The Grzybowski Group - Self Assembly and Adaptive Systems

Bartosz Grzybowski: Fundamentals and Applications of Self-Assembly

SPECIFIC FIELDS: PHYSICAL, INORGANIC, AND ANALYTICAL CHEMISTRY, STATISTICAL PHYSICS AND THERMODYNAMICS,
CELL BIOLOGY AND BIOLOGICAL CHEMISTRY

Our group’s interdisciplinary research – one combining the elements of chemistry, physics, engineering, mathematics, and biology – aims at (i) understanding self-assembly (SA) and self-organization (SO) in both equilibrium and nonequilibrium ensembles at various length-scales and (ii) applying SA/SO in practical applications ranging from micro and nanotechnology through biology to societal/global issues.

In the context of SA/SO theory, our group pioneered the field of dynamic self-assembly (DYSA) and developed design rules that allow “synthesis” of self-assembling systems from various types of interactions and/or phenomena. Our recent work in this area has focused on fundamental statistical-mechanical questions (J.Phys. Chem. B. 2006) concerning the role of energy dissipation in such systems, extension of thermodynamic concepts (e.g., temperature) to nonequilibrium ensembles, the influence of system’s geometry on the emerging structures/patterns (Phys. Rev. Lett. 2005, 2006), and the ability to “reverse-engineer” a desired self-assembled structure into the properties of it constituents.

In experiment, we explore both the “bottom-up” assembly of smaller components into larger architectures, as well as the “top-down” methods, in which smaller structures emerge from larger-scale processes. The bottom-up approach is focused on the nanoscale and capitalizes on our recent discoveries of the unique nature of electrostatic and dipole-dipole interactions in this regime (cf. Science 2006, 2007; Nano Lett. 2006 , 2007, JACS 2006). Here, the existence of the stability threshold and the importance of Debye-like screening enabled electrostatic self-assembly of a variety of supra-structures, including crystalline, quasicrystalline, and semi-periodic arrange-ments. Recent work employing higher electric multipoles – especially, light-induced dipoles tethered onto nanoparticles – has extended these findings to dynamic NP crystals which organize and disintegrate reversibly under the influence of light of different wavelengths.

In the top-down approach, our laboratory pioneered the use of spontaneous chemical reactions as a method of fabricating small-scale structures, devices, and detection systems (Nature Materials 2004, 2005;.Adv. Mater, 2004, 2006, Materials Today 2007) Once the reactions are initiated from well-defined spatial locations, they execute “programs” encoded in their chemical kinetics and their transport properties within the supporting medium. To date, our team has designed and executed a variety of chemical “programs” that enable self-organization of micro and nanoscopic optical devices, 3D structures in metals and semiconductors, systems that display molecular-level events in the form of macroscopic patterns, supports for cell motility studies, and more. On the fundamental level, this approach prompts intriguing questions concerning (i) the limits of its spatial resolution (i.e., the smallest discrete features that can result from spatially continuous reaction-diffusion fields) and (ii) the “biomimetic” ability to perform multiple RD processes at the same time. To understand these issues, our group has combined experiment with theory (nonlinear kinetics and transport, statistical mechanics) and succeeded in extending and rationalizing the method down to the nanoscale (remarkably, to 20 nm resolution), where the classical RD theories fail.

Top-down and bottom up approaches converge in our biology-oriented work on the self-assembly of cell components responsible for cell motility and metastasis (Nature Methods 2005, Soft. Matter 2007). Using special substrates (prepared by top-down reaction-diffusion processes) for controlled cell spreading and motility, we have been able to “deconstruct” (bottom-up) the spatial and temporal aspects of self-assembly of microtubules and actin stress fibers (1,20). The knowledge of how these components assemble and interact with one another is important for the part of our research devoted to the discovery of new antimetastatic drugs.

Finally, we are acutely interested in the societal and global aspects of self-assembly and self-organization. One example here is the study of networks of chemical reactions (cf. Angew. Chem. 2005, 2006), where our group discovered how apparently autonomous agents (here, chemists) give rise to a well defined, higher-order structure of the chemical universe (i.e., the network of all known reactions). By representing this universe as a directed graph and by analyzing it using stochastic modeling and graph theory, we were able to identify a set of statistical laws that govern all synthetic transformations carried out to date or to be carried out in the future. The amazing regularity embodied in these laws allows identification of most useful chemicals, prediction of the efficiencies of new chemical transformations, the properties of most likely products, and more.

Selected Publications:

A.M. Kalsin, M. Fialkowski, M. Paszewski, S.K. Smoukov, K. J.M. Bishop & B.A. Grzybowski Electrostatic self-assembly of binary nanoparticle crystals with a diamond lattice, Science, 312, 420 (2006).

A.M. Kalsin, M. Paszewski, A. Pinchuk, G.C. Schatz & B. A. Grzybowski Electrostatic aggregation and formation of core-shell suprastructures in binary mixtures of charged metal nanoparticles, Nano Lett., 6, 1896 – 1903 (2006).

R. Klajn, K.J.M. Bishop, M. Fialkowski, M. Paszewski, C.J. Campbell, T.P. Gray & B.A. Grzybowski Plastic and moldable metals by self-assembly of sticky nanoparticle aggregates, Science in press, (2007).

K.J.M. Bishop & B.A. Grzybowski Localized chemical wave emission and mode switching in a pat-terned excitable medium, Phys. Rev. Lett. 97, #128702 (2006)

K.J. M. Bishop, R. Klajn & B.A. Grzybowski The core and most useful molecules of organic chemistry Angew. Chem. Int. Ed., 45, 5348 (2006).

C. J. Campbell, S.K. Smoukov, K. J.M. Bishop, E. Baker & B.A. Grzybowski Direct Printing of 3D and Curvilinear Micrometer-Sized Architectures into Solid Substrates with Sub-micrometer Resolution, Adv. Ma-ter. 18, 2004 (2006).

M. Fialkowski, K.J. M. Bishop, R. Klajn, S.K. Smoukov, C.J. Campbell, B.A. Grzybowski Principles and implementations of dissipative (dynamic) self-assembly, J. Phys. Chem. B, 110, 2482 (2006).

B.A. Grzybowski, K.J.M. Bishop, C.J. Campbell, M. Fialkowski, S.K. Smoukov, Micro– and nanotechnology via reaction-diffusion, Soft. Matter, 1, 114 (2005).