AbstractNanoporous gold (np-Au), produced by selectively removing silver from an AuAg alloy, has recently gained considerable attention from the scientific community. Biocompatibility, chemical inertness, increased surface area, relatively low elastic modulus, and ease of synthesis make np-Au an important candidate for biomedical, catalytic, and MEMS applications. Np-Au films also offer substantial ground for theoretical and empirical research, including mechanical characterization, fracture mechanics, and porosity evolution. Even though a significant effort has been directed towards exploring blanket np-Au films (i.e., foils, strips), to our knowledge no work has been done on fabricating or investigating freestanding np-Au structures (i.e., micro-beams, cantilevers). Recently we have developed techniques to create freestanding clamped np-Au beams with widths from 5 to 40 microns and lengths from 20 to 500 microns. The percentage yield was more than 97% for 2880 beams on a 2-inch wafer. A critical step in the fabrication process, necessary to prevent tensile failure of the beams during dealloying, is a thermal heat treatment prior to dealloying. The study of thermal treatment of beams at temperatures between 100°C and 600°C prior to dealloying revealed three distinct beam behavior regimes, namely quasi-elastic buckling, plastic buckling, and material interdiffusion. This paper will present the preliminary results from thermal treatment experiments particularly focusing on how beam dimensions affect percentage yield and beam fracture.
Strong size-dependent stress relaxation in electrospun polymer nanofibers