A novel method for the production of microwires

Abstract

Radio frequency (RF) systems such as cell phones and GPS can perform better and last longer if we can reduce electrical heat loss in the wires. This is typically done in power systems by twisting or weaving the wires, following one of several patterns. Though, at radio frequencies, wire dimensions must scale down by as much as 1000 times in order to achieve the same effects. This project decomposes the problem into two main categories; the manufacturing of micron scale wires and the manipulation of these wires in order to form a twisted bundle. This project aims to produce twisted bundles of wire that have an AC resistance value at GHz frequencies approaching a fundamental limit in which electrical resistance is independent of frequency. This thesis focuses specifically on the first major problem: producing micron scale wires of considerable length. In order to accomplish this, I have developed a bottom-up approach to the manufacturing of microwires. Rather than reducing the diameter of a wire by drawing through successive dies, I have instead formed a wire by metalizing a small nanofiber core to reach the target diameter. Initially, I designed a mechanical system to harvest Nomex nanofibers 200-400 nm in diameter that have been electrospun onto a spinning drum. Next, I designed a system to concentrically coat the harvested nanofibers with a conductive seed layer via sputter deposition. Finally, I have designed a reel to reel system in order to electroplate over a segment of seeded nanofiber in order to achieve the target diameter. This now allows for the creation of microwires of considerable length for use in high frequency applications.