ePTFE Membrane Research Articles

Scientific evaluation on biodegradable and biofunctional polyurethane incorporated chitosan/elastin electrospun membranes in compared with synthetic polymeric expanded polytetrafluoroethylene and polyethylene terephthalate vascular membranes

Cardiovascular disease is a life-threatening health problem. Employing vascular membranes is one of the treatment options in cardiovascular surgery to replace damaged vascular tissues. However, certain limitations associated with synthetic polymeric vascular membranes (expanded polytetrafluoroethylene (e-PTFE) and polyethylene terephthalate (PET)) such as low biodegradability and biofunctional, may lead to thrombosis, inflammatory response, and tissue necrosis. Polyurethane (PU) is commonly applied in vascular engineering, owing to its good biocompatibility and biodegradability. Incorporating chitosan (CS) and elastin (EL) into the PU matrix, specifically in the design of electrospun nanofibrous membrane, is expected to enhance the biological properties of PU. These improvements are crucial to overcome the limitations of synthetic vascular membranes. Previously, there was no scientific comparison between synthetic vascular membranes and the improved design of PU-based nanofibrous membranes. This scientific comparison is pivotal to allow more research exploration on biodegradable and biofunctional materials towards the fabrication of vascular membranes. Herein, the physicochemical, biodegradability, and biofunctional capability of the electrospun PU-based electrospun membranes and two synthetic membranes were compared. Both PU and PU/CS/ES electrospun membranes were annotated with N–H, C–H, and C–N groups with the appearance of elongated fibers. The –CF2 group was presented in the e-PTFE membranes with the view of expanded fibril structure and interconnecting nodes. Whereas for the PET membranes, C=C, C=O, and C–O groups were noticed with the appearance of homogeneous knitted morphology. The PU/CS/ES membranes were found to be more hydrophilic than the PU and the synthetic membranes. The incorporation of CS and EL in the matrix of electrospun PU has improved the PU's biodegradability up to 23.86 ± 5.86 % at 60 days of incubation with the view of swollen and degraded elongated fibers, following the degradation test. Both synthetic polymeric membranes were declared non-biodegradable with less than 7 % degradation at similar incubation timepoint. The PU/CS/ES membranes were also found biofunctional with the most 82 ± 0.49 % of cell viability, protruded cell filopodia, and 44.24 ± 13.99 % scratch cell closure within 24 h of incubation. The incorporation of CS and EL into the PU matrix has improved the biodegradability and biofunctionality compared to the pure PU and synthetic polymeric membranes. Thus, highlight the suitability of PU/CS/ES electrospun membranes to be applied in cardiovascular tissue engineering.

Moisture barriers used in firefighters' protective clothing: Effect of accelerated hydrothermal aging on their mechanical and barrier performance

AbstractFirefighters' protective clothing rely on moisture barriers to safeguard against liquid ingress while enabling sweat evaporation for comfort and safety. However, these moisture barriers can degrade over time, jeopardizing firefighters' safety. Existing evaluation methods, primarily visual inspection, are inadequate for assessing moisture barrier integrity in service. This study examines the effect of accelerated hydrothermal aging on the tear force, water vapor transmission rate (WVTR), and apparent contact angle in three moisture barrier models used in firefighter protective clothing. The moisture barriers studied varied in composition, structure, and base fabric fiber content. Results revealed that moisture barriers' responses to aging are influenced by factors, such as fabric structure, adhesive configuration, finish, and the presence of additional coatings. The hardening of the adhesive layer between the ePTFE membrane and the base fabric was observed in two of the moisture barriers, leading to a slight tear force reduction. Two of the moisture barriers also experienced crack and pit formation on the membrane side, which affected the WVTR. The water‐repellent finish on the fabric side degraded in one moisture barrier. Understanding these complex behaviors is essential for predicting the long‐term moisture barrier performance and enhancing firefighter safety.

Use of the PRECLUDE® pericardial e-PTFE membrane in ophthalmology

This article provides an overview of the diverse applications of the PRECLUDE® pericardial e-PTFE membrane in ophthalmology. The e-PTFE membrane was found to be safe and effective as an alternative surgical procedure for perforating corneal ulcer closures. It could be a method of choice for eye preservation or during delayed corneal transplantation, especially in immunocompromised patients. After membrane removal, penetrating keratoplasty can be performed as a definitive treatment with better prognosis as “à-chaud” keratoplasty in all eyes, as a prognosis of visual acuity improvement is expected. E-PTFE membrane implantation for use after uneventfully performed trabeculectomy with still-uncontrolled postoperative intraocular pressure (IOP) in severe refractory glaucoma represents an additional approach for treating uncontrolled secondary glaucoma. This modified trabeculectomy can be used as surgical treatment and for refractory traumatic glaucoma cases. The e-PTFE membrane can be used in cases where antimetabolite-related risk must be avoided. Our new surgical treatment after trabeculectomy is a simple and safe procedure and can be used as a filtration-modulating device in all refractory glaucomas.

Long-term Outcomes With Expanded Polytetrafluoroethylene Valved Conduits in Pediatric Patients

BackgroundThe expanded polytetrafluoroethylene (ePTFE) valved conduit (VC) has been reported for pulmonary valve replacement (PVR). The purpose of this study was to review long-term outcomes of our trileaflet ePTFE VC. MethodsThis multicenter study was performed with institutional review board approval from each institution. Our VC is fashioned from commercially available ePTFE tube grafts (for the conduit) and 0.1-mm-thick ePTFE membrane (for the trileaflet material). The patients were followed up in our clinic. Valve function was assessed by echocardiography in the operating room and at follow-up clinic visits after implantation. ResultsFifty-five patients received ePTFE VC between 2012 and 2023 (16-28 mm in diameter). Patients’ age at the time of implantation ranged from 6 months to 20 years (median, 7.5 years). Clinical follow-up ranged from 4 days to 10.1 years (average, 3.6 years). There were no hospital deaths. There were 2 non–valve-related late deaths. There have been no cases of endocarditis. Two patients required balloon dilation for the distal pulmonary artery stenosis, and 1 patient required residual ventricular septal defect closure. Five patients have received transcatheter PVR (TPVR) because of increased pressure gradient across the VC. Freedom from TPVR at 10 years was 90%. No valves required explantation or surgical replacement. ConclusionsCompared with historical data for other PVR options, our ePTFE VC shows excellent long-term performance and, when required, provides an easily accessible “landing zone” for TPVR. Our technique is easily learned, is reproducible, and can be a valuable option for surgeons performing PVR in pediatric patients.

Trichome-Like Biomimetic Air Filters via Templated Silicone Nanofilaments.

Air pollution threats to human health have increased awareness of the role of filter units in air cleaning applications. As an ideal energy-saving strategy for air filters, the slip effect on nanofiber surfaces can potentially overcome the trade-off between filtration efficiency and pressure drop. However, the potential of the slip effect in nanofibrous structures is significantly limited by the tight nanofiber stacks. In this study, trichome-like biomimetic (TLB) air filters with 3D-templated silicone nanofilaments (average diameter: ≈74 nm) are prepared based on an in situ chemical vapor deposition (CVD) method inspired by plant purification. Theoretical modeling and experimental results indicate that TLB air filters make significant use of the slip effect to overcome the efficiency-resistance tradeoff. The selectable filter class (up to U15, ≈99.9995%) allows TLB air filters to meet various requirements, and their integral filtration performance surpasses that of most commodity air filters, including melt-blown cloth, ePTFE membranes, electrospun mats, and glass fiber paper. The proposed strategy directly transforms commercial filter media and filters into TLB air filters using a bottom-up, one-step approach. As a proof-of-concept, reusable N95 respirators and air purifiers equipped with TLB air filters are fabricated, overcoming the limitations of existing filter designs and fabrication methods.

Polymeric Semiconductor in Field-Effect Transistors Utilizing Flexible and High-Surface Area Expanded Poly(tetrafluoroethylene) Membrane Gate Dielectrics.

Organic field-effect transistors (OFETs) were fabricated using three high-surface area and flexible expanded-poly(tetrafluoroethylene) (ePTFE) membranes in gate dielectrics, along with the semiconducting polymer poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl)-alt-(2,2':5',2″:5″,2‴-quaterthiophen-5,5‴-diyl)] (PDPP4T). The transistor behavior of these devices was investigated following annealing at 50, 100, 150, and 200 °C, all sustained for 1 h. For annealing temperatures above 50 °C, the OFETs displayed improved transistor behavior and a significant increase in output current while maintaining similar magnitudes of Vth shifts when subjected to static voltage compared to those kept at ambient temperature. We also tested the response to NO2 gas for further characterization and for possible applications. The ePTFE-PDPP4T interface of each membrane was characterized via scanning electron microscopy for all four annealing temperatures to derive a model for the hole mobility of the ePTFE-PDPP4T OFETs that accounts for the microporous structure of the ePTFE and consequently adjusts the channel width of the OFET. Using this model, a maximum hole mobility of 1.8 ± 1.0 cm2/V s was calculated for the polymer in an ePTFE-PDPP4T OFET annealed at 200 °C, whereas a PDPP4T OFET using only the native silicon wafer oxide as a gate dielectric exhibited a hole mobility of just 0.09 ± 0.03 cm2/V s at the same annealing condition. This work demonstrates that responsive semiconducting polymer films can be deposited on nominally nonwetting and extremely bendable membranes, and the charge carrier mobility can be significantly increased compared to their as-prepared state by using thermally durable polymer membranes with unique microstructures as gate dielectrics.

The Impact of Heli-FX EndoAnchor Application on Endograft Material: An Experimental Study

The Impact of Heli-FX EndoAnchor Application on Endograft Material: An Experimental Study

Bone augmentation in dental implants among Indian patients.

It is of interest to compare guided bone regeneration (GBR) with titanium mesh, alveolar distraction osteo-genesis (DO), GBR with auto-genous bone and e-PTFE membranes and onlay bone grafts. This helps to restore vertically lacking alveolar ridges and their capacity to sustain the vertical bone growth acquired both prior to and following implant placement. The parameters such as (i) success and survival of dental implants (ii) peri-implant clinical parameters after prosthetic loading at 1 year, 2 year and 3 year follow up (iii) resorption of alveolar ridge regenerated before placement of dental implants and after placement of dental implants were assessed. Data shows that the distraction osteo-genesis is more predictable for long-term prognosis of vertical bone growth. However, all methods help to repair the vertically resorbed edentulous ridges.

Critical-size defects reconstruction with four different bone grafts associated with e-PTFE membrane: Ahistomorphometric experimental invivo study.

The goal of this study was to assess the newly formed bone and the remnant biomaterial by comparing four different bone grafts used to treat critical-size defects, associated or not with the non-resorbable membrane. Two calvaria critical-size bone defects were created in 50 male Wistar rats. They were divided into blood (G1), autogenous (G2), bioglass (G3), hydroxyapatite (G4), and xenograft (G5) groups, associated or not with e-PTFE. The experimental periods were 15 and 45 days. Sections were prepared for histomorphometric assessment. All data were analyzed by the mixed-effects model with multiple comparisons (significance level, p < .05). A similar level of new bone was observed for all groups, associated with a high level of vascularization. G1 and G2 ensured sovereignty over the greater quantity of new bone. A non-significant result was reported comparing groups with and without membranes. No significant result was found between the experimental synthetic biomaterials (G3 and G4). G5L achieved 22.0% of new bone after 45 days (p > .05). All groups had a stable volume of biomaterial kept in the short term (p > .05). G2 was the best material for new bone formation and final volume of biomaterial, followed by G4 < G5 < G3. Thus, it is possible that G4 had a better degradation profile among the experimental groups. The best results were found in the autogenous group, with higher resorption and integration; non-significative new bone was found among the experimental groups; and the regeneration of critical bone defects using an e-PTFE barrier did not present significant results on new bone formation.

A continuous polytetrafluoroethylene foam-coating to glass fiber mat with superior self-cleaning, antistatic and high filtration efficiency performances

Air pollution has become a significant global environmental issue, leading to adverse health effects and respiratory diseases. To address this challenge, expanded polytetrafluoroethylene (ePTFE) membrane-based fibrous filters have gained popularity in the past decade. However, the thinness and low mechanical strength of ePTFE membranes make them susceptible to damage from particle collisions. As an alternative to ePTFE membranes, PTFE emulsion has emerged as a promising approach to enhance filtration efficiency. However, due to PTFE's low surface energy and high crystallinity, it is difficult for PTFE to self-bond into a membranes and adhere to substrates. Therefore, the filtration efficiency of PTFE-impregnated filter materials does not meet the requirements for ultra-low emissions, and they have poor wear resistance, resulting in a short service life. Herein, we fabricate a PTFE emulsion foam-coating membrane filter. The influences of the contents of PVA on the film morphology, air permeability, pore size and distribution, abrasive resistance and antistatic properties were analyzed. The self-cleaning performance was simulated and the filtration performance was measured as well. Notably, the frictional mass loss index of the PTFE emulsion foam-coating membrane filter was 0.07. After 30 cycles, the filtration efficiency was 98.93%, and the strip ratio was 91.03%. Our design of the PTFE emulsion foam-coating provided a new direction for the application of PTFE emulsion in the filtration field with superior self-cleaning, antistatic and high filtration efficiency performances.

Comparison of microfiltration performances of ePTFE and PCTE membranes in IPA and deionized water

Isopropyl alcohol (IPA) is widely used as a cleaning and drying agent in semiconductor manufacturing. The purity of chemicals is becoming increasingly stricter as the leading-edge node sizes become smaller. The microfiltration of nanoparticles (NPs) in water has been extensively studied by many research groups. However, studies on microfiltration in IPA are rare. In this study, we conducted experiments to determine the filtration of nanoparticles using expanded polytetrafluoroethylene (ePTFE) and polycarbonate track-etched (PCTE) membranes in both deionized water (DIW) and IPA. The zeta potentials (ZP) of the polymers and particles were measured. The Hamaker constant and its effect on particle capture were estimated using Derjaguin–Landau–Verwey–Overbeek theory. The results show that the retention efficiency of the two membranes (five different pore sizes) for Ag NPs (size: 20–100 nm) in IPA was much higher than that in DIW. However, the retention efficiencies of the two membranes in IPA and DIW increase monotonically upon increasing the particle size, which was completely different from the U-shaped curve for aerosol filtration predicted using the previous liquid model. In addition, the absolute ZP value of the NPs and membrane surface in IPA was found to be much smaller than that of DIW.

Modulation of gene expression and bone formation by expanded and dense polytetrafluoroethylene membranes during guided bone regeneration: An experimental study.

Nonresorbable membranes promote bone formation during guided bone regeneration (GBR), yet the relationships between membrane properties and molecular changes in the surrounding tissue are largely unknown. To compare the molecular events in the overlying soft tissue, the membrane, and the underlying bone defect during GBR using dual-layered expanded membranes versus dense polytetrafluoroethylene (PTFE) membranes. Rat femur defects were treated with either dense PTFE (d-PTFE) or dual-layered expanded PTFE (dual e-PTFE) or left untreated as a sham. Samples were collected after 6 and 28 days for gene expression, histology, and histomorphometry analyses. The two membranes promoted the overall bone formation compared to sham. Defects treated with dual e-PTFE exhibited a significantly higher proportion of new bone in the top central region after 28 days. Compared to that in the sham, the soft tissue in the dual e-PTFE group showed 2-fold higher expression of genes related to regeneration (FGF-2 and FOXO1) and vascularization (VEGF). Furthermore, compared to cells in the d-PTFE group, cells in the dual e-PTFE showed 2.5-fold higher expression of genes related to osteogenic differentiation (BMP-2), regeneration (FGF-2 and COL1A1), and vascularization (VEGF), in parallel with lower expression of proinflammatory cytokines (IL-6 and TNF-α). Multiple correlations were found between the molecular activities in membrane-adherent cells and those in the soft tissue. Selective surface modification of the two sides of the e-PTFE membrane constitutes a novel means of modulating the tissue response and promoting bone regeneration.

Construction of Stretchable and Large Deformation Green Triboelectric Nanogenerator and Its Application in Technical Action Monitoring of Racket Sports

The rapid development of E-Skin has attracted researchers’ attention to portable wearable devices. However, it is a great challenge to achieve high-output performance and high-environmental protection simultaneously. Polyhydroxybutyrate (PHB) has excellent electron-withdrawing ability and biodegradability, but its stretching ability is poor, which limits its application in portable wearable devices. In this paper, the biocompatible poly(lactide-co-caprolactone) (PLCL) was innovatively selected to modify the properties of the PHB electrospun membranes, and PHB/PLCL composite membranes with different contents of PLCL were constructed. Then, the expanded polytetrafluoroethylene (ePTFE) membranes and PHB/PLCL electrospun membranes were used as the friction layers to construct a flexible triboelectric nanogenerator (TENG). With the increase of PLCL contents, the elastic recovery rate of the composite membranes increased to 68% of tension at 40% strain. The toughness of the composite membrane was increased by 546%, which exhibits ultratoughness and stretchable properties. Based on the ultratoughness and high elasticity electrospun membranes with 50% PLCL, a stretchable and large deformation sensing device was made. The PHB/PLCL-ePTFE TENG could distinguish pingpong and badminton accurately, as well as their various postures such as forehand, backhand, smash poses, etc., which provided a new idea for large deformation monitoring of TENGs.

Device-modified trabeculectomy for glaucoma.

Glaucoma is an optic neuropathy that leads to visual field defects and vision loss. It is the second leading cause of irreversible blindness in the world. Treatment for glaucoma aims to reduce intraocular pressure (IOP) to slow or prevent further vision loss. IOP can be lowered with medications, laser, or incisional surgery. Trabeculectomy is a surgical approach which lowers IOP by shunting aqueous humor to a subconjunctival bleb. Device-modified trabeculectomy techniques are intended to improve the durability and safety of this bleb-forming surgery. Trabeculectomy-modifying devices include the Ex-PRESS, the XEN Gel Stent, the PreserFlo MicroShunt, as well as antifibrotic materials such as Ologen, amniotic membrane, expanded polytetrafluoroethylene (ePTFE) membrane, Gelfilm and others. However, the comparative effectiveness and safety of these devices are uncertain. To evaluate the benefits and harms of different devices as adjuncts to trabeculectomy on IOP control in eyes with glaucoma compared to standard trabeculectomy. We used standard, extensive Cochrane search methods. The latest search was August 2021. We included randomized controlled trials in participants with glaucoma comparing device-modified trabeculectomy techniques with standard trabeculectomy. We included studies that used antimetabolites in either or both treatment groups. We used standard Cochrane methods. Our primary outcomes were 1. change in IOP and 2. mean postoperative IOP at one year. Our secondary outcomes were 3. mean change in IOP from baseline, 4. mean postoperative IOP at any time point, 5. mean best-corrected visual acuity (BCVA), 6. visual field change, 7. quality of life, 8. proportion of participants who are drop-free at one year, 9. mean number of IOP lowering medications at one year, and 10. proportion of participants with complications. Eight studies met our inclusion criteria, of which seven were full-length journal articles and one was a conference abstract. The eight studies included 961 participants with glaucoma, and compared two types of devices implanted during trabeculectomy versus standard trabeculectomy. Seven studies (462 eyes, 434 participants) used the Ex-PRESS, and one study (527 eyes, 527 participants) used the PreserFlo MicroShunt. No studies using the XEN Gel Stent implantation met our criteria. The studies were conducted in North America, Europe, and Africa. Planned follow-up periods ranged from six months to five years. The studies were reported poorly, which limited our ability to judge risk of bias for many domains. None of the studies explicitly masked outcome assessment. We rated seven studies at high risk of detection bias. Low-certainty of evidence from five studies showed that using the Ex-PRESS plus trabeculectomy compared with standard trabeculectomy may be associated with a slightly lower IOP at one year (mean difference (MD) -1.76 mmHg, 95% confidence interval (CI) -2.81 to -0.70; 213 eyes). Moderate-certainty of evidence from one study showed that using the PreserFlo MicroShunt may be associated with a slightly higher IOP than standard trabeculectomy at one year (MD 3.20 mmHg, 95% CI 2.29 to 4.11). Participants who received standard trabeculectomy may have a higher risk of hypotony compared with those who received device-modified trabeculectomy, but the evidence is uncertain (RR 0.73, 95% CI 0.46 to 1.17; I² = 38%; P = 0.14). In the subgroup of participants who received the PreserFlo MicroShunt, there was a lower risk of developing hypotony or shallow anterior chamber compared with those receiving standard trabeculectomy (RR 0.44, 95% CI 0.25 to 0.79; 526 eyes). Device-modified trabeculectomy may lead to less subsequent cataract surgery within one year (RR 0.46, 95% CI 0.27 to 0.80; I² = 0%). Use of an Ex-PRESS plus trabeculectomy may produce greater IOP reduction at one-year follow-up than standard trabeculectomy; however, due to potential biases and imprecision in effect estimates, the certainty of evidence is low. PreserFlo MicroShunt may be inferior to standard trabeculectomy in lowering IOP. However, PreserFlo MicroShunt may prevent postoperative hypotony and bleb leakage. Overall, device-modified trabeculectomy appears associated with a lower risk of cataract surgery within five years compared with standard trabeculectomy. Due to various limitations in the design and conduct of the included studies, the applicability of this evidence synthesis to other populations or settings is uncertain. Further research is needed to determine the effectiveness and safety of other devices in subgroup populations, such as people with different types of glaucoma, of various races and ethnicity, and with different lens types (e.g. phakic, pseudophakic).

Expanded Polytetrafluoroethylene Membranes for Vascular Stent Coating: Manufacturing, Biomedical and Surgical Applications, Innovations and Case Reports

Coated stents are defined as innovative stents surrounded by a thin polymer membrane based on polytetrafluoroethylene (PTFE)useful in the treatment of numerous vascular pathologies. Endovascular methodology involves the use of such devices to restore blood flow in small-, medium- and large-calibre arteries, both centrally and peripherally. These membranes cross the stent struts and act as a physical barrier to block the growth of intimal tissue in the lumen, preventing so-called intimal hyperplasia and late stent thrombosis. PTFE for vascular applications is known as expanded polytetrafluoroethylene (e-PTFE) and it can be rolled up to form a thin multilayer membrane expandable by 4 to 5 times its original diameter. This membrane plays an important role in initiating the restenotic process because wrapped graft stent could be used as the treatment option for trauma devices during emergency situations and to treat a number of pathological vascular disease. In this review, we will investigate the multidisciplinary techniques used for the production of e-PTFE membranes, the advantages and disadvantages of their use, the innovations and the results in biomedical and surgery field when used to cover graft stents.

Biaxial stretching of polytetrafluoroethylene in industrial scale to fabricate medical ePTFE membrane with node-fibril microstructure.

Expanded polytetrafluoroethylene (ePTFE) is promising in biomedical fields such as covered stents and plastic surgery owing to its excellent biocompatibility and mechanical properties. However, ePTFE material prepared by the traditional biaxial stretching process is with thicker middle and thinner sides due to the bowing effect, which poses a major problem in industrial-scale fabrication. To solve this problem, we design an olive-shaped winding roller to provide the middle part of the ePTFE tape with a greater longitudinal stretching amplitude than the two sides, so as to make up for the excessive longitudinal retraction tendency of the middle part when it is transversely stretched. The as-fabricated ePTFE membrane has, as designed, uniform thickness and node-fibril microstructure. In addition, we examine the effects of mass ratio of lubricant to PTFE powder, biaxial stretching ratio and sintering temperature on the performance of the resultant ePTFE membranes. Particularly, the relation between the internal microstructure of the ePTFE membrane and its mechanical properties is revealed. Besides stable mechanical properties, the sintered ePTFE membrane exhibits satisfactory biological properties. We make a series of biological assessments including in vitro hemolysis, coagulation, bacterial reverse mutation and in vivo thrombosis, intracutaneous reactivity test, pyrogen test and subchronic systemic toxicity test; all of the results meet the relevant international standards. The muscle implantation of the sintered ePTFE membrane into rabbits indicates acceptable inflammatory reactions of our sintered ePTFE membrane fabricated on industrial scale. Such a medical-grade raw material with the unique physical form and condensed-state microstructure is expected to afford an inert biomaterial potentially for stent-graft membrane.

A Stretchable Expanded Polytetrafluorethylene-Silicone Elastomer Composite Electret for Wearable Sensor.

Soaring developments in wearable electronics raise an urgent need for stretchable electrets. However, achieving soft electrets simultaneously possessing excellent stretchability, longevity, and high charge density is still challenging. Herein, a facile approach is proposed to prepare an all-polymer hybrid composite electret based on the coupling of elastomer and ePTFE membrane. The composite electrets are fabricated via a facile casting and thermal curing process. The obtained soft composite electrets exhibit constantly high surface potential (-0.38 kV) over a long time (30 days), large strain (450%), low hysteresis, and excellent durability (15,000 cycles). To demonstrate the applications, the stretchable electret is utilized to assemble a self-powered flexible sensor based on the electrostatic induction effect for the monitoring of human activities. Additionally, output signals in the pressure mode almost two orders of magnitude larger than those in the strain mode are observed and the sensing mechanism in each mode is investigated.

Expanded polytetrafluoroethylene/poly(3-hydroxybutyrate) (ePTFE/PHB) triboelectric nanogenerators and their potential applications as self-powered and sensing vascular grafts

Being able to detect or monitor the onset of thrombosis, recurrent stenosis, or other vascular disorders in newly transplanted vascular grafts will be very beneficial for patients who received the artificial blood vessel through bypass surgeries. The inherent advantages of triboelectric nanogenerators (TENGs) in self-powered signal monitoring presents a feasible solution. In this study, a double-layer TENG intended for self-powered and real-time sensing of vascular graft applications was constructed using two biocompatible materials commonly used in tissue engineering. In particular, an electrospun poly(3-hydroxybutyrate) (PHB) membrane as a positive tribomaterial was combined with an expanded polytetrafluoroethylene (ePTFE) membrane, a strong negative tribomaterial, to construct an ePTFE/PHB TENG. While possessing power generation, charging capacities, and operation stability, the ePTFE/PHB TENG was capable of supporting the growth of human umbilical vein endothelial cells (HUVECs) and monitoring changing hemodynamic conditions. Although many challenges remain and necessary future developments are needed, this study demonstrated the feasibility of a self-powered and sensing TENG vascular graft.

Comparison of the Ammonia Trapping Performance of Different Gas-Permeable Tubular Membrane System Configurations.

The technology of gas-permeable tubular membranes (GPMs) is promising in reducing ammonia emissions from livestock manure, capturing NH3 in an acidic solution, and obtaining final products suitable for valorization as fertilizers, in line with the principles of the circular economy. This study aimed to evaluate the performance of several e-PTFE membrane systems with different configurations for the recovery of NH3 released from pig slurry. Ten different configurations were tested: only a submerged membrane, only a suspended membrane in the same chamber, only a suspended membrane in an annex chamber, a submerged membrane + a suspended membrane in the same chamber, and a submerged membrane + a suspended membrane in an annex chamber, considering in each case the scenarios without and with agitation and aeration of the slurry. In all tests, sulfuric acid (1N H2SO4) was used as the NH3 capture solution, which circulated at a flow rate of 2.1 L·h-1. The results showed that NH3-N removal rates ranged from 36-39% (for systems with a single submerged or suspended membrane without agitation or aeration of the slurry) to 70-72% for submerged + suspended GPM systems with agitation and aeration. In turn, NH3-N recovery rates were found to be between 44-54% (for systems with a single membrane suspended in an annex compartment) and 88-91% (for systems based on a single submerged membrane). However, when choosing a system for farm deployment, it is essential to consider not only the capture and recovery performance of the system, but also the investment and operating costs (ranging from 9.8 to 21.2 €/kg N recovered depending on the selected configuration). The overall assessment suggests that the simplest systems, based on a single membrane, may be the most recommendable.

Outcomes of expanded polytetrafluoroethylene pericardial membrane implantation in left ventricular assist device explantation and heart transplantation.

Redo sternotomy and explantation of left ventricular assist devices (LVAD) for heart transplantation (HT) involve prolonged dissection, potential injury to mediastinal structures and/or bleeding. Our study compared a complete expanded polytetrafluoroethylene (ePTFE) wrap versus minimal or no ePTFE during LVAD implantation, on outcomes of subsequent HT. Between July 2005 and July 2018, 84 patients underwent a LVAD implant and later underwent HT. Thirty patients received a complete ePTFE wrap during LVAD implantation (Group 1), and 54 patients received either a sheet of ePTFE placed in the anterior mediastinum or no ePTFE (Group 2). Baseline characteristics were similar between Groups 1 and 2. Surgeons reported subjective improvements in speed, predictability, and safety of dissection with complete ePTFE compared with minimal or no ePTFE. Time from incision to initiation of cardiopulmonary bypass (CPB) were similar between groups (97 ± 38 vs. 89 ± 29 min, p = .3). Injury to mediastinal structures during the dissection was similar between groups (10% vs. 11%, p > .9). While surgeons reported less intraoperative bleeding in Group 1 (43% vs. 61%), this trend did not reach significance (p = .1). In-hospital mortality, intensive care unit length of stay and hospital length of stay were similar between both groups. In patients undergoing LVAD explant-HT, there was a trend towardreduced surgeon reported intraoperative bleeding with ePTFE placement. Despite qualitatively reported greater ease and speed of mediastinal dissection with ePTFE membrane placement, time to initiation of CPB did not differ, likely because surgeons remained cautious, allowing extra time for unanticipated difficulties.