In situ synthesis of vertical 3-D copper-core/carbon-sheath nanowalls in microfluidic devices

Microfluidic devices with integrated in-channel 3-D nanostructures have been attracting extensive attention because of the potentially superior properties resulting from the synergetic effect of nanomaterials and microfluidics. In this study a novel and facile in situ electrodeposition method was developed to grow nanostructures within a microfluidic channel which was created using PDMS and a 3-electrode system on a silicon substrate. Specifically, novel vertical 3-D copper-core/carbon-sheath nanowalls were obtained using optimized conditions in terms of the concentrations of copper precursor and structure-directing agent, the applied potential and time for electrodeposition, and the flow rate in the microfluidic channel. The mechanism of forming copper-core/carbon-sheath nanowalls is also discussed in conjunction with COMSOL numerical simulation. As the growth of the nanostructures occurs only on the in-channel electrode, the precise growth of nanostructures in a controllable area within the microfluidic device is exhibited and the device is immediately ready for use without further processing. Considering the fact that various metals, metal oxides and polymers can be electrodeposited the developed method opens a new avenue for in situ integration of novel functional nanostructures within microfluidic channels for the development of lab-on-a-chip systems.