ePTFE Membrane Research Articles

Changes in the Fluorescence of Biological Particles Exposed to Environmental Conditions in the National Capitol Region

A variety of methods have been used to study atmospheric bioaerosols. A common technique employed for the detection and measurement of bioaerosols is the measurement of the autofluorescence of biological particles when excited by ultraviolet light. We examined the changes in the fluorescence spectra of bioaerosols when exposed to ambient outdoor conditions for periods of several hours. The bioaerosols in this study were contained in a Captive Aerosol Growth and Evolution (CAGE) chamber that employed two rotating drums constructed with an exterior FEP Teflon film to allow sunlight to penetrate and an inner ePTFE membrane to allow ambient trace gasses to permeate the drums. The bioaerosols were periodically measured with a TSI UV-APS (excited at 355 nm) and a single-particle fluorescence spectrometer (excited at 351 and 263 nm). The data indicate changes in both fluorescence spectral profile and intensity from Bacillus thuringiensis var. kurstaki spores and MS2 bacteriophage particles during the experiments. The changes observed in these particles appear to be due to a combination of the environmental conditions rather than attributable to any single factor. The results of this study indicate that bioaerosols are significantly altered by atmospheric aging processes and that these changes may affect measurements by ultra-violet light induced fluorescence (UV-LIF) or other spectroscopic techniques.

Endoscopic treatment of anterior laryngeal web using keel designed from ePTFE followed by voice therapy: a refined technique

BackgroundTreatment of laryngeal web is challenging due to possibility of recurrence and affected voice quality. Optimal treatment of laryngeal web should emphasize on improving both airway and vocal function. We refined the traditional endoscopic method using a new keel designed from expanded polytetrafluoroethylene (ePTFE) membrane. Our objective is to evaluate the voice outcomes following the endoscopic treatment and voice therapy.ResultsTen subjects presented with anterior laryngeal web. Auditory perceptual assessment, stroboscopic examination and acoustic studies were performed pre- and postoperatively. Endoscopic excision of laryngeal web was performed with cold instruments. An individually designed ePTFE keel was fixed by Nylon thread 2–0 at the anterior commissure and tied subcutaneously in the neck. The keel left for 3–5 weeks followed by voice therapy using abdomino-diaphragmatic breathing exercise and relaxation method. Vocal parameters measured were perceptual voice quality using Grade-Roughness-Breathiness-Asthenia-Strain voice scale (GRBAS), stroboscopic score, fundamental frequency (F0), jitter, shimmer, pitch perturbation question (PPQ), amplitude perturbation question (APQ) and harmonics-to-noise ratio (HNR). Significant decrease in GRBAS (P < 0.001) and significant increase in stroboscopic scores (P < 0.001) were noticed after operation and voice therapy. Also, acoustic voice parameters showed significant improvements. The mean jitter, shimmer, PPQ and APQ showed significant decrease (p = 0.0028, 0.0032, 0.0026, 0.0014, and 0.006 respectively). Overall, 90 % of our subjects have satisfactory voice outcome.ConclusionEndoscopic excision of anterior laryngeal with cold instrument followed by ePTFE keel fixation achieved good long-term voice results. The ePTFE is soft biocompatible material which does not make reaction. The keel should be left in place for sufficient period of time (3–5 weeks). This ensures perfect healing with less or no recurrence. Absence of foreign body reactions in the vocal folds is important for mucosal integrity and good voice outcome. So, the ePTFE could be good alternative for laryngeal keel. Hyperfunctional dysphonia with ventricular hypertrophy may develop in longstanding anterior laryngeal web which needs intensive voice therapy after operation. Our treatment targeted both the organic etiology of dysphonia and the underlying cause of the possible associated functional element of dysphonia.

Graphene Oxide and Metal-Organic Framework-Based Breathable Barrier Membranes for Toxic Vapors.

Garments protective against chemical warfare agents (CWAs) or accidently released toxic chemicals must block the transport of toxic gases/vapors for a substantial time and allow moisture transport for breathability. These demands are challenging: either the barriers block CWAs effectively but have poor breathability or barriers have excellent breathability but cannot block CWAs well. Existing protective garments employ large amounts of active carbon, making them quite heavy. Metal-organic framework (MOF)-based adsorbents are being investigated as sorbents for CWAs. Breathable laminate of graphene oxide (GO) flakes supported on a porous membrane reduces permeation rates of CWA simulants substantially. We developed a multilayered membrane-based flexible barrier: GO laminate-based membrane over a MOF nanocrystal-filled expanded polytetrafluorethylene (ePTFE) membrane having submicrometer pores. The GO laminate-based layer developed a steady breakthrough concentration level almost 2 orders of magnitude below the usual breakthrough level. This highly reduced level of CWA was blocked by the MOF nanocrystal-filled membrane substrate layer over a highly extended period. We demonstrated the blocking of CWAs, mustard (HD), soman (GD), a sarin simulant [dimethyl methyl phosphonate (DMMP)], and ammonia for an extended period while the moisture transmission rate was substantial. The times for complete blockage of ammonia, HD, GD, and DMMP were 2750 min, 1075 min, 176 min, and 7 days, respectively. This remarkable performance resulted from a very low steady-state penetrant permeation through GO-laminate membrane and substantial penetrant sorption by MOF nanocrystals; furthermore, both layers show high moisture vapor transmission.

The effect of experimental diabetes and membrane occlusiveness on guided bone regeneration: A proof of principle study.

To evaluate the effect of membrane occlusiveness and experimental diabetes on early and late healing following guided bone regeneration. A total of 30 Wistar rats were randomly allocated to three groups: healthy (H), uncontrolled diabetic (UD) and controlled diabetic (CD). A critical size calvarial defect (CSD) was created at the mid-portion of one parietal bone, and it was treated with a double layer of e-PTFE membrane presenting 0.5mm perforations. The animals were killed at 7 and 30days of healing, and qualitative and quantitative histological evaluations were performed. Data were compared with the ones previously obtained from other 30 animals (10H, 10UD, 10 CD), where two CSDs were randomly treated with a double-layer e-PTFE occlusive membrane or left empty. Following application of cell occlusive or cell permeable membranes, significant regeneration can be observed. However, at 30days in the H group occlusive compared to cell permeable membranes promoted enhanced bone regeneration (83.9 ± 7.3% vs. 52.5 ± 8.6%), while no significant differences were observed within the CD and UD groups. UD led to reduced regeneration compared to H when an occlusive barrier was applied, whereas comparable outcomes to H and CD were observed when placing perforated membranes. The application of cell permeable membranes may have masked the potentially adverse effect of experimental UD on bone regeneration. Membrane porosity might contribute to modulate the bone regenerative response in UD conditions. Future studies are needed to establish the degree of porosity associated with the best regenerative outcomesas well as the underlying molecular mechanisms.

The “Sling” Technique for Horizontal Guided Bone Regeneration: A Retrospective Case Series

The aim of this retrospective case series was to present a new technique, called the “sling technique”, for massive horizontal alveolar ridge augmentation through the innovative use of an expanded polytetrafluoroethylene (e-PTFE) membrane to reduce the risk of biological complications related to membrane exposure. Materials and Methods: Eligible patients for implant rehabilitation with a horizontal bone defect were enrolled in our study. All patients were treated with our new GBR approach, called the “sling technique” (ST), which consisted of covering the vestibular side of the bone defect with a stretched e-PTFE membrane. This technique allowed the amplification of the membrane surface as long as the compression and the immobilization of the underlying graft material remained (1:1 autologous bone and bovine xenograft). The membrane was placed far from the surgical incision of the mucosa to avoid infective complications. Pre- and post-regenerative surgery CBCT scans were used to assess the tissue gain amount after the GBR. Results: A total of 10 patients (4 females, 6 males; age range: 45–60 years old) were enrolled in our study and 33 implants were placed in regenerated bone. An average of 4 mm bone gain was achieved using the ST. No membrane exposures or biological complications were registered during the post-operative healing period. After a 24-month follow-up, a 100% implant survival rate was observed without hard or soft tissue dehiscence. Conclusion: The e-PTFE membrane positioned with the “sling technique” gave satisfactory results in horizontal bone augmentation. Considering the small sample, further confirmations with larger studies are needed.

Research and clinical translation of trilayer stent-graft of expanded polytetrafluoroethylene for interventional treatment of aortic dissection.

The aortic dissection (AD) is a life-threatening disease. The transcatheter endovascular aortic repair (EVAR) affords a minimally invasive technique to save the lives of these critical patients, and an appropriate stent-graft gets to be the key medical device during an EVAR procedure. Herein, we report a trilayer stent-graft and corresponding delivery system used for the treatment of the AD disease. The stent-graft is made of nitinol stents with an asymmetric Z-wave design and two expanded polytetrafluoroethylene (ePTFE) membranes. Each of the inner and outer surfaces of the stent-graft was covered by an ePTFE membrane, and the two membranes were then sintered together. The biological studies of the sintered ePTFE membranes indicated that the stent-graft had excellent cytocompatibility and hemocompatibility in vitro. Both the stent-graft and the delivery system exhibited satisfactory mechanical properties and operability. The safety and efficacy of this stent-graft and the corresponding delivery system were demonstrated in vivo. In nine canine experiments, the blood vessels of the animals implanted with the stent-grafts were of good patency, and there were no thrombus and obvious stenosis by angiography after implantation for 6 months. Furthermore, all of the nine clinical cases experienced successful implantation using the stent-graft and its postrelease delivery system, and the 1-year follow-ups indicated the preliminary safety and efficacy of the trilayer stent-graft with an asymmetric Z-wave design for interventional treatment.

Outcomes of reconstructive periodontal surgery with different types of barrier membranes

Relevance. Reconstructive periodontal surgery is one of the most effective methods of restoring tooth-supporting apparatus damaged by microbial inflammation and destruction. For this purpose, they use non-resorbable and resorbable biomaterials, which act as a temporary barrier between the tissues with different mitotic potential during early healing. Since the properties of barrier membranes determine the degree of invasiveness and postoperative morbidity, and, finally, the success of the surgery, it is relevant to study the outcomes of periodontal reconstruction with one of the modern collagen membranes cross-linked by ribose.Purpose. To comparatively assess the outcomes of periodontal reconstructions with a resorbable and non-resorbable barrier material.Material and methods. The study is a prospective randomized blind controlled clinical trial. The study included 37 patients (14 men, 23 women) aged 45-65 years, who, after the initial therapy, underwent 62 guided tissue regenerations using e-PTFE and resorbable collagen membrane cross-linked by ribose. The study compared the clinical and radiographic results before and 18 months after the surgery. We evaluated the probing depth (periodontal pocket), gingival recession level, loss of clinical attachment level, width and height of periodontal infrabony defects, gain in clinical attachment level. The material was statistically processed using StatSoft STATISTICA 10.0.1011 for Windows. The statistical unit is a periodontal defect.Results. In the postoperative period, the main (31%) and control (42%) groups exhibited the areas of membrane exposure; 16 periodontal defects, only in the control group, demonstrated the extensive membrane exposure, of which 11 membranes were prematurely removed due to infection of the reconstruction site. In the main group, fibrin allowed exposed area healing in the usual time without medical assistance. After 18 months, the gain in the clinical attachment level was 3.5 mm in the main group versus 2.8 mm in the control group (at p=0.03) with a significant decrease in the probing depth compared to that before treatment; the level of recession also changed positively, although not significantly. The type of periodontal defect (the parameter is higher in three-wall and two-wall defects) appeared to remarkably influence the gain in clinical attachment level.Conclusion. The study evidenced that the resorbable cross-linked collagen membrane demonstrated clinically acceptable outcome of the damaged periodontium reconstruction due to, first of all, increased predictability of the course of the early postoperative period, a significant reduction in morbidity and invasiveness of intervention.

Implants in GBR-Augmented Sites in Patients Treated for Generalized Aggressive Periodontitis: A 10- to 20-Year Prospective Case Series.

The aim of this case series was to evaluate implants inserted in bone after guided bone regeneration (GBR). Fourteen patients with generalized aggressive periodontitis (GAP) who had lost one or two maxillary teeth in the incisor or premolar region were enrolled in the study. Due to bone resorption, the lateral width and vertical height of the bone were insufficient for implant placement. GBR was carried out in a staged approach using titanium-reinforced e-PTFE (expanded polytetrafluoroethylene) membranes. No bone grafts or bone substitute materials were used. After 6 to 8 months, turned-surface implants (n = 47) were inserted in augmented and nonaugmented bone sites and prosthetically treated with single crowns. All patients were examined during a 3- to 6-month recall schedule over a 10- to 20-year period, and clinical and radiographic examinations were performed. GBR yielded mean vertical and lateral bone gains of 4.5 and 7.0 mm, respectively. The implant survival rate was 100%, mucositis was present in 28.8% of sites, and peri-implantitis was not found. The annual bone loss at tooth sites was significantly higher than at implant sites in augmented bone (0.5% vs 0.2%, respectively; P = .000), and the adjacent teeth had significantly higher annual bone loss (0.8%; P = .000). Thus, severely periodontally compromised patients can be managed successfully in the long-term with the described clinical protocol.

Microporous expanded polytetrafluoroethylene layer functionalized hydrophilic groups for excellent mechanical durability and superior performance in proton exchange membrane fuel cell

Introducing hydrophilic groups and increasing the compatibility of the ionomer and reinforcement layer can have a significant impact on the proton conductivity and cell performance of a proton exchange membrane (PEM) under lower relative humidity (RH). In this work, a novel PEM containing expanded polytetrafluoroethylene (ePTFE) functionalized with amino and hydroxyl groups is designed and fabricated to enhance the PEM's proton conductivity and electrochemical performance at low RH, and to improve its mechanical stability. The introduction of the hydrophilic groups and the generation of stable acid–base pairs yield a PFSA ionomer that has better compatibility with and adhesion to the hydrophilic functionalized ePTFE membrane, thereby significantly improving the prepared membrane's proton conductivity, H2 crossover current density, and single-cell performance. In addition, generated water is retained inside the PEM, keeping its cell performance high at low RH. The PEM's mechanical durability is also improved by the increased dimensional stability and compatibility of the ionomer and reinforcement layer. This work provides a promising way to improve the proton conductivity and cell performance of PEMs at low RH and has great application potential for creating PEM fuel cells with high mechanical durability.

Moisture barrier layer with supplemental chemical and biological protective functionality for firefighting clothing applications

One of the primary constituent layers of fire protective clothing is a flame-retardant, waterproof and breathable moisture barrier, which permits the outward transfer of perspiration from the firefighter’s body, while barring the inward entry of water. The introduction of a chemical and biological resistant functionality can greatly enhance the overall applicability of fire protective clothing. In the present work, a chemical &amp; biological resistant waterproof breathable flame retardant moisture barrier fabric was prepared by laminating a biaxially stretched microporous expanded polytetraflouroethylene (ePTFE) membrane with Activated Carbon Fabric using a hot melt reactive breathable polyurethane adhesive. The developed laminate was found to exhibit an excellent balance of waterproofness (23 kPa) and breathability, which was quantified in terms of water vapour transmission rate (WVTR) and water vapour resistance (Ret). High values of WVTR, 1.1025 × 104 ± 9.8×101 g/m2/day complimented with exceptionally low values of Ret, 2.9 m2Pa/W are indicative of its high degree of breathability. Vertical flammability tests clearly revealed the exceptional flame resistance offered by the laminate, where after-flame, after-glow or melt-dripping was not observed and the char length was ∼4.2 cm. Further, the laminate exhibited requisite degree of protection against biological and chemical warfare (CW) agent with no breakthrough of the CW agent being perceived within the time frame of 24 h. The excellent combination of flame retardancy, breathability, waterproofness, chemical and biological protection, bestows the laminate excellent potential for usage as moisture barrier in fire protective clothing applications.

Construction of high-performance triboelectric nanogenerators based on the microstructures of conical nanoneedles

A triboelectric nanogenerator (TENG) based on a hot-embossed PHB membrane and ePTFE membrane displays excellent output performance.

Usage of E-Polytetrafluoroethylene (e-PTFE) Membrane for Managing Trabeculectomy Flap- Related Over-Filtration Due to Unavailability of Scleral Patch Graft during Nation-Wide Lockdown

Scleral flap tears during trabeculectomy are difficult to repair in a predictable fashion. Donor scleral flap reinforcements are commonly preferred for managing trabeculectomy flap-related over-filtration, leading to shallow anterior chamber (AC). Due to the advent of COVID-19 lockdown, especially in the initial phases, eye banking activities almost came to a standstill, with almost no corneal and/or scleral tissue retrievals. Hence, in this manuscript we have presented a mini case series with follow-up of two of our cases; where Gore-Tex (e-polytetrafluoroethylene) implant was used as an alternative to scleral patch graft, for managing trabeculectomy flap-related over-filtration, with their pros and cons. Though Gore-Tex implant stability in both cases were contentious, it still served the purpose of managing the flap-related over- filtration and subsequent shallow AC.

Reduction of Ammonia Emissions from Laying Hen Manure in a Closed Composting Process Using Gas-Permeable Membrane Technology

Nitrogen losses during composting processes lead to emissions problems and reduce the compost fertilizer value. Gas-permeable membranes (GPM) are a promising approach to address the challenge of reducing nitrogen losses in composting processes. This study investigated the applicability of two GPM membrane systems to recover N released during the closed composting process of laying hen manure. The ammonia (NH3) capture process was performed using two different systems over a period of 44 days: the first system (S1) consisted of 120 m of an expanded polytetrafluoroethylene (ePTFE) membrane installed inside a 3.7 m3 portable, closed aerobic composter with forced ventilation; the second system (S2) consisted of 474 m of an ePTFE membrane placed inside as an external module designed for NH3 capture, connected to a closed aerobic composter through a pipe. In both cases, a 1 N H2SO4 acidic NH3 capture solution was circulated inside the membranes at a flow rate of 2.1 L·h−1. The amount of total ammonia nitrogen (TAN) recovered was similar in the two systems (0.61 kg in S1 and 0.65 kg in S2) due to the chosen membrane surface areas, but the TAN recovery rate was six times higher in system S1 (6.9 g TAN·m−2·day−1) than in system S2 (1.9 g TAN·m−2·day−1) due to the presence of a higher NH3 concentration in the air in contact with the membrane. Given that the NH3 concentration in the atmosphere of the membrane compartment directly influences the NH3 capture, better performance of the GPM recovery system may be attained by installing it directly inside the closed aerobic composters. Regardless of the chosen configuration, this technology allows N recovery as a stable and concentrated 1.4% N ammonium salt solution, which can be used for fertigation. The presented GPM systems may be used in community composting systems with low volumes of waste to be treated or in livestock facilities that have implemented best available techniques such as solid–liquid separation or anaerobic digestion, provided that the use of GPM technology in combination with these techniques also contributes to odor mitigation and improves biogas yields.

Pilot Plant for the Capture of Ammonia from the Atmosphere of Pig and Poultry Farms Using Gas-Permeable Membrane Technology.

Gas-permeable membrane (GPM) technology is a possible solution to reduce ammonia (NH3) emissions from livestock housing. This paper presents the results obtained with an NH3-capture prototype based on the use of expanded polytetrafluoroethylene (ePTFE) membranes in real conditions in a gestating sow house and a free-range laying hen house, comparing them with the results obtained in controlled laboratory conditions for the same type of waste. The NH3 present in the air of the livestock housing was captured by reaction with an acidic solution flowing inside the membranes. The periods of continuous operation of the pilot plant were 232 days at the pig farm and 256 days at the poultry farm. The NH3 recovery rate at the end of those periods was 2.3 and 0.4 g TAN·m−2·d−1 in the pig and the poultry farms, respectively. The limiting factor for the capture process was the NH3 concentration in the air, with the highest recovery occurring in the most concentrated atmosphere. Differences in NH3 capture were observed between seasons and farms, with capture efficiencies of 1.62 and 0.33 g·m−2·d−1 in summer and 3.85 and 1.20 g·m−2·d−1 in winter for pig and poultry farms, respectively. The observed differences were mainly due to the higher ventilation frequency in the summer months, which resulted in a lower NH3 concentration inside the houses compared to the winter months. This is especially important when considering the real applicability of this technology. The results obtained suggest that GPM technology holds promise for limiting NH3 emissions from livestock housing with NH3 ambient concentrations close to 20 ppm or as part of manure storage facilities, given that it allows for recovery of nitrogen in a stable and concentrated solution, which can be used as a fertilizer.

A Percutaneous Catheter Solution as a Spacer for Regurgitant Heart Valve Disease

Spacers, such as FORMA (Edwards Lifescience) or Mitraspacer, are used to treat mitral regurgitation or tricuspid regurgitations. However, they require external therapeutic liquid filler injection into the spacer device. This should be leak-tight over the time of implantation, which is a major limitation in device design. Here, we propose a self-expandable spacer with a nitinol inner mesh and expanded poly (tetrafluoroethylene) (ePTFE) coating that also functions as a spacer. We designed nitinol 3D mesh templates, coated with a commercially available low and high durometer ePTFE membrane. Finally, we implanted the spacer into a swine pulmonary artery and right atrium (superior vena cava) as an intervention technique. Twenty-four swine were used, except in two cases suspected of procedural infection. The results were analyzed in the remaining 22 cases and all devices were easily delivered and had good function in self-expansion and implantation. After eight weeks, all individuals were examined for gross and pathological analysis to determine the biological safety of the device. There was no evidence of damage or other abnormalities and increased postoperative endothelialization outside of ePTFE coatings. In conclusion, this study suggests using a self-expandable spacer to complement the medical limitations of the existing filling-type spacer devices.

Pathological Change and Whole Transcriptome Alternation Caused by ePTFE Implantation in Myocardium.

Expanded polytetrafluoroethylene (ePTFE) is commonly used in cardiovascular surgery, but usually causes postoperation complications. Although great efforts have been done to relieve these complications or to understand their mechanism, there are no applicable strategies available and no understanding mechanisms, especially in the myocardium. Here, ePTFE membranes are implanted into the right ventricular outflow tract of rabbits, and the implant-related myocardium is dissected and analyzed by histology and transcriptome sequencing. ePTFE implantation causes myocardium inflammation and fibrosis. There are 1867 differently expressed mRNAs (DEmRNAs, 1107 upregulated and 760 downregulated) and 246 differently expressed lncRNAs (DElncRNAs, 110 upregulated and 136 downregulated) identified. Bioinformatic analysis indicates that the upregulated DEmRNAs and DElncRNAs are mainly involved in inflammatory, immune responses, and extracellular matrix remodeling, while the downregulated DEmRNAs and DElncRNAs are predominantly functioned in the metabolism and cardiac remodeling. Analysis of coexpression and regulatory relationship of DEmRNAs and DElncRNAs reveals that most DElncRNAs are trans-regulated on the relevant DEmRNAs. In conclusion, ePTFE implantation causes severe myocardial tissue damages and alters the transcriptome profiles of the myocardium. Such novel data may provide a landscape of mechanisms underlying the adverse reactions caused by ePTFE implantation and uncover new therapeutic targets for inhibiting the ePTFE-related complications.

Osseointegration of Dental Implants in Ridges with Insufficient Bones Using Different Membranes for Guided Bone Regeneration

Background:The use of membrane with the guided bone regeneration (GBR) has been a controversial aspect of the implant placement, which helps achieve the primary graft stabilization and inhibit early graft loss.Objectives:The present clinical trial was aimed to determine the results of GBR with nonresorbable (expanded polytetrafluoroethylene [e-PTFE]) and resorbable (collagen) membrane both clinically and radiographically for 2 years with dental implant placement.Materials and Methods:16 subjects having 32 sites for implant placement in a split-mouth pattern were included in the study. The sites for implant was prepared and grafted with the autogenous graft procured from the mandibular ramus area followed by graft coverage with either e-PTFE or collagen membrane. Various radiographic and clinical parameters were assessed for 2 years at an interval of 6 months each. The collected data were recorded for each study subject for all the implant sites and were statistically analyzed.Results:The mean values for periodontal probing depth at 6 months, 12 months, 18 months, and 24 months were 2.25 ± 0.17, 2.67 ± 1.84, 2.64 ± 1.21, and 3.01 ± 0.52, respectively, for the e-PTFE group. For the collagen group, the probing depth mean values at 6 months, 12 months, 18 months, and 24 months were 2.30 ± 0.14, 2.59 ± 1.76, 2.62 ± 1.30, and 2.98 ± 0.81, respectively. The corresponding clinical and radiographic parameters at all time intervals were nonsignificant on the intergroup comparison.Conclusion:Dental implants placed with simultaneous GBR have an acceptable survival rate at the end of 2 years irrespective of the resorbable or non-resorbable membrane used.

Enhanced output and wearable performances of triboelectric nanogenerator based on ePTFE microporous membranes for motion monitoring

Triboelectric nanogenerators (TENGs) have attracted significant attentions in wearable electronics as self-powered systems. Endowing TENGs with excellent waterproof and breathable functions is critical for their wearable applications. Herein, the expanded polytetrafluoroethylene (ePTFE) calendared sheets were stretched into microporous membranes and used as negative material of TENG device. The excessively expanded micropores of the membrane were considered to sacrifice the surface area, which was adverse to the triboelectric output. Thereby, a series of lower stretching temperatures were chosen for weakening molecular mobility to obtain a membrane (U-300-40) with smaller pore size but maintain a large porosity. As a result, the open-circuit voltage, short-circuit current and transferred charge reached approximately 120 V, 9.5 μA and 44 nC, respectively. Additionally, the water contact angle of 138° and the moisture permeability of 5200 g/m2·24 h presented the potential wearable applications. In order to further improve the wearable performances, the U-300-40 continued to be transversely stretched. The pore size of the membrane (B-200) was only 0.1 µm, which was almost one order of magnitude smaller than that of the uniaxially-stretched membrane owning a similar porosity. Benefiting from the optimized structure, the moisture permeability was further enhanced to 7000 g/m2·24 h, but the output was less impacted. Finally, the fabricated TENG was demonstrated to be a reliable electronic good at monitoring and distinguishing some knee motions. Accordingly, the optimized ePTFE membrane opens an effective route to balance its output and wearable performances, which exhibits a promising application in automatically monitoring the body motions.

Optimized microporous structure of ePTFE membranes by controlling the particle size of PTFE fine powders for achieving high oil-water separation performances

Advanced functional membranes consisting of low surface energy and tailored micropores are promising materials for oil-water separation applications. However, obtaining a high porosity yet controllable pore sizes to achieve high separation efficiency and flux remains challenging. Herein, four kinds of polytetrafluoroethylene (PTFE) powders with different particle sizes were simply sieved from a commercial resin and corresponding microporous membranes were fabricated through paste extrusion and thermal stretching processes. The microporous structure exhibited that choosing smaller powders caused the decrease of pore size but can still maintain a high porosity in stretched membranes, which was difficult to be realized by controlling processing conditions. The increased contact interfaces among small powders were regarded to promote the fibrillation during extrusion, thereby more entangled sites of fibrils were generated and only required a small amount of extension to get the target deformation during stretching. Consequently, more micropores with a smaller size were owned in the membrane by using smaller powders, which gave rise to superhydrophobicity with an ultrahigh water contact angle of 152° and superfast oil infiltration. As expected, the oil-water separation experiment obtained high separation efficiency closing 100% and the flux of 7500 L/m2·h, which were competitive in comparison to most of previously-reported PTFE microporous membranes. More significantly, such an outstanding separation capacity was suitable for many kinds of oils with different densities and almost stable even after 15 cycles. Meanwhile, the microporous structure of the membrane prepared by using smaller powders was also proven to be deformed more slowly when subjected to a large strain. Accordingly, this work provides a new and practical approach for fabricating PTFE microporous membranes suitable for applying in a wide variety of oil-water separation fields.

Expanded Polytetrafluoroethylene Conduits With Bulging Sinuses and a Fan-Shaped Valve in Right Ventricular Outflow Tract Reconstruction

We developed a handmade expanded polytetrafluoroethylene (ePTFE) pulmonary valvular conduit (PVC) with bulging sinuses and a fan-shaped ePTFE valve for right ventricular outflow tract (RVOT) reconstruction. We aimed to investigate the results of this device in this multicenter study. From 2001 to 2020, 1776 patients underwent RVOT reconstruction using ePTFE PVCs at 65 institutions in Japan. The median age and body weight were 4.1 years (range, 3 days to 67.1 years) and 13.3 (range, 1.8-91.3) kg, respectively. The median PVC size was 18 (range, 8-24) mm. The median Z-value of the ePTFE PVC was 1.1 (range, -3.8 to 5.0). The ePTFE PVC conditions were investigated by cardiac echocardiography and catheterization. The median follow-up period was 3.3 years (range, 0 day to 16.2 years). There were only 9 cases (0.5%) with PVC-related unknown deaths. Reintervention was performed in 283 patients (15.9%), and 190 patients (10.7%) required explantation. Freedom from reintervention and explantation at 5/10 years were 86.7/61.5% and 93.0/69.1%, respectively. At the latest echocardiography, PVC regurgitation grade was better than mild in 88.4% patients. The average peak RVOT gradient was 15.7 ± 15.9 mm Hg at the latest cardiac catheterization. ePTFE PVC infection was detected in only 8 patients (0.5%). Relative stenosis due to somatic growth was the most common cause of PVC explantation. The performance of ePTFE in terms of durability, valvular performance, and the resistance against infection is considerable and may replace conventional prosthetic materials. Further improvement of the ePTFE membrane is essential to prevent valvular dysfunction.