Direct Conversion of Chemical Energy into Macroscopic Mechanical Energy by Use of Nonlinear Dynamics

生物体将化学能直接转化为定向的机械能。另一方面，现代“化学发动机”技术通过产生热量，将化学能转化为机械能。本研究的目的是实现化学能直接转化为定点机械运动。在这个项目过去两年的研究中，我们成功地构建了以下两个不同的实验系统，能够直接进行能量转换。研究了化学驱动马兰戈尼不稳定性诱导油水体系的自运动。根据容器的形状以及油和水溶液的数量，会产生各种运动模式，如随机、旋转和变形虫式运动。该系统最重要的发现是实现了空间定向机械运动。讨论了这种化学-力学转导的机制与界面上非线性振荡引起的界面张力的时间不平衡有关。我们发现，当水相为Belousov-Zhabotinsky （BZ）介质时，空气/水界面表面张力产生周期性变化。结果表明，[Fe (phen)_3]^<3+>与[Fe (phen)_3]^<2+>之间的表面活性差异是这种节律性现象的驱动力。我们还发现了油/水体系的节律性现象，其中油相含有酯，而水相是碱性溶液。这些结果为基于非线性动力学思想实现化学-机械耦合开辟了新的研究领域。

Living organisms convert chemical energy directly into site-directed mechanical energy. On the other hand, the modern technology on "chemical engine" picks up the mechanical energy from chemical energy through the generation of heat. The aim of the present research is to realize the direct energy conversion from chemical energy into site-directed mechanical motion. During the research of the past two years in this project, we have succeeded in constructing the following two different experimental systems, being capable of the direct energy conversion.1. Self-movement of an oil-water system induced by chemically-driven Marangoni instability is studied. Depending on the shape of the vessel and amount of oil and water solutions, various modes of movement are generated, such as random, rotational and amoeba-like motions. The most significant finding in this system is the realization of spatially directed mechanical movement. The mechanism of such chemomechanical transduction is discussed in relation to the temporal imbalance of the interfacial tension due to the nonlinear oscillation at the interface.2. We have found that a periodic change of the surface tension is generated at air/water interface, when the water phase is Belousov-Zhabotinsky (BZ) medium. It has been shown that the difference of the surface activity of the iron-catalyst between [Fe (phen)_3]^<3+> and [Fe (phen)_3]^<2+> is the driving force of this rhythmic phenomenon. We also discovered a rhythmic phenomenon for an oil/water system, where the oil phase contains an ester and the water phase is an alkaline solution. These results indicate a new field of research toward the realization of chemo-mechanical coupling based on the idea of nonlinear dynamics.