Fabrication Of Valves Research Articles

Magnetic polyurethane based composites as contactless valves in microfluidic applications

Magnetoactive polymer composites have garnered significant attention for their potential use in diverse applications, owing to their rapid and reversible response to external magnetic fields. By incorporating magnetic nanoparticles (MNPs) into an elastomeric matrix, these composites exhibit unique properties under static or alternating magnetic fields. In this context, thermo-polyurethane-based magnetic active composites are promising materials for developing microfluidic system components such as valves and peristaltic pumps. In the current study, we investigated the utilization of cobalt ferrite (CoFe2O4) magnetic nanoparticles in conjunction with a non-toxic synthesis method for polyurethane. It was explored the impact, on the overall success of the process, of cobalt ferrite nanoparticles incorporation at various stages of the thermo-polyurethane (TPU) synthesis reaction. Finally, the effects of different amounts of MNPs on the physicochemical properties of the resulting composites and their behavior as actuators under the influence of a magnetic field, was investigated. Our studies reveal that the actuator response of the composites increases proportionally with the percentage of MNPs present.Finally, the performance of a TPU/7.5% (V/V) CoFe2O4 composite strip as a flow control actuator within a microfluidic system was evaluated. This actuator responds to magnetic fields by bending, resulting in a 10% reduction in flow rate of microfluidic system. Reversing the magnetic field restores the flow rate to its initial value. Our cyclic tests illustrate the actuator's capacity to locally and temporarily modulate the microfluidic system's resistance. When combined with tailored TPU elasticity, these materials show significant potential for the fabrication of microfluidic valves and pumps.

Growth of thin-film magnetic nanostructures promising for spintronics applications

Multilayered metallic nanostructures are promising for the fabrication of spin valves based on the giant magnetoresistive effect and for studies of the nature of topological magnetism, aimed at the development of new nanoscale data storage and transfer devices, e.g. those based on magnetic skyrmions. It is still an important task to develop methods of synthesis and configuration of thin-film nanostructures and control of spin textures in those nanostructures under electric and spin currents generated as a result of the spin Hall effect in external electric fields. Thin-film polycrystalline ferromagnetic / heavy metal Ru(10nm)/Co(0,8)/Ru(2), Ru(10)/Co(0,8)/Ru(2)/W(4), Pt(5)/Co(0,8)/MgO(2)/Pt(2) and Pt(15)/Co(0,8)/MgO(2)/Pt(2) nanostructures have been synthesized using magnetron sputtering. Electric contacts and Hall structures with different conductive bridge thicknesses have been synthesized on the specimens using electron beam photolithography. Experimental vibration magnetometric data have been utilized to calculate magnetic parameters of the specimens, i.e., saturation magnetization, magnetic anisotropy energy and field and coercive force as functions of ferromagnetic and heavy metal layer types. The domain structure of the specimens has been studied using Kerr microscopy. The electrical resistivity has been simulated and the critical current and current density of the nanostructures have been assessed. We show that all the film specimens exhibit perpendicular magnetic anisotropy and can be used in the studies of current-induced phenomena and spin moment transfer processes in nanostructures.

Chirality Versus Symmetry: Electron's Spin Selectivity in Nonpolar Chiral Lead-Bromide Perovskites.

In the last decade, chirality-induced spin selectivity (CISS), the spin-selective electron transport through chiral molecules, has been described in a large range of materials, from insulators to superconductors. Because more experimental studies are desired for the theoretical understanding of the CISS effect, chiral metal-halide semiconductors may contribute to the field thanks to their chiroptical and spintronic properties. In this regard, this work uses new chiral organic cations S-HP1A and R-HP1A (HP1A = 2-hydroxy-propyl-1-ammonium) to prepare 2D chiral halide perovskites (HPs) which crystallize in the enantiomorphic space groups P43 21 2 and P41 21 2, respectively. The fourfold symmetry induces antiferroelectricity along the stacking axis which, combined to incomplete Rashba-like splitting in each individual 2D polar layer, results in rare spin textures in the band structure. As revealed by magnetic conductive-probe atomic force microscopy (AFM) measurements, these materials show CISS effect with partial spin polarization (SP; ±40-45%). This incomplete effect is efficient enough to drive a chiro-spintronic device as demonstrated by the fabrication of spin valve devices with magnetoresistance (MR) responses up to 250 K. Therefore, these stable lead-bromide HP materials not only represent interesting candidates for spintronic applications but also reveal the importance of polar symmetry-breaking topology for spin selectivity.

A Review on Heat Treatment of Cast Iron: Phase Evolution and Mechanical Characterization.

The isothermal heat treatment process has been identified as a unique process of fabricating exceptional graphite cast iron due to its remarkable mechanical properties, such as excellent machinability, toughness, and high level of ultimate tensile strength. Austempered ductile iron (ADI), ductile iron (DI), and gray cast iron (GCI), known as spheroidal cast irons, are viable alternative materials compared to traditional steel casting, as well as aluminum casting. The graphite nodules from the microstructures of DI, ADI, and GCI are consistently encompassed by acicular ferrite and carbon-saturated austenite in the matrix, forming a distinctive ausferritic structure. All these materials are extensively used in the fabrication of engine sleeves, engine blocks, valves, gears, and camshafts in the automobile sector. With relative motion and outward loads, these components are regularly exposed to surface contact. In this project, it was observed that austempering temperature and a shorter holding period could also be used to manufacture needle-like ferrite platelets for austempered ductile iron (ADI) and other graphite cast irons. To overcome the brittleness challenges and catastrophic failures encountered by applied loads in present-day applications, it is essential to comprehend the isothermal treatments, morphological behaviors, phase analyses, processing techniques, and mechanical properties needed to properly incorporate these materials into future designs. This review article provides detailed information on the characterization and relevant potential mechanisms of ADI, DI, and GCI.

Design consideration of a novel polymeric transcatheter heart valve through computational modeling

Transcatheter heart valve replacement is becoming a more routine procedure, and this is further supported by positive outcomes from studies involving low-risk patients. Nevertheless, the lack of long-term transcatheter heart valve (TAV) durability is still one of the primary concerns. As a result, more research has been focused on improving durability through various methods such as valve design, computational modeling, and material selection. Recent advancements in polymeric valve fabrication showed that linear low-density polyethylene (LLDPE) could be used as leaflet material for transcatheter heart valves. In this paper, a parametric study of computational simulations showed stress distribution on the leaflets of LLDPE-TAV under diastolic load, and the results were used to improve the stent design. The in silico experiment also tested the effect of shock absorbers in terms of valve durability. The results demonstrated that altering specific stent angles can significantly lower peak stress on the leaflets (13.8 vs. 6.07 MPa). Implementing two layers of shock absorbers further reduces the stress value to 4.28 MPa. The pinwheeling index was assessed, which seems to correlate with peak stress. Overall, the parametric study and the computational method can be used to analyze and improve valve durability.

Design and Characterization of a 3D-Printed Pneumatically-Driven Bistable Valve With Tunable Characteristics

Although research studies in pneumatic soft robots develop rapidly, most pneumatic actuators are still controlled by rigid valves and conventional electronics. The existence of these rigid, electronic components sacrifices the compliance and adaptability of soft robots.} Current electronics-free valve designs based on soft materials are facing challenges in behaviour consistency, design flexibility, and fabrication complexity. Taking advantages of soft material 3D printing, this paper presents a new design of a bi-stable pneumatic valve, which utilises two soft, pneumatically-driven, and symmetrically-oriented conical shells with structural bistability to stabilise and regulate the airflow. The critical pressure required to operate the valve can be adjusted by changing the design features of the soft bi-stable structure. Multi-material printing simplifies the valve fabrication, enhances the flexibility in design feature optimisations, and improves the system repeatability. In this work, both a theoretical model and physical experiments are introduced to examine the relationships between the critical operating pressure and the key design features. Results with valve characteristic tuning via material stiffness changing show better effectiveness compared to the change of geometry design features (demonstrated largest tunable critical pressure range from 15.3 to 65.2 kPa and fastest response time $\leq$ 1.8 s.

Bioengineered percutaneous heart valves for transcatheter aortic valve replacement: a comparative evaluation of decellularised bovine and porcine pericardia

Glutaraldehyde-treated, surgical bioprosthetic heart valves undergo structural degeneration within 10–15 years of implantation. Analogous preliminary results were disclosed for percutaneous heart valves (PHVs) realized with similarly-treated tissues. To improve long-term performance, decellularised scaffolds can be proposed as alternative fabricating biomaterials. The aim of this study was to evaluate whether bovine and porcine decellularised pericardia could be utilised to manufacture bioengineered percutaneous heart valves (bioPHVs) with adequate hydrodynamic performance and leaflet resistance to crimping damage.BioPHVs were fabricated by mounting acellular pericardia onto commercial stents. Independently from the pericardial species used for valve fabrication, bioPHVs satisfied the minimum hydrodynamic performance criteria set by ISO 5840-3 standards and were able to withstand a large spectrum of cardiac output conditions, also during extreme backpressure, without severe regurgitation, especially in the case of the porcine group. No macroscopic or microscopic leaflet damage was detected following bioPHV crimping.Bovine and porcine decellularized pericardia are both suitable alternatives to glutaraldehyde-treated tissues. Between the two types of pericardial species tested, the porcine tissue scaffold might be preferable to fabricate advanced PHV replacements for long-term performance. Condensed abstractCurrent percutaneous heart valve replacements are formulated with glutaraldehyde-treated animal tissues, prone to structural degeneration. In order to improve long-term performance, bovine and porcine decellularised pericardia were utilised to manufacture bioengineered replacements, which demonstrated adequate hydrodynamic behaviour and resistance to crimping without leaflet architectural alteration.

Modelling and Fabrication of Engine Valve To Improve Performance of An I.C Engine

Modelling and fabrication of engine valves are made to increase the turbulence process by swirl. By proving swirl process to increase fast combustion phenomenon and enhance the efficiency of an engine. Engine should work at minimum speeds in order to have decrease the mechanical losses and good combustion enabling improves the combustion efficiency and mechanical efficiency (1). For this process be used to improves brake thermal efficiency and increase the usage of air-fuel mixture in combustion process which less impact pollution release to environment. The main importance of this work is to evaluate the performance of an Engine and to improve it by changing the valve design. Manufacturing of intake valves made to do an experimental work. this being done after modelling of valve and fabrication and then experimental work on test engine to compare two valves. Even if we adapt the this concept and also additional concentration required on inlet manifold.

Advances in Engineering Venous Valves: The Pursuit of a Definite Solution for Chronic Venous Disease.

Native venous valves enable proper return of blood to the heart. Under pathological conditions (e.g., chronic venous insufficiency), venous valves malfunction and fail to prevent backward flow. Clinically, this can result in painful swelling, varicose veins, edema, and skin ulcerations leading to a chronic wound situation. Surgical correction of venous valves has proven to drastically reduce these symptoms. However, the absence of intact leaflets in many patients limits the applicability of this strategy. In this context, the development of venous valve replacements represents an appealing approach. Despite acceptable results in animal models, no venous valve has succeeded in clinical trials, and so far no single prosthetic venous valve is commercially available. This calls for advanced materials and fabrication approaches to develop clinically relevant venous valves able to restore natural flow conditions in the venous circulation. In this study, we critically discuss the approaches attempted in the last years, and we highlight the potential of tissue engineering to offer new avenues for valve fabrication. Impact statement Venous valves prosthesis offer the potential to restore normal venous flow, and to improve the prospect of patients that suffer from chronic venous disease. Current venous valve replacements are associated with poor outcomes. A deeper understanding of the approaches attempted so far is essential to establish the next steps toward valve development, and importantly, tissue engineering constitutes a unique toolbox to advance in this quest.

In Vivo Evaluation of a Decellularized Pericardium-polymer Biohybrid Composite for Use as a Cardiovascular Tissue Substitute

Objective: Glutaraldehyde (GA) fixed bovine pericardium (BP) is the current gold standard for fabrication of bioprosthetic heart valves, despite their poor durability, lack of growth, risk of calcification and structural degeneration over time. These limitations make it unsuitable for use in children. Non-fixed, decellularized BP (dBP) has been tried as an alternative, but failed due to poor mechanical properties. In this study, our objective was to use a biodegradable polymer to treat dBP and improve its mechanical strength (Bio-Hybrid), and understand its remodeling potential in chronic animal implants. Methods: BP was decellularized using 2% sodium deoxycholate and its efficiency confirmed with DNA estimation and matrix analysis. The dBP was then coated with a layer of electrospun Polycaprolactone:Chitosan (PCL:Ch) to fabricate a Bio-Hybrid scaffold. The mechanical properties (uniaxial and biaxial), biocompatibility (cell adhesion, proliferation and cytotoxicity) and hemocompatibility (platelet adhesion, hemolysis and clot formation assay) of Bio-Hybrid material were assessed in comparison to GA treated BP. The in vivo biological response to the Bio-Hybrid material was evaluated in a rat subcutaneous model with GA treated BP as control material. Results: Decellularized BP showed significant reduction (p=0.0017) in DNA (49.05 + 41.09 ng/mg) compared to fresh BP (173.89 + 126.52 ng/mg). Electrospun PCL:Ch adhered to the decellularized BP, confirmed by FT-IR with unique peaks (1638.2, 1044.2 and 877.1 cm-1). Uniaxial mechanical testing showed significant increase in tensile extensibility (p=0.02) and the biaxial testing indicated an increase in the upper (p=0.002) and lower tangent modulus (p=0.0005) in the Bio-Hybrid. In vivo rat subcutaneous explants demonstrated higher cellular infiltration in the Bio-Hybrid scaffold along with remodeling of the extracellular matrix after 1, 4 and 12 weeks, compared to BP and dBP. Conclusions: BP modified with a synthetic polymer demonstrated favorable mechanical and remodeling potential, encouraging its pursuit as an alternative material for heart valve repair/replacement in children. KEYWORD: ICTEHV-O-13 The authors do not declare any conflict of interest.

Automated Addressable Microfluidic Device for Minimally Disruptive Manipulation of Cells and Fluids within Living Cultures.

Cell culturing experiments are ubiquitous to the study of biology, development of new medical treatments, and the biomanufacturing industry. However, there are still major technological barriers limiting the advancement of knowledge and ballooning the experimental costs associated with these systems. For example, currently, it is difficult to perform nondisruptive monitoring and control of the cells in the cultured samples. This often necessitates the use of sacrificial assays and results in product inconsistency. To resolve these bottlenecks, we present a prototype "addressable" microfluidic technology capable of spatiotemporal fluid and cell manipulations within living cultures. As a proof-of-concept, we demonstrate its ability to perform additive manufacturing by seeding cells in spatial patterns (including co-culturing multiple cell types) and subtractive manufacturing by removing surface adherent cells via the focused flow of trypsin. Additionally, we show that the device can sample fluids and perform cell "biopsies" (which can be subsequently sent for ex situ analysis), from any location within its culture chamber. Finally, the on-chip plumbing is completely automated using external electronics. This opens the possibility of performing long-term computer-driven experiments, where the cell behavior is modulated in response to the minimally disruptive observations (e.g., fluid sampling and cell biopsies) throughout the entire duration of the cultures. A limitation of the presented α prototype is that it is only two-dimensional (2D). However, technology serves as a foundation for ultimately extending the concept to three-dimensional (3D). Another limitation of the device is that it is currently made from poly(dimethylsiloxane) (PDMS), while more work needs to be done to manufacture from a material that degrades away or allow the cells to lay down the tissue matrix. Unfortunately, the existing biodegradable materials are typically not strong enough for the fabrication of microfluidic valves. Hence, new ones need to be developed before this technology can become mainstream. Yet, it is the hope of the authors that this will be achieved soon, and the microfluidic plumbing technology will eventually be scaled up to 3D, to overcome the limitations of the conventional cell culturing platforms.

Leveraging Viscous Peeling to Create and Activate Soft Actuators and Microfluidic Devices.

The research fields of microfluidics and soft robotics both involve complex small-scale internal channel networks, embedded within a solid structure. This study examines leveraging viscous peeling as a mechanism to create and activate soft actuators and microchannel networks, including complex elements such as valves, without the need for fabrication of structures with micron-scale internal cavities. We consider configurations composed of an internal slender structure embedded within another elastic solid. Pressurized viscous fluid is introduced into the interface between the two solids, thus peeling the two elastic structures and creating internal cavities. Since the gap between the solids is determined by the externally applied pressure, the characteristic size of the fluid network may vary with time and be much smaller than the resolution of the fabrication method. This study presents a model for the highly nonlinear elastic-viscous dynamics governing the flow and deformation of such configurations. Fabrication and experimental demonstrations of micron-scale valves and channel networks created from millimeter scale structures are presented, as well as the transient dynamics of viscous peeling-based soft actuators. The experimental data are compared with the suggested model, showing very good agreement.

On-ratio PDMS bonding for multilayer microfluidic device fabrication

Integrated elastomeric valves, also referred to as Quake valves, enable precise control and manipulation of fluid within microfluidic devices. Fabrication of such valves requires bonding of multiple layers of the silicone polymer polydimethylsiloxane (PDMS). The conventional method for PDMS–PDMS bonding is to use varied ratios of base to crosslinking agent between layers, typically 20:1 and 5:1. This bonding technique, known as ‘off-ratio bonding’, provides strong, effective PDMS–PDMS bonding for multi-layer soft-lithography, but it can yield adverse PDMS material properties and can be wasteful of PDMS. Here we demonstrate the effectiveness of ‘on-ratio’ PDMS bonding, in which both layers use a 10:1 base-to-crosslinker ratio, for multilayer soft lithography. We show the efficacy of this technique among common variants of PDMS: Sylgard 184, RTV 615, and Sylgard 182.

3D bioprinting of collagen to rebuild components of the human heart.

Collagen is the primary component of the extracellular matrix in the human body. It has proved challenging to fabricate collagen scaffolds capable of replicating the structure and function of tissues and organs. We present a method to 3D-bioprint collagen using freeform reversible embedding of suspended hydrogels (FRESH) to engineer components of the human heart at various scales, from capillaries to the full organ. Control of pH-driven gelation provides 20-micrometer filament resolution, a porous microstructure that enables rapid cellular infiltration and microvascularization, and mechanical strength for fabrication and perfusion of multiscale vasculature and tri-leaflet valves. We found that FRESH 3D-bioprinted hearts accurately reproduce patient-specific anatomical structure as determined by micro-computed tomography. Cardiac ventricles printed with human cardiomyocytes showed synchronized contractions, directional action potential propagation, and wall thickening up to 14% during peak systole.

Bioinspired Heart Valve Prosthesis Made by Silicone Additive Manufacturing

Summary Synthetic implants made by traditional fabrication routes are not patient specific and rarely match the performance of their biological counterparts. We present an additive manufacturing approach for the digital fabrication of tissue-like aortic heart valves featuring customizable geometry and leaflet architectures that resemble those of native valve tissue. Using biocompatible silicones with tunable mechanical properties, heart valves were fabricated by combining spray and extrusion-based additive manufacturing processes. Computer simulations showed that bioinspired leaflet architectures strongly affect the stress distribution throughout the valves, minimizing stresses on the leaflet during a cardiac cycle. Our computational analysis was complemented by in vitro experiments in a pulse duplicator to demonstrate the outstanding hemodynamic performance of the printed heart valves under physiological pressure cycles. The ability to fabricate synthetic implants with tailored designs at multiple length scales is a key contribution toward the digital fabrication of functional implants that perform on par with native body parts.

Facile design and fabrication of capillary valve for mixing using two‐step PDMS moulding

The traditional capillary mixing using a closed channel and a mixing unit without the delay valve encounters problems of backflow and clogging. Here, the polydimethylsiloxane (PDMS) mixing channel with the facile delay valve and open surface design has been demonstrated using the two-step moulding for long-term-hydrophilic capillary-pumping. The triggering of delay valve before the mixing unit is controlled by the specific channel height calculated using capillary theory. It can eliminate the problems of backflow, clogging and bubble defect. Also, the channel height in an open channel is reduced to 150 μm compared to the close one of 250 μm by numerical analysis. The CO 2 -laser-ablated polymethylmethacrylate (PMMA) mother mould can avoid the complicated fabrication process using photolithography and SU8 mould. Using the unique two-step PDMS moulding method can greatly diminish the defect from the laser-ablated PMMA mould for a smoother surface. The naturally hydrophobic PDMS is modified using the polyethylene glycol and O 2 plasma treatment to solve the sticking problem and prolong the hydrophilicity up to 164 h and more which is tested in the contact angle aging measurement.

Simple Way To Fabricate Novel Paper-Based Valves Using Plastic Comb Binding Spines

A novel strategy for fabricating the paper-based valves on microfluidic paper-based analytical devices (μPADs) was described to control fluid in a user-friendly way. Initial prototypes of 3D μPADs manipulate the spatial distribution of fluid within the device. The movable paper channel in a different layer could be achieved using the channel's connection or disconnection to realize the valve function using plastic comb binding spines (PCBS). The entire valve manipulation process was similar to a desk calendar that can be flipped over and turned back. It is notable that this kind of PCBS valve can control a fluid in a simple and easy way without the timing setting or any trigger, and this advantage makes it user-friendly for untrained users to carry out the complex and high throughput operations. The reusable plastic comb binding spines greatly reduce the cost of fabricating paper-based valves. To evaluate the performance, the actual samples of Fe (II) and nitrite were successfully analyzed. We hope this method will introduce a new approach to fabrication of paper-based valves on μPADs in the future.

POTENTIAL BENEFITS FOR USING ePTFE AS A MATERIAL FOR PROSTHETIC HEART VALVES

Background The current study highlights potential benefits of using ePTFE, a polymeric material, as the main component suitable for fabrication of prosthetic heart valves. Novel polymeric materials seem to be promising for replacing biological elements commonly used in medical products for cardiovascular surgery. High biocompatibility and mechanical properties prolong their lifespan during direct blood contact. Nevertheless, it is necessary to conduct a series of specific tests to determine their properties and benefits of their application. Despite well-known biological properties of ePTFE, there are few studies assessing it as a material for heart valve leaflets. Aim To evaluate the mechanical properties of the commercially available sample of ePTFE and to conduct a numerical experiment assessing its potential for the application. Methods The polymer properties (Gore & Associates Inc., USA) were evaluated under uniaxial tension in two mutually perpendicular directions to determine the degree of anisotropy of the material. A xenopericardial patch (ZAO “NeoCor”, Russia), routinely used for the fabrication of bioprosthetic leaflets, was taken as the control sample. The spatial model of the investigated material was carried out in CAD SolidWorks 2016 (Dassault Systemes, USA). Numerical modeling of the samples was performed with the finite element method using the orthotropic material model in the Abaqus/CAE (Dassault Systemes, USA). Results There are significant difference found in the mechanical properties of the studied materials: the tension at stretching of ePTFE in the longitudinal and transverse directions differed from xenopericardium by 1.9 and 7.5 times, respectively (p<0.05). The elongation before rupture of ePTFE in direction I and direction II was greater than that of xenopericardium (2.39 vs. 1.9 times, respectively). Numerical modeling demonstrated insignificant qualitative differences in the valve opening while applying pressure equal to normal physiological pressure>< 0.05). The elongation before rupture of ePTFE in direction I and direction II was greater than that of xenopericardium (2.39 vs. 1.9 times, respectively). Numerical modeling demonstrated insignificant qualitative differences in the valve opening while applying pressure equal to normal physiological pressure and low pressure. In addition, the zones of high stress in commissural racks, which are critical zones for fatigue resistance, have been identified, albeit require additional in vitro research. Conclusion Mechanical properties of ePTFE suggests it to be a promising polymeric material suitable for fabrication of flexible leaflets of the heart valve prosthesis. It has similar leaflet functioning, compared with the xenopericardium sample, routinely used in manufacturing. ePTFE is more resistant to rupture, which confirms its greater fatigue strength. However, it requires further study by advanced methods.

A numerical insight into elastomer normally closed micro valve actuation with cohesive interfacial cracking modelling

Pneumatic NC (normally closed) valves are widely used in high density microfluidics systems. To improve actuation reliability, the actuation pressure needs to be reduced. In this work, we utilize 3D FEM (finite element method) modelling to get an insight into the valve actuation process numerically. Specifically, the progressive debonding process at the elastomer interface is simulated with CZM (cohesive zone model) method. To minimize the actuation pressure, the V-shape design has been investigated and compared with a normal straight design. The geometrical effects of valve shape has been elaborated, in terms of valve actuation pressure. Based on our simulated results, we formulate the main concerns for micro valve design and fabrication, which is significant for minimizing actuation pressures and ensuring reliable operation.

Critical switching characteristics of three-layered spin valve for different materials and alloys with uniaxial anisotropy

We analyze the dependence of the current density and magnetic field switching on the magnetic parameters of the material of the ferromagnetic layers of the spin valve. Comparison of critical characteristics of the spin valve with longitudinal anisotropy of ferromagnetic layers fabricared of different materials showed that the promising materials for the fabrication of spin valve are cobalt, iron, their alloys, ferroborates of cobalt and alloys of cobalt with gadolinium. For these materials we produced and analyzed the bifurcation diagrams of equations describing the switching process of the spin valve. Based on the study of the dynamics of the magnetization vector we obtained the numerical evaluation of time switching.