Poly Ether Ether Ketone Membranes Research Articles

Breaking the trade-off between proton conductivity and mechanical stability through liquid-crystal-modified aramid fibers in sulfonated polyether ether ketone membranes

In the quest for sustainable and high-performance hydrogen fuel cells, proton exchange membranes (PEMs) stand as a pivotal research focus. To overcome the significant challenge posed by the traditional trade-offs between proton conductivity and mechanical stability, this work introduces liquid-crystal-modified aramid fibers (DBAF) with highly ordered molecular arrangements and abundant sulfonic acid groups on the side chains as proton-hopping sites into a sulfonated poly (ether ether ketone) (SPEEK) matrix. The inclusion of components not only improves the proton conductivity of the membrane, but also boosts its mechanical strength. The results of our study demonstrate that the externally attached sulfonic acid groups create extra channels for the transport of protons. Additionally, the organized and consistently stable hydrogen-bond network enables the Grotthuss transport mechanism within the SPEEK membrane. The 1 wt% DBAF-SPEEK composite membrane exhibits a maximum proton conductivity of 0.23 S cm−1 at 80 °C, representing a 64% increase over the baseline SPEEK membrane's 0.14 S cm−1. Simultaneously, the tensile strength at normal room temperature is 39.7 MPa, exhibiting an improvement of 86% compared to the initial value of 21.3 MPa. Additionally, the swelling ratio is lowered by 18.69%. Compared with the baseline membrane, the DBAF-enhanced SPEEK composite membrane exhibits superior mechanical stability and proton conductivity within a moderate temperature range (30–80 °C). Consequently, this work offers valuable insights for the development of novel proton-conductive materials.

Simultaneously Recovery of Thorium and Tungsten through Hybrid Electrolysis-Nanofiltration Processes.

The recovery and recycling of metals that generate toxic ions in the environment is of particular importance, especially when these are tungsten and, in particular, thorium. The radioactive element thorium has unexpectedly accessible domestic applications (filaments of light bulbs and electronic tubes, welding electrodes, and working alloys containing aluminum and magnesium), which lead to its appearance in electrical and electronic waste from municipal waste management platforms. The current paper proposes the simultaneous recovery of waste containing tungsten and thorium from welding electrodes. Simultaneous recovery is achieved by applying a hybrid membrane electrolysis technology coupled with nanofiltration. An electrolysis cell with sulphonated polyether-ether-ketone membranes (sPEEK) and a nanofiltration module with chitosan-polypropylene membranes (C-PHF-M) are used to carry out the hybrid process. The analysis of welding electrodes led to a composition of W (tungsten) 89.4%; Th 7.1%; O2 2.5%; and Al 1.1%. Thus, the parameters of the electrolysis process were chosen according to the speciation of the three metals suggested by the superimposed Pourbaix diagrams. At a constant potential of 20.0 V and an electrolysis current of 1.0 A, the pH is varied and the possible composition of the solution in the anodic workspace is analyzed. Favorable conditions for both electrolysis and nanofiltration were obtained at pH from 6 to 9, when the soluble tungstate ion, the aluminum hydroxide, and solid thorium dioxide were formed. Through the first nanofiltration, the tungstate ion is obtained in the permeate, and thorium dioxide and aluminum hydroxide in the concentrate. By adding a pH 13 solution over the two precipitates, the aluminum is solubilized as sodium aluminate, which will be found after the second nanofiltration in the permeate, with the thorium dioxide remaining integrally (within an error of ±0.1 ppm) on the C-PHF-M membrane.

Facile fabrication of FAS-PDMS/PEEK composite hollow fiber membrane with honeycomb-like structure for CO2 capture from flue gas by membrane absorption

In this study, as an efficient technology membrane absorption was applied with newly developed polyetheretherketone (PEEK) hollow fiber membrane (HFM) to remove CO2 from flue gas. To alleviate membrane wetting issue, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS) was integrated into polydimethylsiloxane (PDMS) and then crosslinked FAS-PDMS was coated on porous PEEK membranes to prepare composite membranes. Surface characterization verified that PDMS layer containing fluoroalkylsilane had been successfully formed on membrane surface. As mass ratio of FAS to PDMS in coating solution raised, an interesting honeycomb-like structure was observed dispersing on composite membrane surface. Meanwhile, water contact angle was improved from 90.0° to 133.5° indicating enhanced membrane hydrophobicity. The effects of gas and liquid flow velocities on CO2 absorption performance of FAS-PDMS/PEEK HFM were systematically studied. The highest CO2 removal efficiency of 99.6% was achieved when gas and liquid velocity were 0.027 and 0.019 m s−1. When gas velocity raised to 0.110 m s−1, the maximum absorption flux of 1.22 × 10-4 mol m−2 s−1 and overall mass-transfer coefficient of 2.69 × 10−5 m s−1 could be obtained. Compared with the original membrane, the CO2 absorption flux of FAS-PDMS-0.6 HFM was increased by 50.9%, and the performance had no degradation in 36 h test. This study provides a novel strategy to alleviate the membrane wetting problem during CO2 membrane absorption process.

High efficiency and flexible construction of hydrophilic polymer brushes on polyether ether ketone hollow-fiber membrane surface for improving permeability separation, and anti-fouling performances

Polyether ether ketone (PEEK) is a high-performance thermoplastic used as a separation membrane for wastewater treatment, purification, and recycling, especially in harsh environments. However, the applications of PEEK membranes are limited by their processing difficulty, low permeability, and membrane fouling. Herein, a PEEK hollow fibre membrane (PHFM) was fabricated by melt-spinning of polyetherimide (PEI)/PEEK blends and extracting PEI. Thereafter, a hydration layer consisting of 2-hydroxylethyl acrylate (HEA) chains was constructed on the PHFM surface based on the surface-initiated atom transfer radical polymerisation method. The grafting density and grafting length of the HEA chains were modulated by varying the bromination time and ATRP reaction time, and the hydrophilicity of the resulting PHFM surface was enhanced significantly without deteriorating its original porous structure. The controllable pores and hydrated layers on the PHFM surface simultaneously improved the permeability, separation performance, and anti-fouling properties of the membrane. Under a bromination time of 6 h and an ATRP reaction time of 8 h, the water flux of the modified PHFM was enhanced by 364 %. The rejection rate of bovine serum albumin (BSA) by the modified membrane exceeded 90 %. According to the extended Derjaguin–Landau–Verwey–Overbeek theory, the improved anti-fouling performance was related to the weakened acid–base attraction between the foulants and membrane with the hydration layer. After multiple separation-washing cycles, the total fouling and irreversible fouling of the modified PHFM were reduced. The normalised water flux and BSA rejection ratio of the modified anti-fouling PHFM remained 216 % and 90 %, respectively.

Constructing a long-range proton conduction bridge in sulfonated polyetheretherketone membranes with low DS by incorporating acid-base bi-functionalized metal organic frameworks

Functionalized metal-organic frameworks (MOFs) are being extensively developed as viable fillers to enhance the proton conductivity of proton exchange membranes. Herein, an amino-pendant sulfonic acid bi-functionalized MOFs material (UNCS)-doped SPEEK membrane with low degree of sulfonation (DS) can improve the proton conductivity as well as maintain the membrane dimensional stability. UNCS can act as bridges of proton donors and acceptors to reduce the activation energy barrier and shorten the distance of long-range proton conduction. Among all as-prepared membranes, SPEEK/UNCS-3 exhibited the highest proton conductivity of 186.4 mS·cm−1 at 75 °C and 100% relative humidity (RH), which is much greater than that of pristine SPEEK and Nafion 117. Benefiting from the acid-base pair interaction between the amino groups of UNCS and the sulfonic acid groups of SPEEK, the dimensional stability and mechanical properties of the composite membranes were enhanced. More interestingly, STEM-HAADF and SAXS characterization consistently revealed that UNCS served as bridges among proton channels in the composite membranes for continuous proton transport.

Fabrication of a cost-effective cation exchange membrane for advanced energy storage in a decoupled alkaline-neutral electrolyte system

Herein, a cost-effective cation exchange membrane (CEM), sulfonated polyether ether ketone membrane (SPEEK-M), is prepared through heat sulfuric acid treatment followed by evaporation induced thermal phase separation. Negative charged sulfonic acid functional groups can be grafted on the polymer chains during this process. Exchange of cations, and repulsion of anions are hence realized using this membrane. To further improve the performance of the SPEEK-M, SiO2 is introduced in. It is found that ionic conductivity is increased to 46.79 mS·cm−1 for the SiO2-SPEEK-M from 19.17 mS·cm−1 for the SPEEK-M. Compared with commercial CEMs, such as DuPont N117 and Huamotech, volume expansion of the SPEEK-M is rather small after immersed in water. The membranes are then used as separators in Zn-ion hybrid capacitors (ZIHCs) with decoupled aqueous electrolytes, which includes a Zn foil anode in an alkaline electrolyte, and an activated carbon (AC) cathode in a neutral electrolyte. The electrolyte decoupling strategy maximizes the operating window of this system to 0.5 ∼ 2.2 V. The specific capacity of the AC can reach 390.0C·g−1 at a current density of 0.5 A·g−1. An energy density of 46.2 Wh·kg−1 at a power density of 3416.1 W·kg−1 can be achieved (counting the weight of AC). After gelation of the electrolytes, the growth of Zn dendrite is successfully eliminated, and capacity retention along cycling is increased to 94.3 % using the SiO2-SPEEK-M, which is better than that using the commercial DuPont N117 and Huamotech. The raw materials used here to prepare the CEMs are cheap and eco-friendly, which makes the membranes promising candidates as separators for decoupled electrolyte systems.

Rigidly and intrinsically microporous polymer reinforced sulfonated polyether ether ketone membrane for vanadium flow battery

Ion exchange membranes (IEMs) blending porous materials have shown great potential for the large-scale energy storage technologies, such as flow battery. However, it remains challenging to overcome the compatibility issue between polymer and porous fillers. In this work, the polymer of intrinsic microporosity (PIM) was successfully introduced into sulfonated polyether ether ketone with high degree of sulfonation (HDS-SPEEK) membrane. PIM exhibited desirable compatibility with HDS-SPEEK due to the natural polymer property. Meanwhile, the rigid skeleton structure of PIM effectively solved the problems of HDS-SPEEK involving poor mechanical property and low vanadium resistance. With increasing the doping of carboxyl grafting modified PIM, the tensile strength increased from 15.22 to 29.94 MPa and the vanadium permeability declined from 4.4 × 10−6 to 1.6 × 10−7 cm2 min−1. As a result, the vanadium flow battery equipped with the optimized blend membrane showed significantly enhanced coulombic efficiency from 55% to 99% at the current density of 20 mA cm−2, and had good long-term stability. This work presents a new route to prepare high-performance IEMs based on porous PIM materials for flow battery.

Functionalized carbon black modified sulfonated polyether ether ketone membrane for highly stable vanadium redox flow battery

Sulfonated polyether ether ketone (SPEEK) membranes have attracted much attention as ion exchange membranes for vanadium redox flow batteries (VRFBs) owing to their affordability and low vanadium permeability. It's noted that they suffer from poor proton conductivity at low degree of sulfonation (DS) while poor mechanical stability at high DS. Therefore, it is a challenge to balance their performance and DS. In this work, functionalized carbon black (FCB) particles with sulfonic acid substituents were prepared and used as fillers to obtain advanced SPEEK composite membranes. This kind of SPEEK/FCB composite membranes show outstanding ion selectivity, low vanadium permeability, high proton conductivity and excellent stability. The VRFB cell with the optimized SPEEK/FCB composite membrane shows high energy efficiency (94.26%, at 50 mA cm−2), low-capacity fade rate (0.052% per cycle, at 120 mA cm−2) and long cycle life.

An overview on the progress and development of modified sulfonated polyether ether ketone membranes for vanadium redox flow battery applications

Vanadium redox flow batteries (VRFB) are among the most promising approaches to efficiently store renewable energies. In such battery type, Nafion is commonly used as membrane material but suffers from high vanadium crossover and cost. These drawbacks negatively influence the widespread commercial application of VRFBs. Alternative membrane materials with high performance and low cost are thus being developed to address these shortfalls. Among those, possible materials for the VRFB membrane is sulfonated polyether ether ketone (SPEEK), which recently attracted considerable attention due to its low cost, combined with mechanical and chemical stability, and ease of preparation. This review summarizes the research activities related to the development of SPEEK-based membranes for VRFB applications and gives an overview of the properties of PEEK and its sulfonated form. A critical analysis on the challenges of SPEEK-based membranes is also discussed.

Friedel-Crafts self-crosslinking of sulfonated poly(etheretherketone) composite proton exchange membrane doped with phosphotungstic acid and carbon-based nanomaterials for fuel cell applications

In this work, self-crosslinked sulfonated polyether etherketone membrane (C-SPEEK) was synthesized by Friedel-Crafts alkylation at 130 °C with chloromethylated sulfonated polyether etherketone (SPEEK-Cl). The water uptake (WU) of the C-SPEEK was 47.75% with a 8.69% swelling rate (SR) at 60 °C, compared with the sulfonated polyether etherketone membrane (SPEEK) with WU of 110.60% and SR of 57.99%. The contradiction between dimensional stability and proton conductivity under high sulfonation degree was overcome. The self-crosslinking composite membranes were prepared by doping with carbon nanomaterials (Graphite oxide, GO; reduced graphene oxide, rGO and carbon nanotubes, CNTs) and phosphotungstic acid (HPW). Since HPW and carbon nanomaterials incorporated in membrane facilitate protons conduction via both Grotthuss and Vehicle mechanisms, the hybrid membranes demonstrated the improved conductivities. At 80 °C, C-SPEEK/HPW/GO showed proton conductivity as high as 119.04 mS/cm, which was 2.4 folds higher than that of the C-SPEEK. Furthermore, the superior performance of C-SPEEK/HPW/GO was further validated through H2/O2 single cell test. The C-SPEEK/HPW/GO produced a higher power output of 876.80 mW/cm2, whereas only 776.72 mW/cm2 for C-SPEEK was recorded. Thus, C-SPEEK/HPW/GO and C-SPEEK may be promising membrane materials for potential applications in fuel cells.

Waste heat recovery from the stripped gas in carbon capture process by membrane technology: Hydrophobic and hydrophilic organic membrane cases

AbstractIn this study, hydrophobic polytetrafluoroethylene (PTFE) and hydrophilic polyetheretherketone (PEEK) membranes were used as heat exchangers in rich‐split CO2 capture process to recover the waste heat from the stripped gas (i.e., mixture of water vapor and CO2). Technical feasibilities of these two membrane exchangers were assessed by heat recovery and energy intensity in the monoethanolamine (MEA)‐based carbon capture process. The heat recovery of these two membrane exchangers with different pore sizes were then systematically compared under various operating parameters. The underlying mass and heat transfer mechanisms of two membranes were also investigated and compared to figure out the suitable candidate for heat recovery. Additionally, the potential risks of using these membrane exchangers were identified and investigated. Results showed that the PTFE membrane displays a better heat recovery performance than the PEEK membrane with the same pore size. The heat recovery of both PTFE and PEEK membranes first increases to a plateau and then drops slightly with the increased CO2‐rich solvent flow rate. The heat recovery of PTFE and PEEK membranes decreases with the increased flow rate and water vapor fraction of the inlet stripped gas, MEA temperature, and MEA concentration. Furthermore, the larger pore size results in higher heat recovery for both PTFE and PEEK membranes. PTFE membranes displayed lower MEA transfer flux than PTFE membranes at any rich MEA flow rate as the enhanced MEA transfer from the cold solution to the other side via PEEK membrane pores filled with liquid water. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Strong acid- and solvent-resistant polyether ether ketone separation membranes with adjustable pores

Polyether ether ketone (PEEK) is composed of repeating phenyl ether and benzophenone units and exhibits strong chemical resistance in harsh solvents due to their inherent structural characteristics. In view of its stability and un-processability, the traditional methods of preparing membranes limited further application. In this work, we proposed a facile route toward the preparation of PEEK membranes via traditional non-solvent-induced phase separation (NIPS) and a facile one-step heat treatment for the first time to the best of our knowledge. Most intriguingly, the morphologies, pore size, water permeability and selectivity of PEEK membranes could be simply modified by heat treatment. The effect of the pore size on permeability and selectivity was investigated for bovine serum albumin (BSA, 66.4 K Da), rose bengal sodium salt (RB, 1017 Da) and methyl blue (MB, 799 Da). Aside from a high selectivity (rejection higher than 90% for different molecular structures) being obtained, the membranes showed excellent reproducibility in organic solvents and strong acid. Moreover, the separation performance remained unchanged in a long-term operation. The application of this simple and highly economical method expands the research direction of PEEK membranes and promotes the further application in separation and purification.

Incorporation of silver graphene oxide and graphene oxide nanoparticles in sulfonated polyether ether ketone membrane for power generation in microbial fuel cell

This study aims to design a new membrane for Microbial Fuel Cell (MFC) applications, where the membrane should have good proton conductivity, low oxygen permeability and anti-biofouling properties. The self-fabricated composite membranes are Graphene Oxide/Sulfonated Polyether Ether Ketone (GO-SPEEK) and Silver Graphene Oxide/Graphene Oxide/Sulfonated Polyether Ether Ketone (AgGO-GO-SPEEK). The proton conductivity of AgGO-GO-SPEEK membrane is 54.2% higher and the oxygen diffusion coefficient is 76.7% lower than Nafion® 117 membrane, yielding higher selectivity as separator in MFC applications. At the earlier optimum stage, MFC with GO-SPEEK generates the highest maximum power density (1134 mW m−2). Voltage achieved for first three feed cycles after enrichment are 620 mV–650 mV for all MFC system. However, the highest maximum power density (896 mW m−3) is attained by MFC with AgGO-GO-SPEEK membrane after 100 days of operation. The Electrochemical Impedance Spectroscopy (EIS) results show that AgGO-GO-SPEEK membrane has the lowest increment in terms of the membrane's resistance. AgGO-GO-SPEEK,a better anti-biofouling property membrane, leads to a longer and stable power production, caused by the better ion transport through membrane. The results indicated that AgGO-GO-SPEEK membrane is a promising alternative membrane to replace Nafion® 117 as a separator in the MFC.

A Multimaterial Scaffold With Tunable Properties: Toward Bone Tissue Repair.

Polyetheretherketone (PEEK)/β‐tricalcium phosphate (β‐TCP) scaffolds are expected to be able to combine the excellent mechanical strength of PEEK and the good bioactivity and biodegradability of β‐TCP. While PEEK acts as a closed membrane in which β‐TCP is completely wrapped after the melting/solidifying processing, the PEEK membrane degrades very little, hence the scaffolds cannot display bioactivity and biodegradability. The strategy reported here is to blend a biodegradable polymer with PEEK and β‐TCP to fabricate multi‐material scaffolds via selective laser sintering (SLS). The biodegradable polymer first degrades and leaves caverns on the closed membrane, and then the wrapped β‐TCP is exposed to body fluid. In this study, poly(l‐lactide) (PLLA) is adopted as the biodegradable polymer. The results show that large numbers of caverns form on the membrane with the degradation of PLLA, enabling direct contact between β‐TCP and body fluid, and allowing for their ion‐exchange. As a consequence, the scaffolds display the bioactivity, biodegradability and cytocompatibility. Moreover, bone defect repair studies reveal that new bone tissues grow from the margin towards the center of the scaffolds from the histological analysis. The bone defect region is completely connected to the host bone end after 8 weeks of implantation.

Physico-chemical studies of amoxycillin loaded sulfonated polymer

This study involves in the selection of polymer, poly etherether ketone (PEEK), and its modification to serve the purpose of drug carrier. The polymer is sulfonated to increase the hydrophilic character, thereby making it feasible for functioning as a drug carrier. A blend of sulphonated PEEK and drug was made into thin membrane and characterized using FT-IR and surface morphology studies. Physico-chemical properties such as partition coefficient, permeability coefficients and diffusivity constant were measure for the sulphonated PEEK membranes.

Synthesis of polyether ether ketone membrane with pendent phosphonic acid group and determination of proton conductivity and thermal stability

Incorporation of phosphonic acid groups in the polymer backbone by direct phosphonation or by polymerization of prefunctionalized monomers requires harsh reaction conditions. The present research work reported an easy synthesis strategy of phosphonic acid-containing diphosphonated polyether ether ketone (P-PEEK) by polycondensation of difluoro benzophenone and phosphonated bisphenol A (BPA). Phosphonation of BPA was carried out by monophosphoazylation followed by rearrangement in the presence of organolithium compound at −78°C. Nuclear magnetic resonance (NMR) imaging, Fourier transform infrared, and electrospray ionization mass spectrometry were performed to acquire complete structural information about the synthesized monomer and polymer. Degree of phosphonation of the synthesized polymer calculated from proton NMR spectra was as high as 70%. Thermal properties of the P-PEEK were checked using a differential scanning calorimeter (DSC) and a thermogravimetric analyzer. Moderate increase in melting point and glass transition temperature ( Tg) were observed from the DSC analysis. Solubility of the polymer was improved significantly in the common organic solvents that permitted the polymer to be solution casted. Solid electrolyte membrane exhibited through plane proton conductivity of 7.5 × 10−5 S cm−1 at 25°C under fully hydrated conditions.

Preparation of Poly Eter Eter Keton as Alternative Membrane for Direct Methanol Fuel Cell (DMFC)

The objective of this study focuses on the characterization of polyetheretherketone (PEEK) membranes for direct methanol fuel cells (DMFC) application. The PEEK membrane was modified with sulfonation and charged surface modifying macromolecule (cSMM) using MDI, DEG and HBS in NMP solvent. The characterized of membrane were done using Scanning Electron Microscopy (SEM), water uptake, contact angle, thermal stability, methanol permeability, proton conductivity and DMFC test. DMFC tests were performed at room temperature to obtain polarization curves that show voltages and power density of each variable. The results showed that the cSMM methode of the polymer increases water uptake, thermal stability, methanol permeability and proton conductivity. In terms of morphology, it was found that cSMM method can be applied for membrane modification for DMFC application. In terms of the DMFC tests of the membranes, SPEEK without modification proved to have the best performance in stability because of its low methanol permeability. In contrast, the best performance was achieved by the SPEEK/cSMM (with modification) in highest voltage and power density because of its high proton conductivity.

Post-combustion CO2 capture using super-hydrophobic, polyether ether ketone, hollow fiber membrane contactors

The feasibility of utilizing a super-hydrophobic polyether ether ketone (PEEK) hollow fiber membrane contactor in combination with chemical solvents to separate and capture CO2 from simulated flue gases was investigated. Greater than 90% CO2 capture with greater than 95% CO2 purity has been achieved in one stage with both activated methyldiethanolamine (aMDEA) and activated K2CO3 solvents. The measured volumetric mass transfer coefficient was as high as 1.7s−1, which is more than 20 times greater than the mass transfer coefficient of a packed column. Preliminary tests indicated that the CO2 capture performance was not affected by flue gas contaminants, including O2, NO2, and SO2, with aMDEA solvent. The PEEK membrane module showed good mechanical properties and stable permeation properties at process design conditions for duration of the test (120h). The process economics were evaluated assuming direct substitution of the conventional absorber by the membrane contactor, while using a conventional packed column in the regeneration step. Relative to the cost estimation with no CO2 capture, the evaluation indicates a 56% increase in the levelized cost of electricity (LCOE) for the PEEK membrane contactor technology, which is 29% lower than DOE’s benchmark amine absorption technology (85% increase in LCOE).

A Modified CDC Biofilm Reactor to Produce Mature Biofilms on the Surface of PEEK Membranes for an In Vivo Animal Model Application

Biofilm-related infections have become a major clinical concern. Typically, animal models that involve inoculation with planktonic bacteria have been used to create positive infection signals and examine antimicrobial strategies for eradicating or preventing biofilm-related infection. However, it is estimated that 99.9% of bacteria in nature dwell in established biofilms. As such, open wounds have significant potential to become contaminated with bacteria that reside in a well-established biofilm. In this study, a modified CDC biofilm reactor was developed to repeatably grow mature biofilms of Staphylococcus aureus on the surface of polyetheretherketone (PEEK) membranes for inoculation in a future animal model of orthopaedic implant biofilm-related infection. Results indicated that uniform, mature biofilms repeatably grew on the surface of the PEEK membranes.

Microvalves for Natural-Gas Analysis With Poly Ether Ether Ketone Membranes

We present the use of poly ether ether ketone (PEEK) as a membrane material for a new type of gas microvalve, which is suitable for the harsh environments of natural gas. The design, fabrication, and experimental characterization of the PEEK-based microvalves are presented first, revealing leakage levels of less than 230 nL·min-1 under nitrogen and helium. Then, the main mechanical properties of the PEEK membranes are derived from both static and dynamic measurements, leading to a Young's modulus of 3.1 GPa and an inplane anisotropic stress field, with both tensile and compressive components in two perpendicular directions and whose magnitudes are + 33.9 MPa and -6.8 MPa, respectively. A blister test gave an adhesion energy estimated between 61 and 158 J·m-2. Finally, temperature cycles have been conducted on the microvalve, showing a resistance of up to 300°C, together with an improved closing of the membrane.