Mechanical energy metamaterials in interstellar travel

Nanoscale spacecrafts have shed light on an audacious but promising vision for interstellar travel to neighboring planets beyond the solar system. The nanocrafts can be accelerated to a significant fraction of light speed, which leads to the possibility of completing the otherwise millennia space missions using the current rocket propulsion technology in several decades. However, electrical energy is a severe challenge for long-term interstellar travel. Mechanical energy metamaterials have been proposed as a promising technology integrated multiscale architected structures with energy materials, which have opened an exciting venue for energy harvesting under extreme conditions such as the cosmic environment. Mechanical energy metamaterials are envisioned as an alternative energy solution to address the power issue of nanocrafts in interstellar travel. Here, this article comprehensively overviews the debut and development of mechanical energy meta -materials and discusses the potential and application paradigm for energy harvesting in the cosmic environment. We first clarify the main feature and functionality of mechanical meta -materials and summarize the recent findings on typical mechanical energy metamaterials. Next, we identify the characteristics and challenges of the cosmic environment, deliberate the funda-mental energy issue of interstellar travel, and examine the stringent criteria to design mechanical energy metamaterial nanosails for electrical power. Discussion indicates that kinetic energy resulted in cosmic dust grains collision and photovoltaic energy from starlight can be the main energy sources for mechanical energy metamaterials. In the end, we propose the applications of mechanical energy metamaterial nanosails in the nano space energy systems (nano-SES) to address the energy challenges in interstellar travel by generating electrical power from the kinetic and photovoltaic energies.