She is a biologist working at the interface of phylogenetics, biomechanics, and materials science to study the architecture, structure, and function of spider silks and of other arthropods, non-silk proteins such as glues, and comparative analysis of spider silk biomechanics. Her findings, recognized by the John D. and Mary T. McArthur Foundation in the 2007 McArthur Foundation Awards, are influencing the development of biomimetic material for a variety of applications, from biodegradable fishing lines to medical sutures to protective armor cloth. Hayashi is contributing to a fundamental rethinking of arachnid phylogeny and revealing key information about spider silks to support the development of new synthetic materials.