Electrically Induced Morphological Instabilities in Free Dendrite Growth

We describe a new instability mechanism in free dendrite growth, which arises from electrically enhanced diffusion of polar molecules near the dendrite tip. For a small applied potential, the dendrite tip velocity increases slowly with potential, as is described by an extension of normal solvability theory. Above a threshold potential, however, capillarity is insufficient to stabilize growth. We present observations that confirm this instability, which brings about a transition from enhanced normal dendrite growth to a rapidly growing needle morphology with strongly suppressed sidebranching.