulk measurements. Similarly in papermaking, pulp refining has been
tuned to select the most useful building blocks and drainage, retention, and formation
aids are used to control the structure development in the shear and compressive fields
that occur on the paper machine in papermaking. Again many of these developments
have been empirical but have benefited from recent microcopy developments.
The new disciplines of soft matter physics and nanotechnology are leading people to
the study of self-assembling systems and offer the opportunity to leverage the findings
into the world of forest products. Some of the areas that should be of value are:

∼

1. block copolymer reactions;
2. drying moderated assembly;
3. hydrophobic/hydrophilic assembly;