Yeojin Jung, City College of New York
Programming Bombyx Mori Silk’s Water-Responsive Actuation Using Silica Nanoparticles
Written by Jessalyn Hui Ying Low
Spider silk is a water-responsive material found in nature and is known to be a great water-responsive actuator, but faces the issue of low availability. In this talk, Yeojin Jung shows how by engineering the Bombyx (B.) mori (silkworm) silk, water-responsiveness actuation can be enhanced, and even surpass that of natural muscles and spider silk. “Our findings could help apply natural silks as simple and scalable, but powerful water-responsive materials for practical applications,” says Jung.
Jung first explains that microstructure engineering can be used to increase the water-responsiveness of B. mori silk. By subjecting the silk to water vapor or methanol treatment, β-sheet crystallinity is increased. β-sheet nanostructures are capable of translating water energy into mechanical energy, thereby showing the potential for B. mori as actuators. Moreover, Jung shares that by adding stiff silica nanoparticles to mimic stiff β-sheet crystals, water-responsiveness could be significantly increased. Fourier-transform infrared spectroscopy (FTIR) studies additionally confirmed that the silica nanoparticles had minimal effect on the silk’s microstructure, with increase in water-responsiveness energy density due to the nanoparticles instead. With the addition of silica nanoparticles, water-responsiveness energy density of B. mori silk was found to be increased to ~ 700 kJ m-3, a value much higher than that of spider silk.