Exceptionally high work density of a ferroelectric dynamic organic crystal around room temperature

Abstract

Dynamic organic crystals are rapidly gaining traction as a new class of smart materials for energy conversion, however, they are only capable of very small strokes (<12%) and most of them operate through energetically cost-prohibitive processes at high temperatures. We report on the exceptional performance of an organic actuating material with exceedingly large stroke that can reversibly convert energy into work around room temperature. When transitioning at 295–305 K on heating and at 265–275 K on cooling the ferroelectric crystals of guanidinium nitrate exert a linear stroke of 51%, the highest value observed with a reversible operation of an organic single crystal actuator. Their maximum force density is higher than electric cylinders, ceramic piezoactuators, and electrostatic actuators, and their work capacity is close to that of thermal actuators. This work demonstrates the hitherto untapped potential of ionic organic crystals for applications such as light-weight capacitors, dielectrics, ferroelectric tunnel junctions, and thermistors.

A theoretical framework for the design of molecular crystal engines

“…Taken together, these results reveal several important features of these photomechanical crystals: first, the model predicts photomechanical crystal work densities of ∼10 7 J m −3 , which is several orders of magnitude larger than the experimental work densities that have been reported experimentally to-date for thermosalient and photomechanical organic crystal actuators (∼10–10 5 J m −3 ) 13,81,105 or photomechanical polymers (up to ∼10 5 J m −3 ). 13,106 It will be important to see if future experiments can confirm these high predicted work densities.…”

Global Analysis of the Mechanical Properties of Organic Crystals

“…Although ah igh hardness is necessary to qualify organic crystals as cyclable and robust actuating materials that can be coupled to other elements and are integrable in devices,when coupled with ah igh Youngsm odulus,t he material becomes brittle with high resistance to strain. [44] Finding the optimal combination of H and E that enables organic crystals to withstand high stresses and strains and improving their toughness is key to progressing this class of materials into applications.A sc an be inferred from Figure 2a, l-threonine (2.06 AE 0.09, 1.98 AE 0.11, and 1.35 AE 0.12 GPa on (01 ¯1 ¯), (001 ¯), and (1 ¯1 ¯0), respectively), [40] sucrose (2.02 AE 0.10 GPa on (001)), [41] and d-xylose (1.67 AE 0.23 GPa on (010)) have the highest hardness among the analyzed organic crystals,f ollowed by methylparaben (1.41 AE 0.44 GPa on (111 ¯), [45] famotidine (form A, 1.34 AE 0.23 GPa, crystal face not specified), [46] l-arabinose (1.25 AE 0.04 GPa on (11 ¯0)), and the salt glucosamine hydrochloride (1.23 AE 0.12 GPa on (001);see Table S1 and Figures S7-S13 in the Supporting Information). Note that the values of H for other amino acids and peptides are not available,but are expected to be high based on the very high E values discussed above.…”

“…Investigating indentation properties independently can offer insights into the structure-function relationship between the chemical makeup of organic crystals and their mechanical performance.N otably,t he collective strength of their intermolecular interactions is reflected in elastic moduli (E)higher than those of most soft materials.A ss hown in Figure 1a, which shows the values obtained by standard nanoindentation, simple amino acids and peptides stand out as the stiffest organic crystalline materials,most having E > 25 GPa. Examples of this subset of organic crystals include a-glycine (44 AE 1GPa on face (001)), [39] l-threonine (40.95 AE 1.03 GPa on (001 ¯)), [40] l-alanine (34.4 AE 0.2 GPa on (011)), [39] g-glycine (28 AE 1GPa on (100)), [39] and glycylglycine (26 AE 2GPa, on (001)) [39] (see Notes 4a nd 5i nt he Supporting Information). Theexceedingly high stiffness observed with these crystals is clearly related to the exceptionally strong hydrogen bonds between their respective zwitterions,which indicates that-at least with this subset of structures-the strength of the hydrogen bonds determines their high E values.C lose inspection of Figure 1a,h owever,r eveals as econd subset of very stiff crystals.A lthough being composed of neutral molecules and, therefore,not being capable of charge-assisted hydrogen bonding,d isaccharides such as sucrose (35.96 AE 0.36 GPa on (001);s ee Note 3i nt he Supporting Information), [41] d-xylose (28.0 AE 2.3 GPa on (010)), and l-arabinose (25.0 AE 0.6 GPa on (1 ¯10)), as well as l-ascorbic acid (36.5 AE 4.0 GPa on (001)) have particularly high elastic moduli (see Note 6and Figures S7-S12 in the Supporting Information).…”

Near-room-temperature martensitic actuation profited from one-dimensional hybrid perovskite structure

“…Fig.6| Comparison of working temperatures of reported systems and actuation device of 1. a Response temperature deviating from room temperature of reported thermosalient molecular crystals. NBFB 39 ,[7]Helquat salt47 , TIP-P19 , HMB48 , 6-CAN49 , ditBu-BTBT19 , TPA17 , NDI derivant50 , DABCO(CZ) 2 51 , TBB52 , GN53 , [Ni II (en) 3 ] (ox)54 , [Co(NO 3 ) 2 (L)]55 , ABN40 , TCB18 . T tr and RT represent phase transition temperature and room temperature of 293 K, respectively.…”