Negative Pressure in Water for Efficient Heat Utilization and Transfer

Thermodynamic metastable water in negative pressure providesapossible solution to elevate the upper limit of evaporative heat transfercapacity and the efficiency of low-grade heat utilization, but practicalimplementations are challenging due to the difficulty in generatingand maintaining large negative pressure. Herein, we report a novelstructure with a hydrogel film as the evaporation surface and a permeablesubstrate as the functional layer to suppress cavitation. Based onthe structure, we achieve an evaporation-driven flow system with negativepressure as low as -1.67 MPa. Molecular dynamics simulationselucidate the importance of strong water-polymer interactionsin negative pressure generation. With the large negative pressure,we demonstrate a streaming potential generator that spontaneouslyconverts environmental energy into electricity and outputs a voltageof 1.06 V. Moreover, we propose a "negative pressure heat pipe",which achieves a high heat transfer density of 9.6 kW cm(-2) with a flow length of 1 m.