美国得州大学达拉斯分校Jeremiah J. Gassensmith带领的合作小组取得一项新突破。他们研制了把热能转换成机械能的快速可逆的有机晶体开关。 这一研究成果发表在2021年4月6日出版的国际学术期刊《美国化学会杂志》上。

在这项工作中，研究人员展示了一种完全可逆的热变形性执行元件，该执行元件可在室温下保持多年稳定，并且能够在接近室温的条件下执行200个以上的循环。具体来说，这种晶体在温度超过45℃时瞬间收缩到原来长度的90%，在温度低于35℃时又膨胀回原来的长度。另外，这一相变是瞬时发生的，几乎没有滞后现象，使其可以作为能在开和关之间快速循环实时温控保险丝。

据介绍，固态热弹性行为，即固态化合物随着温度变化和相变而突然施加膨胀或收缩物理力的现象，在有机晶体中很少见，且几乎没有可逆的系统。大多数这样的化合物在晶体降解之前只能循环十几次，或者要花数十分钟甚至几小时才能缓慢回到原来的状态。与热敏性——即晶体相变引起能量变化——相比，热变形性通过一致的、几乎瞬间的可预测方向力实现物理做功。

附：英文原文

Title: Rapidly Reversible Organic Crystalline Switch for Conversion of Heat into Mechanical Energy

Author: Madushani Dharmarwardana, Srimanta Pakhira, Raymond P. Welch, Carlos Caicedo-Narvaez, Michael A. Luzuriaga, Bhargav S. Arimilli, Gregory T. McCandless, Babak Fahimi, Jose L. Mendoza-Cortes, Jeremiah J. Gassensmith

Issue&Volume: April 6, 2021

Abstract: Solid-state thermoelastic behavior—a sudden exertion of an expansive or contractive physical force following a temperature change and phase transition in a solid-state compound—is rare in organic crystals, few are reversible systems, and most of these are limited to a dozen or so cycles before the crystal degrades or they reverse slowly over the course of many minutes or even hours. Comparable to thermosalience, wherein crystal phase changes induce energetic jumping, thermomorphism produces physical work via consistent and near-instantaneous predictable directional force. In this work, we show a fully reversible thermomorphic actuator that is stable at room temperature for multiple years and is capable of actuation for more than 200 cycles at near-ambient temperature. Specifically, the crystals shrink to 90% of their original length instantaneously upon heating beyond 45 °C and expand back to their original length upon cooling below 35 °C. Furthermore, the phase transition occurs instantaneously, with little obvious hysteresis, allowing us to create real-time actuating thermal fuses that cycle between on and off rapidly.

DOI: 10.1021/jacs.1c01549

Source: https://pubs.acs.org/doi/10.1021/jacs.1c01549