Poor Interfacial Properties Research Articles

Mechanical performance of epoxy matrix composites reinforced by physically and chemically treated hemp fiber

AbstractHemp fiber is one of the most common reinforcements for polymer matrix composites and it is widely used in various applications due to its environmentally friendliness, favorable physical and mechanical properties. In spite of the numerous merits of the hemp fiber reinforced polymer composites, improvement of poor interfacial properties between the hemp fiber and polymer matrix is limited. The main objective of this work is to investigate the effect of increased fiber surface area and alkaline surface treatment on the mechanical performance of hemp fiber reinforced epoxy composites. An elevated temperature aqueous debundling treatment was employed to generate a large number of individual fibers from fiber bundles and was associated with a threefold increase in specific fiber surface area. The fiber dimension and surface properties were investigated through optical microscopy, confocal microscopy, and scanning electron microscopy. The effects of different debundling treatment times and additional alkaline treatment on the mechanical properties were studied. It was found that composites reinforced by the debundled hemp fiber with further alkaline treatment exhibited the best tensile and flexural properties in comparison to other composites reinforced with debundled hemp fiber without further alkaline treatment or with untreated hemp fiber.Highlights Provided a new physical method for separating hemp fiber bundle into individual hemp fibers using boiling water and blending. Debundled fibers resulted in a 3.5 times increase in fiber surface area for better bonding with epoxy matrix. Debundling process combined with chemical (alkaline) treatment to further improve the compatibility between individual fiber and epoxy. The effects of the debundling only, alkaline treatment only, and combined debundling + alkaline treatment on composite properties were studied.

Efficient toughening of epoxy anhydride thermosets with modified PVA fibers

ABSTRACT The poor interfacial properties of polyvinyl alcohol (PVA) fibers and epoxy resin seriously affect the toughening effect of PVA fibers on epoxy resin. To solve this problem, the surface of PVA fibers was modified with 3-aminopropyltriethoxysilane (KH550) and 3-glycidoxypropyltrimethoxysilane (KH560), as well as the surface of PVA fibers with tannic acid (TA) and KH560. The acid-cured epoxy resin toughening mechanism of the modified PVA fibers was systematically investigated by multiscale analysis. The experimental data showed that the epoxy resin performed best when TA and KH560 synergistically modified PVA fibers. The impact strength of the epoxy resin increased by 76.3% and the tensile strength by 20.3%. The toughening mechanism of modified PVA fibers on the epoxy resin was revealed by a series of characterizations such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). Because KH560 can participate in the curing reaction of the epoxy resin, it greatly enhances the adhesion between the fiber and the resin. The toughening mechanism of TA and KH560 working together on PVA fibers to strengthen epoxy resin is summarized through the analysis of different scales. This also offers theoretical and experimental support for using PVA fibers in composites.

“Like binding a book”: Interfacial improvement of pre-melted ultrahigh molecular weight polyethylene by pulse vibration molding

Ultrahigh molecular weight polyethylene (UHMWPE) is widely used in industrial, military, and civilian applications owing to its excellent properties. However, the high entanglement degree of UHMWPE melt leads to great difficulties in diffusion and crystallization, which causes poor interfacial strength and mechanical properties of pre-melted UHMWPE, restricting its high-quality processing and high-value recycling. To this end, we propose a rapid interface stitching technology with a pulsed vibration force driving free volume homogenization and chain segment orientation. For the first time, pulse vibration molding (PVM) is applied for the hot-pressing of pre-melted UHMWPE, successfully realizing the interface stitching and product strengthening. Compared with those of the convention molding (CM) samples at 180 °C, the interfacial adhesive fracture toughness of the adhesive samples processed using PVM is increased by 105.9 % and the work of tension of the recycled samples processed using PVM is also increased by 49.09 %, respectively. The fracture strength of the PVM recycled samples at 180 °C reaches 91.77 % of that of the pure samples and the yield strength is also higher, which significantly enhances the recycling of UHMWPE. The characterization results of the interfacial molecular chain entanglement and crystallization show that PVM strengthens the molecular chain diffusion and induces crystallization by promoting the orientation of chain segments, especially at the interface. Consequently, we believe that the proposed technology can play a significant role in the UHMWPE processing methods that involve surface healing.

Design and evaluation of a kind of polymer-bonded explosives with improved mechanical sensitivity and thermal properties

The emergence of TKX-50, an energetic ionic salt with a high enthalpy of formation and low sensitivity, has opened a new path for the development of high-energetic, insensitive composite explosives. However, due to the poor interfacial binding properties of TKX-50 with conventional binders, there is a lack of effective guidance for the design of TKX-50 based composite explosives. To address the above issues, the interactions between carboxymethyl cellulose acetate butyrate (CMCAB) and other binders with explosives TKX-50/HMX were compared using the molecular dynamics method. Based on the simulations, TKX-50/HMX/CMCAB-based polymer-bonded explosives (PBXs) were prepared with CMCAB as binder, which displays a high binding energy (Ebind) with TKX-50 and high cohesive energy density (CED), and the effect of TKX-50 content on the performance of PBXs was investigated. The physical properties of PBXs, specifically the morphology, mechanical sensitivity, and thermal conductivity, were analyzed by SEM, sensitivity apparatus, and thermal conductivity meter, respectively. The specific heat capacity (Cp) and non-isothermal decomposition temperature of PBXs were tested by DSC, and then the corresponding thermal kinetic parameters were analyzed to evaluate their thermal safety. The adiabatic thermal decomposition processes of PBXs were tested using an ARC instrument. The decomposition mechanism and kinetics were also explored to further analyze their thermal stability and thermal safety under adiabatic conditions. The computer code EXPLO5 was used to predict the detonation parameters of PBXs. The results showed that CMCAB and TKX-50 displayed favorable interfacial bonding properties, and TKX-50 can be bonded with HMX to form a molding powder with a desirable morphology and safety profile. The TKX-50 in PBXs effectively improves the mechanical sensitivity and thermal safety of PBX and has a significant effect on the detonation performance of PBX. This research demonstrates a novel method suitable for screening and investigating high-energetic insensitive explosive systems compatible with TKX-50.

Design and fabrication of prototypes with modified materials for race & automotive applications

The use of CFs in automotive industry due to the need for lightweight, durable components has led to significant improvements in vehicle efficiency and safety. Despite initial predominance in luxury sports vehicles, the automotive CF market is rapidly expanding. Ongoing research focuses on enhancing Carbon Fiber Reinforced Polymers (CFRPs), addressing issues like poor through-thickness properties and interfacial properties crucial for load transfer. This work strategy involves incorporating block copolymers (BCPs) into thermoset matrices and modifying fiber surfaces to improve mechanical integrity and durability. A novel compression molding manufacturing method, aim to streamline production processes, making CFRP energy absorbers feasible for broader automotive applications. Mechanical testing reveals promising results, with modified materials showing enhancements in interlaminar shear strength and energy absorption performance.

Enhancing composite electrode performance: insights into interfacial interactions.

Propelled by the widespread adoption of portable electronic devices, electrochemical energy storage systems, particularly lithium-ion batteries (LIBs), have become ubiquitous in modern society. The electrode is the critical battery component, where intricate interactions between the materials govern both the energy output and the overall lifespan of the battery under operational conditions. However, the poor interfacial properties of traditional electrode materials fall short in meeting escalating performance demands. To facilitate the advent of next-generation lithium-ion batteries, attention must be devoted to the interfacial chemistry that dictates and modulates the various dynamic and transport processes across multiple length scales within the composite electrodes. Recent research has concentrated on systematically understanding the properties of distinct electrode components to engineer meticulously tailored electrode formulations. These are geared towards composite electrodes with heightened chemical stability, thermal robustness, enhanced local conductivities, and superior mechanical resilience. This review elucidates the latest advances in understanding the impact of interfacial interactions in achieving high-capacity, high-stability electrodes. Through comprehensive insights into the interfacial interactions between the various electrode components, we can create improved integrated systems that outperform those developed through empirical methods. In light of this, the adoption of a holistic approach to enhance the interactions among electrode materials becomes of paramount importance. This concerted effort ensures the attainment of heightened rate capability, facilitation of lithium-ion transport, and overall system stability throughout the entirety of the cyclic process.

Silica aerogel added lightweight cement-based composite mortars for thermal insulation purposes in sustainable structures: A comprehensive study

It has been discovered in recent years that the use of silica aerogel in cement-based materials contributes to the thermal insulation properties of the materials, and studies on this subject have gained importance. However, it was determined that the studies mostly remained at the level of the thermal conductivity coefficient and the main physical and mechanical properties of the materials. In this study, a comprehensive research was carried out with the replacement of micro-sized aerogel particles with quartz sand in different ratios (0, 1, 1.6, 2.4, 3.2, 4 and 4.5 wt%) in lightweight cement-based composite mortar (LCCM) combinations. Specifically, the effect of silica aerogel granules (SAG) on flowability, fresh and hardened densities, porosity, water absorption, compressive strength, macro/microstructural properties (by optic microscope, SEM, XRD analysis), thermal conductivity, specific heat, thermal diffusivity and heat storage capability of LCCMs were investigated. While SAG could increase the flowability (up to 8.4 %) at low using rates, it decreased it at higher rates. It is very effective in reducing fresh and hardened densities. However, it highly increased porosity and water absorption, and greatly decreased compressive strength. On the other hand, generally the poor interfacial properties of the cement matrix and the aerogel were moderately improved in this study. The lowest thermal conductivity was determined as 0.155 W/mK in the highest SAG usage. SAG increased specific heat, decreased thermal diffusivity and decreased heat storage capability of LCCMs up to 45.23 %, 63.49 % and 46.32 %, respectively. As a result of the study, aerogel has been identified as a very suitable material that can be used to highly improve thermal properties in LCCMs.

Synergistically enhancing weavability and interface behavior by applying PDMS/MXene on carbon fiber surface through ultrasound assistance

The poor interfacial properties and weavability of carbon fiber reinforced polymer (CFRP) composites stem from the surface chemical inertness and low wear resistance of carbon fiber (CF). Herein, we developed an effective approach to fabricate the CF@Polydimethylsiloxane/MXene (CF@PDMS/MXene) using ultrasound-assisted techniques, to improve both wear resistance and interfacial properties. The effectiveness of the modified treatment was assessed by Fourier transform infrared spectroscopy (FT-IR), microscopic confocal laser Raman spectrometer (Raman), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The success of the graft was evaluated using field emission scanning electron microscopes (FE-SEM) and energy dispersive spectrometry (EDS). The interfacial shear strength (IFSS) of the composite was evaluated through fiber pull-out experiments. Different weight ratios of MXene nanoparticles were employed during the grafting process to investigate their impact on surface morphology, wear resistance, and interfacial properties. The results demonstrated that CF@PDMS/MXene-1.5 wt% exhibited a residual fracture tensile strength 14.8 % higher than desized CF when the MXene concentration was increased to 1.5 wt%. Additionally, the IFSS of CF@PDMS/MXene-1.5 wt% was observed to be 113 % greater than desized CF. Consequently, this novel modification strategy holds great promise for enhancing the mechanical performance of CFRP composites.

Lignins emulsifying properties according to pH to control their behavior at oil–water interface

This study focuses on the mechanisms governing the ability for fractionated lignins to stabilize emulsion depending on the pH. It is hypothesized that adsorption mechanisms of lignins at the oil/water interface sharply impact their ability to stabilize emulsions. Stabilization mechanisms may vary because lignins could exist either in the form of particles and/or in the form of surfactants depending on pH treatment. The interfacial layer formed by lignins was examined by both interfacial tension and interfacial viscoelasticity as a function of pH history. Emulsifying capacity of corresponding lignins dispersions was investigated and correlated with both the lignins adsorption performance at the oil/water interface and the interfacial rheological properties. The coexistence of two distinct mechanisms responsible for O/W stabilization as a function of pH was identified. First, for lignins in the form of surfactants, emulsion is formed but a marked coalescence occurs rapidly. Secondly, when lignin mainly exists in the form of particles, rapid phase separation occurs due to poor interfacial properties. Finally, when both lignin particles and lignin surfactants coexist, a synergy between Pickering and micellization mechanisms leads to stable emulsion. This study proves a synergistic effect between lignin particles and lignin surfactants resulting in optimal interfacial stabilization.

Annealing effects on Al/polyimide adhesion in flexible optical solar reflectors

Flexible optical solar reflectors are made of single and multi-layered metal thin films on polymer substrates and will encounter around 6000 thermal cycles exceeding +/-100°C during one year of operation in low earth orbit. The candidate thin film system of Inconel/silver (Ag)/Teflon (FEP) recently demonstrated early damage formation (cracks and voids) after only a few thermal cycles, most likely due to the poor interfacial properties between Ag and FEP. An alternative material system that could be used is colourless polyimide, Tormed, instead of FEP. Additionally, aluminium (Al) has demonstrated very good interfacial properties with polyimide even after thermal cycling and has suitable optical properties. The adhesion of the Al/Tormed and Ag/Tormed interfaces were evaluated with tensile induced delamination. Generally, Al/Tormed has a much higher interface adhesion energy compared to Ag/Tormed, and there is no significant degradation after bake-out in vacuum (200°C, 10-6 mbar) for 10 and 24 hrs. Thus, the Al/Tormed system could be a more robust coating system for future flexible solar reflectors.

Strengthened Surface Modification for High-Performance Inorganic Perovskite Solar Cells with 21.3% Efficiency.

Metal halide inorganic perovskites show excellent thermal stability compared to organic-inorganic perovskites. However, the performance of inorganic perovskite solar cells (PSCs) is far from theoretical values, together with unsatisfactory stability, mainly due to the poor interfacial properties. In this work, a facial but effective method is reported to realize high-performance inorganic PSCs by post-modifying the perovskite surface with 2-thiophene ethylamine (TEA). It is found that amine group from TEA can favorably interact with the undercoordinated Pb2+ via Lewis acid-based coordination, while thiophene ring with electron-rich sulfur assists such interaction by functioning as an electron donor. The synergetic interaction allows TEA to passivate perovskite film defects more efficiently, as compared to phenethylamine (PEA) with less electron-donating ability. Moreover, perovskite valence band is slightly upward shift to match with hole transport material and facilitate hole transfer. These combinations result in a reduced non-radiative charge recombination and improved charge carrier lifetime. Consequently, PSCs with TEA modification shows a drastic improvement of VOC by 54mV, yielding a champion PCE of 21.3%, much higher than the control PSCs (19.3%), along with improved ambient stability. This work demonstrates that surface modifier with an electron-rich moiety is critical for achieving efficient and stable inorganic PSCs.

Excellent and effective interfacial transition layer with an organic/inorganic hybrid carbon nanotube network structure for basalt fiber reinforced high-performance thermoplastic composites

Basalt fiber reinforced high-performance thermoplastic (BFRHTP) composites are promising materials for application in military, aerospace, chemical, automobile, and other high-tech industries. However, their mechanical properties are still largely limited by poor interfacial properties because of the smooth, inert, and low-energy surface of BF. In this study, an organic/inorganic hybrid sizing agent was used for BF surface modification to construct an appropriate modulus transition layer for the interface with a combination of soft and rigid phases. Organic poly(ether nitrile) (PEN) and inorganic carboxylic multi-walled carbon nanotubes (MWCNT-COOH) in hybrid sizing agents (PEN/CNT) were respectively used as soft and rigid phases to design the interfacial structure. The tensile strength, flexural strength, interlaminar and interfacial shear strength of the basalt fiber reinforced poly(phthalazinone ether nitrile ketone) composites were increased by 60, 33, 62, and 144%, respectively. This approach provides a simple, green, and promising strategy for enhancing the interfacial properties of BFRHTP composites.

Simultaneously reducing the modulus difference and smoothing the modulus transition through bi-directional structural design for enhancing interfacial properties of carbon fiber/epoxy composites

The modulus mismatch between CF and resin and the weak interfacial bonding strength result in poor interfacial properties, limiting its application in the field of structural materials. In this study, the modulus difference reduction and the gentle modulus transition would be achieved by simultaneously designing structures of the carbon fiber (CF) and resin to enhance the interfacial properties of the composite. The modulus difference was narrowed by improving resin modulus. Meanwhile, the multi-scale structural design on CF surface smoothed the transition modulus from fibers to resin. In brief, under the above combined effects, a multi-stage modulus gradient decreasing structure was constructed, which could make the external stress more effectively dispersed for excellent interface properties. The bi-directional structural design increased the ILSS of CF/EP composites to 82.6 MPa, which was 17.7% and 8.0% higher than that of CF surface modification only and EP modification only, respectively. This work was expected to provide new ideas for improving the mechanical properties of CF composite through multi-scale structural design to meet the needs of different fields.

Promising potential of bio-sourced amphiphilic xanthan as an emulsifier in O/W dispersions

The emulsification properties of hydrophobically modified xanthan (HMX) obtained through green esterification using alkenyl succinic anhydrides (ASA) as grafting agents were investigated by preparing oil-in-water emulsions without adding any surfactant, in order to better understand the stability phenomenon at the oil-water interface. This study demonstrated that new-brand bio-sourced HMX owns emulsifying potential compared to pristine xanthane, known for its poor interfacial properties as a non-absorbing polymer. A complete approach for studying the stability of the dispersions was carried out at different levels: a) macroscopic level: visual identification of stability, b) microscopic level: coupled optical microscopy and droplet size distribution and c) deep microstructure stability monitoring over time by Static Multiple Light Scattering. First, a series of HMX differing in alkenyl chain length and grafting density added at 0.2% w/w in emulsions were compared. Increased grafting density or hydrophobic chain length provided a highly stable and homogeneous emulsion over 30 days. In the case of less stable emulsions, two solutions are proposed: 1) increasing HMX concentration thus improving emulsifying properties, 2) adding native xanthan as a thickening agent, which slows down the creaming destabilization mechanism. This original article shows that the new-brand bio-sourced amphiphilic xanthan obtained under green modification synthesis behave promising and effective emulsifying capacities to stabilize oil-in-water emulsions, which offers promising potential for industrial applications.

Improving the performance of carbon/graphite composites through the synergistic effect of electrostatic self-assembled carbon nanotubes and nano carbon black

Superior performance fillers are considered as an effective means to enhance the performance of carbon/graphite composites. However, poor interfacial properties and incomplete filler networks limit the performance enhancement of the composites. In this study, a new method was proposed to weaken this impact through the synergistic effect of the electrostatic self-assembly of nano carbon black (NCB) onto carbon nanotubes (CNTs). The results showed that the synergistic effect between NCB and the CNTs significantly improved the mechanical and electrical properties of the composites. NCB reduces the porosity of the composites and increases the interaction between the CNTs and matrix. The compressive strength of the composite was 143.2 Mpa, and the flexural strength was 46.3 MPa, which is 210% higher than that of the pristine carbon/graphite composites. Moreover, NCB and CNTs form a globally connected synergistic network in the carbon skeleton. Composites filled with CNTs/NCB exhibited the lowest resistivity and highest thermal conductivity, with a resistance that was 42% lower than that of pristine carbon/graphite composites at 44.8 μΩ m. All of these results suggest that the synergistic effect of CNTs/NCB show great potential to improve the performance of carbon/graphite composites.

Gellan gum conjugation with soy protein via Maillard-driven molecular interactions and subsequent clustering lead to conjugates with tuned technological functionality.

Soy proteins are frequently used in the food industry; however, they have rigid and compact structure with relatively poor interfacial properties and solubility. This study was therefore aimed to modify techno-functional characteristics of soy protein isolate (SPI; 0.1% w/v) by conjugating to low acyl gellan gum (LAGG; 0.1, 0.2, and 0.3% w/v), through the Maillard reaction (at 90°C for 90min). The SPI-LAGG conjugates were confirmed by changes in pH, glycation degree (DG; up to 48%), Fourier transform infrared spectroscopy, and sodium dodecyl sulphate polyacrylamide electrophoresis. The conjugates were then classified into three clusters of low, medium, and high DG, via K-means clustering method. The low DG conjugate had lower surface hydrophobicity and foaming capacity, and higher thermal stability, solubility, emulsifying properties, foam stability, and antioxidant activity compared to the other clusters. This indicated that a low DG is required to enhance the functional properties of proteins.

Environmentally friendly water-soluble epoxy emulsions nano sphere improved the interfacial performance of high modulus carbon fiber reinforced epoxy composites based on robust van der Waals force

High modulus carbon fibers (CFs) are widely desirable in aerospace, robotics, etc. However, their high degree of graphite microcrystalline structure leads to poor interfacial properties with host matrices, deteriorating the mechanical properties of carbon fiber reinforced polymer composites (CFRPs). Here, to improve interfacial properties of CFRPs, we present to construct a uniform and continuous active sizing nanolayer on the surface of CFs via synthetic water-based epoxy (WEP) emulsion nanospheres with strong van der Waals force. The WEP emulsions were prepared by introducing polar polyethylene glycols into epoxy resin chain. The modified CFRPs showed robust interfacial properties, improving by 25% over the untreated counterparts. Moreover, the proposed method can retain monofilament tensile strength of fibers and protect CFs from being destroyed during processing at industrial scales. This work opens an avenue toward the development of materials with superior interfacial performance for various inert high modulus fibers.

Enhanced Interfacial Affinity of the Supercapacitor Electrode with a Hydrogel Electrolyte by a Preadsorbed Polyzwitterion Layer.

Polymer hydrogel-based solid-state supercapacitors exhibit great potential applications in flexible devices. Nevertheless, the poor electrode-electrolyte interfacial properties restrict their advances. Herein, by taking the well-developed polyvinyl alcohol (PVA)/H2SO4 gel electrolyte and the graphene film electrode as the prototype, a very simple strategy is demonstrated to improve the interfacial affinity between the electrode and the hydrogel electrolyte by a preadsorbed highly hydrophilic polyzwitterion layer of poly(propylsulfonate dimethylammonium propylmethacrylamide) (PPDP) on the electrode surface. Electrochemical measurements confirm that the charge-transfer resistance on the interface is effectively reduced after modification with PPDP. Consequently, the obtained areal capacitance experiences a 3-fold increase compared to the unmodified ones. Results from electrochemical quartz crystal microbalance with dissipation demonstrate that more ions can be reversibly transferred on the modified interface during the change-discharge cycles, suggesting that the accessible surface area on the electrode is also increased. The hydrophilic PVA layer shows a similar function but with a much smaller efficiency. The strategy depicted here is highly universalizable and can be generalized to different electrode/electrolyte systems or other electrochemical energy storage devices.

Microstructural characterization, driving mechanisms, and improvement strategies for interlayer bond strength of additive-manufactured cementitious composites: A review

3D printed cementitious composites (3DPCC) are one of the contemporary digitization and fabrication techniques being adopted by the construction industry. Improving interlayer bond strength (IBS) is one of the most significant barriers to commercializing 3DPCC. This article focuses on the characterization of interlayer bond mechanism via microstructural characterization techniques such as scanning electron microscopy, computed tomography imaging, and mercury intrusion porosimetry. Moreover, different driving mechanisms that result in poor IBS of 3DPCC are critically analyzed, including thixotropic behavior, surface moisture content, mix design, surface roughness, time gap, nozzle standoff distance, and curing regime. Finally, this article thoroughly reviews mitigation strategies (such as mechanical interlocking and chemical bonding agent) to determine the best appropriate strategy for enhancing the IBS of 3DPCC. The results reveal that the poor IBS of 3DPCC is due to the formation of voids between the layers, which is caused primarily by a loss of surface moisture content and thixotropic behavior. However, because of its complex dependence on various parameters, the precise cause of weak interfacial properties is still unknown. With the use of a chemical bonding agent and mechanical interlocking mechanisms, the IBS of 3DPCC can be increased by 20–30% and 50–60%, respectively. The long-term performance of mitigation strategies, on the other hand, has not been thoroughly investigated. This article will help researchers understand the mechanism underlying 3DPCC's poor interfacial properties and develop new or improved enhancement strategies to promote 3DPCC preparation in the construction industry.

Transparent, Low-Impedance Inkjet-Printed PEDOT:PSS Microelectrodes for Multi-modal Neuroscience.

Transparent microelectrodes that facilitate simultaneous optical and electrophysiological interfacing are desirable tools for neuroscience. Electrodes made from transparent conductors such as graphene and indium tin oxide (ITO) show promise but are often limited by poor interfacial charge-transfer properties. Here, microelectrodes are demonstrated that take advantage of the transparency and volumetric capacitance of the mixed ion-electron conductor Poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Ring-shaped microelectrodes are fabricated by inkjet-printing PEDOT:PSS, encapsulating with Parylene-C, and then exposing a contact site that is much smaller than the microelectrode outer diameter. This unique structure allows the encapsulated portion of the microelectrode volume surrounding the contact site to participate in signal transduction, which reduces impedance and enhances charge storage capacity. While using the same 100 μm diameter contact site, increasing the outer diameter of the encapsulated electrode from 300 to 550 μm reduces the impedance from 294±21 to 98±2 kΩ, respectively, at 1 Hz. Similarly, the charge storage capacity is enhanced from 6 to 21 mC cm-2. The PEDOT:PSS microelectrodes provide a low-haze, high-transmittance optical interface, demonstrating their suitability for optical neuroscience applications. They remain functional after a million 1 V stimulation cycles, up to 600 μA of stimulation current, and more than 1000 mechanical bending cycles.