Spider silk has exceptional mechanical and biocompatibility properties. The goal of this study was optimization of the mechanical properties of synthetic spider silk thin films made from synthetic forms of MaSp1 and MaSp2, which compose the dragline silk of Nephila clavipes. We increased the mechanical stress of MaSp1 and 2 films solubilized in both HFIP and water by adding glutaraldehyde and then stretching them in an alcohol based stretch bath. This resulted in stresses as high as 206 MPa and elongations up to 35%, which is 4× higher than the as-poured controls. Films were analyzed using NMR, XRD, and Raman, which showed that the secondary structure after solubilization and film formation in as-poured films is mainly a helical conformation. After the post-pour stretch in a methanol/water bath, the MaSp proteins in both the HFIP and water-based films formed aligned β-sheets similar to those in spider silk fibers.

Spider silks have unique mechanical properties but current efforts to duplicate those properties with recombinant proteins have been unsuccessful. This study was designed to develop a single process to spin fibers with excellent and consistent mechanical properties. As-spun fibers produced were brittle, but by stretching the fibers the mechanical properties were greatly improved. A water-dip or water-stretch further increased the strength and elongation of the synthetic spider silk fibers. Given the promising results of the water stretch, a mechanical double-stretch system was developed. Both a methanol/water mixture and an isopropanol/water mixture were independently used to stretch the fibers with this system. It was found that the methanol mixture produced fibers with high tensile strength while the isopropanol mixture produced fibers with high elongation.

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The transient electrothermal technique is a powerful tool to obtain thermal properties of fine fibers. However, the technique suffers from several inherent pitfalls, which affect measurement accuracy, especially with application to coated, nonconductive samples. In this paper, measurement challenges are described and quantified for several associated parameters and physics including: sample length, time of Joule-heating initiation, sample resistance including measurement uncertainty as well as evolving resistance for coated samples, coating influence, lateral surface heat losses, vacuum level, and variable heat generation. Several methods to overcome these challenges to ensure good measurement accuracy are provided. These methods are applied to the measurement of thermal conductivity and thermal diffusivity of gold-coated glass fibers (nonconductor). The resulting measured thermal conductivity of 1.35 Wm−1 K−1, and thermal diffusivity of 7.6 × 10−7 m2 s−1 compare well to literature values. Additionally, an analytic formula is developed along with limiting conditions for simplified application, which accounts for neglected heat losses. The result is a factor that can be applied to correct a more straightforward heat model of the sample, which neglects heat losses. To further validate the method and quantify measurement variability, a detailed uncertainty analysis is performed using methods based on the Taylor series method for propagation of uncertainty and Monte Carlo simulation. The resulting measurement uncertainty is found to be ~7% for thermal conductivity and ~4% for thermal diffusivity.