Session: IMECE Undergraduate Research and Design Exposition

Paper Number: 120878

120878 - Replating of Carbon Fiber Composites Metallized Through Sacrificial Nanotransfer 

Polymer-based materials are low-cost, lightweight, and formable materials that suffer from poor electrical conductivity, poor erosion resistance, and low operating temperature. This makes the metallization of polymers an attractive approach to overcoming deficiencies through the addition of metallic layers that serve as a functional skin on a polymeric surface.

Through the combination of sacrificial nanoimprint lithography and transfer printing, sacrificial nanotransfer (SNT) lithography can be used to create metalized polymer surfaces that enable lightweight conductive surface composite. These surface composites have a determined thickness and electrical conductivity that can be increased via replating for thicker metallic layers.

The approach in this work combines sacrificial nanoimprint lithography (SNIL) and transfer printing. The combination of SNIL, which has structures embedded with ZnO imprinted and transferred onto a molded material, with transfer printing, results in SNT and the establishment of metalized polymeric surfaces with lightweight conductive surface composites.

To produce a sample of SNT, a layer of gold was first electroplated onto a mirror polish 304 stainless steel metal mold with a 3”x3” area cleaned and prepared for electroplating. A thin layer of bright nickel was then plated on top of the gold to provide an interdiffusion layer. A thick layer of copper was plated to finish on top of the gold and nickel, chosen because it shares an oxide with ZnO and easily plates into a thick electrically conductive layer for the completed metal stack.

A seedless hydrothermal approach was taken to grow ZnO on the top layer of the plated copper using zinc nitrate hexahydrate and ammonium hydroxide. The concentration of zinc nitrate hexahydrate was held constant at 20 mM. The ratio of ammonium hydroxide to solution was 2.86% and the solution to container ratio was 0.40.

To begin growth, 733.4 mL of deionized water was heated to 50°C in the glass. 4.17 g of zinc nitrate hexahydrate was stirred into the water for 2 minutes before 20.20 mL of ammonium hydroxide was stirred in for 10 s. The electroplated mold was placed copper layer facing down to prevent interference from condensation into the solution jar. The ZnO was then grown at 80°C for 2.5 hours.

After the ZnO nanorods were grown, the electroplating masking tape was removed and a wet layup transfer onto carbon fiber occurred. The resin was spread atop each layer of the carbon fiber and stacked together with the growth region pressed against the top layer. Pressure was applied through a vice to ensure proper contact between the growth region, resin, and carbon fiber while wrapped in PTFE film. This allowed the resin to solidify in contact with the ZnO nanostructures, ensuring that the ZnO nanorods were embedded in the top layer of the resin. After curing and upon removal of the mold from the carbon fiber, the metallic multilayer was transferred onto the carbon fiber.

To measure the thickness of the metal layer, the resistance of the replated sample was measured using a four-point probe. The equation for resistivity was used to calculate thickness. Calculations were completed assuming the only significant resistance occurred from the copper layer. The transferred and plated layers of metal were considered as resistors in series.

Plated-up samples exhibited smoother surfaces measured using an optical profilometer compared to the initial SNT samples. The replated samples also provided thicker metallic layers. This occurred at the cost of certain surface defects that disrupted the mirror finish.

Sacrificial nanotransfer (SNT) lithography offers an inexpensive approach to metalize polymeric surfaces with an exposed metal layer and a durable interface. The SNT process has the ability to scale even higher with a post-transfer replating process. This scalability provides a promising outlook on the future of cost-effective polymer metallization processes that are adjustable for a diverse array of metal thicknesses. Since the replating processes causes the appearance of surface defects, further research into preserving the mirror finish while increasing thickness is necessary.

Presenting Author: Iris You Rutgers University

Presenting Author Biography: Iris You is an undergraduate student at Rutgers University studying materials science and engineering.

Authors:

Iris You Rutgers University
Bryan Llumiquinga Rutgers University
Jonathan Singer Rutgers University