Investigation of fluidic assembly of nanowires using a droplet inside microchannels

Nanowires are common building blocks for the bottom-up assembly of electronic and photonic devices. A significant challenge is to introduce a single nanowire into an oriented assembly in order to express its unique anisotropic properties or to fabricate a nanodevice. In this work we focused on the development of a micrometer length scale approach, based on a fluidic method for alignment and assembling of nanowires. The alignment is achieved by manipulating a droplet composed of a dilute nanowire suspension by creating thermocapillary motion inside a microchannel. Our purpose is to explore the nanowires’ alignment mechanism in the middle region between the droplet’s front and rear menisci, and their interaction with the free surface and the contact lines. Experimental results show that nanowires which are found in the middle region of the droplet are generally aligned with the flow direction. Nanowires which reach the front meniscus move together with the displacing fluid which undergoes a “rolling” type motion, and are finally adsorbed to the surface of the microchannel. The adsorbed nanowires were found in most cases to align with the droplet’s flow direction. However, in certain cases nanowires may become reoriented by the passage of the rear-contact line.