Patterning of bioinorganic thin films by combining soft lithography and a biomimetic crystallization process

The biomimetic synthesis of patterned mineral films, based on a combination of the microcontact printing technique and a novel mineralization process, called the Polymer-Induced Liquid-Precursor (PILP) process, was demonstrated. Self-assembled monolayers (SAMs) patterned by micro-contact printing are able to act as synthetic templates for biomimetic mineralization, mimicking the role of biological organic matrices, which spatially confine the deposition of biominerals, as well as template the nucleation and growth of the crystals. The PILP process enables the deposition of calcitic mineral films (100–500 nm in thickness) under low-temperature and aqueous-based conditions. A liquid-phase mineral precursor can be preferentially deposited onto specific areas templated with the SAMs of alkanethiolate on gold. The patterned precursor films then transform under constrained conditions, leading to control over both the location and morphology of patterned films. Based on microscopic analysis of the surface texture of the mineral films, we propose that the formation of these patterned calcite thin films is accomplished by the deposition of colloidal droplets of the liquid-phase precursor generated in solution.; In order to further investigate crystal nucleation and growth which occurs via a precursor phase transformation, the cooperation of various functionalized endgroups of the SAMs and acidic macromolecules was extensively studied. It was observed that the morphology of the mineral phase depended on numerous variables, such as impurity ion concentration, polyelectrolyte concentration, mineral solution supersaturation level, pH and temperature. It was determined that the interaction of template functionality and the colloidal PILP particles has significance for controlling the trend of deposition, and that optimization of solution conditions is required to generate patterned thin films with a high level of resolution and reproducibility.; An unexpected result was found when a surplus of acidic polymer is added- the patterned mineral films act as a secondary template for directing new crystal outgrowths, which over time form into complex morphologies of calcite, such as fibrous mats and “horsetails”. Two interdependent factors, the polymer and Ca-ion concentration, which change the local solution environment over time, appear to modulate the creation of these different structures.; This approach provides a viable biomimetic model system for the investigation of crystal nucleation and growth, as well as phase transformations and morphology of mineral phases, and for unraveling the long-standing mystery of how biological systems fabricate their sophisticated and complex morphologies.