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

Abstract

Solid state thermosalience-a sudden exertion of an expansive or contractive physical force following a temperature change in a solid state compound-is rare, 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. In this work, we show a fully reversible actuator that is stable at room temperature for multiple years and is capable of actuation for more than two hundred cycles at near ambient temperature. Specifically, the crystals shrink to 90% of its original length instantaneously upon heating beyond 45 °C and expands back to its original length upon cooling below 35 °C. This temperature regime is important because it occurs around physiologically important temperatures. 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.

A Tale of Two Transitions: Unraveling Two Distinct Polymorph Transition Mechanisms in One n-Type Single Crystal for Dynamic Electronics

“…We suggest engineering of these alkyl side chains may be crucial in facilitating the I-II cooperative behavior. While recently rotation of bulky side chains have been shown to be critical for expressing cooperative behavior in molecular crystals 15,16,18 , cooperative polymorph transition has rarely been studied in molecules with alkyl side chain motifs -a dominant side chain design in organic crystals 23,60,61 . Until now, their role in facilitating cooperative transitions has not been well understood.…”

“…dynamic rotation, other systems have shown the importance of molecular tilting and order-disorder mechanisms to resolve cooperative behaviors [20][21][22] . The switching of electronic properties coupled with the rapid mechanical effects of cooperative phase transitions presents a wide design space for novel organic electronics such as thermally activated actuators and highly flexible devices 9,23 .…”

Multifunctional Deformable Organic Semiconductor Single Crystals

“…[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Thep rospects of using dynamic crystals have already been demonstrated with lab-scale applications that include prototypical fuses, [31] transistors, [32] and switches. [33] Of particular interest are the effects of mechanically induced structural transitions in semiconducting single-crystal electrical devices. [34] Conductivity of flexible semiconducting radical crystals and their potential use as flexible devices was also reported.…”

Thermosalience of 1,2,4,5‐Tetrachlorobenzene

“…[9,10] Perhaps the most striking demonstration of the exceedingly high speed of structural transformation during a martensitic transition is the so-called thermosalient effect, where the transition of smallmolecule crystals oftentimes results in motion, ballistic events, and even shape-memory effects of molecular crystals. [11][12][13][14][15][16][17][18][19][20][21][22][23] Over the past decade, such thermosalient crystals have attracted attention due to their potential applications in fast organic microactuators, sensors or fuses. [6,24,25] The structural change due to the thermosalient phase transition generates internal strain, and subsequent release of the strain results in visually striking explosion and/or jumping of the crystals.…”