Search

Recent work in structure–processing relationships of polymer semiconductors have demonstrated the versatility and control of thin-film microstructure offered by meniscusguided coating (MGC) techniques. Here, we analyze the qualitative and quantitative aspects of solution shearing, a model MGC method, using coating blades augmented with arrays of pillars. The pillars induce local regions of high strain rates—both shear and extensional—not otherwise possible with unmodified blades, and we use fluid mechanical simulations to model and study a variety of pillar spacings and densities. We then perform a statistical analysis of 130 simulation variables to find correlations with three dependent variables of interest: thin-film degree of crystallinity and transistor field-effect mobilities for charge-transport parallel (Μpara) and perpendicular (Μperp) to the coating direction. Our study suggests that simple fluid mechanical models can reproduce substantive correlations between the induced fluid flow and important performance metrics, providing a methodology for optimizing blade design. Polymer semiconductors have opened up a new frontier of electronics that can be flexible, stretchable, implantable, or biodegradable. While the chemical and electronic properties of these materials are important for their function as the active material in organic electronic devices, the manner by which these organic semiconductors are deposited onto a substrate can significantly influence its charge-transport properties. While a variety of techniques have been investigated to enhance charge-transport behavior, there are few reports approaching the issue in terms of the fluid dynamical considerations relevant during deposition from the solution phase. In this article, we analyze the fluid flow that occurs during thin-film deposition by solution shearing, a representative meniscusguided coating method amenable to high-throughput processing. We investigate a variety of variables related to fluid flow that can be estimated from fluid mechanical simulations of solution shearing with a coating blade patterned with a regular array of pillars used to induce higher fluid strain rates. We find correlations suggestive of underlying relationships between strain rates associated with certain directions and polymer charge-transport properties in the final deposited film. This article establishes a statistical approach using simulation data that can guide patterned blade design to enhance polymer deposition and realize high-performance devices.

The use of grazing-incidence scattering methods for the characterization of 2D patterned organic thin films is limited due to the elongated 1D footprint of the X-ray beam on the sample. However, this characteristic feature can be turned into an advantage, when combined with tomographic reconstruction. In this pilot study we show how the use of a chosen texture reflection and a diffuse reflectivity signal can each provide 2D images of the deposits, simultaneously revealing the organic film’s crystal orientation and the location of the metal electrodes.

Background Occult and missed surgical neck fractures can be found in patients diagnosed with isolated greater tuberosity (GT) fracture during the follow up period. The purpose of this study was to retrospectively assess the incidence rate of occult and missed surgical neck fractures in those initially diagnosed with isolated GT fracture. Methods Records of patients diagnosed as having an isolated GT fracture were retrieved from a database in a medical center. Two senior orthopedic surgeons blindly reviewed all images of these patients three times to classify GT fracture types (split, avulsion and depression types), and recorded any surgical neck fractures found. Then a meeting was help to confirm the fracture types and presence of surgical neck fracture. Results Occult surgical neck fractures were found in 5 out of 68 (7.4%) patients, whereas missed surgical neck fractures were found in 3 out of 68 (4.4%) patients. In total, 32 patients had split type GT fracture, 32 had avulsion type and 4 had depression type. For those with occult surgical neck fractures, 7 had the split type GT fracture, while the remaining one had the avulsion type. Although the proportion of occult surgical neck fracture was higher in the split-type GT fracture (21.9%) than in the avulsion-type GT fracture (3.1%), the difference was not statistically significant (p = 0.056). Conclusion Occult humeral surgical neck fractures occurred in 7.4% of isolated greater tuberosity fractures after re-evaluation, while missed humeral surgical neck fractures occurred in 4.4%.

In large or massive rotator cuff tears, successful repairs are difficult and complication rates are high, because the torn tendon is contracted and the superior capsule is disrupted. Recent studies have shown that superior capsule reconstruction (SCR) in massive irreparable rotator cuff tears results in better clinical scores and preserves stable glenohumeral stability without significant complications. In this article, we propose a simple, efficient SCR technique to reinforce the repair of large or massive rotator cuff tears. For this technique, the long head of the biceps tendon is used as a local autograft for the SCR, therefore eliminating comorbidities related to graft harvesting. The proximal part of the long head of the biceps tendon is transposed posteriorly and fixed onto the footprint as the SCR, which not only can maintain the stability of the glenohumeral joint, but also can preserve the vascular supply to help healing.

BackgroundA two-stage minimally invasive surgery (MIS) protocol with oblique lumbar interbody fusion (OLIF) combined with posterior instrumentation is becoming popular in the treatment of adult spinal deformities (ASDs) because of lower complication rates and less blood loss when compared with the open traditional posterior approach. The objective of this study is to determine the efficacy of correction and the causes of suboptimal correction in two-stage OLIF.MethodsThis retrospective study included 27 patients who underwent both two-stage and single-stage OLIF with posterior instrumentation for treatment of ASD. Patients treated with two-stage OLIF were sorted into Group A (Improved Lenke-Silva classification after the first-stage OLIF) and Group B (Unchanged Lenke-Silva classification after the first-stage operation) to evaluate the correction efficacy of OLIF in a two-stage MIS protocol. Statistical analyses were performed to compare the clinical and radiological outcomes. The causes of complications and suboptimal corrections (Group B) in patients treated with the two-stage MIS protocol were analyzed.ResultsAll 27 patient patients showed significant improvement (P < 0.05) in the visual analog scale, the Oswestry Disability Index, and EuroQol. A total of 14 patient were treated with the two-stage protocol, with ten patients included in group A and four patients with insufficient correction angles included in group B. The radiographic outcome of Group A showed significant corrections (P < 0.05) in pelvic tilt, pelvic incidence-lumbar lordosis (PI-LL) mismatch, sagittal vertical axis, and max Cobb angles. In group B, surgical limitations of OLIF were the cause of unsatisfactory correction in two patients because the deformities involved the T-L junction, which was not accessible using the approach. Severe preoperative PI-LL mismatch (41°) and cage subsidence with an anterior endplate fracture were the cause of poor correction in two other patients.ConclusionOLIF can provide significant corrections that reduce the need for a Smith-Petersen osteotomy (SPO) or a pedicular subtraction osteotomy (PSO) for additional correction during posterior instrumentation. Deformities involving the T-spine or T-L junction, severe PI-LL mismatches, and cage subsidence are the possible causes of suboptimal corrections with OLIF using the two-stage protocol.

To retrospectively assess the clinical outcomes of the patients with large to massive reparable RCTs treated by arthroscopic rotator cuff repair (ARCR) combined with modified superior capsule reconstruction (mSCR) using the long head of biceps tendon (LHBT) as reinforcement with a minimum of 2 years of follow-up.We retrospectively evaluated 40 patients with large to massive reparable RCTs who underwent ARCR and mSCR (group I) between February 2017 and June 2018 (18 patients) or underwent ARCR and tenotomy of LHBT performed at the insertion site (group II) between January 2015 and January 2017 (22 patients). The pain visual analog score (VAS) was assessed preoperatively and 1, 3, 6, 12, 24 months postoperatively. American Shoulder and Elbow Surgeons (ASES) scores, the University of California, Los Angeles (UCLA) shoulder rating scale, and active range of motion (AROM) were assessed before surgery and 6, 12, and 24 months after surgery. The integrity of the rotator cuff and mSCR was evaluated using magnetic resonance images at 12 months postoperatively.After surgery, both groups had significantly improved in VAS, ASES, UCLA and AROM scores in the final follow-up. There were no significant between-group differences in the characteristics of the patients before surgery. Group I had improved pain relief at 1 month (P.001) and at 3 months (P.01) after surgery. For the AROM, group I (flexion, external rotation, internal rotation) demonstrated better improvement than group II 6 months after surgery (all P.05) and better internal rotation 12 and 24 months after surgery (all P.05). The mSCR survival rate was 94.4% (17/18). The retear rate of repaired rotator cuffs for groups I and II was 16.7% (3/18) and 40.9% (9/22), respectively, and the differences were significant (P.046).ARCR combined with mSCR using LHBT as reinforcement may lead to a lower retear rate and earlier functional recovery than conventional ARCR with tenotomy of LHBT for large to massive reparable RCTs.Level III, retrospective therapeutic comparative trial.

One major advantage of organic electronics is their superior processability relative to traditional silicon-based materials. However, most high-performing polymer semiconductors exhibit poor solubility and require toxic chlorinated solvents coupled with inefficient coating methods such as spin-coating for device fabrication. Therefore, developing polymer semiconductors that are processable in environmentally benign solvents and compatible with effective printing techniques while maintaining good charge transport properties is crucial for the industrialization of low-cost and lightweight plastic electronics. In this study, alkyl flexible linkers with branched tertiary carbon atoms are inserted to a high-mobility diketopyrrolopyrrole-based polymer backbone to suppress polymer aggregation in solution, decrease crystallinity, and increase free volume. The polymer readily dissolves in industrial solvents and shows a 70-fold increase in solubility compared to its fully conjugated counterpart. Furthermore, due t...

Crucial to the development and refinement of organic electronics is a fundamental understanding of how deposition processes affect the active material’s resulting microstructure in the thin film. Meniscus-guided coating (MGC) methods are attractive because of their amenability to high-throughput, industrially relevant continuous processes like roll-to-roll deposition, but the mechanism of solid film formation has not been elucidated and is valuable for the precise control of thin-film morphology and thus ultimate device performance. In this work, we investigate the microstructural evolution of thin films of a diketopyrrolopyrrole–terthiophene donor–acceptor polymer semiconductor using both in situ and ex situ X-ray diffraction methods. On the basis of a comparison of disorder between the film bulk and the top surface and a depth profiling of the out-of-plane orientation of crystallites, we find that faster coating speeds introduce more disorder into the resulting films because the stochastic nucleation of...

For miniaturized capacitive energy storage, volumetric and areal capacitances are more important metrics than gravimetric ones because of the constraints imposed by device volume and chip area. Typically used in commercial supercapacitors, porous carbons, although they provide a stable and reliable performance, lack volumetric performance because of their inherently low density and moderate capacitances. Here we report a high-performing electrode based on conductive hexaaminobenzene (HAB)-derived two-dimensional metal−organic frameworks (MOFs). In addition to possessing a high packing density and hierarchical porous structure, these MOFs also exhibit excellent chemical stability in both acidic and basic aqueous solutions, which is in sharp contrast to conventional MOFs. Submillimetre-thick pellets of HAB MOFs showed high volumetric capacitances up to 760 F cm−3 and high areal capacitances over 20 F cm−2. Furthermore, the HAB MOF electrodes exhibited highly reversible redox behaviours and good cycling stability with a capacitance retention of 90% after 12,000 cycles. These promising results demonstrate the potential of using redox-active conductive MOFs in energy-storage applications. Metal–organic frameworks (MOFs) are attractive electrodes for supercapacitors but generally suffer from low electric conductivity and chemical stability. Here the authors report stable conductive MOFs based on hexaminobenzene linker with volumetric and areal capacitances in excess of 700 F per cm3 and 15 F per cm2, respectively.

The promise of wearable and implantable devices has made stretchable organic semiconductors highly desirable. Though there are increasing attempts to design intrinsically stretchable conjugated polymers, their performance in terms of charge carrier mobility and maximum fracture strain is still lacking behind extrinsic approaches (i.e., buckling, Kirigami interconnects). Here, polymer crosslinking with flexible oligomers is applied as a strategy to reduce the tensile modulus and improve fracture strain, as well as fatigue resistance for a high mobility diketopyrrolopyrrole polymer. These polymers are crosslinked with siloxane oligomers to give stretchable films stable up to a strain e = 150% and 500 strain-and-release cycles of 100% strain without the formation of nanocracks. Organic field-effect transistors are prepared to assess the electrical properties of the crosslinked film under cyclic strain loading. An initial average mobility (μavg) of 0.66 cm2 V−1 s−1 is measured at 0% strain. A steady μavg above 0.40 cm2 V−1 s−1 is obtained in the direction perpendicular to the strain direction after 500 strain-and-release cycles of 20% strain. The μavg in the direction parallel to strain, however, is compromised due to the formation of wrinkles.

Though peripheral halogen substitution is a known strategy to lower the lowest unoccupied (LUMO) and highest occupied (HOMO) molecular orbital energy levels of planar molecular semiconductors, this strategy has not been explored in conformationally contorted systems. We demonstrate that substitution of peripheral hydrogens with fluorine and chlorine can effectively lower the energy levels of contorted hexabenzocoronene (cHBC) despite its nonplanar conformation. The HOMO energy level lowers comparably with fluorine and chlorine substitution. Due to chlorine’s ability to accommodate more electron density than fluorine, chlorination lowers the LUMO energy level more effectively compared to fluorination (31–60 meV/F versus 53–83 meV/Cl), resulting in a narrowing of the optical bandgap. We find the preference for electron transport to increase with increasing halogenation of cHBC. As an example, thin-film transistors fabricated with 8F-8Cl-cHBC demonstrated electron mobilities as high as 10–2 cm2/(V s) and sol...

Increasing performance demands and shorter use lifetimes of consumer electronics have resulted in the rapid growth of electronic waste. Currently, consumer electronics are typically made with nondecomposable, nonbiocompatible, and sometimes even toxic materials, leading to serious ecological challenges worldwide. Here, we report an example of totally disintegrable and biocompatible semiconducting polymers for thin-film transistors. The polymer consists of reversible imine bonds and building blocks that can be easily decomposed under mild acidic conditions. In addition, an ultrathin (800-nm) biodegradable cellulose substrate with high chemical and thermal stability is developed. Coupled with iron electrodes, we have successfully fabricated fully disintegrable and biocompatible polymer transistors. Furthermore, disintegrable and biocompatible pseudo-complementary metal–oxide–semiconductor (CMOS) flexible circuits are demonstrated. These flexible circuits are ultrathin ( 2 ) with low operating voltage (4 V), yielding potential applications of these disintegrable semiconducting polymers in low-cost, biocompatible, and ultralightweight transient electronics.

Organic field-effect transistors have gained much attention for their potential use in low-cost, large-area, flexible electronics. High-performance organic transistors require a low density of grain boundaries in their organic films and a reduction of charge traps at the semiconductor-dielectric interface for efficient charge transport. In this respect, the role of the dielectric material is crucial because it primarily determines the growth of the film and the interfacial trap density. Here, we demonstrate the use of chemical-vapor-deposited hexagonal boron nitride (CVD h-BN) as a scalable growth template/dielectric for high-performance organic field-effect transistors. The field-effect transistors based on C60 films grown on single-layer CVD h-BN exhibit an average mobility of 1.7 cm^2V^-1s^-1 and a maximum mobility of 2.9 cm^2V^-1s^-1 with on/off ratios of 10^7. The structural and morphology analysis shows that the epitaxial, two-dimensional growth of C60 on CVD h-BN is mainly responsible for the superior charge transport behavior. We believe that CVD h-BN can serve as a growth template for various organic semiconductors, enabling large-area, high-performance flexible electronics.

While the chemical structure of organic semiconductors has an obvious effect on their proclivity for charge transport, the ways with which they are processed have a dramatic effect on the performance of plastic electronics devices incorporating them. In some cases, morphological defects and misalignment of crystalline grains can completely obscure the materials' intrinsic charge transport properties. Although some deposition methods, especially vapor-phase ones, can produce single crystals and thus avoid some of these problems, it is desirable to gain a fundamental understanding of how to improve charge transport when using solution-phase deposition techniques. In this review, we present both a survey of solution-based processing techniques for plastic electronics relevant on both the commercial and research scale and a set of strategies to control thin film morphology towards enhancing their electronic transport properties.

Hydrogen fuel cells can potentially reduce greenhouse gas emissions and the dependence on finite fossil fuel resources. Improvements in the storage of hydrogen are needed for more widespread use of hydrogen fuel cells. To help better understand the hydrogen storage needs in the future, this study analyzes opportunities for the near-term deployment of H2-fueled fuel cells in man-portable power devices and personal electronics. The analysis engaged end users, equipment manufacturers, and technical experts to determine not only the most feasible devices for near-term deployment of hydrogen fuel cells but also the meaningful and realistic requirements for hydrogen storage in these applications. It was found that military personnel power generators, consumer battery rechargers, and specialized laptop computers offer the most potential for the incorporation of fuel cell technology. However, large improvements must be made in energy storage densities for hydrogen fuel cells to compete with batteries or direct methanol fuel cells in order to make fuel cells attractive if an inexpensive and convenient hydrogen supply is not available.

Introduction: Breast reconstruction using silicone implants is a widespread choice, however, breast capsular contracture (BCC), a response of the immune system to foreign materials, is the most affliction and frustration fibrosis complications after silicone implantation. Chronic inflammation-associated fibrosis is regarded as a main cause of BCC. Hyaluronic acid (HA) is an effective anti-adhesive and anti-fibrotic agent. Furthermore, 1,4-butanediol diglycidyl ether-cross-linked hyaluronan hydrogel (cHA) is a non-resorbable cross-linked hyaluronan-derived polymer with no cytotoxicity and high stability. This study aims to evaluate the potential of cHA on preventing BCC in breast surgery using silicone implants. Methods: The effect of cHA on BCC will be examined in breast BCC rat model. Results: Our study showed that cHA decreased fibrosis-regulated factors transforming growth factor beta 1 (TGF-β1) and tissue inhibitor of metalloproteinase (TIMP) expressions and increased metalloproteinase (MMP) MMP-9 expression in capsule tissue. cHA significantly decreased inflammatory mediators tumor necrosis factoralpha (TNF-α), interleukin IL-6, nitric oxide (NO), as well as inducible nitric oxide synthase (iNOS) expressions. In addition, cHA significantly decreased transcription factor nuclear factor kappa B (NF-κB) activation in silicone surrounded tissue. Conclusions: cHA showed prevention in BCC formation through inhibiting NF-κB -associated inflammation in rats with silicone implantation.

The electronic devices that play a vital role in our daily life are primarily based on silicon and are thus rigid, opaque, and relatively heavy. However, new electronics relying on polymer semiconductors are opening up new application spaces like stretchable and self-healing sensors and devices, and these can facilitate the integration of such devices into our homes, our clothing, and even our bodies. While there has been tremendous interest in such technologies, the widespread adoption of these organic electronics requires low-cost manufacturing techniques. Fortunately, the realization of organic electronics can take inspiration from a technology developed since the beginning of the Common Era: printing. This review addresses the critical issues and considerations in the printing methods for organic electronics, outlines the fundamental fluid mechanics, polymer physics, and deposition parameters involved in the fabrication process, and provides future research directions for the next generation of printed polymer electronics., A primary advantage of polymer semiconductors compared to silicon-based semiconductors lies in its capability of being solution-processed for the large-scale fabrication of electronics that can be flexible, stretchable, implantable, biodegradable, and self-healing. Here, Gu and Shaw et al. review recent developments in meniscus-guided coating that can control thin-film morphology.

The alignment of organic semiconductors (OSCs) in the active layers of electronic devices can confer desirable properties, such as enhanced charge transport properties due to better ordering, charge transport anisotropy for reduced device cross-talk, and polarized light emission or absorption. The solution-based deposition of highly aligned small molecule OSCs has been widely demonstrated, but the alignment of polymeric OSCs in thin films deposited directly from solution has typically required surface templating or complex pre- or postdeposition processing. Therefore, single-step solution processing and the charge transport enhancement afforded by alignment continue to be attractive. We report here the use of solution shearing to tune the degree of alignment in poly(diketopyrrolopyrrole-terthiophene) thin films by controlling the coating speed. A maximum dichroic ratio of ∼7 was achieved on unpatterned substrates without any additional pre- or postdeposition processing. The degree of polymer alignment was found to be a competition between the shear alignment of polymer chains in solution and the complex thin film drying process. Contrary to previous reports, no charge transport anisotropy was observed because of the small crystallite size relative to the channel length, a meshlike morphology, and the likelihood of increased grain boundaries in the direction transverse to coating. In fact, the lack of aligned morphological structures, coupled with observed anisotropy in X-ray diffraction data, suggests the alignment of polymer molecules in both the crystalline and the amorphous regions of the films. The shear speed at which maximum dichroism is achieved can be controlled by altering deposition parameters such as temperature and substrate treatment. Modest changes in molecular weight showed negligible effects on alignment, while longer polymer alkyl side chains were found to reduce the degree of alignment. This work demonstrates that solution shearing can be used to tune polymer alignment in a one-step deposition process not requiring substrate patterning or any postdeposition treatment.

As a highly reactive gas, hydrogen presents significant challenges for its acquisition and safe storage. Consequently, the viability of a sustainable hydrogen economy greatly depends on the development of an efficient, cost-effective method of hydrogen production. One model for addressing this challenge is to deploy portable hydrogen generators for the home. The Princeton University Chapter of the International Association for Hydrogen Energy (IAHE-PU) has designed and created a generator that produces hydrogen through water electrolysis and optimizes cost effectiveness and portability while maximizing hydrogen output. For our proof-of-concept, the system utilizes simple household items with a Sharp ND130UJF 130W solar panel. In our design, Ni electrodes submerged in 8 M KOH solution in six glass containers were utilized to power an external circuit. Over 1 h, our system produced 8.61 L of hydrogen gas at an estimated cost of $8.58 per kilogram of hydrogen gas over the 25-year lifetime of the solar panel.

Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility., Solution printing is a desirable route for manufacturing organic solar cells, whilst the major challenge lies with morphology control. Here, Diao et al. use a microstructured blade to guide the solution flow during printing, which improves polymer crystallization and the resulting device performance.

The electronic properties of solution-processable small-molecule organic semiconductors (OSCs) have rapidly improved in recent years, rendering them highly promising for various low-cost large-area electronic applications. However, practical applications of organic electronics require patterned and precisely registered OSC films within the transistor channel region with uniform electrical properties over a large area, a task that remains a significant challenge. Here, we present a technique termed “controlled OSC nucleation and extension for circuits” (CONNECT), which uses differential surface energy and solution shearing to simultaneously generate patterned and precisely registered OSC thin films within the channel region and with aligned crystalline domains, resulting in low device-to-device variability. We have fabricated transistor density as high as 840 dpi, with a yield of 99%. We have successfully built various logic gates and a 2-bit half-adder circuit, demonstrating the practical applicability of our technique for large-scale circuit fabrication.

The solid-state packing and polymer orientation relative to the substrate are key properties to control in order to achieve high charge carrier mobilities in organic field effect transistors (OFET). Intuitively, shorter side chains are expected to yield higher charge carrier mobilities because of a denser solid state packing motif and a higher ratio of charge transport moieties. However our findings suggest that the polymer chain orientation plays a crucial role in high-performing diketopyrrolopyrrole-based polymers. By synthesizing a series of DPP-based polymers with different branched alkyl side chain lengths, it is shown that the polymer orientation depends on the branched alkyl chain lengths and that the highest carrier mobilities are obtained only if the polymer adopts a mixed face-on/edge-on orientation, which allows the formation of 3D carrier channels in an otherwise edge-on-oriented polymer chain network. Time-of-flight measurements performed on the various polymer films support this hypothesis by showing higher out-of-plane carrier mobilities for the partially face-on-oriented polymers. Additionally, a favorable morphology is mimicked by blending a face-on polymer into an exclusively edge-on oriented polymer, resulting in higher charge carrier mobilities and opening up a new avenue for the fabrication of high performing OFET devices.

Although solution processing has been hailed as a more industrially relevant route for the deposition of organic semiconductors to be used in devices, the quality and performance of solution-deposited thin films of these materials have not been able to reach that of vapor-grown single crystals until recently. Single crystals and single-crystalline films benefit from the absence of grain boundaries and the reduction of crystalline defects that impede effective charge transport through the solid. Although solution-phase deposition techniques for high-quality single-crystal growth have been reported, high-throughput, large-area deposition methods for single-crystalline films remain challenging. However, a shift toward this direction has emerged in recent years and has produced a diversity of techniques to grow, deposit, and pattern organic semiconductor single crystals and thin films. In this review, we survey the physical basis for a variety of solution-based single-crystal growth and deposition methods and discuss their advantages and shortcomings in the hopes of inspiring new ways to approach these challenges.