Molecular Ferroelectric‐Based Flexible Sensors Exhibiting Supersensitivity and Multimodal Capability for Detection

Abstract

Although ferroelectricity was discovered in molecular materials (Rochelle salt, KNaC 4 H 4 O 6 ⋅4H 2 O) in 1920, [5] the field has been long dominated by perovskite oxides represented by barium titanate (BTO) and lead zirconate titanate (PZT) and synthetic polymers including poly(vinylidene fluoride) and polyamides, which have led to a wide range of industrial applications such as film capacitors, transducers, actuators, sensors, and memories. [6][7][8][9][10][11][12] The research activities on molecular ferroelectrics are being rejuvenated owing to the most recent breakthroughs such as the discovery of the molecular crystals with large spontaneous polarization (e.g., P S = 22 µC cm -2 ) close to that of BTO (P S = 26 µC cm -2 ) and higher transition temperatures than that of BTO (e.g., T 0 = 448 K vs 390 K), [13] the ultrafast polarization switching in thin films based on biaxial molecular ferroelectrics, [14] and the pyroelectric figures-of-merit outperforming the current ferroelectric Although excellent dielectric, piezoelectric, and pyroelectric properties matched with or even surpassing those of ferroelectric ceramics have been recently discovered in molecular ferroelectrics, their successful applications in devices are scarce. The fracture proneness of molecular ferroelectrics under mechanical loading precludes their applications as flexible sensors in bulk crystalline form. Here, self-powered flexible mechanical sensors prepared from the facile deposition of molecular ferroelectric [C(NH 2 ) 3 ]ClO 4 onto a porous polyurethane (PU) matrix are reported. [C(NH 2 ) 3 ]ClO 4 -PU is capable of detecting pressure of 3 Pa and strain of 1% that are hardly accessible by the state-of-the-art piezoelectric, triboelectric, and piezoresistive sensors, and presents the ability of sensing multimodal mechanical forces including compression, stretching, bending, shearing, and twisting with high cyclic stability. This scaling analysis corroborated with computational modeling provides detailed insights into the electro-mechanical coupling and establishes rules of engineering design and optimization for the hybrid sponges. Demonstrative applications of the [C(NH 2 ) 3 ]ClO 4 -PU array suggest potential uses in interactive electronics and robotic systems.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202104107.

A Biodegradable and Recyclable Piezoelectric Sensor Based on a Molecular Ferroelectric Embedded in a Bacterial Cellulose Hydrogel

“…Passion for molecular ferroelectrics has been reignited since the recent discovery of their high ferroelectric, piezoelectric, and pyroelectric performance. For example, high polarization and fast switching ability of dipoles were demonstrated in diisopropylammonium bromide and N -methylmorpholinium trinitrophenolate, and high pyroelectric figures of merits were revealed in di- n -butylaminium trifluoroacetate and guanidinium perchlorate. − In addition, both favorable piezoelectric and pyroelectric responses have been revealed in trimethylamine borane, a molecular ferroelectric with harnessing plasticity, which holds great potential to serve as the core element for mechanical and thermal sensing . More notably, molecular ferroelectrics outperform conventional inorganic ferroelectrics and ferroelectric polymers on processability, as many molecular ferroelectrics could be crystallized just by volatilizing their saturated solutions.…”

Polymer Nanocomposite Dielectrics: Understanding the Matrix/Particle Interface

“…Dielectric polymers have been widely utilized in energy storage, transmission, and conversion. − The demand for greater comprehensive performance of dielectric polymers has been spurred by the rapidly increasing need of energy in domestic, industry, and transport sectors. For instance, electric drive vehicles would benefit from high-energy-density, low-loss, and compact-size dielectric film capacitors; − High-voltage power cable transmission lines entail greater voltage endurance of polymer insulations; − Electroactive polymer actuators − and advanced piezoelectric transducers and sensors − all require dielectrics with high energy-conversion efficiency and decent mechanical durability.…”

High-performance piezoelectric nanogenerators featuring embedded organic nanodroplets for self-powered sensors

“…With the global rise of Internet of Things (IoT), wearable electronics and sensor networks with a exible machinery and functional electrons are undergoing great development. [1][2][3][4] In particular, the emergence of wireless wearable sensor networks offers an innovative method to extract parameters indicating the status of motion in real time, and continuously transmits data to a user device. [5][6][7] Although extensive efforts have until now been made for the development of novel sensors and the improvement of wearability, most sensor prototypes are still powered by bulky and rigid battery packs, and fabricated by a traditional high-cost process with limited structures.…”