Improved performance of biohybrid muscle-based bio-bots doped with piezoelectric boron nitride nanotubes

Biohybrid robots, or bio-bots, integrate living and synthetic materials following a synergistic strategy to acquire some of the unique properties of biological organisms, like adaptability or bio-sensing, which are difficult to obtain exclusively using artificial materials. Skeletal muscle is one of the preferred candidates to power bio-bots, enabling a wide variety of movements from walking to swimming. Conductive nanocomposites, like gold nanoparticles or graphene, can provide benefits to muscle cells by improving the scaffolds mechanical and conductive properties. Here, we integrate boron nitride nanotubes (BNNTs), with piezoelectric properties, in muscle-based bio-bots and demonstrate an improvement in their force output and motion speed. We provide a full characterization of the BNNTs, and we confirm their piezoelectric behavior with piezometer and dynamometer measurements. We hypothesize that the improved performance is a result of an electric field generated by the nanocomposites due to stresses produced by the cells during differentiation, which in turns improves their maturation. We back this hypothesis with finite element simulations supporting that this stress can generate a non-zero electric field within the matrix. With this work, we show that the integration of nanocomposite into muscle-based bio-bots can improve their performance, paving the way towards stronger and faster bio-hybrid robots.