An official website of the United States government
Electrochemical‐based memristors are highly attractive that are capable of nonvolatile analog tuning, long‐term state stability, low power consumption, device scalability, and fast switching speeds. Through the combination of film deposition techniques, i.e., vapor phase polymerization and screen printing, fabrication of a poly(4‐(6‐hexyl)‐4H‐dithieno[3,2‐b:2′,3′‐d]pyrrole) (p6DTP)‐based synaptic‐emulating three‐terminal memristor is designed. Through voltage‐driven pulse programming, and square waves with an amplitude of 100 mV and duration of 100 msec, the device exhibits a power consumption of 1 pJmm−2per synaptic event. By analyzing the fundamental operational trends of the p6DTP‐based device, simple and advanced integrated applications can be demonstrated along with synaptic‐like responses. This effort is the first presentation of the vapor phase polymerization technique for any dithienopyrrole‐based monomers, along with the physical implementation of any memristive system as an advanced logical circuit, demonstrated here as a cascaded combinational logic gate.
more »
« less
Exploiting multiple percolation in two-terminal memristor to achieve a multitude of resistive states
As the most likely prospect for the construction of neuromorphic networks, the emulation of synaptic responses with memristors has attracted attention in both the microelectronic industries and the academic environment. To that end, a newly synthesized hybrid conjugated polymer with pendant carbazole rings, that is, poly(4-(6-(9 H -carbazol-9-yl)hexyl)-4 H -dithieno[3,2- b :2′,3′- d ]pyrrole) (pC6DTP), was employed in the fabrication of a two-terminal memristor with a Al/pC6DTP/ITO configuration where the polymer was electrochemically doped. Signature biological synaptic responses to voltage spikes were demonstrated, such as potentiation & depression and spike timing dependent plasticity. The device was able to be programed through a 1 mV pulse, requiring only 100 fJ of energy. The voltage-dependent conductive nature of the polymer was speculated to occur through two synergistic mechanisms, one associated with the conjugation along the backbone of the conjugated polymer and one mechanism associated with the pendant heterocyclic rings.
more »
« less
- PAR ID:
- 10280310
- Date Published:
- Journal Name:
- Journal of Materials Chemistry C
- Volume:
- 9
- Issue:
- 28
- ISSN:
- 2050-7526
- Page Range / eLocation ID:
- 8975 to 8986
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Like their chemical counterparts, electrical synapses show complex dynamics such as rectification and voltage dependence that interact with other electrical processes in neurons. The consequences arising from these interactions for the electrical behavior of the synapse, and the dynamics they create, remain largely unexplored. Using a voltage-dependent electrical synapse between a descending modulatory projection neuron (MCN1) and a motor neuron (LG) in the crustacean stomatogastric ganglion, we find that the influence of the hyperpolarization-activated inward current ( I h ) is critical to the function of the electrical synapse. When we blocked I h with CsCl, the apparent voltage dependence of the electrical synapse shifted by 18.7 mV to more hyperpolarized voltages, placing the dynamic range of the electrical synapse outside of the range of voltages used by the LG motor neuron (−60.2 mV to −44.9 mV). With dual electrode current- and voltage-clamp recordings, we demonstrate that this voltage shift is not due to a change in the properties of the gap junction itself, but is a result of a sustained effect of I h on the presynaptic MCN1 axon terminal membrane potential. I h -induced depolarization of the axon terminal membrane potential increased the electrical postsynaptic potentials and currents. With I h present, the axon terminal resting membrane potential is depolarized, shifting the dynamic range of the electrical synapse toward the functional range of the motor neuron. We thus demonstrate that the function of an electrical synapse is critically influenced by a voltage-dependent ionic current ( I h ). NEW & NOTEWORTHY Electrical synapses and voltage-gated ionic currents are often studied independently from one another, despite mounting evidence that their interactions can alter synaptic behavior. We show that the hyperpolarization-activated inward ionic current shifts the voltage dependence of electrical synaptic transmission through its depolarizing effect on the membrane potential, enabling it to lie within the functional membrane potential range of a motor neuron. Thus, the electrical synapse’s function critically depends on the voltage-gated ionic current.more » « less
-
Abstract Recent work on non‐conjugated pendant electroactive polymers (NCPEPs) has demonstrated significant impacts of structural parameters such as backbone stereoregularity and the spacer connecting the pendant to the backbone on properties, most notably on charge carrier mobilities. Tuning of the pendant group however has not been reported for stereoregular NCPEPs. Here we present a family of novel isotactic poly((carbazolyl‐alkyl‐triazolyl)methyl methacrylates) (PCzATMMAs) for which the effects of increasing the pendant group from carbazole to 3,6‐bis(4‐(2‐ethylhexyl)thiophen‐2‐yl)‐carbazole were investigated. Based on unsuccessful post‐polymerization functionalization with this extended group via previously reported transesterification and thiol‐ene methodologies, we report functionalization via copper‐catalyzed azide‐alkyne cycloaddition which was demonstrated to be highly effective. The effect of spacer length was also investigated for comparison with previously established effects with alkyl spacers. Within the family of PCzATMMAs, hole mobilities were found to increase with longer spacer length and with thermal annealing. The incorporation of an extended pendant with alkyl solubilizing chains was found to result in a lower hole mobility than the equivalent polymer with an unfunctionalized pendant group. Importantly, the copper catalyzed azide‐alkyne cycloaddition proved to be an effective method of post‐polymerization functionalization for stereoregular NCPEPs when extending beyond a simple carbazole pendant.more » « less
-
Pendant alkyl chains are widely used to successfully obtain a wide variety of soluble linear 1D π-conjugated polymers. Over the past several decades, a wide variety of π-conjugated polymers have been synthesized to realize the desired properties and improve the performance of organic electronic devices. However, this strategy is not suitable for generating soluble 2D-π-conjugated materials, including ladder polymers, nanoribbons, and 2D-π-conjugated polymers, due to strong van der Waals interactions between the ribbons and sheets. The drive to synthesize higher dimensional polymers and to enhance polymers' properties has spurred the exploration of a novel direction in materials chemistry—the synthesis of unconventional monomers and polymers. The Gavvalapalli research group has developed and used cycloalkyl straps containing aryl building blocks for the synthesis of conjugated polymers. These cycloalkyl straps, positioned either above or below the π-conjugation plane, have been shown to directly control the π–π interactions between the polymer chains. We have demonstrated that π-face masking cycloalkyl straps hinder interchain π–π interactions. The first part of this review article highlights the use of cycloalkyl straps for the synthesis of higher dimensional π-conjugated polymers. In this section, we discuss the synthesis of 2D-H-mers, dispersible hyperbranched π-conjugated polymers, and conjugated porous polymers without the pendant solubilizing chains. The second part of the feature article highlights how the cycloalkyl straps can be used to gain control over polymer–acceptor interactions, including the interaction strength and the location of the acceptor along the polymer backbone. We conclude the article with the future outlook on cycloalkyl strap-containing building blocks in the world of conjugated polymers.more » « less
-
Abstract Organic semiconducting donor–acceptor polymers are promising candidates for stretchable electronics owing to their mechanical compliance. However, the effect of the electron‐donating thiophene group on the thermomechanical properties of conjugated polymers has not been carefully studied. Here, thin‐film mechanical properties are investigated for diketopyrrolopyrrole (DPP)‐based conjugated polymers with varying numbers of isolated thiophene moieties and sizes of fused thiophene rings in the polymer backbone. Interestingly, it is found that these thiophene units act as an antiplasticizer, where more isolated thiophene rings or bigger fused rings result in an increased glass transition temperature (Tg) of the polymer backbone, and consequently elastic modulus of the respective DPP polymers. Detailed morphological studies suggests that all samples show similar semicrystalline morphology. This antiplasticization effect also exists inpara‐azaquinodimethane‐based conjugated polymers, indicating that this can be a general trend for various conjugated polymer systems. Using the knowledge gained above, a new DPP‐based polymer with increased alkyl side chain density through attaching alky chains to the thiophene unit is engineered. The new DPP polymer demonstrates a record lowTg, and 50% lower elastic modulus than a reference polymer without side‐chain decorated on the thiophene unit. This work provides a general design rule for making low‐Tgconjugated polymers for stretchable electronics.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1tc00987g
