Electrochemical actuation of growing copper dendrimers in water

We report the observation of electrochemical actuation in growing dendritic fibers made of self-assembled copper nanostructures (of 100 nm or less in diameter), on the metallic cathode of an ordinary aqueous electrochemical cell. This could be achieved when a copper anode and another metal cathode is placed in aqueous solution of either dilute HCl or CuSO(4), or CuCl(2), or H(2)O, and upon application of a DC voltage in the range of 1.5-12.0 V. The actuation could be observed with an on-off cycle of the applied voltage in the above range. The phenomenon was also observed with the growth of bimetallic structures using a number of electrolytes such as Ag(NO(3)), Pb(NO(3))(2), CoCl(2), NiCl(2), CdCl(2), ZnCl(2), and HAuCl(4). The fibrous structures remained stretched as they grew longer with time in the presence of an applied voltage. The extent of actuation was dependent on the applied voltage, the concentration of Cu(2+) ions in the solution, and also on ions such as Na(+), which did not get deposited at the cathode. The observed phenomena under different conditions have been explained on the basis of electrocapillarity.