Chemistry in Motion
Reaction-Diffusion Systems for Micro- and Nanotechnology
April 2009
302 Pages, Hardcover
Wiley & Sons Ltd
Change and motion define and constantly reshape the world around
us, on scales from the molecular to the global. In particular, the
subtle interplay between chemical reactions and molecular transport
gives rise to an astounding richness of natural phenomena, and
often manifests itself in the emergence of intricate spatial or
temporal patterns. The underlying theme of this book is that by
"setting chemistry in motion" in a proper way, it is
not only possible to discover a variety of new phenomena, in which
chemical reactions are coupled with diffusion, but also to build
micro-/nanoarchitectures and systems of practical importance.
Although reaction and diffusion (RD) processes are essential for
the functioning of biological systems, there have been only a few
examples of their application in modern micro- and nanotechnology.
Part of the problem has been that RD phenomena are hard to bring
under experimental control, especially when the system's
dimensions are small. Ultimately this book will guide the reader
through all the aspects of these systems - from understanding
the basics to practical hints and then to applications and
interpretation of results.
Topics covered include:
* An overview and outlook of both biological and man-made
reaction-diffusion systems.
* The fundamentals and mathematics of diffusion and chemical
reactions.
* Reaction-diffusion equations and the methods of solving
them.
* Spatial control of reaction-diffusion at small scales.
* Micro- and nanofabrication by reaction-diffusion.
* Chemical clocks and periodic precipitation structures.
* Reaction-diffusion in soft materials and at solid
interfaces.
* Microstructuring of solids using RD.
* Reaction-diffusion for chemical amplification and sensing.
* RD in three dimensions and at the nanoscale, including
nanosynthesis.
This book is aimed at all those who are interested in chemical
processes at small scales, especially physical chemists, chemical
engineers, and material scientists. The book can also be used for
one-semester, graduate elective courses in chemical engineering,
materials science, or chemistry classes.
List of Boxed Examples xiii
1 Panta Rei: Everything Flows 1
1.1 Historical Perspective 1
1.2 What Lies Ahead? 3
1.3 How Nature Uses RD 4
1.4 RD in Science and Technology 9
2 Basic Ingredients: Diffusion 17
2.1 Diffusion Equation 17
2.2 Solving Diffusion Equations 20
2.3 The Use of Symmetry and Superposition 31
2.4 Cylindrical and Spherical Coordinates 34
2.5 Advanced Topics 38
3 Chemical Reactions 45
3.1 Reactions and Rates 45
3.2 Chemical Equilibrium 50
3.3 Ionic Reactions and Solubility Products 51
3.4 Autocatalysis, Cooperativity and Feedback 52
3.5 Oscillating Reactions 55
3.6 Reactions in Gels 57
4 Putting It All Together: Reaction-Diffusion Equations and the Methods of Solving Them 61
4.1 General Form of Reaction-Diffusion Equations 61
4.2 RD Equations that can be Solved Analytically 62
4.3 Spatial Discretization 66
4.4 Temporal Discretization and Integration 80
4.5 Heuristic Rules for Selecting a Numerical Method 87
4.6 Mesoscopic Models 87
5 Spatial Control of Reaction-Diffusion at Small Scales: Wet Stamping (WETS) 93
5.1 Choice of Gels 94
5.2 Fabrication 98
6 Fabrication by Reaction-Diffusion: Curvilinear Microstructures for Optics and Fluidics 103
6.1 Microfabrication: The Simple and the Difficult 103
6.2 Fabricating Arrays of Microlenses by RD and WETS 105
6.3 Intermezzo: Some Thoughts on Rational Design 109
6.4 Guiding Microlens Fabrication by Lattice Gas Modeling 111
6.5 Disjoint Features and Microfabrication of Multilevel Structures 117
6.6 Microfabrication of Microfluidic Devices 121
6.7 Short Summary 124
7 Multitasking: Micro- and Nanofabrication with Periodic Precipitation 127
7.1 Periodic Precipitation 127
7.2 Phenomenology of Periodic Precipitation 128
7.3 Governing Equations 130
7.4 Microscopic PP Patterns in Two Dimensions 137
7.5 Two-Dimensional Patterns for Diffractive Optics 145
7.6 Buckling into the Third Dimension: Periodic 'Nanowrinkles' 152
7.7 Toward the Applications of Buckled Surfaces 155
7.8 Parallel Reactions and the Nanoscale 158
8 Reaction-Diffusion at Interfaces: Structuring Solid Materials 165
8.1 Deposition of Metal Foils at Gel Interfaces 165
8.2 Cutting into Hard Solids with Soft Gels 178
8.3 The Take-Home Message 192
9 Micro-chameleons: Reaction-Diffusion for Amplification and Sensing 195
9.1 Amplification of Material Properties by RD Micronetworks 197
9.2 Amplifying Macromolecular Changes using Low-Symmetry Networks 203
9.3 Detecting Molecular Monolayers 205
9.4 Sensing Chemical 'Food' 208
9.5 Extensions: New Chemistries, Applications and Measurements 215
10 Reaction-Diffusion in Three Dimensions and at the Nanoscale 227
10.1 Fabrication Inside Porous Particles 228
10.2 Diffusion in Solids: The Kirkendall Effect and Fabrication of Core-Shell Nanoparticles 240
10.3 Galvanic Replacement and De-Alloying Reactions at the Nanoscale: Synthesis of Nanocages 248
11 Epilogue: Challenges and Opportunities for the Future 257
References 263
Appendix A: Nature's Art 265
Appendix B: Matlab Code for the Minotaur (Example 4.1) 271
Appendix C: C++ Code for the Zebra (Example 4.3) 275
Index 283
the reaction-diffusion field. It is a quick, informative survey of
what types of syntheses are possible in reaction-diffusion systems;
it provides the necessary framework to begin an in-depth project in
the field; and most importantly, it is an enjoyable read."
(Angewandte Chemie, 2010)