Selective growth of highly crystalline hydroxyapatite in a micro-reaction cell of agar gel

High quality, idiomorphic hydroxyapatite (HAp) nanocrystals were directly, selectively and successfully grown on the hydrophobic/hydrophilic patterned surface via gel method. The patterned agar gel acted successfully as the micro reaction cell between raw materials. The HAp nanocrystals densely covered the hydrophilic surface, but their shape depended greatly on growth period. After 20 d growth, they were highly crystalline and well developed, and their crystal shape changed to form the one-dimensional (1-D) structure. Furthermore, idiomorphic, hexagonal cylindrical HAp nanocrystals were obtained after annealing at 600 °C for 5 h. It is expected to become considerably important in researching the direct growth/patterning of biocrystals.