Teflon Layer Research Articles

Delamination imaging in composites using cross-correlation method by non-contact air-coupled Lamb waves

This paper presents a cross-correlation damage detection technique using damage scattered waves of all directions cross-correlate with the incident waves for delamination imaging in carbon fiber reinforced polymer (CFRP) composite plate. The presented imaging can not only detect the delamination but also precisely quantify the damage with locations and sizes. First, a CFRP composite sample with interlaminar delamination by inserting the Teflon layer is designed and manufactured in house using the hot-press machine. And a three-dimensional model of composite sample is simulated using the finite element method. Next, the cross-correlation imaging algorithm is introduced in detail, and the cross-correlation imaging proof-of-concept study is conducted with the simulated Lamb waves in the composite sample. Finally, a fully non-contact air-coupled transducer and scanning laser Doppler vibrometer system with a single-mode Lamb wave method is established to actuate and sense the interrogating Lamb waves in the structure. The imaging method is experimentally implemented for the one delamination and two delaminations imaging and quantification.

Fabrication and characteristics of electret ultrasonic‐sensor using laser patterning

AbstractIn this study, in an electret capacitor sensor (ECS), which is an electromechanical exchange device consisting of an electret sandwiched between two electrodes, ridges as spacers and grooves as gaps were formed in the PTFE (polytetrafluoroethylene) layer of the insulating electrode by laser ablation. The ECSs were then fabricated using PTFE electrets, and the charge retention and airborne ultrasonic wave transmitting and receiving characteristics were investigated. The charge retention characteristics of the ECS with laser‐patterned insulating electrodes were slightly lower than those of the silica‐aggregate electret. As the thickness of the insulating layer increased or the groove width decreased, the transmitting and receiving sensitivity increased significantly and then peaked and degraded at the measurements of transmitting and receiving. The ECS with the highest peak sensitivity obtained by laser patterning had a bandwidth comparable to that of the conventional ECS with silica aggregate electret, but the peak sensitivity was improved by up to 8 dB. Therefore, laser patterning could contribute to the improvement of ECS performance.

A super wear-resistant coating for Mg alloys achieved by plasma electrolytic oxidation and discontinuous deposition

Magnesium alloys are lightweight materials with great potential, and plasma electrolytic oxidation (PEO) is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys. However, the ∼14 µm thick and rough PEO protection layer has inferior wear resistance, which limits magnesium alloys as sliding or reciprocating parts, where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting. Here a novel super wear-resistant coating for magnesium alloys was achieved, via the discontinuous sealing (DCS) of a 1.3 µm thick polytetrafluoroethylene (PTFE) polymer layer with an initial area fraction (Af) of 70% on the necessary PEO protection layer by selective spraying, and the wear resistance was exceptionally enhanced by ∼5500 times in comparison with the base PEO coating. The initial surface roughness (Sa) under PEO+DCS (1.54 µm) was imperfectly 59% higher than that under PEO and conventional continuous sealing (CS). Interestingly, DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS. DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks, and DCS also provided extra space for the movement of nano-blocks, which resulted in rolling friction and nano lubrication. Further, DCS promoted mixed wear of the PTFE polymer layer and the PEO coating, and the PTFE layer (HV: 6 Kg·mm−2, Af: 92.2%) and the PEO coating (HV: 310 Kg·mm−2, Af: 7.8%) served as the soft matrix and the hard point, respectively. Moreover, the dynamic decrease of Sa by 29% during wear also contributed to the super wear resistance. The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.

Investigation of wear and corrosion characteristics of PTFE/TiN composite coating on SS-304 fabricated by two-step sputtering technique

Polytetrafluoroethylene (PTFE) and titanium nitride (TiN) composite coatings have proved to be quite effective anti-corrosion applications owing to the inertness of PTFE and wear resistance of TiN. However, there has been a significant research gap due to the lack of detailed investigation into the mechanisms and characterizations. Inspired by this, our work is focused on investigating the in-depth electrochemical corrosion characteristics of PTFE/TiN composite coating while exploring the contact angles and wear-resistant mechanisms. The PTFE/TiN composite was directly coated on stainless steel (SS-304) substrate by RF magnetron sputtering in two steps. The experimental results indicated that the coating of the PTFE layer modified the characteristic hydrophilic character (θw ~ 78.2° ± 2°) of the SS-304 surface into an almost superhydrophobic character (θw ~ 142.6° ± 2°), indorsing the superior protection of SS-304 from aqueous species. Our electrochemical studies revealed that after long-time immersion (6 h) in an alkaline medium, our coating demonstrated a corrosion rate as slow as 0.0026 μm/year with a low surface energy of 4.81 mN/m and high hardness of 16.78 ± 0.36 GPa. Besides, the maximum wear resistance and maximum resistance to fatigue fracture ratios were obtained as H/Er ~ 0.064 and H3/E 2– 0.068 GPa, respectively. Furthermore, the coating also displayed excellent durability when exposed to air and immersion in chloride solution for a longer time. Lastly, we have included an in-depth discussion of the process steps as well as the mechanism of corrosion initiation.

Guest Editorial: Polymer electrets and ferroelectrets

Guest Editorial: Polymer electrets and ferroelectrets

A compound‐structured piezoelectret system and its applications in wearable health monitoring

AbstractPiezoelectrets, also called ferroelectrets, can exhibit promising piezoelectric properties and have plenty of applications in wearable health monitoring. Usually, the cellular structure of piezoelectrets is of outstanding importance for their sensing properties, and structure improvement and optimisation would be a possible way to realise high‐performance piezoelectrets. The authors proposed a compound‐structured piezoelectret system, where a layer of polypropylene foam was sandwiched between two layers of solid polytetrafluoroethylene, resulting in a combination of a foam‐structured and a layer‐structured piezoelectrets. The compound systems are thin and flexible, they can exhibit stable electrical outputs, they have relatively broader linear working range under pressure, and promising mechanical sustainability for multiple testing. The results reveal that the compound system can be considered as a simple addition of both components, and each component contributes linearly and independently to the whole system. The application potential of this proposed compound system has been demonstrated by sleep monitoring together with carotid and radial pulse recordings, where many useful physiological information including breath, heartbeat, and pulse details can be extracted from the signals acquired by the compound system. A type of flexible sensor system that is very competitive for future portable and wearable applications may be provided.

Janus Membrane with Hydrogel-like Coating for Robust Fouling and Wetting Resistance in Membrane Distillation

Membrane distillation (MD) is a promising technique for water reclamation from hypersaline wastewater. However, fouling and wetting of the hydrophobic membranes are two prominent challenges for the widespread application of MD. Herein, we developed an antiwetting and antifouling Janus membrane comprising a hydrogel-like polyvinyl alcohol/tannic acid (PVA/TA) top layer and a hydrophobic polytetrafluoroethylene (PTFE) membrane substrate via a facile and benign strategy combining mussel-amine co-deposition with the shrinkage-rehydration process. Interestingly, the vapor flux of the Janus membrane was not compromised, though a microscale PVA/TA layer was introduced, possibly due to the high water uptake and reduced water evaporation enthalpy of the hydrogel-like structure. Moreover, the PVA/TA-PTFE Janus membrane sustained stable MD performance while treating a challenging saline feed containing surfactants and mineral oils. The robust wetting resistance arises from the synergistic effects of the elevated liquid entry pressure (1.01 ± 0.02 MPa) of the membrane and the retardation of surfactant transport to the substrate PTFE layer. Meanwhile, the hydrogel-like PVA/TA layer hinders oil fouling due to its strongly hydrated state. Furthermore, the PVA/TA-PTFE membrane exhibited improved performance in purifying shale gas wastewater and landfill leachate. This study provides new insights into the facile design and fabrication of promising MD membranes for hypersaline wastewater treatment.

Novel Hydrophobic Ultrafiltration Membranes for Treatment of Oil-Contaminated Wastewater

Cutting fluids are the main source of oily wastewater in the metalworking industry. This study deals with the development of antifouling composite hydrophobic membranes for treatment of oily wastewater. The novelty of this study is that a low energy electron-beam deposition technique was applied for a polysulfone (PSf) membrane with a molecular-weight cut-off of 300 kDa, which is promising for use in the treatment of oil-contaminated wastewater, by using polytetrafluoroethylene (PTFE) as target materials. The effect of the thickness of the PTFE layer (45, 660, and 1350 nm) on the structure, composition, and hydrophilicity of membranes was investigated using scanning electron microscopy, water contact angle (WCA) measurements, atomic force microscopy, and FTIR-spectroscopy. The separation and antifouling performance of the reference and modified membranes were evaluated during ultrafiltration of cutting fluid emulsions. It was found that the increase in the PTFE layer thickness results in the significant increase in WCA (from 56° up to 110-123° for the reference and modified membranes respectively) and decrease in surface roughness. It was found that cutting fluid emulsion flux of modified membranes was similar to the flux of the reference PSf-membrane (7.5-12.4 L·m-2·h-1 at 6 bar) while cutting fluid rejection (RCF) of modified membranes increased compared to the reference membrane (RCF = 58.4-93.3% for modified and RCF = 13% for the reference PSf membrane). It was established that despite the similar flux of cutting fluid emulsion, modified membranes demonstrate 5-6.5 times higher flux recovery ratio (FRR) compared to the reference membrane. The developed hydrophobic membranes were found to be highly efficient in oily wastewater treatment.

An Ultrawideband Frequency Selective Surface Absorber With High Polarization-Independent Angular Stability

An ultrawideband frequency selective surface (FSS) absorber with high angular stability and polarization independency applied in a microwave band is proposed. The absorber is composed of three identical Teflon layers and dual FSS layers with distinct patterns. The miniaturized FSSs with unique patterns demonstrate advantages of facile manipulation of the impedance and multiple resonances in an ultrawide frequency range. The use of identical dielectric substrate greatly reduces the complexity in the absorber design, compared with the conventional way that requires variable dielectric constants for a multilayer structure. Experimental results reveal that more than 90% absorption rate in the frequency range of 2.79–20.62 GHz for normal incidence is achieved. The absorption rate can still retain more than 80% in the range of 4.41–20.93 GHz for both TE and TM polarizations with an incidence of 60°.

Flexible Low-Loss Thin Flimsy Stripline for High-Speed Connections.

Increasing numbers of antennas are being placed inside laptop screen bezels. Connections between antennas and laptop bases have become challenging owing to space limitations. Thus, this paper proposes a flexible low-loss thin flimsy stripline structure for high-speed applications. The cable should be sufficiently thin to avoid causing a water ripple effect while under the screen panel. Furthermore, the cable should be sufficiently flexible to traverse the hinges between the laptop screen and base. This study aims to design a cable with a total thickness of less than 0.6 mm and an insertion loss of less than 10 dB/m at a frequency of 6 GHz. Polytetrafluoroethylene (PTFE), a flexible material, can be used to meet these requirements. We simulate the characteristics of various PTFE layer thicknesses. The trend shows a thicker PTFE layer and lower insertion loss. Finally, we fabricate and test two structures with different thicknesses. Both thicknesses are less than 0.6 mm, and the insertion losses are less than 10 dB/m at 6 GHz. We demonstrate the feasibility of the proposed design and fabrication process for these applications through simulations and measurements.

Self-Pumping Janus Hydrogel with Aligned Channels for Accelerating Diabetic Wound Healing.

Excessive exudate secreted from diabetic wounds often results in skin overhydration, severe infections, and secondary damage upon dressing changes. However, conventional wound dressings are difficult to synchronously realize the non-maceration of wound sites and rapid exudate transport due to their random porous structure. Herein, a self-pumping Janus hydrogel with aligned channels (JHA) composed of hydrophilic poly (ethylene glycol) diacrylate (PEGDA) hydrogel layer and hydrophobic polyurethane (PU)/graphene oxide (GO)/polytetrafluoroethylene (PTFE) layer is designed to rapidly export exudate and accelerate diabetic wound healing. In the design, the ice-templating process endows the hydrophilic hydrogel layer with superior liquid transport ability and mechanical strength due to the formation of aligned channel structure. The hydrophobic layer with controlled thickness functions as an effective barrier to prevent exudate from wetting the skin surface. Experiments in diabetic rat model show that JHA can significantly promote re-epithelialization and collagen deposition, shorten the inflammation phase, and accelerate wound healing. This unique JHA dressing may have great potential for real-life usage in clinical patients.

Triboelectric Energy-Harvesting Floor Tile.

The aim of this study was to investigate the real-world electrical parameters that strongly affected the performance of a triboelectric energy-harvesting floor tile design: triboelectric material thickness, cover plate displacement distance or gap width, and cover plate pressing frequency, so that real-world specifications of the harvesting floor tile can be accurately specified. The structure of the designed triboelectric energy harvester, with readily available polytetrafluoroethylene (PTFE) film and aluminum foil, was simple and hence easy to fabricate, and the material cost was low. A square wave was used to simulate the pressing frequency on the test bench's cover plate. The results showed that the voltage and current were proportional to the gap width, and the thinner the triboelectric layer thickness, the higher the output voltage and current. A test bench with a 0.2 mm thick PTFE triboelectric layer generated the highest energy output. In a later experiment, a triboelectric energy-harvesting floor tile (TEHFT) prototype was constructed with 0.1 and 0.2 mm thick PTFE layers. We found that at 2 Hz stepping frequency and 0.1 mm PTFE thickness, the optimal load and cumulative energy of the TEHFT were 0.8 MΩ and 3.81 mJ, respectively, while with 0.2 mm PTFE thickness, these two parameters were 1.1 MΩ and 7.69 mJ, respectively. The TEHFT with 0.2 mm thick PTFE layer was able to illuminate a series of 100 to 150 LEDs, sufficient power to drive small electronics and sensor nodes. This discovery provides important data on the structure, material, and contact surface area of a TEHFT that can be adjusted to suit specific requirements of a special function triboelectric energy harvester.

Robust Superhydrophobic Coatings for Enhanced Corrosion Resistance and Dielectric Properties

Multifunctional super-repellent composite coatings play an important part in academic and industrial fields, while it is still a great challenge to effectively integrate a variety of functions into one material. Mg alloys having low density, high strength-to-weight ratio, and good shielding, are widely used in electronic devices, while it is susceptible to sever corrosion especially in moist air and ocean atmosphere. Here, a versatile superhydrophobic coating with organic-inorganic hybrid structure and hierarchical surface textures, integrating robust wettability with design manipulation is synthesized by assembling modified SiO2 nanoparticles on polytetrafluoroethylene (PTFE) layer on the AZ31 Mg alloy. The composite coating has good water repellency with a contact angle of 170.5°, due to the micro/nano textures and low surface energy. The composite coating increases the corrosion potential of AZ31 Mg from −1.483 V to −1.243 V, and reduces the corrosion current density by 3 orders of magnitude. Remarkably, the superhydrophobic coating displays enticing damage-resistance (>40 cycles), superior environmental stability (thermal shock and outdoor placement) and self-cleaning function. Moreover, the composite coatings display excellent electrical properties with superior voltage resistance (>30 V/μm), and high resistivity (>1012 Ω∙cm), as well the coating has a low dielectric constant (≈3.91) and dielectric loss (0.0094), which are great advantages for the electronic or electrical engineering applications. We expect that the versatile super-repellent coating can be used as candidates for novel advanced energy materials, especially in harsh environments.

Comprehensive experimental and theoretical studies on material-gap and water-gap membrane distillation using composite membranes

Experimental and theoretical studies on material-gap membrane distillation (MGMD) and water-gap membrane distillation (WGMD) are presented in this paper to demonstrate the effect of gaps filled with different materials on permeation flux. A flat-sheet composite membrane composed of an active polytetrafluoroethylene layer and a support polypropylene layer was employed in the experiments. Graphite, water, silica gel, and zeolite were used to measure the effects of these materials on permeation flux and thermal resistance. In the experiments and simulations, the size of the material and water gaps was kept constant at 5 mm. The graphite-filled MGMD permeation flux was approximately 11–22% higher than that of the WGMD at inlet feed temperatures in the range of 40–70 °C. However, the permeation flux of MGMD filled with silica gel and zeolite was 17–24% and 18–27% lower than that of WGMD, respectively. At thermal conductivities below 5 W/mK, the permeation flux of the MGMD with a material packing density of 40% was higher than that with a material packing density of 60%. The MGMD permeation flux with a material packing density of 60% was higher than that with a material packing density of 40% above a thermal conductivity of 5 W/mK. Furthermore, the MGMD permeation flux and overall thermal resistance were primarily controlled by the material gap, with materials having thermal conductivities below 30 and 20 W/mK for the bead- and pellet-type materials (i.e., packing densities of 40 and 60%), respectively.

Confined Oxygen Promotes Radical Generation for Methane Oxidation Toward Liquid Oxygenates

The activation of methane (CH4) gas to produce value-added liquid hydrocarbons has been a challenging issue in catalytic research. Electrochemical oxidation is one of the alternative methods to oxidize methane and can be usually performed at ambient temperature, which can solve the problems of methane steam reforming caused by high temperature. However, electrochemical direct methane oxidation still have limitations that it should competes with oxygen evolution reaction, resulting in low efficiency. Also, oxygenates generated from methane oxidation can be easily overoxidized to carbon dioxide which is not appropriate product for the purpose of electrochemical system to make liquid hydrocarbons , suggesting solution to transport problem in the industry.Therefore, we suggest new system to convert methane into liquid products via oxygen reduction reaction using cathode. Recently in some papers, oxygen is used as an oxidant in photocatalytic system to oxidize methane into liquid hydrocarbons. Herein, hydrogen peroxide (H2O2) generated from oxygen reduction reaction can produce hydroxyl radical, superoxide radical, and hydroperoxide radical with strong activity to break first C-H bond from CH4. By combining methyl radical activated from methane and radicals generated from H2O2, we could make formic acid with high selectivity. Through the reduction reaction on cathode and oxidation reaction by radicals, intermediate products, such as methanol and methyl hydroperoxide, were finally converted into formic acid. Furthermore, overoxidation, one of important limitation in direct methane oxidation, can be prevented by using cathode where reduction reaction occurs on electrode.In this work, we synthesized metal organic framework (MOF)-derived cobalt single atom using ZIF-67. The cobalt single atom has high faradaic efficiency (FE) in acidic media with low onset potential, which is over 80% at 0.5 V (vs RHE). To efficiently utilize H2O2 produced by oxygen reduction reaction, additional hydrophobic layer was introduced with gas diffusion electrode (GDE) by coating poly tetra fluoro ethylene (PTFE) on catalyst layer. Additional PTFE layer on GDE confined H2O2 and CH4 together, offering higher possibilities to be reacted. In addition, liquid oxygenates generated from the reaction have hydrophilic properties that prevents further reactions by reducing the diffusion of liquid products toward cathode due to hydrophobic layer. By applying new system into flow cell, the low solubility of methane in the electrolyte can be alleviated to achieve high production rate. At last, This new system using oxygen reduction reaction to oxidize methane can make a new pathway for many chemical reaction area in the point that the system can be applied in any industrial reactions where H2O2 included. Figure 1

Enhancement of visible light detection for indium–gallium–zinc oxide-based transparent phototransistor via application of porous-structured polytetrafluoroethylene

In this paper, a transparent phototransistor with improved visible light detection by applying sub gap states engineering and a porous polytetrafluoroethylene (PTFE) layer on the indium–gallium–zinc oxide (IGZO) thin film is introduced. The porous PTFE film was sputtered with the selective etching process through an oxygen plasma process after removing nickel nanoparticles dispersed by a magnetic field with a liftoff process. The photoresponse characteristics of porous PTFE/IGZO (PPI) phototransistors were tested with various thicknesses of PTFE (15–75; 15 nm steps). The PPI phototransistor with the PTFE thickness of 30 nm showed the highest photoresponse properties. Although the measured optical bandgap energy of the IGZO film was 3.87 eV, the PPI phototransistors could detect visible light due to the trap-assisted electron/hole pair generation by the sub gap states of the IGZO film induced by plasma damage during PTFE deposition. In addition, it was possible to maximize the efficiency of detecting visible light by capturing and scattering light with the porous structure of PTFE. The PPI phototransistors had a photoresponsivity of 73.45 ± 16.14 A/W, photosensitivity of (1.60 ± 0.57) × 106, and detectivity of (2.62 ± 2.37) × 1010 Jones under illumination by red light with a wavelength of 635 nm and an intensity of 10 mW/mm2.

A self-priming air filtration system based on triboelectric nanogenerator for active air purification

Air pollution is becoming more and more serious, which has a huge impact on human production and life. Dust particulate matter (PM) is one of the main pollutants in the air, threatening human life and health. In this work, a triboelectric air filtration system (TAFS) based on triboelectric nanogenerators (TENGs) was developed for active removal of outdoor PM2.5 and harmful bacteria. The TAFS consists of a layer of industrial filter media (filter cotton or sponge) and a layer of polytetrafluoroethylene (PTFE). Due to frictional electrification effect of these two layers, the filtration efficiency of the low-efficiency and low-resistance filter material for particulate matter is greatly improved. The filtration efficiencies of PM1.0 and PM2.5 are increased by 20 %-40 %. Moreover, the frictional positive charge also greatly improves the interception efficiency of the material against Staphylococcus aureus. A self-priming air filtration system composed of an air pump and TENG are used to remove PM2.5 up to 99 % in a confined space filled with cigarettes for 30 min. In addition, the wind cup design makes the system take full advantage of the wind energy in the environment, realizing self-power supply, zero carbon emission and high efficiency and environmental protection. The self-powered TAFS can be used in outdoor dusty construction sites, dust factories, sand and haze weather and other places to remove particulate pollution. This work also provides a novel self-powered air purification strategy.

Thermal radiative switching interface for energy-efficient temperature control

Materials with dynamically switchable optical properties can modulate their interaction with sunlight, potentially saving significant energy for heating and air-conditioning if used as building exteriors. This study proposes a new technique for solar-thermal regulation using porous polytetrafluoroethylene (PTFE) layers integrated with a spectrally-selective absorber (PTFE-SS). This multilayered structure can provide tunable optical properties by wetting or dewetting the porous PTFE with a refractive index-matching liquid, allowing a highly reversible change in solar transmittance of 0.62. This variation allows the multilayered structure to switch between highly reflecting and absorbing states that is tunable using different PTFE thicknesses. With this multilayered structure as building exteriors, sunlight can be reflected or absorbed to reduce dependence on conventional heating and cooling systems driven by non-renewable primary energy sources. When exposed to 1 sun illumination under ideal conditions, this variation allows a 51 °C change in PTFE-SS steady temperatures. When applied to buildings as roofing materials, the PTFE-SS promises significant energy reduction with annual cooling and heating savings of around 77% and 27%, respectively. Hence, the proposed PTFE-SS structure presents a new paradigm for passive thermal management of buildings by controlling their interaction with sunlight and decreasing our dependence on fossil fuels.

High Gain Compact UWB Antenna for Ground Penetrating Radar Detection and Soil Inspection.

An ultrawide bandwidth (UWB) antenna for ground-penetrating radar (GPR) applications is designed to check soil moisture and provide good-quality images of metallic targets hidden in the soil. GPR is a promising technology for detecting and identifying buried objects, such as landmines, and investigating soil in terms of moisture content and contamination. A paddle-shaped microstrip antenna is created by cutting a rectangular patch at one of its diametrical edges fed by the coplanar waveguide technique. The antenna is loaded by stubs, shorting pins, and a split-ring resonator (SRR) metamaterial structure to increase the antenna’s gain and enhance the bandwidth (BW) towards both the lower and higher end of the working BW. The antenna’s performance in soil inspection is studied in terms of the operating frequency range, different types of soil, different distances (e.g., 50 cm) between the antenna arrays and soil, S-parameters, and gain. Following this, the antenna’s ability to find a metallic target in the soil is tested, considering different array numbers, multi-targets, and locations. The antenna is designed on a thin layer of economic polytetrafluoroethylene (PTFE) substrate with dimensions 50 × 39 × 0.508 mm3 and works in the frequency range 1.9–9.2 GHz. In addition, two more resonances at 0.9 and 1.8 GHz are also achieved; hence, the antenna works for more than two application bands, such as the ISM- and L-bands. The measurement results validated excellent agreement with the simulated results. Furthermore, the recommended antenna offering a high gain of about 10.8 dBi and maximum efficiency above 97% proved able to discriminate between hidden objects and even recognize their shapes. Moreover, the reconstructed images show that the antenna can detect an object in the soil at any location.

Efficacy and Safety of a Polytetrafluoroethylene Membrane Wrapped a Single Layer of Sirolimus-Eluting Stent in a Porcine Coronary Perforation Model.

Covered stents are effective in treating coronary artery perforation (CAP), however, the high rate of immediate device deployment failure and in-stent restenosis have limited the application of the currently covered stents. We designed a covered stent system consisting of a single layer of drug-eluting stent and a layer of polytetrafluoroethylene (PTFE) membrane wrapped at the outer layer of the stent. The immediate sealing effect of our novel covered stent was observed by using an Ellis type III CAP model. The device's success was defined as its ability to seal the perforation, assessed by visual estimation and final thrombolysis in myocardial infarction (TIMI) 3 flow. The antiproliferative effect was evaluated in 12 swine, which were randomly assigned to treatment (sirolimus-eluting covered stents) and control (bare metal covered stents) groups. Coronary angiography and optical coherence tomography (OCT) were performed at index procedure, 1- and 6-month after stent implantation. All swine were sacrificed for histopathological analyses at 6-month. The device success rate was 100%. All swine were alive at 6-month follow-up. At 1-month, the treatment group had a larger minimal luminal diameter (MLD) (1.89 0.29 mm vs. 0.63 0.65 mm, p = 0.004) and lower late luminal loss (LLL) (0.47 0.15 mm vs. 1.80 0.34 mm, p 0.001) compared with control group. At 6-month, the treatment group had a numerically higher MLD (0.94 0.75 mm vs. 0.26 0.46 mm; p = 0.230) and lower LLL (1.43 0.85 mm vs. 2.17 0.28 mm; p = 0.215) compared with control group. Histological analyses revealed the mean plaque area was lower in the treatment group (2.99 0.81 vs. 4.29 0.77 , p = 0.035) than in the control group. No in-stent thrombosis was observed in either group. In the porcine model of coronary perforation, the PTFE membrane wrapped sirolimus-eluting stent showed a high device success rate in sealing the perforation. The drug-eluting covered stent demonstrated a relatively sustained antiproliferative effect up to 6 months post-implantation.