Sabrina M. Rosa-Ortiz and Arash Takshi, Ph.D.
University of South Florida
FL, USA
A novel technique called hydrogen evolution assisted (HEA) electroplating, has dramatically shown enhancement to the deposition rate of copper compared to galvanostatic conventional electroplating methods, opening new venues for the direct integration of devices to fabrics leading to the development of useful wearable electronics.
HEA can be used for both printing copper tracks on a multi-wall carbon nanotubes (MWCNTs) coated template tracks and soldering surface mount electronic devices (SMD) to such tracks, demonstrating its versatility to be used for specific applications in which fabric mutilation wants to be prevented. However, in this project we studied how copper deposition takes place at different voltage ranges using 1000 Denier Coated Cordura Nylon, Laminated Polyester Ripstop and 100% Virgin Vinyl in the constant presence of the hydrogen evolution technique.
Cupric sulfate (CuSO4) and sulfuric acid (H2SO4) were used as the medium to allow a lateral deposition over a multi-wall carbon nanotube track of 0.1mm by the application of a voltage ranging between -0.5V to -2.0V using a potentiostat to employ the cyclic voltammeter technique in order to achieve a uniform deposition. Structure of the fabrics and variation of the copper deposits with respect to the type of fabric used were observed using a scanning electron microscopy (SEM).
Copper electrodeposition assisted by the hydrogen evolution technique at voltage variation of -0.5 V to -2.0 V had shown a constant and uniform copper growth suitable for printing a circuit layout, soldering components and creating integrated circuits into fabrics. The hydrogen evolution effect was observed during the electrodeposition resulting in a dramatic increase of copper deposition while the electroplating was taking place.
Due to the agglomerations of hydrogen bubbles a more porous copper structure was observed while using the 1000 Denier Coated Cordura Nylon fabric instead of a more compact structure as observed while using Laminated Polyester Ripstop fabric. Although the porous copper structure was not as uniform as we were expecting significant advantage of the HEA electroplating method can be gain from this structure.
As it was shown copper electrodeposition over fabrics is a viable method which doesn’t require any soldering machine to achieve a proper metal deposition facilitating the commercialization and development of several applications.
There is no mention of organic additives being used in the plating solution. I would expect both a porous deposit and a higher deposition rate without organic additives.
