Generation of a Net Flow Using a Two-phase Büttiker–Landauer Ratchet Pump in a Nucleate Boiling Region

Effective utilization of unused heat below 200 °C is a vital issue for a zero-emission society. Here, we propose a two-phase Büttiker–Landauer (BL) ratchet pump using nucleate boiling. Specifically, by fabricating a periodical structure consisting of hot regions (where bubbles and water rise) and cold regions (where water descends diagonally while dissipating heat), we demonstrate that a net flow of ∼13 mm/s can be generated in a nucleate boiling regime (e.g., 115 °C). In addition, we find that a net flow of ∼1 mm/s occurs even in a bubble-free temperature region (e.g., 80 °C), and thus our BL pump works both in temperature regions with and without bubbles seamlessly. Moreover, we explain our experimental results fairly well by proposing a simple model that considers buoyancy force due to the bubbles in a nucleate boiling region. Our findings should contribute to the effective use of energy in the future.