An All-Organic Composite System for Resistive Change Memory via the Self-Assembly of Plastic-Crystalline Molecules

A Bioinspired Artificial Injury Response System Based on a Robust Polymer Memristor to Mimic a Sense of Pain, Sign of Injury, and Healing

Flexible electronic skin with features that include sensing, processing, and responding to stimuli have transformed human-robot interactions. However, more advanced capabilities, such as human-like self-protection modalities with a sense of pain, sign of injury, and healing, are more challenging. Herein, a novel, flexible, and robust diffusive memristor based on a copolymer of chlorotrifluoroethylene and vinylidene fluoride (FK-800) as an artificial nociceptor (pain sensor) is reported. Devices composed of Ag/FK-800/Pt have outstanding switching endurance >10⁶  cycles, orders of magnitude higher than any other two-terminal polymer/organic memristors in literature (typically 10² -10³ cycles). In situ conductive atomic force microscopy is employed to dynamically switch individual filaments, which demonstrates that conductive filaments correlate with polymer grain boundaries and FK-800 has superior morphological stability under repeated switching cycles. It is hypothesized that the high thermal stability and high elasticity of FK-800 contribute to the stability under local Joule heating associated with electrical switching. To mimic biological nociceptors, four signature nociceptive characteristics are demonstrated: threshold triggering, no adaptation, relaxation, and sensitization. Lastly, by integrating a triboelectric generator (artificial mechanoreceptor), memristor (artificial nociceptor), and light emitting diode (artificial bruise), the first bioinspired injury response system capable of sensing pain, showing signs of injury, and healing, is demonstrated.

Hydrothermally grown ZnO nanowire array as an oxygen vacancies reservoir for improved resistive switching

Resistive switching (RS) devices based on self-assembled nanowires (NWs) and nanorods (NRs) represent a fascinating alternative to conventional devices with thin film structure. The high surface-to-volume ratio may indeed provide the possibility of modulating their functionalities through surface effects. However, devices based on NWs usually suffer from low resistive switching performances in terms of operating voltages, endurance and retention capabilities. In this work, we report on the resistive switching behaviour of ZnO NW arrays, grown by hydrothermal synthesis, that exhibit stable, bipolar resistive switching characterized by SET/RESET voltages lower than 3 V, endurance higher than 1100 cycles and resistance state retention of more than 10⁵ s. The physical mechanism underlying these RS performances can be ascribed to nanoionic processes involving the formation/rupture of conductive paths assisted by oxygen-related species in the ZnO active layer. The reported results represent, to the best of our knowledge, the best resistive switching performances observed in ZnO NW arrays in terms of endurance and retention.

Highly Robust Organometallic Small-Molecule-Based Nonvolatile Resistive Memory Controlled by a Redox-Gated Switching Mechanism

Although organic small-molecule-based memory devices (OSMDs) have been demonstrated to show great potential for the application in next-generation data-storage technology, progress toward their further development has been hugely hindered by the ambiguity of their electrical switching mechanism. Thus, purposely fabricating OSMDs with a definite switching behavior is very urgent. Here, we reported a redox-gated nonvolatile rewritable memory device using an organometallic small molecule as an active material. By introducing the redox-active ferrocene into an organic skeleton, the target small molecule exhibits reliable and robust FLASH-type bistable electrical characteristics with a clear redox-controlled switching mechanism, which leads to low operational voltages, good endurance, and long retention. Our study offers a proof-of-concept strategy to design controllable OSMDs with excellent performances.

Asymmetric Fullerene Nanosurfactant: Interface Engineering for Automatic Molecular Alignments

Since the molecular self-assembly of nanomaterials is sensitive to their surface properties, the molecular packing structure on the surface is essential to build the desired chemical and physical properties of nanomaterials. Here, a new nanosurfactant is proposed for the automatic construction of macroscopic surface alignment layer for liquid crystal (LC) molecules. An asymmetric nanosurfactant (C₆₀ NS) consisted of mesogenic cyanobiphenyl moieties with flexible alkyl chains and a [60]fullerene nanoatom is newly designed and precisely synthesized. The C₆₀ NS directly introduced in the anisotropic LC medium is self-assembled into the monolayered protrusions on the surface because of its amphiphilic nature originated by asymmetrically programmed structural motif of LC-favoring moieties and LC-repelling groups. The monolayered protrusions constructed by the phase-separation and self-assembly of asymmetric C₆₀ NS nanosurfactant in the anisotropic LC media amplify and transfer the molecular orientational order from surface to bulk, and finally create the automatic vertical molecular alignment on the macroscopic length scale. The asymmetric C₆₀ NS nanosurfactant and its self-assembly described herein can offer the direct guideline of interface engineering for the automatic molecular alignments.