Christopher Williams, an assistant professor with Virginia Tech’s College of Engineering, will use a National Science Foundation Faculty Early Career Development (CAREER) Award to explore 3-D ink-jet printing with copper as a conductivity tool.
Copper is highly valuable to engineers for its thermal properties, and is used in wiring to conduct electricity into millions of homes and business, and on a smaller scale to dissipate heat from personal computers and consumer electronics.
Yet, it thus far has not been used in the burgeoning field of 3-D printing, or additive manufacturing. In this process, a binder is selectively inkjet-printed onto a bed of powdered material – be it plastic, metal, or ceramic -- to create successive cross-sectional layers and forming a pre-designed shape.
The problem: Copper is such a stand-out conductor that it is extremely difficult to control during the heating and then cooling process found in other additive manufacturing processes that use lasers to selectively melt metal or polymers. When given focused energy, the heat is conducted throughout the copper material, which prevents precise printing control. Think of the process as akin to placing a copper pot on a stove, filling it with soup, turning on a heat source, and trying only to heat a portion of the food.
That’s where Williams and his CAREER Award, totaling $400,000 for a total five years, comes in.
“We’re trying to give engineers more choices of what they have to print with,” said Williams, an assistant professor with Virginia Tech’s Departments of Mechanical Engineering and Engineering Education. “They can’t use copper and other materials right now, and were trying to fix that.”
In his research, Williams will test the use of copper oxide powders in an ink-jetting 3-D printing process to create small, complex copper parts. The demand for printing complex, lightweight products in copper is strong: Because engineers are always looking for better structural heat exchangers to aid in thermal management of many mechanical and electrical products, such as cell phones. Copper is the ideal source.
Williams’ National Science Foundation proposal will explore jetting a glue blinder filled with copper nanoparticles into a bed of copper oxide powder to form the desired shape, followed by a thermal-chemical post-process to convert the printed part to metallic copper. The post-process would involve “cooking” the copper oxide object in a gaseous environment of hydrogen and argon, thereby eliminating the oxide in the original powder form. Only copper would be left.
The first year of the study will include 3-D printing simple, flat shapes to perfect the printing process and to test strength and conductivity. Then more complex shapes and designs will be explored, Williams said. The ultimate goal is to produce copper parts with cellular structures – solid parts with designed porosity throughout – such as observed in natural materials such as wood, bone, and coral.
The CAREER grant is the National Science Foundation’s most prestigious award, given to creative junior faculty likely considered to become academic leaders of the future.
Williams, director of Virginia Tech’s DREAMS, or Design, Research, and Education for Additive Manufacturing Systems, Laboratory, earned a bachelor’s of science degree in mechanical engineering from the University of Florida in 2000, and his master’s and doctoral degrees in mechanical engineering from Georgia Tech in, respectively, 2003 and 2007.