Crystallization in Patterns: A Bio-Inspired Approach
Original Entry by Michelle Borkin, AP225 Fall 2009
J. Aizenberg, Advanced Materials, 2004, 16, 1295-1302.
Biomineralization, Artificial Crystallization, Self-assembled monolayers (SAMs), Nucleation
Many examples in nature can be found of biomineralization in which inorganic salts are assembled to form "functional minearlized tissues". This process occurs in very specific environments and is controlled by cells and various macromolecules. The research presented in this paper is a study of these processes and how to apply them to artificially produce crystals in a "bottom-up" approach. Conventional crystal production techniques take a "top-down" approach: grow one large single crystal and then cut-it-down into pieces meeting the correct size, orientation, etc. requirements. In a "bottom-up" approach, the growth of the crystals are governed by their initial physical and chemical conditions to produce the desired crystal. Examples in nature, as shown in Figure 1, are more complex than contemporary manufacturing technology can produce. Creating an effective approach is of great interest to the materials science industry.
This paper presents strategies for artificially mimicing natural "bottom-up" approaches to crystallization. The experimental set-up's presented attempt to incorporate the following features: crystal nucleation is governed by membranes, crystal properties are adjusted by ionic and soluable "organic growth modifiers", crystals have precise predetermined patterns, and crystallization can occur through a "transformation of a transient amorphous phase". The new experimental approaches presented are able to control during the crystallization process at the micrometer scale the transfer of mass across the surface, the molecular structure, and the sites of nucleation.