Some precipitates take regular, sinuous and oddly lifelike forms, and are known as biomorphs. Juan Manuel García-Ruiz of the University of Granada, Spain, and his colleagues describe an intriguing chemical feedback mechanism that creates the microcrystals responsible. In biomorphs built from barium carbonate crystals, the formation of these elongated crystals has the effect of locally reducing pH, which allows the precipitation of silica onto the crystals, halting their growth and defining their shape. The properties of these microcrystals, which the authors observed using time-lapse video microscopy and electron microscopy, are responsible for the smooth curves and furled edges of the biomorphs.
The work opens the way for new approaches to the synthesis of biological and biomimetic materials, and to the exclusion of false positives when looking for life-like forms in poorly characterized environments.
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Crystal growth: Getting their morph on. Nature 457, 360 (2009). https://doi.org/10.1038/457360a