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| Transfer curves of a transistor of Mixtures A (A) and B (B) prepared by electrospinning under different strain: 0% (▬), 10% (▬), 20% (▬), 30% (▬), 40% (▬) and 50% (▬), at a V DS of -0.6 V.
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Stretchable conductors and organic electrochemical transistors (OECT) were fabricated from PEDOT:Tos (poly (3,4-ethylenedioxythiophene):iron tosylate) nanofibers. The devices were prepared by a combination of electrospinning and electrode printing followed by vapor phase polymerization (VPP). The impact of both the processing time and the compositi...
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... produced from the mixture B showed the best results during the stretching tests while the ones produced from A led to higher currents, making both of them promising for use in stretchable transistors. Transistors were successively strained in 10% increments and both their transfer characteristics were subsequently recorded (Figure 8). ...
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This work describes a versatile electrospinning equipment with rapid, independent, and precise x–y–z movements for large-area depositions of electrospun fibers, direct writing or assembly of fibers into sub-millimeter and micron-sized patterns, and printing of 3D micro- and nanostructures. Its versatility is demonstrated thought the preparation of...
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... Conventional electrospun fibers possess outstanding properties such as simple fabrication, large surface area, and complex structure. These properties make them promising in various fields, such as biomedicine, tissue engineering [2] and chemistry [3]. The presence of microporous structures on electrospun fibers leads to higher porosity, larger specific surface area, and better pore connectivity [4], which significantly enhancing their performance for tissue engineering applications [5]. ...
Electrospun fibers are widely used in various fields of biology, medicine, and chemistry due to their unique morphological characteristics that determine their distinct application properties. Accurate and rapid classification of these fibers based on their morphology is critical for their effective utilization. Non-destructive and low-cost imaging methods are highly desirable for this purpose, so we obtained the polarization images of different forms of electrospun fibers (smooth surfaces, microporous, and beaded microspheres) by polarized light microscopy. In this study, we have explored the automatic classification of electrospun fibers based on their Mueller matrix depolarization parameter, which is highly correlated with the rough microporous structures on the surface of the object. To achieve this, we employed transfer learning and various convolutional neural networks (CNNs). Our proposed method outperformed the conventional approach that only utilizes a single Mueller matrix M44 image for classification, thus enabling researchers to effectively classify electrospun fibers. Given the high accuracy of our method, it may find significant utility in fields such as material science, nanotechnology, and bioengineering.
... [43][44][45] The overall performance of the stretchable OECTs is summarized in Figure 4d and Table S1, Supporting Information. [13,21,[24][25][26]28,[46][47][48][49] To conclude, the device showed record-high on/off ratio (≈10 4 ), high mobility (≈1 cm 2 V −1 s −1 ), and intrinsically stretchability (>50%). This is the first time these merits can be harvested in one intrinsically stretchable OECT, encouraging its immediate use for various soft bioelectronics applications. ...
Intrinsically stretchable organic electrochemical transistors (OECTs) are being pursued as the next‐generation tissue‐like bioelectronic technologies to improve the interfacing with the soft human body. However, the performance of current intrinsically stretchable OECTs is far inferior to their rigid counterparts. In this work, for the first time, the authors report intrinsically stretchable OECTs with overall performance benchmarkable to conventional rigid devices. In particular, oxygen level in the stretchable substrate is revealed to have a significant impact on the on/off ratio. By employing stretchable substrates with low oxygen permeabilities, the on/off ratio is elevated from ≈10 to a record‐high value of ≈104, which is on par with a rigid OECT. The device remained functional after cyclic stretching tests. This work demonstrates that intrinsically stretchable OECTs have the potential to serve as a new building block for emerging soft bioelectronic applications such as electronic skin, soft implantables, and soft neuromorphic computing. It is observed that the poor electrical performance of stretchable organic electrochemical transistors (OECTs) can be significantly improved by controlling the oxygen permeability of the elastic substrate. The overall performance of the optimized device is verified benchmarkable to a conventional rigid OECT.
... The advantage of electrospun PEDOT:PSS fibers relative to their contiguous thin film counterparts that are prepared by spincoating is the consistent conductivity of surfaces with stretching and bending. Indeed, conductive PEDOT:tosylate fibers that can reorganize their structure with applied strain have enabled stretchable organic electrochemical transistors [34]. ...
... This was attributed to the orientation of the fibrillar polymer inside the nanofibers, arising from the strong strain forces in the polymer jets during electrospinning. Previously, we also observed a similar relationship between the fiber diameter and the elastic modulus for PEDOT:tosylate fiber mats [34]. Mats with small diameter fibers could be stretched to a higher strain than thicker fibers. ...
Stretchable electrochromic devices were fabricated from electrospun PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate) fibers. Stretchable and transparent electrodes with a sheet resistance of 1200 Ω/sq were prepared by depositing the conductive fibers on elastomeric substrates that were prepared from polydimethylsiloxane. The conductive substrates replaced the ITO coated glass electrodes that are typically used in electrochromic devices. The functioning device was prepared from a flexible chitosan electrolytic gel and a 4,7-bis(4-diphenylaminophenyl)-2,1,3-benzothiaziazole (TPA-BZT-TPA) electrochrome that were deposited on the streatchable transparent electrodes. The assembled device could be stretched to 150% its original length and bent to a curvature of 0.1. The device could be operated and switched between its yellow (off) and blue (on) states while being stretched and bent with a maximum contrast ΔT ≈30% at 805 nm and a coloration efficiency of 168 cm2/C. The stretchable device had an electrochromic contrast that was 30% greater than its counterpart that was prepared from conventional ITO-glass electrodes. The critical composition required for making devices truly stretchable was possible by evaluating the performance of five types of devices consisting of different layers.
... Therefore, innovations such as coaxial electrospinning, mixing and multiple electrospinning, core-shell electrospinning, blow-assisted electrospinning, and bubble electrospinning have been proposed [1][2][3]. Several technologies have been combined with electrospinning to produce materials, e.g., electrospinning and electrode printing [4], electrospinning and electrospraying [5], and other techniques [6]. Unlike other membrane production methods (for instance, the non-solvent-induced phase separation process and solution phase inversion method), electrospinning does not require additional solvents, the fiber diameters and porosity are relatively easy to control, and the membrane consists entirely of fibers (not only porous but also completely fibrous) with high surface area-to-volume or length-to-diameter ratios [7,8]. ...
Electrospun polymer nanofiber materials have been studied as basic materials for various applications. Depending on the intended use of the fibers, their morphology can be adjusted by changing the technological parameters, the properties of the spinning solutions, and the combinations of composition. The aim of the research was to evaluate the effect of electrode type, spinning parameters, polymer molecular weight, and solution concentration on membranes morphology. The main priority was to obtain the smallest possible fiber diameters and homogeneous electrospun membranes. As a result, five electrode types were selected, the lowest PVA solution concentration for stable spinning process was detected, spinning parameters for homogenous fibers were obtained, and the morphology of electrospun fiber membranes was analyzed. Viscosity, conductivity, pH, and density were evaluated for PVA polymers with five different molecular weights (30–145 kDa) and three concentration solutions (6, 8, and 10 wt.%). The membrane defects and fiber diameters were compared as a function of molecular weight and electrode type. The minimum concentration of PVA in the solution allowed more additives to be added to the solution, resulting in thinner diameters and a higher concentration of the additive in the membranes. The molecular weight, concentration, and electrode significantly affected the fiber diameters and the overall quality of the membrane.
Organic electrochemical transistors (OECTs) and OECT-based circuits may find applications in biosensing and bioelectronics. However, most OECTs are fabricated on rigid substrates, and we concern the integration with truly stretchable elastomeric platforms and biological tissues (e.g., human skin), since excellent mechanical agility and stable electrical performance are required for reliable signal processing. In this article, we highlight recent advances on structurally stretchable OECTs with micro-/nano-structures, which exhibit good stretchability and steady output signal under deformation. These devices have great potential in wearable electronics.
Organic electrochemical transistors (OECTs) exhibit great application potential in healthcare and human-machine interfaces, due to their tunable synthesis, facile deposition, and excellent biocompatibility. Expanding OECTs to the wearable bioelectronics will significantly promote contact with the skin and enable a stable and reliable performance. In this review, we provide an overview of the device physics of flexible OECTs, aiming to offer a basic understanding and guideline for material selection and device layout. Particular focus is given to the advanced manufacturing approaches, including photolithography and printing techniques, which establish a robust foundation for the commercialization and large-scale fabrication. And abundantly demonstrated examples ranging from biosensors, artificial synapse/neurons, and bioinspired nervous systems are summarized to highlight the considerable prospects of smart healthcare. In the end, the challenges and opportunities of flexible OECTs are proposed. The purpose of this review is not only to elaborate on the basic design principles of flexible OECTs, but also to act as a roadmap for further exploration of wearable OECTs in advanced bio-applications.
Fluorescence resonance energy transfer (FRET) within a coaxial (core@shell) nanofibre structure is explored. Using a host polyvinylpyrrolidone (PVP), the donor BODIPY was incorporated into the core of the coaxial nanofibre...
Stretchable electronic devices are expected to play an important role in wearable electronics. Solution-processable conducting materials are desirable because of their versatile processing. Herein, we report the fabrication of fully stretchable organic electrochemical transistors (OECTs) by printing all components of the device. To achieve the stretchability of the whole body of the devices, a printed planar gate electrode and polyvinyl alcohol (PVA) hydrogel electrolyte were employed. Stretchable silver paste provided a soft feature to drain/source, gate and interconnect, without any additional strategies needed to improve the stretchability of the metallic components. The resulting OECTs showed a performance comparable to inkjet or screen-printed OECTs. The maximum transconductance and on/off ratio were 1.04 ± 0.13 mS and 830, respectively. The device was stable for 50 days and stretched up to 110% tensile strain, which makes it suitable for withstanding the mechanical deformation expected in wearable electronics. This work paves the way for all-printed and stretchable transistors in wearable bioelectronics.
The fern leaf-like surface topography of poly(EDOT-PBA)/Ag/Cu/GCE increases the specific surface area of the sensor, thereby enhancing the glucose sensing performance.
Electrospun conductive nanofibers were obtained from a blend of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEG-PPG-PEG). The effect of the treatment with sulfuric acid (H2SO4) on the electromechanical performances of the fibers was investigated. Fibrillar mats treated with H2SO4 could be stretched up to 200% of their initial length with minimal loss (≈20%) of the current. Stretchable organic electrochemical transistors (OECTs) were fabricated by printing silver drain and source electrodes directly on the conductive electrospun fiber mats. The fabricated devices showed transistor behavior up to 100% strain and their transistor performance was maintained during 100 stretching/release cycles. The overall electronic and mechanical performances of the stretchable OECTs were better, even after stretching, than their counterparts that were prepared from spincoated thin films.
