Simon Cory M, Carraro Carlo
School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR, USA.
Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA, USA.
Proc Math Phys Eng Sci. 2019 Feb;475(2222):20180703. doi: 10.1098/rspa.2018.0703. Epub 2019 Feb 27.
In the two-balloon experiment, two rubber balloons are connected and allowed to exchange gas. Owing to the non-monotonic relationship between the radius of the balloon and the pressure of gas inside it, the two-balloon system presents multi- and in-stabilities. Herein, we consider a two-adsorbent system, where two different adsorbents are allowed to exchange gas. We show that, for rigid adsorbents, the thermodynamic equilibrium state is unique. Then, we consider an adsorbent-balloon system, where an adsorbent exchanges gas with a rubber balloon. This system can exhibit multiple states at thermodynamic equilibrium- two (meta)stable and one unstable. The size of the balloon, pressure of gas in the balloon, and partitioning of gas between the adsorbent and the balloon differ among the equilibrium states. Temperature changes and the addition/removal of gas into/from the adsorbent-balloon system can induce catastrophe bifurcations and show hysteresis. Furthermore, the adsorbent-balloon system exhibits a critical temperature where, when approached from below, the discrepancy of balloon size between the two (meta)stable states decreases and, beyond, bistability is impossible. Practically, our findings preclude multiple partitions of adsorbed gas in rigid, mixed-linker or stratified metal-organic frameworks and may inspire new soft actuator and sensor designs.
在双气球实验中，两个橡胶气球相连并允许气体交换。由于气球半径与其内部气体压力之间存在非单调关系，双气球系统呈现出多种不稳定性。在此，我们考虑一个双吸附剂系统，其中两种不同的吸附剂允许气体交换。我们表明，对于刚性吸附剂，热力学平衡态是唯一的。然后，我们考虑一个吸附剂 - 气球系统，其中吸附剂与橡胶气球进行气体交换。该系统在热力学平衡时可呈现多种状态——两个（亚）稳态和一个不稳定态。在不同的平衡态下，气球的大小、气球内气体的压力以及吸附剂与气球之间气体的分配情况各不相同。温度变化以及向吸附剂 - 气球系统中添加/移除气体可引发突变分岔并表现出滞后现象。此外，吸附剂 - 气球系统存在一个临界温度，当从低于该温度的方向接近时，两个（亚）稳态之间气球大小的差异会减小，超过该温度则不可能出现双稳态。实际上，我们的研究结果排除了刚性、混合连接体或分层金属有机框架中吸附气体的多种分配情况，并可能启发新型软致动器和传感器的设计。
