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Soft Matter. Vols. 1 & 2. Edited by Gerhard Gompper and Michael Schick

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Soft Matter
Vols. 1 & 2. Edited
by Gerhard Gompper and Michael
Schick. Wiley-VCH,
Weinheim 2003.
285/287 pp., hardcover E each
119.00.—ISBN
3-527-30500-9/
3-527-31369-9
What exactly is “soft matter”, and why
are two volumes needed to enable the
reader to learn about this subject? It can
be said right at the outset that the
editors of these volumes, Gerhard
Gompper and Michael Schick, have
answered both questions very effectively, and that after reading them one
is left hoping that further volumes on
this subject, in the same form, might be
forthcoming. Soft matter has now
become adopted as the all-embracing
expression for a broad area of research
that is difficult to define precisely. Its
origins extend back to the early 1970s,
and its applications range from modern
nanotechnology to biology. The term is
understood to cover the study of the
structure and dynamics of systems that
involve distances much larger than typical molecular dimensions. Polymer
melts and mixtures are examples of
such systems that have already been
studied intensively, and these are covered in Volume 1. Volume 2 is devoted
to complex colloidal mixtures, including
suspensions of viruses.
What is the common feature that
links together such widely different
systems as polymers, mesophases of
surface-active agents, and viruses? In
the introduction to Volume 1 the editors
7874
explain that clearly, by reference to the
nowadays well-known phenomenon of
colloidal crystals. If, for example, one
looks at the shear modulus of ordered
solids, it can be shown immediately by a
simple consideration that this modulus
is reduced by about 14 orders of magnitude when one goes from conventional
solids (e.g., metals or ionic crystals) to
soft matter. Thus, a colloidal crystal is
extremely soft, and even very small
forces are sufficient to distort it. Similar
considerations also apply to the dynamic
behavior of such systems, which is
extremely slow compared with hard
solids. Also, the dimensions of soft
matter are in the region of a few mm,
and their structure and dynamics can be
studied easily by optical microscopy.
The authors further show that these
systems have many properties in
common, which justifies their treatment
under a single subject heading. They
also serve as model systems for understanding conventional “hard matter”,
since the interaction between the
“atoms” and building blocks of soft
matter can be altered continuously. An
example of this is the depletion forces
that are discussed by E. Eisenriegler in
Chapter 2 of the second volume. In this
case the soft matter researcher, in a
certain sense, “creates” his own atoms
with adjustable interaction potentials,
which then become capable of forming
quite new and unusual phases. Furthermore, many phenomena that are
observed in such systems are universal,
in other words they do not depend on
the atomic or chemical details of the
particular system. As a consequence of
this one can, for example, compare rodshaped micelles with viruses or polymers. It is this aspect of soft matter that
has generated much of the fascination
that the subject of soft matter now has
for researchers throughout the world.
Volume 1 begins with a description
of polymer dynamics in melts, a topic on
which the authors, Wischnewski and
Richter, have made important contributions to knowledge. This mature field of
research is presented very clearly here.
Following that, Chapters 2 and 3 are
devoted to the theoretical treatment of
polymer melts and concentrated polymer solutions. In Chapter 2, M. Matsen
describes the self-consistent field theory
(SCFT), and in Chapter 3 M. M6ller
* 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
compares this theory with Monte Carlo
simulation methods. These two chapters
are not written only for specialists, but
include detailed introductions to the
techniques, so that even readers with
limited mathematical knowledge can at
least work through the beginning sections of these reviews. Both chapters
give a general impression that the
authors have tried to ease the way also
for those readers who, although they do
not yet feel at home with these discussions, can use the theory to guide their
experiments.
In Volume 2, Dogic and Fraden deal
with an especially fascinating part of
modern research on soft matter, namely
that concerned with the phase behavior
of rod-shaped viruses. This is actually a
long-standing classical problem: Onsager developed the first theory of the
isotropic–nematic phase transition as
long ago as 1949, and thus established
the starting-point for the modern theoretical treatment of such systems. The
phase transitions in these types of suspensions have recently been studied
intensively by Fraden and co-workers,
who have now also observed nematic–
smectic transitions. A further very interesting aspect is the behavior of mixtures
of polymers or colloidal suspensions of
spheres with rod-shaped viruses, in
which new and unusual phases are
observed. This clearly shows that, with
modern soft matter physics, one can
generate and study structures that have
no analogues in the world of “hard
matter”.
In Chapter 2 of Volume 2, E. Eisenriegler discusses the depletion forces
that were mentioned earlier. However,
the reader will perhaps regret that the
theory described here is not compared
with results from the many experiments
that have recently been carried out in
this area. Volume 2 ends with a chapter
by J. Dhont and W. Briels on the
dynamics of rod-shaped particles under
shear flow conditions, in which the main
emphasis is clearly on the authors>
comprehensive theoretical treatment of
this problem.
Considered as a whole, these two
volumes form a good beginning to a
comprehensive treatment of this fastgrowing field of research. One certainly
hopes that the series will be extended to
cover some other, equally important,
Angew. Chem. Int. Ed. 2006, 45, 7874 – 7875
Angewandte
Chemie
aspects, such as the glass transition in
colloidal suspensions. These volumes
definitely belong on the desk of every
experimentalist working in this field,
and they will undoubtedly also be useful
for introductory courses on this subject.
Matthias Ballauff
Institut f3r Physikalische Chemie I
Universit7t Bayreuth (Germany)
DOI: 10.1002/anie.200685409
Introduction to Microfluidics
By Patrick Tabeling.
Oxford University
Press, Oxford 2005.
288 pp., hardcover
E 92.90.—ISBN
0-19-856864-9
Compacting an entire chemical plant or
an analytical laboratory onto a small
chip is a vision that has fascinated
scientists all over the world for several
decades. The rapid progress in the
design and functioning of microelectromechanical systems (MEMS) that began
in the 1980s laid the cornerstone for the
microfluidic vision to become reality. In
his book Introduction to Microfluidics,
Patrick Tabeling describes the development of this very young discipline, its
physical and chemical background, the
know-how of microfluid chip fabrica-
Angew. Chem. Int. Ed. 2006, 45, 7874 – 7875
tion, and the applications of these devices.
How is microfluidics different from
the fluidics that has been known for
several centuries? Tabeling answers that
question in the first five chapters of the
book. First, forces that are irrelevant for
large dimensions, such as van der Waals
forces, become important on the microscale. Second, a special microhydrodynamics comes into play, since the Reynolds numbers are small in microfluidic
devices, and fluids can slip over a solid
surface (which means that it is no longer
necessary for the velocity of the fluid to
be zero at the interface). Third, the
surface-to-volume ratio is so large that
the influence of the channel walls
cannot be neglected. For example, if
one sort of molecules in the microfluidic
system can become adsorbed at the wall,
these molecules can be separated from
other, non-adsorbed, ones. This chapter
also highlights diffusion and mixing in
microfluidic systems, which are both
important issues for the fast reaction
kinetics in lab-on-a-chip devices. Fourth,
electric fields can influence the flow of
charged particles (and vice versa),
resulting in phenomena such as the
streaming potential, which can be summarized by the keyword “electrohydrodynamics”.
Here,
Tabeling
also
describes electroosmosis and electrophoresis, both of which are highly relevant for technical applications, such as
the commercially available microfluidic
chips for separating DNA or proteins.
The fifth chapter addresses heat transfer
in micro-scale systems. Two additional
chapters outline the fabrication and
industrial applications of lab-on-a-chip
devices.
Patrick Tabeling is professor at the
Bcole SupCrieur for industrial physics
and chemistry (ESPCI) in Paris, and is
actively involved in basic research.
Accordingly, the references at the end
of each chapter are comprehensive and
up-to-date. In explaining the physical
and chemical fundamentals of microfluidics concisely in this book, it was
impossible for Tabeling to cover all
details, and therefore he recommends
further reading when appropriate, and
gives references to special publications
or state-of-the-art textbooks.
The book is ideal for scientists
moving into this new field, for example
in preparation of a masters or PhD
thesis, as it will give them a thorough
grasp of the relevant phenomena, methods, and concepts. It is written in a lucid
and instructive way, the chapters are
clearly structured, and many worked
examples and footnotes further clarify
the subject. Moreover, each chapter
begins with a motivating introduction
and ends with a summary. The readers
who will benefit most from the book are
those with a sound background in physics, who will not be fazed by a stress
tensor or a Laplace operator. However,
also for readers who cannot usefully
study the theoretical subchapters, the
book will provide relevant knowledge in
physics, chemistry, and the life sciences
for everybody dealing with microfluidics.
Karin Jacobs
Institut f3r Experimentelle Physik
Universit7t des Saarlandes
Saarbr3cken (Germany)
* 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
7875
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