Optical sensor assembly in catheter-based medical devices

Abstract

To provide an optical sensor assembly for protecting a sensor during pump insertion, facilitating adhesion of the sensor to a pump housing, and preventing contamination of optical sensor assembly components.SOLUTION: An optical sensor assembly 200 for use in a blood pump assembly comprises a visor 202 affixed to a pump housing 222 of the blood pump assembly. A support jacket 208 is in contact with an inner surface of the visor 202, and defines a cavity 210 in which an optical sensor 212 is disposed. A silicone composition 218 is introduced into the cavity 210, and cured therein. The silicone composition comprises a silicone component and a plasticizer with a silicone-to-plasticizer ratio selected to provide one or more of the desired rigidity, tackiness, adhesion strength, viscosity, shelf life, pot life, and curing properties. The silicone composition may comprise multiple silicone components.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 868,517, filed June 28, 2019, and U.S. Provisional Patent Application No. 62 / 868,527, filed June 28, 2019, the disclosures of both applications are incorporated herein by reference in their entireties. [Background technology]

[0002] background An intravascular blood pump assembly, such as an assembly with an intracardiac blood pump, may be introduced into the heart to deliver blood from the heart to the arteries. The intravascular blood pump may be introduced percutaneously through the vascular system during a cardiac procedure, such as by catheterization. Some blood pumps are designed to assist the left side of the heart, drawing blood from the left ventricle of the heart and discharging the blood through a cannula into the aorta. Some blood pumps that assist the left side of the heart are introduced by catheterization through the femoral artery into the ascending aorta, across the aortic valve, and into the left ventricle. Some systems are designed to assist the right side of the heart, and the blood pump is introduced through a vein and through the venous system (e.g., the vena cava) into the right side of the heart. Blood pump systems may also be surgically implanted or inserted through the subclavian and / or carotid arteries. During insertion of the blood pump assembly into the patient through the blood vessels, it may be difficult to advance the blood pump through the patient's tortuous pathways or calcified anatomy.

[0003] Complications with pump installation due to these tortuous paths can potentially cause damage to the blood pump assembly or to the patient. For example, the blood pump or its components may be damaged or may damage the patient's vasculature during insertion or operation. Blood pump components may become detached from the pump during installation and operation due to, for example, the vasculature or shear forces exerted on the blood pump components by the blood. A damaged blood pump may require removal and replacement, or may no longer be accurate or operational. For example, damage to a pump sensor may prevent accurate pump installation or operation.

[0004] Blood pump sensors (e.g., optical sensors) may be particularly susceptible to damage during insertion or operation of the pump. For example, shear forces exerted on such optical sensors placed with the blood pump in a patient's body may cause the sensor to crack. In addition, these shear forces may at least partially dissolve, erode, or damage the sensor membrane. Incorporation of dissolved silicone particles may be detrimental to the patient's health. In other circumstances, the optical sensor or components thereof may become separated from the rest of the system, such as from the blood pump housing. Damage to the optical sensor may prevent the sensor from communicating important signals captured by the sensor to the physician. Similarly, separation of blood pump components within the patient's vasculature may also adversely affect the patient's health.

[0005] One approach protects the optical sensor with a single layer of cured silicone gel applied to the surface of the sensor. Additional layers of silicone gel provide additional protection. However, silicone gel is hydrophobic and may become unstable and overflow due to capillary pressure acting on the sensor during operation. Silicone gel overflow compromises adhesion of the optical sensor to the pump housing. Poor adhesion between the optical sensor and the pump housing may cause the device to break in the patient due to shear forces exerted on the assembly by blood. Additionally, silicone gel overflow may cause contamination of various components in the area of ​​the pump housing.

[0006] To protect the measuring surface of the optical sensor (e.g., the diaphragm of the optical sensor) from the forces exerted on the measuring surface by the blood during insertion and operation of the blood pump assembly, the measuring surface of the optical sensor is covered with a layer of cured silicone. Due to the unique conditions in which the blood pump assembly with the optical sensor is placed, there are several mechanical properties that must be considered in determining a suitable silicone composition for application to the measuring surface of the optical sensor. The silicone must have the appropriate viscosity, adhesive strength, hardness and tackiness while being biocompatible to ensure patient safety. The desired mechanical properties are unique for a silicone composition for use in a blood pump assembly because the conditions in which the pump assembly operates are themselves unique. Specifically, these mechanical properties allow the composition to be easily handled during manufacturing. In addition, such mechanical properties allow the composition to flow within the area of ​​the support jacket of the optical sensor assembly without contaminating the visor of the assembly. Furthermore, a composition with these properties provides sufficient protection for the measuring surface of the optical sensor during insertion of the blood pump assembly into a patient. In addition, these unique silicone mechanical properties are preferably obtained without interfering with the manufacturing process. In particular, these mechanical properties preferably provide protection to the measurement surface of the optical sensor without a lengthy curing process. In addition, the silicone should also have a desirable shelf life and pot life.

[0007] Thus, it would be desirable to have an improved optical sensor assembly that provides one or more of the following advantages: protecting the sensor during pump insertion, facilitating adhesion of the sensor to the pump housing, preventing contamination of the optical sensor assembly components, and preventing undesired overflow of silicone gel (or other adhesive components) when the blood pump assembly is placed in a patient. Moreover, it would be desirable to be able to easily manufacture such an improved optical sensor assembly when incorporated into an existing blood pump assembly without impeding or slowing the manufacturing process. In addition, it would be desirable to create a composition that has the desired mechanical properties to protect an optical sensor for use in a blood pump assembly and that can also be incorporated into existing manufacturing methods. Summary of the Invention

[0008] Quick Overview The systems, methods, and devices described herein provide an optical sensor assembly with an improved sensor protection system for use in an intravascular blood pump system (or other blood pump system). The blood pump system has a blood pump (e.g., an Impella® pump) with a sensor system including a sensor (such as an optical sensor) located in a support jacket attached or positioned relative to the blood pump. In use, the sensor aids in positioning the pump as well as monitoring the performance and impact of the pump. The blood pump may have a rotor in a pump housing, a cannula to receive blood pumped through the system, a delivery mechanism (such as a catheter or surgical delivery set) for inserting the pump into a patient, and a drive unit to power the pump. The drive unit may be an external motor and electrical connections. Alternatively, the drive unit may be a mechanical cable connecting the rotor to an external motor. The cannula may extend distally of the pump and include a flexible, atraumatic protrusion extending distally of the cannula.

[0009] The optical sensor assembly may include an optical sensor selected to cooperate with the pump and disposed within a support jacket, which is affixed or otherwise secured to the pump. The support jacket may be configured with a gap or other cavity to receive the sensor. The support jacket may include a polymer or metal. For example, the support jacket may include polyimide or stainless steel. The support jacket may be formed of a polymer or other material that can be adhered or positioned to the pump (or one of the pump's components) to support the sensor. For example, the sensor is positioned in sufficient proximity to the pump to be useful for monitoring pump performance. The support jacket may be configured in the shape of a tube or any suitable elongated body having an inner surface, an outer surface, and defining a cavity. The support jacket may have a circular, rectangular, oval, or elliptical cross section. In some conformations, the cavity of the support jacket is configured to include a sufficient amount of silicone composition or other material to secure the sensor within the cavity. For example, the amount of silicone composition or other material fills the cavity in which the sensor is located and surrounds the sensor. A visor may be included that covers the outer surface of the support jacket to further shield the optical sensor. In some implementations, the visor is in contact with the outer surface of the support jacket. In other implementations, there is a space between the visor and the outer surface of the support jacket. In certain implementations, a portion of the visor is in direct contact with the outer surface of the support jacket and another portion of the visor is separated from the outer surface of the support jacket by a space.

[0010] According to a first implementation, the optical sensor assembly includes a visor, a support jacket (e.g., a polymer tube or another elongated body having an inner surface and an outer surface and defining a cavity), an optical sensor, and a silicone composition. The inner surface of the visor is disposed around the support jacket (e.g., a polymer tube) so as to contact the outer surface of the jacket (e.g., a surface of the polymer tube) and to shield the sensor disposed within the cavity. In a particular adaptation, the support jacket (e.g., a polymer tube or a metal tube) defines a cavity within its frame. The optical sensor of the assembly is disposed within the cavity. The inner surface of the optical sensor is in contact with the inner surface of the jacket. For example, the inner surface of the optical sensor can be glued to the inner surface of the jacket. In another example, the inner surface of the optical sensor can be fused to the inner surface of the jacket.

[0011] In some implementations, the inner surface of the visor at least partially covers the outer surface of the jacket (e.g., polymer tubing). In further implementations, the inner surface of the visor surrounds a portion of the jacket such that the portion not covered by the visor does not contact the pump housing. In other implementations, the inner surface of the visor surrounds a portion of the jacket such that the portion not covered by the visor contacts the pump housing. In some implementations, the jacket is glued to the visor. In other implementations, the jacket is fused to the visor. In certain implementations, the jacket is fused to the pump housing. In some implementations, the jacket is glued to the pump housing. At least one layer of a silicone composition or another similar material (e.g., platinum-based silicone) covers the outer surface of the optical sensor and fills the cavity defined by the jacket. The silicone composition serves to protect the optical sensor of the blood pump assembly from shear forces exerted on the optical sensor by the blood during percutaneous insertion and operation of the pump within the patient. An additional layer of the silicone composition or another similar material provides further protection to the sensor. In some embodiments, the silicone composition is a silicone gel.

[0012] The jacket (e.g., polymer tube) can be any one of a variety of polymers or other similar materials. In some implementations, the polymer includes polyimide. The polymer jacket can be comprised of a polymer blend. In some implementations, the polymer blend includes polyimide and one or more other polymers. The particular polymer the polymer jacket includes is selected to facilitate handling. Additionally, the support jacket can include a metal that also facilitates handling. For example, the metal can be stainless steel. In other implementations, the metal is Nitinol. The visor can include a metal, a plastic, or a composite material. In certain implementations, the visor can be stainless steel. In other implementations, the metal includes an alloy. In some examples, the alloy is Nitinol. In other implementations, the alloy is an iron alloy. In certain implementations, the plastic is polyurethane. The polyurethane can include a polyether or polyester.

[0013] Additionally, the inner surface of the visor can be configured to adhere to the pump housing. In some implementations, the inner surface of the visor is coupled to the pump housing by an adhesive. The adhesive forms a bond between the visor and the pump housing that can withstand the shear forces exerted by the blood. In certain implementations, the adhesive is an epoxy. For example, the adhesive can be a two-part epoxy or a UV light-bonded epoxy. In other implementations, the inner surface of the visor is fused directly to the pump housing.

[0014] The silicone composition can be applied to the optical sensor in the cavity of the jacket. In some embodiments, the silicone composition is a silicone gel. The inner surface of the jacket (e.g., a polymer tube) inhibits the flow of the silicone composition so that it remains in the cavity and a constant amount of silicone composition can surround the sensor without overflowing or having to be added and cured one layer at a time. The ability to add the silicone composition volumetrically provides a thicker protective layer to the sensor and allows the silicone composition (or other bonding material) to be cured in the cavity in a single step rather than using a layer-by-layer approach. Thus, the polymer tube allows additional silicone composition to protect the optical sensor without slowing down the manufacturing process.

[0015] The cavity in the jacket (e.g., polymer tube) can be structured to have a range of lengths or radii. In some implementations, the cavity has a length of about 1 centimeter to about 5 centimeters. In other implementations, the cavity has a length of about 2 centimeters to about 4 centimeters. In certain implementations, the cavity has a length of about 3 centimeters. In certain implementations, the cavity has a radius of about 0.1 millimeters to about 0.25 millimeters. In some implementations, the cavity has a radius of about 0.15 millimeters to about 0.20 millimeters. In further implementations, the cavity has a radius of about 0.175 millimeters. At least one advantage of having a polymer tube or other cavity with a range of acceptable lengths is that tubes of various lengths can accommodate various amounts of silicone composition, all of which provide additional protection to the optical sensor.

[0016] Generally, applying the silicone composition or other bonding material as a thicker layer of silicone composition within the cavity can provide greater protection for the sensor system. This feature can be useful in some procedures where the system is subjected to high shear forces. Such procedures can be completed with an optical sensor assembly having a larger polymer tube containing a larger amount of silicone composition to provide additional protection for the sensor. The size cavity and volume of the silicone composition can be adjusted as needed for a given patient's anatomy. For example, femoral insertion of some blood pumps into obese patients exerts more force on the blood pump because the blood vessels are deeper to the insertion point than in healthy weight patients. In that case, the cavity size and silicone composition fill level can be set to increase the strength of adhesion and protection of the optical sensor components of the blood pump, for example, by increasing the length of the support jacket to create a larger cavity volume. Thus, a larger cavity volume can accommodate a larger amount of silicone composition, which protects the optical sensor from large shear forces. Cardiac procedures in pediatric patients with smaller anatomical structures can be completed using an optical sensor assembly with a smaller polymer tube, allowing an additional layer of silicone to be applied to the surface of the optical sensor while minimizing the damage inflicted by the larger pump on the smaller vasculature of pediatric patients.

[0017] In some implementations, the optical sensor assembly includes a visor configured to mate with a polymer tube or other jacket. The visor is configured to surround the supporting jacket to protect the sensor within a cavity defined by the jacket. The visor provides the jacket with protection from shear forces exerted on the optical sensor by the patient's blood during insertion and operation of the pump into the patient. The visor is attached to the housing by an adhesive strong enough to withstand the shear forces exerted on the optical sensor assembly during insertion.

[0018] The visor and the jacket each have an inner surface and an outer surface, and in various adaptations, the inner surface of the visor is configured to contact the outer surface of the jacket (e.g., the outer surface of the polymer tube). A cavity is defined within an outer periphery of the jacket (e.g., within an outer periphery of the polymer tube and within an inner surface of the elongated body defining the cavity) and can be sized to receive an optical sensor. The cavity is configured to be filled with a silicone composition to protect the optical sensor disposed within the cavity. In some implementations, the optical sensor is a silicone optical sensor. The polymer tube further shields the silicone composition from the visor to reduce contamination of the outer surface of the visor. The size of the cavity and the amount of silicone composition are configured to protect the optical sensor from damage due to forces exerted on the optical sensor during percutaneous insertion of the blood pump assembly into a patient.

[0019] In some implementations, the visor surrounds the support jacket and is secured to a component of the pump assembly. In certain implementations, the visor is secured to the pump housing. The visor may be glued to the pump housing or, in some implementations, fused to the pump housing. The visor comprises a material that provides a sufficiently strong bond between the visor and the pump housing. In some implementations, the visor comprises a metal. The metal may include stainless steel, or another similar material. The visor must further comprise a material that provides sufficient protection for the support jacket.

[0020] In another implementation, a method of manufacturing packaging for an optical sensor for use in a blood pump assembly includes disposing an optical sensor in a cavity of a support jacket, such as in a polymer tube that defines a cavity. The method further includes filling a portion of the cavity with a material (e.g., a silicone composition) and curing the material. The method then includes surrounding a portion of the support jacket (e.g., a portion of the polymer tube) with a visor and bonding an inner surface of the visor to the blood pump, e.g., to a pump housing of the blood pump. In certain implementations, about 30 percent to about 90 percent of the cavity is filled with the silicone composition. In other implementations, about 50 percent to about 70 percent of the cavity is filled with the silicone composition. In further implementations, about 60 percent of the cavity is filled with the silicone composition. Since a larger amount of silicone composition requires a longer curing time, the portion of the volume of the cavity that is filled with the silicone composition can be selected to obtain the desired protection for the optical sensor and also to obtain the desired manufacturing time. In some embodiments, the silicone composition is a silicone gel. In some implementations, the optical sensor is a silicone optical sensor. In other implementations, the support jacket (e.g., a polymer tube) includes polyimide. In certain implementations, the visor includes a metal. The metal may include stainless steel. The material from which the visor is formed is selected to obtain certain mechanical properties of the visor. In some implementations, the visor is bonded to the pump housing by an adhesive. In certain implementations, the adhesive may be a two-part epoxy. In other implementations, the adhesive may be a UV light-bonding epoxy. In further implementations, the visor is configured to be fused to the pump housing. The means by which the visor is attached to the pump housing is selected to ensure sufficient adhesive strength of the bond between the visor and the pump housing and to allow the bond between the visor and the pump housing to withstand shear forces exerted by blood on the pump assembly during insertion and operation of the pump assembly.

[0021] The systems, methods, and devices described herein also provide a silicone composition for use in a sensor assembly, such as an optical sensor assembly. An exemplary optical sensor assembly may be configured for use in a blood pump assembly. In general, the blood pump assembly includes a blood pump having a rotor with a pump housing surrounding one or more blades, and a drive unit. A cannula extends distally from the pump housing, and a flexible, atraumatic protrusion extends distally from the cannula. The blood pump assembly further includes an optical sensor assembly. A silicone composition is disposed on the optical sensor to accommodate the environment in which the blood pump assembly operates. The composition includes a silicone component and a plasticizer with a ratio selected to provide one or more of desired stiffness, adhesion, adhesive strength, viscosity, shelf life, pot life, and cure properties. The composition may include a silicone and a plasticizer in a mass or molar ratio. The values ​​of the properties corresponding to the composition are configured to protect the optical sensor without impairing the sensor's ability to take accurate measurements from within the patient's body. In some implementations, the composition includes two or more silicone components. In such implementations, the components may be mixed in sequence to prevent undesired residual reactions from occurring. In a first implementation, a method of making a silicone composition for use in an optical sensor assembly includes first mixing a first silicone component with a plasticizer to form a first silicone mixture. Subsequently, the second silicone component is mixed with the plasticizer to form a second silicone mixture. The first silicone mixture is then combined with a second silicone mixture to obtain a silicone composition configured to protect a measurement surface of the optical sensor. The optical sensor assembly may be suitable for use in a blood pump assembly, and the silicone composition may be suitable for protecting the sensor from shear forces exerted during insertion and operation of the blood pump assembly in a patient. The composition may be vacuum degassed. In general, each silicone component may be biocompatible.

[0022] In some embodiments, the first silicone component includes an activator. In certain implementations, the activator includes fumed silica. In certain embodiments, the second silicone component has a catalyst, such as a metal (e.g., platinum-based) catalyst. In other embodiments, the catalyst is rhenium-based. In some embodiments, the catalyst has an organometallic compound configured to enhance compatibility of the catalyst with the silicone component. In some embodiments, the first silicone component and the plasticizer are different materials. In some embodiments, the first silicone component, the second silicone component, and the plasticizer are different from each other. In some embodiments, at least one of the first silicone component and the plasticizer is NuSil MED4088. In further embodiments, both the first silicone component and the plasticizer are NuSil MED4088. In some embodiments, the plasticizer is a silicone oil plasticizer. In certain embodiments, the plasticizer is NuSil MED360.

[0023] The concentrations of the first and second silicone components and the plasticizer can be selected so that the ratio of these components in the composition is at a desired level. For example, the ratio of the first silicone component to the plasticizer and the ratio of the second silicone component to the plasticizer can be selected so that the silicone composition has a desired mechanical property and a desired final ratio within the composition. Specifically, the composition has at least the desired viscosity, sufficient adhesive strength and tack to adhere to the optical sensor, and the composition can advantageously have sufficient rigidity to facilitate handling. An exemplary plasticizer is silicone oil, which reduces the viscosity of the first and second silicone components so that the composition has one or more of the desired mechanical properties described above and is easy to handle during manufacturing. However, applying too much silicone oil unnecessarily increases the length of time the composition must be cured.

[0024] Thus, the specific ratios between the components, as well as the mechanical properties of the final composition, may be suitably selected to protect the optical sensor from the shear forces exerted on the sensor during insertion and use, while also allowing for efficient handling and manufacturing times.

[0025] In some implementations, the ratio of the first silicone component to the plasticizer is about 1:4 to about 4:1. In certain implementations, the ratio of the second silicone component to the plasticizer is about 1:4 to about 4:1. In further implementations, the ratio of the first silicone component to the plasticizer is about 1:3 to about 3:1. In certain implementations, the ratio of the second silicone component to the plasticizer is about 1:3 to about 3:1. In some implementations, the ratio of the first silicone component to the plasticizer is about 1:2 to about 2:1. In certain implementations, the ratio of the second silicone component to the plasticizer is about 1:2 to about 2:1. In some implementations, the ratio of the first silicone component to the plasticizer is about 1:1. In further implementations, the ratio of the second silicone component to the plasticizer is about 1:1.

[0026] In certain implementations, the ratio of the first silicone component to the second silicone component to the plasticizer of the final composition is about 1:1:8 to about 2:2:1. In further implementations, the ratio of the first silicone component to the second silicone component to the plasticizer of the final composition is about 1:1:6 to about 3:3:2. In certain implementations, the ratio of the first silicone component to the second silicone component to the plasticizer of the final composition is about 1:1:4 to about 1:1:1. In further implementations, the ratio of the first silicone component to the second silicone component to the plasticizer of the final composition is about 1:1:2.

[0027] The plasticizer may be added separately to each of the first and second silicone components to avoid undesirable reactions between the plasticizer and the first and second silicone components. For example, adding the plasticizer separately to the first and second silicone components avoids undesirable interactions between two or more components that may result in a non-uniform mixture. As described below, this separate addition of the plasticizer to the first and second silicone components may further help achieve a desired viscosity of the silicone composition. A composition configured with a desired viscosity may optimally protect the optical sensor during insertion and operation of the blood pump assembly, and may also facilitate handling of the composition during manufacturing.

[0028] The mechanical properties of the silicone composition can be selected such that the composition is suitable for use in an optical sensor assembly for a blood pump. For example, the adhesive strength of the silicone composition can be selected to prevent the silicone layer from detaching from the measurement surface (e.g., diaphragm) of the optical sensor due to shear forces exerted on the composition. In some implementations, the adhesive strength of the silicone composition is such that the composition can withstand a maximum load of about 120N to about 500N, and in some conformations, the strength allows the composition to withstand a maximum load of about 160N to about 340N. In further implementations, the strength allows the composition to withstand a maximum load of about 210N to about 290N. In other implementations, the silicone composition is configured to have an adhesive strength such that the composition can withstand a maximum load of about 250N.

[0029] Generally, the silicone composition is configured to have an adhesive strength such that the composition can withstand a maximum load greater than a certain threshold. In some implementations, the adhesive strength threshold of the composition is about 50N to about 150N. In other implementations, the adhesive strength threshold of the composition is about 75N to about 125N. In certain implementations, the adhesive strength threshold of the composition is about 100N.

[0030] The viscosity should also be configured such that the composition can be easily handled during manufacturing and protect the sensor in a manner that is less likely to overflow during operation of the blood pump assembly. In some implementations, the viscosity of the composition is about 2,000 cP to about 8,000 cP. In further implementations, the viscosity of the composition is about 3,000 cP to about 7,000 cP. In certain implementations, the viscosity of the composition is about 4,000 cP to about 6,000 cP. In further implementations, the viscosity of the composition is about 5,000 cP. In other implementations, the viscosity of the composition is about 2,400 cP to about 7,000 cP.

[0031] The viscosity of each silicone component can be considered in addition to the viscosity of each silicone mixture and the viscosity of the entire final composition. For example, in some implementations, the first silicone component and the second silicone component are configured to have a viscosity of about 20,000 cP to about 50,000 cP. In other implementations, the first silicone component and the second silicone component are configured to have a viscosity of about 25,000 cP to about 45,000 cP. In certain implementations, the first silicone component and the second silicone component are configured to have a viscosity of about 30,000 cP to about 40,000 cP. In further implementations, the first silicone component and the second silicone component are configured to have a viscosity of about 35,000 cP. The plasticizer has a lower viscosity than the first silicone mixture and the second silicone mixture. Thus, adding the plasticizer to the first silicone component and the second silicone component results in a silicone mixture that has a lower viscosity than the viscosity of the respective components to which the plasticizer is added. In certain implementations, the plasticizer is configured to have a viscosity of about 100 cP to about 500 cP. In further implementations, the plasticizer is configured to have a viscosity of about 200 cP to about 400 cP. In some implementations, the plasticizer is configured to have a viscosity of about 300 cP. The plasticizer can be further configured to have a viscosity of less than about 300 cP. In certain implementations, the plasticizer is configured to have a viscosity of less than 200 cP. The viscosity of the plasticizer correlates with the molecular weight of the plasticizer, such that a plasticizer with a lower molecular weight has a lower viscosity than a plasticizer with a higher molecular weight. For example, the plasticizer can be configured such that its molecular weight matches the ranges listed above.

[0032] In certain implementations, the first silicone mixture and the second silicone mixture are configured to have a viscosity of about 2,000 cP to about 5,000 cP. In further implementations, the first silicone mixture and the second silicone mixture are configured to have a viscosity of about 3,000 cP to about 4,000 cP. In some implementations, the first silicone mixture and the second silicone mixture are configured to have a viscosity of about 3,500 cP.

[0033] In some implementations, the plasticizer is configured such that its molecular weight provides a viscosity below the threshold of the silicone composition. In some implementations, the viscosity threshold of the composition is about 3,000 cP to about 4,000 cP. In certain implementations, the viscosity threshold of the composition is about 3,250 cP to about 3,750 cP. In other implementations, the viscosity threshold of the composition is about 3,500 cP. By adding the plasticizer separately to the first silicone component and the second silicone component, the first silicone component is prevented from reacting with the second silicone component to form an undesirable heterogeneous mixture. Thus, adding the plasticizer separately to the first component and the third component helps to form the composition such that the composition has a viscosity below the appropriate threshold.

[0034] The stiffness should also be configured to allow the silicone to provide sufficient protection to the measurement surface of the sensor while the blood pump is placed in the patient's vasculature while still allowing the silicone to be handled during manufacturing. The composition is configured to have a stiffness greater than a threshold value. At least one advantage of the stiffness of the composition being greater than a threshold value is that the stiffness allows the composition to be compatible with existing manufacturing processes. Additionally, the stiffness being greater than a threshold value makes the composition easier to apply to the optical sensor. In some implementations, the stiffness threshold of the composition is about 0.5 N to about 1.5 N. In other implementations, the stiffness threshold of the composition is about 0.75 N to about 1.25 N. In certain implementations, the stiffness threshold of the composition is about 1 N.

[0035] In addition, the silicone composition can be configured such that its tackiness allows it to adhere to the measurement surface of the optical sensor. Specifically, the composition is configured to have an adhesion energy below a certain threshold that provides sufficient adhesion to the sensor while also allowing for easy handling during manufacturing. The tackiness of a material can be measured by piercing the material with a probe and determining the energy required to break the bond formed between the material and the probe. A more tacky material has a greater adhesion energy. In some implementations, the adhesion energy per unit area of ​​the composition is about 3,500 J / cm. 2 ~Approx. 7,500J / cm 2 In other implementations, the adhesive energy per unit area of ​​the composition has a minimum value of about 4,500 J / cm 2 ~Approx. 6,500J / cm 2 In a further implementation, the adhesive energy per unit area of ​​the composition has a minimum value of about 5,400 J / cm 2 has a minimum value of

[0036] The process for making the composition may also include a step of curing the silicone composition. Specifically, the curing process helps to increase the stiffness, adhesive strength, and viscosity of the composition. Generally, the silicone composition may be cured after its application to the sensor. The silicone composition may be cured for a period of time to fully cure a certain percentage of the composition, thereby allowing the remainder of the composition to cure by residual reaction. In some implementations, the period of time for curing the composition results in about 85 percent to about 100 percent of the composition being fully cured. In such implementations, about 15 percent to about 0 percent of the composition being cured by residual reaction. In other implementations, the period of time for curing the composition results in about 90 percent to about 95 percent of the composition being fully cured. In such implementations, about 10 percent to about 5 percent of the composition being cured by residual reaction. In certain implementations, the period of time for curing the composition results in about 92 percent to about 94 percent of the composition being fully cured. In such implementations, about 8 percent to about 6 percent of the composition being cured by residual reaction. In certain implementations, the composition is cured for a period of about 1 hour to about 9 hours. In other implementations, the composition is cured for a period of about 3 hours to about 7 hours. In certain implementations, the composition is cured for a period of about 5 hours.

[0037] In some implementations, the composition is cured at a temperature between about 100 degrees Celsius and about 200 degrees Celsius. In certain implementations, the composition is cured at a temperature between about 125 degrees Celsius and about 175 degrees Celsius. In further implementations, the composition is cured at about 150 degrees Celsius. A combination of cure temperature and cure time is selected such that a desired percentage of the composition is fully cured after curing at the cure temperature for the time period. At least one advantage of allowing a portion of the composition to cure by residual reaction is that it speeds up the manufacturing process compared to processes where the entire composition must be actively cured, since there is no need to wait for the entire composition to fully cure.

[0038] The curing process also configures the silicone composition to have a desired shelf life and a desired pot life. In some implementations, the silicone composition is configured to have a shelf life of about 12 months to about 14 months. In other implementations, the silicone composition is configured to have a shelf life of about 13 months. In some implementations, the silicone composition is further configured to have a pot life of about 4 hours to about 10 hours. In other implementations, the silicone composition is configured to have a pot life of about 5 hours to about 9 hours. In some implementations, the silicone composition is configured to have a pot life of about 6 hours to about 8 hours. In certain implementations, the silicone composition is configured to have a pot life of about 7 hours.

[0039] The length of time the first silicone component and the plasticizer are mixed and the speed at which they are mixed can be adjusted to provide the desired mechanical properties of the first silicone mixture. In some implementations, the first silicone component and the plasticizer are mixed for about 10 seconds to about 3 minutes to create the first silicone mixture. In other implementations, the first silicone component and the plasticizer are mixed for about 70 seconds to about 110 seconds. In other implementations, the first silicone component and the plasticizer are mixed for about 80 seconds to about 100 seconds. In further implementations, the first silicone component and the plasticizer are mixed for about 90 seconds. In certain implementations, the first silicone component and the plasticizer are mixed at a speed of 600 rpm to about 2,000 rpm. In other implementations, the first silicone component and the plasticizer are mixed at a speed of 1,000 rpm to about 1,600 rpm. In another implementation, the first silicone component and the plasticizer are mixed at a speed of about 1,300 rpm.

[0040] In certain implementations, the second silicone component and the plasticizer are mixed for about 10 seconds to about 3 minutes to create the second silicone mixture. In some implementations, the second silicone component and the plasticizer are mixed for about 70 seconds to about 110 seconds. In further implementations, the second silicone component and the plasticizer are mixed for about 80 seconds to about 100 seconds. In certain implementations, the second silicone component and the plasticizer are mixed for about 90 seconds. In some implementations, the second silicone component and the plasticizer are mixed at a speed of about 600 rpm to about 2,000 rpm. In other implementations, the second silicone component and the plasticizer are mixed at a speed of 1,000 rpm to about 1,600 rpm. In certain implementations, the second silicone component and the plasticizer are mixed at a speed of about 1,300 rpm.

[0041] The first silicone mixture and the second silicone mixture are mixed to create the final composition. In some implementations, the first silicone mixture and the second silicone mixture are mixed for about 10 seconds to about 3 minutes. In some implementations, the first silicone mixture and the second silicone mixture are mixed for about 70 seconds to about 110 seconds. In further implementations, the first silicone mixture and the second silicone mixture are mixed for about 80 seconds to about 100 seconds. In other implementations, the first silicone mixture and the second silicone mixture are mixed for about 90 seconds. In certain implementations, the first silicone mixture is mixed with the second silicone mixture at a speed of about 600 rpm to about 2,000 rpm. In other implementations, the first silicone mixture is mixed with the second silicone mixture at a speed of about 1,000 rpm to 1,600 rpm. In further implementations, the first silicone mixture is mixed with the second silicone mixture at about 1,300 rpm.

[0042] After the first silicone mixture is mixed with the second silicone mixture, the composition is vacuum degassed. In some implementations, the composition is degassed at about room temperature. In other implementations, the composition is degassed at about 22 degrees Celsius. In further implementations, the composition is degassed at about 25 degrees Celsius. The composition may be vacuum degassed for about 30 minutes to about 50 minutes. In other implementations, the silicone composition is vacuum degassed for about 40 minutes.

[0043] According to another implementation, the blood pump assembly described above includes an optical sensor assembly. The optical sensor assembly is coupled to the pump housing, and the optical sensor assembly includes an optical sensor having a measurement surface. In some implementations, the optical sensor assembly includes a visor surrounding a support jacket (e.g., a polymer tube or another elongated body having an inner surface, an outer surface, and defining a cavity) that defines a cavity into which the optical sensor is inserted. In certain implementations, the support jacket includes a polyimide. The particular material from which the support jacket is made can be selected to provide particular mechanical properties of the support jacket and to facilitate handling of the polymer during manufacturing. In some implementations, the visor includes a metal. The metal can include stainless steel. Similarly, the metal from which the visor is made can be selected to provide particular mechanical properties and to ensure sufficient adhesion of the visor to the pump housing of the blood pump assembly. The silicone composition coats the measurement surface of the optical sensor to protect the optical sensor from damage caused by shear forces exerted on the optical sensor by the patient's blood during introduction and operation of the blood pump assembly in the patient's body. The silicone composition disposed on the optical sensor is configured to harden. The silicone composition can be configured to cure within the cavity. Curing the silicone composition disposed on the optical sensor within the cavity helps speed up the manufacturing process since only one curing step needs to be performed to cure the entire composition within the cavity. In some implementations, the visor is coupled to the pump housing by an adhesive. In certain implementations, the adhesive can be an epoxy. For example, the adhesive can be a two-part epoxy. In other implementations, the adhesive can be a UV light-bonding epoxy. In other implementations, the visor can be fused to the housing. In some implementations, the optical sensor is a silicone optical sensor. In some aspects, the silicone composition can be, for example, a silicone gel. [Brief description of the drawings]

[0044] These and other objects and advantages will become apparent from the following detailed description considered in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout.

[0045] [Figure 1] 1A and 1B show an example blood pump assembly having an optical sensor assembly and an example interface between a blood pump housing and an optical sensor assembly. [Diagram 2] 1 illustrates an exemplary optical sensor assembly for use in a blood pump assembly. [Diagram 3] 1A-1C illustrate an exemplary method of manufacturing packaging for an optical sensor for use in a blood pump assembly. [Figure 4] FIG. 1 illustrates an exemplary method for making a silicone composition for an optical sensor for use in a blood pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] Detailed Description Aspects of the present disclosure will be described in detail with reference to the drawings in which similar or identical elements are identified by similar reference numerals. It should be understood that the disclosed aspects are merely examples of the present disclosure and may be embodied in various forms. Well-known functions or structures are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein should not be interpreted as limitations, but merely as a basis for claims and as a representative basis for teaching those skilled in the art to use the present disclosure in various ways in substantially any appropriately detailed structure.

[0047] To provide an overall understanding of the systems, methods, and devices disclosed herein, certain exemplary implementations are described. Although the implementations and features described herein are specifically described for use in connection with blood pump assemblies, it will be understood that the teachings may be adapted and applied to other pumps and other types of medical devices.

[0048] FIG. 1A illustrates an exemplary blood pump assembly 100 having a pump 102, a motor 104, a rotor 106, a pump housing 108, a cannula 110, an atraumatic extension 112, and an optical sensor assembly 114. The optical sensor assembly 114 includes a visor, a support jacket, an optical sensor, at least one layer of a silicone composition, and an optical fiber 116, as further described in connection with FIG. 2 below. The pump 102 includes a motor 104 and a rotor 106. The rotor 106 has at least one blade for conveying fluid through the pump 102. The pump housing 108 is configured to surround the at least one blade of the rotor 106. The cannula 110 extends distally from the pump housing 108. The atraumatic extension 112 extends distally from the cannula 110. In certain implementations, the atraumatic extension 112 is a pigtail. The optical sensor assembly 114 is configured to couple to the pump housing 108 by a visor of the optical sensor assembly.

[0049] FIG. 1B illustrates an exemplary interface between the pump housing 108 and the optical sensor assembly 114. The adhesive means between the optical sensor assembly 114 and the pump housing 108 is selected to adjust the strength of the adhesive between the optical sensor 114 and the pump housing 108. The adhesive strength is advantageously selected based on the operation of the pump and the shear forces exerted by the blood on the pump during insertion. For example, a weak adhesive between the optical sensor assembly 114 and the pump housing 108 may cause the two components to separate when subjected to shear forces that exceed the adhesive strength. In some implementations, the visor of the optical sensor assembly 114 is bonded to the pump housing 108 by an adhesive. In certain implementations, the adhesive is a two-part epoxy, while in other implementations, the adhesive is a UV light adhesive. In further implementations, the visor is fused to the pump housing 108. In some implementations, the epoxy used to adhesive the visor to the pump housing 108 is selected based on the tack of the epoxy, with a higher value of tack corresponding to a stronger adhesive between the visor and the pump housing 108. The adhesion of a material can be measured by piercing the material with a probe and determining the energy required to break the bond formed between the material and the probe. Such a measurement yields the adhesion energy of the material, with greater adhesion energy corresponding to a stickier material that forms bonds that require more energy to break. In a particular implementation, the adhesion energy of epoxy is approximately 2 J / cm 2 ~about 10J / cm 2 In other implementations, the adhesive energy of the epoxy is about 4 J / cm 2 ~about 8J / cm 2 In a further implementation, the adhesive energy of the epoxy is about 6 J / cm 2Additionally, the greater the amount of a given epoxy used to bond the visor to the pump housing 108, the stronger the bond between the visor and the pump housing 108. The optical sensor assembly may be further welded to the pump housing 108. Additionally, the visor may be glued to the pump housing 108 and welded to the pump housing 108, alternating at different areas along the area of ​​the visor. At least one advantage of the configuration in which the visor is glued or fused to the pump housing 108 is that both bonding methods can be used to provide the strongest bond between the visor and the pump housing 108.

[0050] FIG. 2 illustrates an exemplary optical sensor assembly 200 for use in a blood pump assembly (e.g., blood pump assembly 100 of FIG. 1). The optical sensor assembly 200 includes a visor 202 having a visor inner surface 204 and a visor outer surface 206, a support jacket 208 defining a cavity 210, an optical sensor 212 having an optical sensor first surface 214 and an optical sensor second surface 216, a silicone composition 218, an optical fiber 220, and a pump housing 222. The visor outer surface 206 and the visor inner surface 204 are configured to surround the support jacket 208. In some implementations, the support jacket includes a polymer tube. The optical sensor 212 is disposed within the cavity 210 defined by the support jacket 208. The optical sensor has a first surface 214 and a second surface 216. Depending on the orientation of the sensor 212 within the cavity 210, the first surface 214 can be a distal surface or an inner surface. Similarly, the second surface 216 can be a proximal surface or an outer surface. In some implementations, the first surface 214 is connected to an optical fiber 220. In other implementations, the first surface 214 is connected to the visor inner surface 204. In certain implementations, the second surface 216 is configured to receive the silicone composition 218. As mentioned above, the visor inner surface 204 is configured to adhere to a pump housing 222 of the blood pump assembly. The pump housing may also be, for example, the pump housing 108 of FIG. 1. In some implementations, the visor inner surface 204 is adhered to the pump housing 222 of the blood pump assembly by an adhesive. For example, the adhesive may be an epoxy. The adhesive may be a two-part epoxy or a UV light cured epoxy. In other implementations, the visor inner surface 204 is fusion bonded to the pump housing 222 of the blood pump assembly. The adhesive means between the visor inner surface 204 and the pump housing 222 of the blood pump assembly is selected so that the adhesive between the visor inner surface 204 and the pump housing 222 is capable of withstanding the shear forces exerted on the blood pump assembly by the blood during insertion and operation of the blood pump assembly within the patient's body.As mentioned above, the specific adhesive means between the visor inner surface 204 and the pump housing 222 of the blood pump assembly can be varied to provide the strongest bond between the visor inner surface 204 and the pump housing 222. For example, in some implementations, the amount of epoxy and the tackiness of the epoxy used to bond the elements together is selected to ensure a bond having a given adhesive strength. In other implementations, the visor inner surface 204 is welded to the pump housing 222. As mentioned above, at least one advantage of the configuration in which the visor inner surface 204 is glued or fused to the pump housing 222 is that both adhesive methods can be used to provide the strongest bond between the visor inner surface 204 and the pump housing 222.

[0051] The cavity 210 defined by the support jacket 208 prevents contamination of the visor outer surface 206 with the silicone composition 218 (e.g., the silicone composition made by the method of FIG. 4). In addition, the shape of the cavity 210 defined by the support jacket 208 is configured to accommodate a particular amount of the silicone composition 218. Different amounts of the silicone composition provide different amounts of protection to the optical sensor of the blood pump assembly. Different amounts of protection to the optical assembly are required due to various magnitudes of shear forces exerted on the optical sensor assembly during installation and operation of the pump. The shear forces exerted on the optical sensor assembly during installation and operation of the pump may vary in magnitude based on the patient's anatomy. For example, in an obese patient, the blood vessel into which the blood pump assembly must be inserted is further below the surface of the skin than the same blood vessel is in a patient of healthy weight. This requires that the blood pump assembly bend to align with the blood vessel after it is inserted at the surface of the skin. Thus, insertion of a blood pump assembly into an obese patient places greater strain on the blood pump assembly than insertion of the same assembly into a patient of healthy weight, and the insertion angle allows the blood pump assembly to be introduced more directly into the blood vessel.

[0052] To account for the various forces that may be exerted on the blood pump assembly, the size of the support jacket and cavity is adjusted to adequately protect the optical sensor with an appropriate amount of silicone composition. Cardiac procedures that subject the optical sensor assembly to greater forces can be completed with an optical sensor assembly having a larger polymer tube that contains a greater amount of silicone composition 218 to provide additional protection to the sensor. Conversely, cardiac procedures in pediatric patients with smaller anatomical structures can be completed with an optical sensor assembly having a smaller polymer tube, which allows for the application of an additional layer of silicone to the surface of the optical sensor while minimizing the damage inflicted by the larger pump on the smaller vasculature of the pediatric patient.

[0053] The length or radius of the support jacket 208 can be adjusted to vary the volume of the cavity 210 defined by the support jacket 208. Generally, a support jacket having a larger length corresponds to a larger cavity volume. As mentioned above, in some implementations, the cavity 210 defined by the support jacket 208 has a length of about 1 centimeter to about 5 centimeters. In other implementations, the cavity 210 has a length of about 2 centimeters to about 4 centimeters. In a particular implementation, the cavity 210 has a length of about 3 centimeters. Furthermore, a cavity 210 having a larger radius corresponds to a larger cavity volume. In some implementations, the cavity 210 has a radius of about 0.1 millimeters to about 0.25 millimeters. In other implementations, the cavity 210 has a radius of about 0.15 millimeters to about 0.20 millimeters. In a further implementation, the radius of the cavity 210 is about 0.175 millimeters. For a given length of cavity 210, a particular volume of cavity 210 may be filled with silicone composition 218. Since a larger amount of silicone composition requires a longer cure time, the portion of the volume of cavity 210 that is filled with silicone composition 218 may be selected to obtain the desired protection for the optical sensor and also to obtain the desired manufacturing time. In certain implementations, between about 30 percent and about 90 percent of the cavity is filled with the silicone composition. In other implementations, between about 50 percent and about 70 percent of the cavity is filled with the silicone composition. In a further implementation, about 60 percent of the cavity is filled with the silicone composition.

[0054] FIG. 3 illustrates an exemplary manufacturing method 300 of packaging for an optical sensor for use in a blood pump assembly. In step 302 of the method 300, an optical sensor (e.g., optical sensor 212 of FIG. 2) is disposed within a support jacket (e.g., polymer tube 208 of FIG. 2) configured to define a cavity (e.g., cavity 210 of FIG. 2). In step 304, the cavity between the optical sensor and the support jacket is filled with a silicone composition. The silicone composition is then cured in step 306. In step 308, a portion of the support jacket is surrounded by a visor, and in step 310, an inner surface of the visor is bonded to a pump housing of the blood pump assembly (e.g., pump housing 108 of blood pump assembly 100 of FIG. 1 or pump housing 222 of FIG. 2). In some implementations, the optical sensor disposed within the support jacket is a silicone optical sensor. In certain implementations, the polymer tube includes polyimide. In further implementations, the visor includes metal. The metal may include stainless steel or another metal such that the visor has desired mechanical properties and is easy to handle during manufacturing. In certain implementations, the visor is bonded to the pump housing by an adhesive. In some implementations, the adhesive is an epoxy. In other implementations, the adhesive is a two-part epoxy, and in further implementations, the adhesive is a UV light-bonded epoxy.

[0055] FIG. 4 illustrates an exemplary method 400 for making a silicone composition for use in an optical sensor assembly for use in a blood pump assembly. Step 402 includes mixing a first silicone component and a plasticizer to form a first silicone mixture. In some embodiments, the first silicone component and the plasticizer are different materials. In some embodiments, at least one of the first silicone component and the plasticizer is NuSil MED4088. In further embodiments, both the first silicone component and the plasticizer are NuSil MED4088. In some embodiments, the plasticizer is a silicone oil plasticizer. In certain embodiments, the plasticizer is NuSil MED360. The length of time the first silicone component and the plasticizer are mixed and the speed at which they are mixed are adjusted to provide the desired mechanical properties of the first silicone mixture. In some embodiments, the first silicone component and the plasticizer can be mixed for about 10 seconds to about 3 minutes to produce the first silicone mixture. In other embodiments, the first silicone component and the plasticizer are mixed for about 70 seconds to about 110 seconds. In other embodiments, the first silicone component and the plasticizer are mixed for about 80 seconds to about 100 seconds. In further embodiments, the first silicone component and the plasticizer are mixed for about 90 seconds. In certain embodiments, the first silicone component and the plasticizer are mixed at a speed of 600 rpm to about 2,000 rpm. In other embodiments, the first silicone component and the plasticizer are mixed at a speed of 1,000 rpm to about 1,600 rpm. In other embodiments, the first silicone component and the plasticizer are mixed at a speed of about 1,300 rpm.

[0056] Step 404 includes mixing the second silicone component with the plasticizer to form a second silicone mixture. In certain embodiments, the second silicone component and the plasticizer are mixed for about 10 seconds to about 3 minutes to create the second silicone mixture. In some embodiments, the second silicone component and the plasticizer are mixed for about 70 seconds to about 110 seconds. In further embodiments, the second silicone component and the plasticizer are mixed for about 80 seconds to about 100 seconds. In certain embodiments, the second silicone component and the plasticizer are mixed for about 90 seconds. In some embodiments, the second silicone component and the plasticizer are mixed at a speed of about 600 rpm to about 2,000 rpm. In other embodiments, the second silicone component and the plasticizer are mixed at a speed of 1,000 rpm to about 1,600 rpm. In certain embodiments, the second silicone component and the plasticizer are mixed at a speed of about 1,300 rpm. In some embodiments, the first silicone component, the second silicone component, and the plasticizer are different from one another.

[0057] In step 406, the first silicone mixture and the second silicone mixture are subsequently mixed together to obtain a silicone composition. In some embodiments, the first silicone mixture and the second silicone mixture are mixed for about 10 seconds to about 3 minutes. In some embodiments, the first silicone mixture and the second silicone mixture are mixed for about 70 seconds to about 110 seconds. In further embodiments, the first silicone mixture and the second silicone mixture are mixed for about 80 seconds to about 100 seconds. In other embodiments, the first silicone mixture and the second silicone mixture are mixed for about 90 seconds. In certain embodiments, the first silicone mixture is mixed with the second silicone mixture at a speed of about 600 rpm to about 2,000 rpm. In other embodiments, the first silicone mixture is mixed with the second silicone mixture at a speed of about 1,000 rpm to 1,600 rpm. In further embodiments, the first silicone mixture is mixed with the second silicone mixture at about 1,300 rpm.

[0058] Then, at step 408, the silicone composition is vacuum degassed such that the composition is configured to protect a measurement surface of an optical sensor for use in a blood pump assembly from shear forces exerted on the sensor by blood during percutaneous insertion or operation of the blood pump assembly within a patient. In some embodiments, the composition is degassed at about room temperature. In other embodiments, the composition is degassed at about 22 degrees Celsius. In further implementations, the composition is degassed at about 25 degrees Celsius. In some embodiments, the composition is vacuum degassed for about 30 minutes to about 50 minutes. In other embodiments, the silicone composition is vacuum degassed for about 40 minutes.

[0059] The above process results in a silicone composition having the mechanical properties described above such that the composition is suitable for use in an optical sensor assembly for a blood pump. As previously mentioned, the silicone composition may be configured to have an adhesive strength such that the composition can withstand a maximum load of about 160N to about 340N. In a further embodiment, the silicone composition is configured to have an adhesive strength such that the composition can withstand a maximum load of about 210N to about 290N. In another embodiment, the silicone composition is configured to have an adhesive strength such that the composition can withstand a maximum load of about 250N. Generally, the silicone composition is configured to have an adhesive strength such that the composition can withstand a maximum load greater than a certain threshold. In some embodiments, the adhesive strength threshold of the composition is about 50N to about 150N. In other embodiments, the adhesive strength threshold of the composition is about 75N to about 125N. In a particular embodiment, the adhesive strength threshold of the composition is about 100N.

[0060] Furthermore, the first silicone component and the second silicone component may be configured to have a viscosity of about 20,000 cP to about 50,000 cP. In other embodiments, the first silicone component and the second silicone component are configured to have a viscosity of about 25,000 cP to about 45,000 cP. In certain embodiments, the first silicone component and the second silicone component are configured to have a viscosity of about 30,000 cP to about 40,000 cP. In further embodiments, the first silicone component and the second silicone component are configured to have a viscosity of about 35,000 cP. Adding a plasticizer to the first silicone component and the second silicone component results in a silicone mixture having a lower viscosity than the viscosity of the respective components to which the plasticizer is added. In certain embodiments, the first silicone mixture and the second silicone mixture are configured to have a viscosity of about 2,000 cP to about 5,000 cP. In further embodiments, the first silicone mixture and the second silicone mixture are configured to have a viscosity of about 3,000 cP to about 4,000 cP. In some embodiments, the first silicone mixture and the second silicone mixture are configured to have a viscosity of about 3,500 cP.

[0061] Additionally, as previously described, the plasticizer may be configured such that its molecular weight imparts a viscosity of about 100 cP to about 250 cP. In further embodiments, the plasticizer may be configured such that its molecular weight imparts a viscosity of about 125 cP to about 225 cP. In other embodiments, the plasticizer may be configured such that its molecular weight imparts a viscosity of about 150 cP to about 200 cP. In certain embodiments, the plasticizer may be configured such that its molecular weight imparts a viscosity of about 175 cP. The plasticizer may be configured such that its molecular weight imparts a viscosity below the threshold of the silicone composition. In some implementations, the viscosity threshold of the composition is about 3,000 cP to about 4,000 cP. In certain embodiments, the viscosity threshold of the composition is about 3,250 cP to about 3,750 cP. In other embodiments, the viscosity threshold of the composition is about 3,500 cP.

[0062] Additionally, the composition is configured to have a stiffness greater than a threshold value above which the stiffness of the composition facilitates handling during manufacturing. In some embodiments, the stiffness threshold of the composition is from about 0.5 N to about 1.5 N. In other embodiments, the stiffness threshold of the composition is from about 0.75 N to about 1.25 N. In certain embodiments, the stiffness threshold of the composition is about 1 N. The composition is also configured to have an adhesion energy below a certain threshold value below which the adhesive energy of the composition provides sufficient adhesion to the sensor while facilitating handling during manufacturing. In some embodiments, the adhesive energy per unit area of ​​the composition is about 3,500 J / cm. 2 ~Approx. 7,500J / cm 2 In another embodiment, the adhesive energy per unit area of ​​the composition is about 4,500 J / cm 2 ~Approx. 6,500J / cm 2 In a further embodiment, the adhesive energy per unit area of ​​the composition is about 5,400 J / cm 2 has a minimum value of

[0063] In some embodiments, the silicone composition is configured to cure after application of the composition to the sensor. The silicone composition is cured for a period of time to fully cure a percentage of the composition, thereby allowing the remainder of the composition to cure by residual reaction. In some embodiments, the period of time for which the composition is cured results in about 85 percent to about 100 percent of the composition being fully cured. In such embodiments, about 15 percent to about 0 percent of the composition being cured by residual reaction. In other embodiments, the period of time for which the composition is cured results in about 90 percent to about 95 percent of the composition being fully cured. In such embodiments, about 10 percent to about 5 percent of the composition being cured by residual reaction. In certain embodiments, the period of time for which the composition is cured results in about 92 percent to about 94 percent of the composition being fully cured. In such embodiments, about 8 percent to about 6 percent of the composition being cured by residual reaction. In certain embodiments, the period of time for which the composition is cured is about 1 hour to about 9 hours. In other embodiments, the period of time for which the composition is cured is about 3 hours to about 7 hours. In certain embodiments, the period during which the composition is allowed to cure is about 5 hours.

[0064] As mentioned above, the curing process also configures the silicone composition to have a desired shelf life and a desired pot life. In some embodiments, the silicone composition is configured to have a shelf life of about 12 months to about 14 months. In other embodiments, the silicone composition is configured to have a shelf life of about 13 months. In some embodiments, the silicone composition is further configured to have a pot life of about 4 hours to about 10 hours. In other embodiments, the silicone composition is configured to have a pot life of about 5 hours to about 9 hours. In some embodiments, the silicone composition is configured to have a pot life of about 6 hours to about 8 hours. In certain embodiments, the silicone composition is configured to have a pot life of about 7 hours.

[0065] As mentioned above, in some embodiments, the composition is cured at a temperature between about 100 degrees Celsius and about 200 degrees Celsius. In certain embodiments, the composition is cured at a temperature between about 125 degrees Celsius and about 175 degrees Celsius. In further embodiments, the composition is cured at about 150 degrees Celsius. A combination of cure temperature and cure time is selected such that a desired percentage of the composition is fully cured after curing at the cure temperature for the time period. At least one advantage of allowing a portion of the composition to cure by residual reaction is that it speeds up the manufacturing process since it is not necessary to wait for the entire composition to fully cure.

[0066] The foregoing is merely illustrative of the principles of the present disclosure, and the device may be practiced with other than the described aspects, which are presented for purposes of illustration and not limitation. It should be understood that while the device disclosed herein is shown for use in percutaneous insertion of a blood pump, it may also be applied to devices for other applications requiring optical sensors.

[0067] Variations and modifications will occur to those skilled in the art after considering this disclosure. The features disclosed may be implemented in any combination and subcombination (including multiple subcombinations and subcombinations) with one or more other features described herein. The various features described or illustrated above and below may be combined or integrated in other systems, including any components thereof. Furthermore, certain features may be omitted or not implemented.

[0068] Exemplary Implementations The following examples are given as specific illustrations of the claimed invention. It should be understood, however, that the invention is not limited to the specific details described in the following categories of exemplary implementations.

[0069] Category A: A1. A visor having an inner surface and an outer surface; a support jacket in contact with an inner surface of the visor and defining a cavity; an optical sensor having an outer surface and an inner surface disposed within the cavity, the inner surface of the optical sensor being in contact with the supporting jacket; a silicone gel covering an exterior surface of the optical sensor and filling the cavity; 1. An optical sensor assembly for use in a blood pump assembly, comprising: A2. The optical sensor assembly of A1, where the supporting jacket is a polymer tube. A3. The optical sensor assembly of any of A1 to A2, wherein the supporting jacket is a polyimide tube. A4. An optical sensor assembly according to any one of A1 to A3, wherein the visor includes metal. A5. An optical sensor assembly according to any one of A1 to A4, wherein the metal is stainless steel. A6. Any of the optical sensor assemblies A1 to A5, wherein the inner surface of the visor is configured to be attached to a pump housing of a blood pump assembly. A7. Any optical sensor assembly of A1-A6 where the inner visor surface is attached to the pump housing with either a two-part epoxy or a UV light-bonding epoxy. A8. The optical sensor assembly of any of A1 to A7, wherein the silicone gel is configured to harden within the cavity. A9. Any of the optical sensor assemblies of A1 to A8, wherein the support jacket has an open end and a closed end, and the open end is configured to be closed after the optical sensor is placed within the cavity. A10. The optical sensor assembly of any of A1 to A9, wherein the support jacket has a length of about 1 centimeter to about 5 centimeters. A11. The optical sensor assembly of any of A1 to A10, wherein the support jacket has a length of about 2 centimeters to about 4 centimeters. A12. Any of the optical sensor assemblies of A1 to A11, wherein the support jacket has a length of about 3 centimeters. A13. Any of the optical sensor assemblies of A1 to A12, wherein the silicone gel is configured to protect an outer surface of the optical sensor from cracking due to forces exerted on the optical sensor when the blood pump assembly is used for percutaneous insertion into a patient.

[0070] Category B: B1. A visor having an inner surface and an outer surface; a support jacket having an inner surface and an outer surface and defining a cavity, the inner surface of the visor contacting the outer surface of the support jacket; an optical sensor disposed within the cavity, the cavity being filled with a silicone gel, the size of the cavity being configured and the amount of silicone gel being selected such that the support jacket is disposed within the support jacket to flowably confine the silicone gel within the support jacket and protect the optical sensor from damage due to forces exerted on the optical sensor during percutaneous insertion of the blood pump assembly into a patient; 1. An optical sensor assembly for use in a blood pump assembly, comprising: B2. The optical sensor assembly of B1, wherein the support jacket comprises a polymer tube. B3. The optical sensor assembly of any one of B1 to B2, wherein the optical sensor is a silicone optical sensor. B4. The optical sensor assembly of any of B1-B3, wherein the polymer tube comprises polyimide. B5. An optical sensor assembly according to any one of B1 to B4, wherein the visor includes metal. B6. An optical sensor assembly of any of B1 to B5, wherein the metal is stainless steel. B7. The optical sensor assembly of any of B1-B6, wherein a silicone gel is configured for curing within the cavity. B8. An optical sensor assembly of any of B1-B7, wherein the silicone gel fills the cavity without contacting the exterior surface of the visor so as to prevent contamination of the exterior surface of the visor. B9. An optical sensor assembly of any of B1-B8, wherein the support jacket prevents the silicone gel from contaminating the exterior surface of the visor.

[0071] Category C: C1. A pump including a motor and a rotor, the rotor having blades, a pump, A pump housing that surrounds the blades; a cannula extending distally of the pump housing; an atraumatic extension extending distally from the cannula; and An optical sensor assembly coupled to the pump housing by a visor a visor surrounding a support jacket defining a cavity, an optical sensor disposed within the cavity, and a silicone gel covering the optical sensor within the cavity. C2. The optical sensor assembly of C1, wherein the optical sensor is a silicone optical sensor. C3. The optical sensor assembly of any of C1-C2, wherein the support jacket comprises a polymer tube. C4. The optical sensor assembly of any of C1 to C3, wherein the polymer tube is a polyimide tube. C5. An optical sensor assembly of any of C1 to C4, wherein the visor includes metal. C6. An optical sensor assembly of any of C1-C5, wherein the metal is stainless steel. C7. The optical sensor assembly of any of C1-C6, wherein the silicone gel is configured to harden. C8. The optical sensor assembly of any of C1-C7, wherein the visor is bonded to the pump housing by an adhesive. C9. An optical sensor assembly of any of C1-C8, where the adhesive is epoxy. C10. An optical sensor assembly of any of C1-C9, wherein the visor is fused to the pump housing. C11. The optical sensor assembly of any of C1-C10, wherein the support jacket is disposed within the visor along the pump housing. C12. The optical sensor assembly of any of C1-C11, wherein the support jacket further includes an outer surface in contact with the outer surface of the pump housing. C13. An optical sensor assembly of any of C1-C12, wherein the outer surface of the support jacket is in contact with the inner surface of the visor.

[0072] Category D: D1. A method of manufacturing an optical sensor assembly for use in a blood pump assembly, comprising the steps of: disposing an optical sensor within a support jacket defining a cavity; filling a portion of a cavity between the optical sensor and the supporting jacket with silicone gel; curing the silicone gel; enclosing a portion of the support jacket with a visor; and Bonding the inner surface of the visor to a pump housing of the blood pump. D2. The method of D1, wherein the optical sensor is a silicone optical sensor. D3. Any of the methods of D1-D2, wherein the support jacket comprises a polymer tube. D4. Any of the methods of D1-D3, wherein the polymer tube comprises polyimide. D5. Any of the methods D1 to D4, in which the visor contains metal. D6. Any of the methods D1-D5, wherein the metal is stainless steel. D7. Any of the methods of D1-D6, wherein the visor is bonded to the pump housing by epoxy. D8. Any of the methods of D1-D7, wherein the epoxy is one of a two-part epoxy or a UV light cured epoxy. D9. Any of the methods D1-D8, wherein the visor is fused to the pump housing.

[0073] Category E: E1. A method for making a silicone composition for use in a blood pump assembly, comprising the steps of: mixing a first silicone component and a plasticizer to form a first silicone mixture; combining a second silicone component with a plasticizer to form a second silicone mixture; combining the first silicone mixture with the second silicone mixture into a silicone composition; and A process for vacuum degassing a silicone composition, the composition being configured to protect a measurement surface of an optical sensor for use in a blood pump assembly from shear forces exerted on the sensor by blood during percutaneous insertion of the blood pump assembly into a patient. E2. The method of E1, wherein the first silicone component is an activator. E3. Any of the methods of E1-E2, wherein the second silicone component comprises a platinum-based catalyst. E4. Any of the methods E1-E3, wherein the plasticizer is a silicone oil plasticizer. E5. Any of the methods E1-E4, wherein the ratio of the first and second components to the plasticizer is 1:1 such that the composition has a ratio of the first component to the second component to the plasticizer of 1:1:2. E6. Any of the methods E1-E5, wherein the adhesive strength of the silicone composition is configured such that the composition can withstand a maximum load of about 160 N to about 340 N. E7. Any of the methods of E1-E6, wherein the adhesive strength of the silicone composition is configured such that the composition can withstand a maximum load of about 210 N to about 290 N. E8. Any of the methods of E1-E7, wherein the adhesive strength of the silicone composition is configured such that the composition can withstand a maximum load of about 250 N. E9. Any of the methods of E1-E8, wherein the adhesive strength of the silicone composition is configured such that the composition can withstand a maximum load of greater than about 50 N. E10. The method of any of E1-E9, wherein the first and second silicone components are configured to have a viscosity of about 30,000 cP to about 40,000 cP. E11. The method of any of E1-E10, wherein the first and second silicone components are configured to have a viscosity of about 35,000 cP. E12. The method of any of E1-E11, wherein the first and second silicone mixtures are configured to have a viscosity of about 3,000 cP to about 4,000 cP. E13. The method of any of E1-E12, wherein the first and second silicone mixtures are configured to have a viscosity of about 3,500 cP. E14. The method of any of E1-E13, wherein the silicone oil plasticizer is configured to have a low molecular weight such that the viscosity of the silicone composition is less than 200 cP. E15. The method of any of E1-E14, wherein a plasticizer is added separately to the first and third components to form a composition having a viscosity of less than 300 cP. E16. The method of any of E1-E15, wherein the silicone composition is configured to have a viscosity of about 2,400 cP to about 7,000 cP. E17. The method of any of E1-E16, wherein the silicone composition is configured to have a viscosity of about 3,000 cP to about 6,000 cP. E18. The method of any of E1-E17, wherein the silicone composition is configured to have a viscosity of about 4,000 cP to about 6,000 cP. E19. The method of any of E1-E18, wherein the silicone composition is configured to have a viscosity of about 5,000 cP. E20. The method of any of E1-E19, wherein the composition is configured to have a stiffness greater than about 1.5 N. E21. The method of any of E1-E20, wherein the composition is configured to have a stiffness greater than about 1.2 N. E22. The method of any of E1-E21, wherein the composition is configured to have a stiffness greater than about 0.9 N. E23. The method of any of E1-E22, wherein the composition is configured to harden after application to the sensor. E24. Any of the methods of E1-E23, wherein the composition is cured for a period of time such that about 90 to about 95 percent of the composition is cured. E25. Any of the methods E1 to E24, wherein the duration is from about 1 to about 9 hours. E26. Any of the methods E1 to E25, wherein the duration is from about 3 to about 7 hours. E27. Any of the methods E1 to E26, wherein the duration is about 5 hours. E28. Any of the methods of E1-E27, wherein the composition is cured at a temperature of about 100 degrees Celsius to about 200 degrees Celsius. E29. Any of the methods of E1-E28, wherein the composition is cured at a temperature of about 125 degrees Celsius to about 175 degrees Celsius. E30. Any of the methods of E1-E29, wherein the composition is cured at a temperature of about 150 degrees Celsius. E31. Any of the methods of E1-E30, wherein the composition is configured such that the amount of silicone used allows for protection of the sensor while limiting the tack of the composition below a tack threshold. E32. The method of any of E1-E31, wherein the composition has a tack such that the minimum load exerted by the composition on the probe is from about -2.1 N to about 0 N. E33. The method of any of E1-E32, wherein the composition has a tack such that the minimum load exerted by the composition on the probe is from about -1.0 N to about 0 N. E34. The method of any of E1-E33, wherein the composition has a viscosity such that the maximum load exerted by the composition on the probe is about -0.1 N. E35. The method of any of E1-E34, wherein the adhesion threshold is configured to be low enough that the sensor can be adhered to a visor for use in a blood pump assembly. E36. Any of the methods of E1-E35, wherein the first and second silicone components and the plasticizer are biocompatible. E37. The method of any of E1-E36, wherein the ratio of silicone to silicone oil plasticizer is configured to allow the composition to adhere to the visor while also having a viscosity that allows for easy handling. E38. The method of any of E1-E37, wherein the first silicone component and the plasticizer are mixed for about 10 seconds to about 3 minutes. E39. The method of any of E1-E38, wherein the first silicone component and the plasticizer are mixed for about 90 seconds. E40. The method of any of E1-E39, wherein the first silicone component and the plasticizer are mixed at about 600 rpm to about 2000 rpm. E41. Any of the methods of E1-E40, wherein the first silicone component and the plasticizer are mixed at about 1000 rpm to about 1600 rpm. E42. Any of the methods of E1-E41, wherein the first silicone component and the plasticizer are mixed at about 1300 rpm. E43. The method of any of E1-E42, wherein the second silicone component and the plasticizer are mixed for about 10 seconds to about 3 minutes. E44. Any of the methods of E1-E43, wherein the second silicone component and the plasticizer are mixed for about 90 seconds. E45. Any of the methods of E1-E44, wherein the second silicone component and the plasticizer are mixed at about 600 rpm to about 2000 rpm. E46. Any of the methods of E1-E45, wherein the second silicone component and the plasticizer are mixed at about 1000 rpm to about 1600 rpm. E47. Any of the methods of E1-E46, wherein the second silicone component and the plasticizer are mixed at about 1300 rpm. E48. The method of any of E1-E47, wherein the first silicone mixture and the second silicone mixture are mixed for about 10 seconds to about 3 minutes. E49. The method of any of E1-E48, wherein the first silicone mixture and the second silicone mixture are mixed for about 90 seconds. E50. The method of any of E1-E49, wherein the first silicone mixture and the second silicone mixture are mixed at about 600 rpm to about 2000 rpm. E51. Any of the methods of E1-E50, wherein the first silicone mixture and the second silicone mixture are mixed at about 1000 rpm to about 1600 rpm. E52. Any of the methods of E1-E51, wherein the first silicone mixture and the second silicone mixture are mixed at about 1300 rpm. E53. The method of any of E1-E52, wherein the silicone composition is vacuum degassed at room temperature. E54. Any of the methods of E1-E53, wherein the silicone composition is vacuum degassed for about 30 minutes to about 50 minutes. E55. Any of the methods of E1-E54, wherein the silicone composition is vacuum degassed for about 40 minutes. E56. Any of the methods E1 to E55, in which the measuring surface is a diaphragm. E57. Any of the methods of E1-E56, wherein the silicone composition is configured to have a shelf life of about 12 months to about 14 months. E58. Any of the methods of E1-E57, wherein the silicone composition is configured to have a pot life of about 5 hours to about 9 hours.

[0074] Category F: F1. A pump including a motor and a rotor having at least one blade; a pump housing enclosing at least one blade of the rotor; Cannula, an atraumatic extension extending distally from the cannula; and A silicone optical sensor assembly bonded to a pump housing, the sensor assembly including an optical sensor having a measuring surface, the measuring surface having a silicone coating, the silicone coating including a mixture of a first silicone component, a plasticizer, and a second silicone component. 1. A blood pump assembly comprising: F2. The blood pump assembly of F1, wherein the silicone coating comprises any of the compositions of A1-A54. F3. The blood pump assembly of any of F1-F2, wherein the optical sensor assembly further includes a visor and a supporting jacket. F4. The blood pump assembly of any of F1-F3, wherein the support jacket defines a cavity in which the optical sensor and silicone coating are disposed. F5. Any of the blood pump assemblies F1-F4, wherein the visor radially surrounds the supporting jacket.

[0075] Category G: G1. A pump including a motor and a rotor having at least one blade; a pump housing surrounding at least one blade of the rotor; Cannula, an atraumatic extension extending distally from the housing; and Silicone optical sensor including a measuring surface wherein the measurement surface is configured to receive a coating of silicone comprising a mixture of a first silicone component, a plasticizer, and a second silicone component, the silicone being configured with at least one of a desired viscosity, stiffness, lap shear, and tackiness. Blood pump assembly. G2. The blood pump assembly of G1, wherein the silicone coating comprises any of the compositions E1-E54.

[0076] From the above and with reference to the various drawings, those skilled in the art will understand that certain modifications can be made to the present disclosure without departing from the scope of the present disclosure. Although the drawings show some aspects of the present disclosure, it is not intended to limit the present disclosure thereto, and it is intended that the present disclosure has as broad a scope as the art permits, and the specification should be read in the same manner. Therefore, the above description should not be interpreted as limiting, but merely as an illustration of certain aspects. Other modifications will occur to those skilled in the art within the scope and spirit of the appended claims. All references cited herein are incorporated by reference in their entirety and are made part of this application.

Claims

1. a visor having an inner surface and an outer surface; a support jacket defining a cavity in contact with the inner surface of the visor along a length of the support jacket; an optical sensor disposed within the cavity; a silicone composition disposed within the cavity, the silicone composition coating a surface of the optical sensor; an optical fiber not in contact with the support jacket; 1. An optical sensor assembly for use in a blood pump assembly, comprising:

2. An optical sensor assembly as described in claim 1, wherein the inner surface of the visor is configured to be attached to a pump housing of a blood pump assembly.

3. An optical sensor assembly as described in claim 1, wherein the silicone composition comprises a first silicone mixture of a first silicone component and a first plasticizer, and a second silicone mixture of a second silicone component and a second plasticizer, and the first silicone component, the second silicone component, the first plasticizer, and the second plasticizer are different from each other.

4. An optical sensor assembly as described in claim 3, wherein the second silicone component includes a metal catalyst.

5. An optical sensor assembly as described in claim 3, wherein the first plasticizer or the second plasticizer is a silicone oil plasticizer.

6. An optical sensor assembly as described in claim 1, wherein the support jacket has an open end and a closed end, and the open end of the support jacket is configured to be closed after the optical sensor is placed within the cavity.

7. An optical sensor assembly as described in claim 1, wherein the support jacket is a polymer tube.

8. An optical sensor assembly as described in claim 3, wherein in the silicone composition, the ratio of the first silicone component to the first plasticizer is about 1:4 to about 4:1, and the ratio of the second silicone component to the second plasticizer is about 1:4 to about 4:

1.

9. An optical sensor assembly as described in claim 8, wherein in the silicone composition, the ratio of the first silicone component to the second silicone component to the total of the first plasticizer and the second plasticizer is from about 1:1:8 to about 2:2:

1.

10. An optical sensor assembly as described in claim 1, wherein the silicone composition is configured to harden within the cavity.

11. An optical sensor assembly as described in claim 1, wherein the silicone composition is configured to protect the optical sensor from damage caused by forces exerted on the optical sensor when the blood pump assembly is used for percutaneous insertion into a patient.

12. An optical sensor assembly as described in claim 1, wherein approximately 30 percent to approximately 90 percent of the cavity is configured to be filled with the silicone composition that protects the optical sensor from damage due to forces exerted on the optical sensor during percutaneous insertion of the blood pump assembly into a patient.

13. An optical sensor assembly as described in claim 1, wherein the optical sensor is a silicone optical sensor.

14. A blood pump assembly for insertion into a patient, said blood pump assembly comprising: a pump including a motor and a rotor having at least one blade; a pump housing surrounding the at least one blade; a cannula extending distally of the pump housing; an atraumatic extension extending distally from the cannula; An optical sensor assembly, comprising: With a visor, a support jacket defining a cavity; an optical sensor disposed within the cavity; a silicone composition disposed within the cavity that coats the optical sensor; and an optical sensor assembly including an optical fiber not in contact with the support jacket, the optical sensor assembly being attached to the pump housing by the visor; A blood pump assembly for insertion into a patient, comprising:

15. A blood pump assembly as described in claim 14, wherein the optical sensor is a silicone optical sensor.

16. A blood pump assembly as described in claim 14, wherein the silicone composition comprises a first silicone mixture of a first silicone component and a first plasticizer, and a second silicone mixture of a second silicone component and a second plasticizer, and the first silicone component, the second silicone component, the first plasticizer, and the second plasticizer are different from each other.

17. A blood pump assembly as described in claim 14, wherein the silicone composition is configured to harden within the cavity.

18. A blood pump assembly as described in claim 16, wherein in the silicone composition, the ratio of the first silicone component to the first plasticizer is about 1:4 to about 4:1, and the ratio of the second silicone component to the second plasticizer is about 1:4 to about 4:

1.

19. A blood pump assembly as described in claim 14, wherein the silicone composition coats the measuring surface of the optical sensor.

20. A blood pump assembly as described in claim 18, wherein in the silicone composition, the ratio of the first silicone component to the second silicone component to the total of the first plasticizer and the second plasticizer is from about 1:1:8 to about 2:2:1.

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