Microcontact Printing via a Polymer-Induced Liquid-Precursor (PILP) Process
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Microcontact Printing via a Polymer-Induced Liquid-Precursor (PILP) Process Yi-yeoun Kim and Laurie B. Gower Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32611, USA ABSTRACT Our biomimetic approach for patterned crystallization is based on the combination of the Micro-Contact Printing technique and a novel mineralization process, called the PolymerInduced-Liquid-Precursor (PILP) process, which enables the deposition of mineral films under low-temperature and aqueous-based conditions. We demonstrate that a liquid-phase mineral precursor is deposited onto specific areas templated with self-assembled monolayers of alkanethiolate on gold, and then the patterned calcitic films grow under constrained conditions via transformation of the PILP phase, leading to control over the location and morphology of calcitic films.
INTRODUCTION The patterning capabilities of inorganic films derived from a biomimetic, bottom-up approach, are of interest in microelectronics and bioelectronics applications that require high performance mechanical, electrical and/or optical properties resulting from controlled nano- and microstructural design. Biomimetic processing techniques are also desirable for biomedical applications that incorporate thermally sensitive components, such as proteins or cells, into devices such as biochips for sensor applications, bioseparations, biocatalysis, and hard-tissue biomaterials. Biological mineralization differs from traditional crystallization in that the crystallization process is mediated with organic materials, leading to a high degree of control over the mineral properties. This occurs through the incorporation of both soluble proteins, which are thought to modulate crystal shape, and an insoluble matrix, which presumably regulates crystal nucleation [1], and enhances the mechanical properties of the bioceramic composite. The performance of synthetic inorganic materials could be significantly advanced by precise control over crystal size, orientation, morphology, and location, as occurs in biominerals; yet rarely can control over all of these properties be accomplished in one synthetic system [2, 3]. We have proposed that a polymer-induced liquid-precursor (PILP) process may play a fundamental role in biomineralization (in both vertebrates and invertebrates) [4,5], and if the mechanisms utilized by biomineralizing systems can be determined, significant advances could occur in the biomimetics field. In the PILP process, micromolar quantities of acidic polymers are added to the crystallizing solution of an inorganic salt (such as calcite), and the charged polymer sequesters the ions and generates liquid-liquid phase separation. The phase boundaries of the minor phase ultimately define the shape of the final crystal products that form upon solidification and densification of the precursor phase, thus producing a variety of non-equilibrium crystal morphologies [5,6]. The elaborate morphologies and composite structures found in biominerals have long been the envy o
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