When an isolated conducting substrate in a solution is subjected to a parallel electric field, it can become a bipolar electrode, that is, an electrode that simultaneously acts as both anode and cathode. This type of electrochemistry has made possible the studying of chemical reactions without physical contact to a circuit, for instance, in electrogenerated chemiluminescence applications.Recently, Bjorefors and co-workers successfully created molecular gradients on a bipolar electrode. For example, self-assembled monolayers on gold were converted to a gradient surface by the cathodic desorption of thiols. Reported electrochemical or bipolar patterning has all been based on deposition or desorption of organic/polymeric molecules or inorganic materials involved at the surface of a conducting substrate. The challenge to gradually convert the composition of molecular or polymeric film in-plane using a simple technique is quite important in view of the widely expanding research into polymer-based soft matter gradients.
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