Effects of extreme hydrostatic pressure on the molecular structure and properties of the elastomeric material for soft robots

The successful exploration of the Mariana Trench, Earth's deepest trench, by soft robots inspired by deep-sea organisms, showcasing the potential of soft robots for extreme deep-sea exploration. However, deep-sea extreme pressure significantly alters the structure and properties of robot materials, affecting their detectability. In this study, to ensure soft robots maintain excellent performance even in such extreme environments, meticulous attention is devoted to these pressure-induced changes before designing them. The results demonstrate that applying pressure (416.67 MPa) can induce the glass transition in silicone rubber (SR) even at room temperature. Unlike the traditional realization mechanism (cooling material to its glass transition temperature (Tg)), the realization mechanism through pressurizing is reported that adjusting the Tg of target material to approach a specific temperature. Furthermore, the different transition mechanisms under the two realizations are also revealed. Based the dynamic analysis of SR under extremely low temperature and high pressure, the glass transition pressure (Pg) is proposed, and the glass transition strategy by jointly regulating temperature and pressure to construct equivalent extreme pressure environment is also investigated. This study, taking SR as the case study, holds significant importance for the future development of extreme pressure-resistant soft robots for extreme environment exploration.