WO2024056534A1

WO2024056534A1 - Actuator element, actuator assembly, medical instrument and operating method and manufacturing method

Info

Publication number: WO2024056534A1
Application number: PCT/EP2023/074703
Authority: WO
Inventors: Sebastian Wolfram; Jochen Hampe; Christoph Gommel; René Körbitz; Franz Brinkmann; Kai Uhlig; Matthieu Fischer; Andreas Richter; Konrad Henkel; Ronny Hüttner
Original assignee: Leibniz-Institut Für Polymerforschung Dresden E.V.; Contronix Gmbh; Technische Universität Dresden
Priority date: 2022-09-13
Filing date: 2023-09-08
Publication date: 2024-03-21
Also published as: DE102022123314A1

Abstract

The invention relates to an actuator element (3) for controlling flexible, invasive, medical instruments and having the following features: - the actuator element (3) has a guide sleeve (5) made of a polymer material, - the actuator element (3) has an actuator material strand (6) for position-related control of an instrument head, - wherein the actuator material strand is formed with a shape memory alloy and is arranged inside the guide sleeve (5). An essential feature is that a gap (7) is formed between an inner side of the guide sleeve (5) and an outer side of the actuator material strand (6). The invention also relates to a corresponding actuator assembly and a medical instrument and a corresponding manufacturing method.

Description

Actuator element, actuator composite, medical instrument as well as methods of operation and manufacturing processes

Description

The invention relates to an actuator element according to claim 1, an actuator composite according to claim 9, a medical instrument according to claim 14, a method for operating an actuator composite and / or medical instrument according to claim 15 and a manufacturing method for an actuator element or an actuator composite according to claims 19 and 20.

In recent years, medical instruments such as endoscopes, laparoscopes, intravascular catheters and arthroscopes have enabled new minimally invasive, diagnostic and therapeutic options across a wide range of medical disciplines, including gastroenterology, gynecology, urology, otolaryngology and visceral surgery. Ultimately, the basic design of the instruments has hardly changed in recent years:

Flexible endoscopes:

Endoscopes refer to devices that are inserted through natural body openings (e.g. mouth, nose, anus, vagina, urethral opening) and can flexibly follow the course of the respective anatomical structures such as the esophagus, intestines, trachea and urethra. It is common for flexible endoscopes to be controlled using cable pulls (Bowden cables), which are guided in channels in the device and are operated manually using adjusting wheels.

Endoscopic accessories:

Endoscopic accessories are inserted through the working channel of the endoscopes. The accessories are usually flexible in order to be able to pass through the working channel and are moved in and out mechanically using handles. Few instruments (e.g. papillotomes) can be steered in your direction. This is also technically achieved by tensioning control wires mechanically using handles. Laparoscopes and laparoscopic instruments:

Laparoscopes, i.e. instruments with optics that can be inserted into the abdominal cavity as part of a surgically created capno- or pneumoperitoneum, are usually rigid and have no working channel. The technical limitations of these devices are that these devices (unlike endoscopes, which are inserted through natural body openings) must be sterilized. This means that flexible parts, device joints and working channels cause hygiene problems. Therapeutic instruments such as scissors and grasping forceps for laparoscopy are usually rigid for the same reasons.

Arthroscopes and arthroscopic instruments:

Arthroscopes are inserted into the joint space to inspect joint and cartilage structures. Absolute sterility is required here, which is typically achieved using rigid and sterilizable instruments.

Intravascular catheters:

Intravascular catheters are inserted into the arterial or venous system to deliver medications, position stents, or perform ablations.

Furthermore, it is known from the prior art to use shape memory alloys as actuators as an alternative to control via cable pulls. For example, the document US 55314664 A describes a device with a wire made of shape memory alloys for controlling a medical instrument.

Shape memory alloys are special materials that can seemingly “remember” a previous shape after being deformed. The shape transformation between a high-temperature phase (called austenite) and a low-temperature phase (called martensite) usually occurs through a change in the temperature of the material. The mechanical properties of the shape memory alloys are usually controlled indirectly electrically by applying electricity and thus by heating and cooling the material. The disadvantage of the previously known solutions from the prior art is that they cannot be used for fine, continuous, controlled movements, but only reliably allow binary movements such as the opening and closing of valves or flaps. This is due to the steep phase transitions of the shape memory alloys, which make it difficult to reliably stabilize intermediate positions.

The present invention is therefore based on the object of enabling the control of medical instruments with soft, stable and controlled movements. At the same time, the manufacturing process should enable the cost-effective production of disposable instruments in order to meet the sterility requirements for medical instruments.

In the context of this description, the term “control” is not only understood to mean the control of instrument mobility, but also the execution of additional actuator functions such as the closing and opening of instruments such as pliers or scissors, the movement of an Albarran lever or the release of implants.

This task is solved by an actuator element for controlling invasive medical instruments according to claim 1 and by an actuator assembly for controlling invasive medical instruments according to claim 9. Preferably embodiments of the actuator element can be found in claims 2 to 8, preferably embodiments of the actuator assembly can be found in Claims 10 to 13. A medical instrument according to the invention can be found in claim 14. A method according to the invention for operating an actuator element or an actuator assembly according to the invention can be found in claims 15 to 18. A manufacturing method according to the invention can be found in claim 19 and claim 20.

The wording of all claims is hereby explicitly included in the description in order to avoid unnecessary repetitions.

The invention relates, as is known per se, to an actuator element for controlling medical instruments with the following features:

-the actuator element has a guide sleeve made of a polymer material, -the actuator element has an actuator material strand for position-related control of an instrument head,

-The actuator material strand is formed with a shape memory alloy and arranged inside the guide sleeve.

It is important that a gap is formed between an inside of the guide sleeve and an outside of the actuator material strand.

The mobility of the actuator material strand is ensured by the gap between the inside of the guide sleeve and the outside of the actuator material strand. The thickness of the gap is preferably dimensioned such that mobility is ensured even when the actuator element is bent in a flexible instrument. At the same time, the insulation resulting from the gap leads to faster heating of the actuator material strand and thus enables faster and more precise position-related control of the instrument head through the thermal insulation.

According to the invention, the air gap represents a thermal resistance. While from a structural point of view it is advantageous - as is known from the prior art - to make the air gap as small as possible, according to the invention from a thermal point of view it is necessary that the air gap can develop its thermal effect.

Medical instruments such as endoscopes, laparoscopes, intravascular catheters or arthroscopes usually have a tubular or rod-shaped instrument body that is located in the patient's body during treatment. The actuator element preferably extends into the tubular or rod-shaped instrument body. Particularly preferred in such a way that the actuator element extends essentially over the entire longitudinal extent of the instrument body.

In a preferred embodiment of the invention, the actuator material strand is designed as an SMA wire (abbreviated for shape memory alloy). Unless explicitly stated otherwise, the terms shape memory alloy and SMA wire are used as synonyms below. In order to ensure the required mobility of the medical instruments, correspondingly thin SMA wires are advantageous as an actuator material strand. Due to the greater working capacity of shape memory alloys compared to other actuator materials, the required actuating forces can be achieved even with such small diameters.

The actuator material strand is preferably made of a material from the family of metallic shape memory alloys, such as nickel-titanium (NiTi) alloys. The actuator material strand is preferably made of Nitinol.

The exact design of the SMA wire depends on the medical instrument in which the actuator material strand is to be used. Preferably the SMA wire has a diameter between 20 pm and 250 pm. The actuator material strand and/or the actuator element preferably have a length between 30 and 250 cm.

Preferably the SMA wire has a diameter greater than 100 pm. Larger diameters from 100 pm have the advantage that larger actuator forces can be developed. At the same time, due to the larger diameter, the risk of the guide sleeve being damaged when the actuator material strand is bent is reduced.

The guide sleeve is preferably made of a polymer from the family of polyimides or polyether ketones, such as polyetherimide (PEI), polyamideimide (PAI) or polyetheretherketone (PEEK).

The medical instrument is preferably designed as a flexible and/or invasive medical instrument. Thanks to their flexible design, these instruments can flexibly follow the course of the respective anatomical structures such as the esophagus, intestines, trachea and urethra.

In a preferred embodiment of the invention, a surface of the actuator material strand has, at least in some areas, a coating with high conductivity. This means that the SMA wire of the actuator material strand remains cooler in the coated areas because the current predominantly flows in these areas is passed through the coating. In the coated areas, the contraction is reduced or suppressed depending on the coating thickness due to the lower temperature. At the same time, the uncoated areas in between contract. The travel adjustment can therefore be adjusted very precisely and precisely to the application. At the same time, the position of the thermally critical zones can be adjusted.

As a result, the electrical resistance of the actuator material strand and thus of the entire actuator material strand advantageously decreases in the coated areas, so that overall no voltage values critical for the human body are required to achieve the desired contraction of the actuator material strand.

The coating is preferably in the form of a metallic coating, particularly preferably made of copper, gold, chromium or platinum. The required layer thicknesses depend on the material and the planned application and are preferably between 2 pm and 30 pm, preferably between 3 and 10 pm or alternatively preferably between 8 and 30 pm.

In a preferred embodiment of the invention, the coating is arranged depending on the thermal load on the actuator material strand. This results in the advantage that, particularly in the case of long medical instruments, the energy and thus the thermal load can be distributed favorably over the longitudinal extent of the actuator material strand.

In a preferred embodiment of the invention, the coating is carried out in ring-shaped elements in such a way that between 20% and 80%, preferably 40% - 60% of the total length of the surface of the actuator material strand is coated. The coating is preferably carried out more extensively in areas with a high thermal load compared to an average thermal load on the actuator material strand than in areas with a lower thermal load compared to an average thermal load on the actuator material strand.

In a preferred embodiment of the invention, the coating is applied in short sections with a segment length between 5 and 20 mm. A section consists of coating segments that cover x% of the surface of the actuator material strand, while (100 - x)% of the surface of the actuator material strand remains uncoated. These sections are then strung together.

Such areas with a high thermal load compared to a medium thermal load on the actuator material strand are, for example, in the joint area at the tip of the instrument. This also applies, especially with long instruments, to the part of the instrument that is in the patient's body during the examination. This has the advantage that the coating can help ensure that parts of the instrument that are located in the patient's body are not heated above a certain limit, preferably 45 ° C, otherwise tissue damage can occur.

In a preferred embodiment, the coating is formed on a portion of the surface of the actuator material strand in such a way that an operating voltage of the actuator element is below 25 V / meter of actuator length alternating current (50 V with an instrument length of 2 meters) and 37.5 V / meter of direct current (75 V on 2 meters). The low voltage criteria according to the Low Voltage Directive (2014/35/EU) and IEC 60449 are preferably met. This has the advantage that safety requirements are easier to meet and the operation of the medical instrument is comparatively less dangerous. In a preferred embodiment of the invention, the coating is designed in a ring shape in the form of a plurality of coating rings distributed along a longitudinal extent of the actuator material strand. This results in the advantage that the coating rings can be formed in a simple manner along the actuator material strand.

Preferably, the coating rings are arranged along the longitudinal extent of the actuator material strand in order to achieve a defined temperature profile along the actuator material strand. In this case, the coating rings are preferably arranged narrower and thus more extensively in areas of high thermal load compared to an average thermal load of the actuator material strand, while in areas of lower thermal load the coating rings are arranged less compared to an average thermal load of the actuator material strand Coating rings are arranged. In the areas with coating rings arranged over the entire area, the contraction of the actuator material strand is reduced due to the lower temperature. In the areas with fewer coating rings, however, there is comparatively greater heating and thus a stronger contraction. By arranging the coating rings, the travel adjustment can be easily adapted to the desired application.

A further advantage is that the optimization of the temperature described above can be carried out in a simple manner along the actuator material strand by arranging the coating rings.

In a preferred embodiment of the invention, the gap between the inside of the guide sleeve and the outside of the actuator material strand has a dimension of 1 pm - 150 pm, preferably 50 pm -100 pm. The specified dimensions describe the distance between the inside of the guide sleeve and the outside of the actuator material strand in the resting state, i.e. H. in the stretched state. Of course, it is within the scope of the invention that the distance between the inside of the guide sleeve and the outside of the actuator material strand can be both reduced and increased during operation, particularly in the bent state.

As already mentioned, from a structural point of view - as is known from the prior art - it is advantageous to make the air gap as small as possible, while according to the invention, from a thermal point of view, it is necessary that the air gap can only develop its thermal effect with a certain amount of expansion.

If the thermal resistance between the heat source (wire) and the sink (actuator assembly) is too small, the heat generated is dissipated immediately. This means that much more energy must be supplied to the wire in order to heat it to its conversion temperature. The system therefore becomes inefficient from an energy perspective. However, if the air gap is made too large, it hinders heat dissipation when the actuator material strand is deactivated and thus increases the time required for its resetting. The system dynamics would therefore become worse. Preferably, the gap is filled with a gas and/or a fluid, preferably with air or an oil. The thermal and mechanical properties can be adjusted by the type of filler. An oil-filled gap improves friction properties as a lubricant and thermal conductivity so that heat can be better dissipated. This reduces the cooling time of the actuator element and thus increases the actuator speed.

The object according to the invention is further solved by an actuator network for controlling invasive medical instruments with at least one actuator element according to the invention, as described above. The actuator network has the following features:

- The actuator composite includes a support structure made of a polymer,

- The support structure is formed with channels and/or grooves at least along a longitudinal axis of the actuator assembly. The at least one actuator element is guided in one of the channels and/or grooves.

- The actuator assembly is designed with a casing. This casing encloses at least the support structure and the at least one actuator element.

The actuator composite is preferably characterized by the separation ability of the materials used.

The actuator assembly preferably has several actuator elements. This has the advantage that the position-related control can be adjusted more precisely and larger actuating forces can be realized.

The support structure enables the arrangement of the at least one actuator element together with further actuator elements and/or additional functional elements, such as medical devices, cooling or elements for data and/or energy transfer.

The actuator elements are preferably arranged in a form-fitting and non-positive manner in the grooves, so that easy assembly and dentability is guaranteed. Preferably, the channels and/or grooves are designed to accommodate medical tools and/or the channels and/or grooves are designed to transmit data and/or energy.

As already described, medical instruments such as endoscopes, laparoscopes, intravascular catheters or arthroscopes usually have a tubular or rod-shaped instrument body that is located in the patient's body during treatment. Preferably, at least this tubular or rod-shaped instrument body is essentially formed by the actuator composite. The actuator network therefore essentially extends over the entire longitudinal extent of the medical instrument.

It is within the scope of the invention that additional casings and/or coatings can be provided around the actuator composite as part of the medical instrument.

The arrangement of the actuator composite or the actuator material strand or strands of actuator material in the instrument body can cause the actuator composite and thus the instrument body to heat up during operation. Since the instrument body is located at least partially in the body during the examination or treatment, there is a risk of the instrument body and thus also the patient's surrounding tissue overheating.

In a preferred embodiment, a cooling system is provided for a cooling fluid which circulates in the support structure. The cooling system is preferably designed in such a way that a constant operating temperature of the medical instrument is set, preferably in the range between 25 ° C and 40 ° C, and this temperature on a surface of the actuator composite does not have a defined limit value, for example 45 ° C for medical instruments exceeds.

In addition to avoiding injury to the patient's adjacent tissue, cooling also plays a crucial role in the performance of the system. Since the thermal boundary conditions of the system are constantly changing (for example due to the penetration depth of the instrument or the use of the actuator), precise control and a consistent response behavior of the actuators is essential challenging. Active cooling achieves a stable thermal working point.

The cooling fluid preferably circulates in the channels and/or grooves of the carrier structure. The grooves can be embossed into the support structure in a free geometric arrangement, for example in a meander shape. A minimum distance of 5 pm from the actuator strand is preferably maintained in order to ensure electrical insulation from the cooling fluid. An arrangement of the grooves and/or channels in the outer region of the support structure is particularly advantageous. This also has the advantage that the surface temperature of the instrument is also reduced more efficiently.

The channels in which the cooling fluid circulates preferably have a cross section with the largest possible circumference in order to improve the heat transfer between the cooling fluid and the actuator assembly. Furthermore, a hose and/or a hose system can be provided for the cooling fluid. A closed fluid circuit is preferably provided for the cooling fluid. Alternatively, the cooling fluid, such as water, can exit at defined points of the actuator assembly and be sucked off, for example, via the working channel. This depends in particular on the medical application. In sterile applications it is usually necessary for the cooling fluid to circulate in a closed circuit, while in endoscopes an escape of the cooling fluid is often harmless.

The support structure is preferably formed from a polymer, such as polytetrafluoroethylene (PTFE), fluoroethylene propylene (FEP), perfluoroalkoxylalkane (PFA), ethylene tetrafluoroethylene (ETFE), polyamide (PA), polyurethane (PUR), polyamideimide (PAI), polyetherimide (PEI), polyphenylene sulfide (PPS) or polyetheretherketone (PEEK).

The support structure is preferably designed to be pressure-resistant and flexible. This results in the advantage that the actuator material strand can be prestressed in a simple manner in order to ensure that the shape memory alloys function. These properties are preferred by embedding a Polymer or metal spring implemented into the support structure. This allows the necessary prestressing of the shape memory materials of 100-300 N/mm ² SMA diameter to be achieved in the overall composite.

The casing is preferably designed as a support structure made of PTFE, FEP, PFA, ETFE, PA, PUR, PPS, PEEK PAI or PEI and can optionally have an integrated fabric or braided structure.

In a further advantageous embodiment of the invention, the casing is designed to be pressure-resistant and flexible. This results in the advantage that the support structure is supported in its corresponding function by the casing. These properties are preferably achieved by embedding a polymer or metal spring in the casing. This allows the necessary pretension of the shape memory materials of 100-300 N/mm ² to be achieved in the overall composite.

The object according to the invention is further achieved by a medical instrument, preferably an endoscope, laparoscope, bronchoscope or arthroscope, with an actuator element and/or an actuator assembly as described above. Such a medical instrument combines the advantages of the embodiments of the actuator assembly and/or the actuator element described above or the preferred embodiments described above.

A particular advantage of such medical instruments according to the invention is that they can be easily integrated into cyber-medical systems since fully electronic control is possible.

Another advantage of such medical instruments according to the invention is that they can be manufactured as sterile disposable instruments in a simple and cost-effective manner, particularly due to the modular structure. This eliminates the need to sterilize instruments after each use.

The object according to the invention is further achieved by a method for operating an actuator train and/or an actuator assembly and/or a medical instrument according to one of the preceding claims as described above. The method preferably provides that a cooling fluid circulates in order to absorb the heat generated during operation of the actuator elements. The cooling fluid particularly preferably circulates in the support structure.

By cooling via the support structure, the medical instrument can be cooled in a simple manner over the entire length of the instrument.

The cooling fluid preferably has a flow temperature, preferably between 20 ° C and 37 ° C, preferably 25 ° C.

In a preferred embodiment of the method for operating an actuator element and/or an actuator assembly and/or a medical instrument, a flow rate of the cooling fluid and/or a temperature of the cooling fluid is regulated such that a stable operating temperature (25°C - 40°C) is set and a temperature on the surface of the actuator assembly does not exceed a limit according to IEC 60601-1, preferably a limit of 45° C. In other words, this means that the cooling media flow and the cooling media temperature are regulated in such a way that a temperature of the medical instrument at a Surface of the actuator composite does not exceed a defined limit, for example 45 ° C for medical instruments. This has the advantage that damage to the patient's tissue due to overheating is avoided and precise and dynamic control of the instrument is possible. A volume flow of between 100 and 500 ml / h is preferably set in the instrument. This has the advantage that the actuator speed can be increased by a factor of 2 to 6 due to the cooling.

In a preferred embodiment of the method, a closed fluid circuit is provided for the cooling fluid and the cooling fluid circulates in the fluid circuit without loss. This has the advantage that the cooling fluid does not leak into the patient's surrounding tissue. In an alternative embodiment of the method according to the invention, the cooling fluid exits at defined points of the actuator assembly. Such a configuration is possible, for example, if the application does not have to be sterile.

The object according to the invention is further solved by a manufacturing method according to claim 19. The manufacturing method according to the invention for an actuator element with an actuator material strand with a shape memory alloy and a guide sleeve made of a polymer material is carried out by means of an extrusion method.

It is essential that in the extrusion process a gap is formed between the actuator material strand and the guide sleeve by introducing a supporting gas, preferably air or nitrogen. This results in the advantage that actuator elements for corresponding medical instruments can be produced in large quantities and in a highly scalable manner using the extrusion process. Corresponding medical instruments can therefore be produced easily and comparatively inexpensively as disposable instruments.

It is also within the scope of the invention that the manufacturing process for an actuator composite with a support structure, at least one actuator element and a casing is also based on an extrusion process, with at least the support structure being produced by means of an extrusion process. In a process step downstream of the extrusion process of the support structure, at least one actuator element or one of the preferred embodiments of an actuator element described above is introduced into grooves in the support structure. It is also within the scope of the invention that the actuator element is also produced using an extrusion process.

It is preferred to coat the actuator material strand before inserting it into the actuator element, i.e. H. applied before the extrusion process. This can preferably be done via electrochemical processes or sputtering.

In a preferred embodiment of the invention, an oxide layer on the metallic shape memory alloy of the actuator material strand is removed before the coating process. This results in a low transition resistance stood between the metallic shape memory alloy of the actuator material strand, in particular Nitinol, and the coating metal. The oxide layer usually present on the surface of the metallic shape memory alloy as delivered would act as an electrical insulator and significantly reduce the efficiency of the coating.

The actuator material strand according to the invention and the actuator composite according to the invention are fundamentally suitable for applications in which control is to take place in medical instruments. As described, these can be, for example, the position-related control of an instrument head or additional actuator functions of the medical instrument. It is only through the basic idea of an air gap according to the invention that thermal optimization and mechanical performance for precision and speed of mobility of the medical instrument are achieved, so that medical use for precise movements is possible. The various optimizations through the preferred embodiments, such as the thermal optimization of the entire system and the control of the cooling liquid, further improve the mechanical performance for precision and speed of mobility of the instrument tip, so that the acceptability and possible uses for medical use are further increased.

Further advantageous features and embodiments of the invention are explained below using exemplary embodiments and the figures. This shows:

Figure 1 with partial images a, b and c shows three schematic representations of an exemplary embodiment of an actuator assembly according to the invention;

Figure 2 shows a schematic representation of a section of an exemplary embodiment of an actuator assembly according to the invention in detail;

Figure 3 shows a schematic representation of an exemplary embodiment of an actuator element according to the invention with a coating. Figure 4A shows a schematic representation of an exemplary embodiment of a pressure-stable and flexible actuator composite.

Figure 4B shows a schematic representation of an exemplary embodiment with a pressure-stable and flexible casing.

In the exemplary embodiments and the figures, the same reference numbers designate the same or identically acting elements. The dimensions given are to be understood purely as examples and do not contain any restrictions that go beyond the claims.

Figure 1a shows a schematic representation of an actuator assembly 1 for controlling flexible, invasive medical instruments with a support structure 2, an actuator element 3 and a casing 4.

The actuator element 3 has a guide sleeve 5 and an actuator material strand 6. The guide sleeve 5 is made of a polymer material, in this case PEEK.

The actuator material strand 6 is designed as an SMA wire (wire made of a shape memory alloy), in the present case made of NiTi. The SMA wire has a diameter of 100 pm and a length of 150 cm.

The actuator material strand 6 is designed for position-related control of a dockable instrument head and is arranged inside the guide sleeve 5.

A gap 7 is formed between the inside of the guide sleeve 5 and an outside of the actuator material strand. The gap 7 between the inside of the guide sleeve and the outside of the actuator material strand 6 is 50 pm in the resting state, that is, in the stretched state.

In the present case the gap 7 is filled with air.

The support structure 2 has several grooves 8a, 8b, 8c, 8d all around, in this case four grooves 8a, 8b, 8c, 8d. Furthermore, several channels are provided in the support structure 2. In the present case, two channels 9a, 9b are provided in the outer region. The channels in the outer region 9, 9b are designed to transport a cooling medium. In addition, another channel 10 is provided in the middle of the support structure. The channel 10 is designed for the passage of endoscopic tools.

In the present case, the support structure 2 is designed to be pressure-resistant and flexible in order to ensure pre-stressing of the actuator material strand.

Furthermore, a casing 4 is provided as described. The casing 4 is made of a polymer material, in this case PTFE.

The casing 4 encloses the support structure 2 with the grooves 8 and channels 9 as well as the actuator element 3.

Of course, it is within the scope of the invention that several actuator elements 3 are provided, which are arranged in the grooves 8a, 8b, 8c, 8d. For better clarity, only the actuator element 3 is shown in the groove 8a in FIG.

By applying current, the SMA wire as an actuator material strand 6 is heated or cooled, so that the dimensions of the SMA wire change and enable position-related control of a coupled instrument head.

The actuator assembly 1 described above is particularly suitable for use in an endoscope or a laparoscope. With the exemplary embodiment described, movements of the controlled instrument tip of ±100 degrees can be realized with a frequency of 1 Hz.

Medical instruments such as endoscopes, laparoscopes, intravascular catheters or arthroscopes usually have a tubular or rod-shaped instrument body that is located in the patient's body during treatment. This tubular or rod-shaped instrument body in the present case, per is formed by the actuator assembly 1 described above. The actuator assembly 1 therefore extends over the entire longitudinal extent of the medical instrument.

The arrangement of the actuator assembly 1 in the instrument body causes the actuator assembly 1 and thus the instrument body to heat up during operation. Since the instrument body is located at least partially in the patient's body during the examination or treatment, there is a risk of overheating of the instrument body and thus also of the patient's adjacent tissue. For this reason, the channels 10 are provided for the cooling system in the actuator network 1.

Figure 1 b shows a schematic representation of an actuator assembly 1 for controlling flexible, invasive medical instruments. To avoid repetition, reference is only made to the differences to Figure 1a.

The grooves and channels 9a, 9b, 9c, 9d are in the present case arranged in the outer region of the support structure 2. This has the advantage that the surface temperature of the instrument is efficiently reduced.

The channels 9a, 9b, 9c, 9d, in which the cooling fluid circulates, have a cross section with the largest possible circumference in order to improve the heat transfer to the cooling fluid. In the present case, the channels 9a, 9b, 9c, 9d are formed ovally along the outer circumference of the support structure 2. The actromaterial strands 6 are provided on the outer circumference of the support structure 2 between the channels 9a, 9b, 9c, 9d. There is a minimum distance of 5 pm between the channels 9a, 9b, 9c, 9d for the cooling fluid and the actuator material strands 6.

Figure 1c shows a schematic representation of an actuator assembly 1 for controlling flexible, invasive medical instruments. To avoid repetition, reference is only made to the differences to Figure 1a.

The channels 9a, 9b, 9c, 9d for cooling fluid are not closed in this case, but are open. Hoses can be provided in the open channels to transport the cooling fluid. Figure 2 shows a detailed representation of a section from Figure 1 with the actuator element 3 in detail.

The actuator element 3 has a guide sleeve 5 and an actuator material strand 6.

The guide sleeve 5 is made of a polymer material, in this case PEEK.

The actuator material strand 6 is designed as an SMA wire (wire made of a shape memory alloy), in this case NiTi.

The SMA wire has a diameter of 100 pm and a length of 150 cm.

A gap 7 is formed between the inside of the guide sleeve 5 and an outside of the actuator material strand 6. In the present case, the gap 7 is filled with air.

The gap 7 between the inside of the guide sleeve and the outside of the actuator material strand 6 is 50 pm in the resting state, that is, in the stretched state.

The actuator element 3 described above is particularly suitable for use in an endoscope, alternatively also for endoscopic instruments, laparoscopes, laparoscopic instruments, bronchoscopes or arthroscopes. With the exemplary embodiment described, movements of the controlled instrument tip of ±100 degrees can be realized with a frequency of 1 Hz. Figure 3 shows an actuator element with coatings in partial figures a) and b), the coatings being arranged differently in partial figures a) and b).

The actuator material strand 6 is designed as an SMA wire made of a shape memory alloy. In the present case, a coating in the form of several coating rings 11a, 11b, 11c, 11d, 11e, 11f is formed on the actuator material strand 6. The coating rings 11a, 11b, 11c, 11d, 11e, 11f are designed to run around the actuator material strand 6 and in the present case are designed in the form of a metallic coating made of Au.

Partial figure a) shows an embodiment with four coating rings 11a, 11b, 11c, 11d on the route shown, which cover a portion of the surface of the actuator material strand 6. As a result, in partial figure a), 50% of the surface of the actuator material strand 6 is coated.

In partial figure b), an embodiment with six coating rings 11a, 11b, 11c, 11d, 11e, 11f is shown on the route shown, which cover a smaller proportion of the surface of the actuator material strand 6 compared to partial figure a). As a result, in partial figure b), 33% of the surface of the actuator material strand 6 is coated.

Since the current in the coated areas 11a, 11b, 11c, 11d, 11e, 11f is predominantly conducted through the coating, the SMA wire of the actuator material strand 6 remains comparatively cooler. In the coated areas 11a, 11b, l lc, 11d, 11e, 11f, the contraction of the actuator material strand 6 is reduced due to the lower temperature. The uncoated areas in between are heated more and therefore contract more strongly.

At the same time, the coated areas 11a, 11b, 11c, 11d, 11e, 11f and thus the entire actuator material strand 6 have a lower electrical resistance, so that a lower voltage is required overall in order to achieve the desired contraction of the actuator material strand 6.

In the embodiments described here for partial figures a) and b), the coatings 11a, 11b, 11c, 11d, 11e, 11f are on a portion of the Surface of the actuator material strand 6 is designed so that an operating voltage of the actuator element 3 is below 25 volts / meter alternating current and 75 V direct current and the criteria for a low voltage according to the Low Voltage Directive (2014/35 / EU) and IEC 60449 are met. This has the advantage that safety requirements are easier to meet and the operation of the medical instrument is comparatively less dangerous.

Figure 4A shows a schematic representation of an exemplary embodiment of a pressure-stable and flexible actuator composite.

In order to avoid unnecessary repetitions, only the differences from Figure 1 will be discussed below.

As described in Figure 2, the support structure 2 in the present case is designed to be pressure-resistant and flexible in order to ensure pre-stressing of the actuator material strand.

This preload is generated by embedding a spring 12 in the support structure 2. The spring 12 is presently arranged in the central channel 10. The spring 12 extends through the channel 10 along the entire longitudinal extent of the instrument body.

Figure 4B shows a schematic representation of an exemplary embodiment with a pressure-stable and flexible casing 4.

In the present case, the pretensioning of the actuator material strand is realized by embedding a spring 13 in the casing 4. The spring 13 extends in the casing along the entire longitudinal extent of the instrument body. Reference symbol list

1 actuator network

2 Support structure 3 Actuator element

4 jacket

5 guide sleeve

6 actuator material strand

7 gap 8a, 8b, 8c, 8d grooves

9a, 9b, 9c, 9d channels

10 channel

11a, 11 b, 11c, 11d, 11e, 11f coating/coating rings

12 Spring in the support structure 13 Spring in the casing

Claims

Expectations

1. Actuator element (3) for controlling medical instruments with the following features: the actuator element (3) has a guide sleeve (5) made of a polymer material, the actuator element (3) has an actuator material strand (6) for controlling the medical instrument,

- wherein the actuator material strand is formed with a shape memory alloy and is arranged inside the guide sleeve (5), characterized in that a gap is formed between an inside of the guide sleeve (5) and an outside of the actuator material strand (6).

2. Actuator element according to claim 1, characterized in that the medical instrument has a tubular or rod-shaped instrument body and the actuator element extends in the tubular or rod-shaped instrument body.

3. Actuator element according to claim 1 or 2, characterized in that a surface of the actuator material strand (6) has at least partially a coating (11 a, 1 1 b, 1 1 c, 1 1 d, 11 e, 11 f) with high conductivity , preferably in the form of a metallic coating (11a, 11b, 11c, 11d, 11e, 11f), most preferably made of copper, gold, chromium or platinum, preferably with a layer thickness of 2-30 pm, particularly preferably 8 -30 p.m.

4. Actuator element according to claim 3, characterized in that the coating (11a, 11b, 11c, 11d, 11e, 11f) depending on the thermal load on the actuator material strand (6), preferably in segments in the form of repeating similar segments, is arranged, preferably that the coating (11 a, 11 b, 11 c, 11 d, 1 1 e, 11 f) is designed such that it is in areas with a high thermal load Compared to a medium thermal load along the actuator material strand (6), a larger area on the actuator material strand (6) is covered.

5. Actuator element according to one of the preceding claims 3 or 4, characterized in that the coating (11 a, 11 b, 11 c, 11 d, 11 e, 11 f) is formed on a portion of the surface of the actuator material strand (6), so that an operating voltage of the actuator element (3) is below 50 V alternating current and 75 V direct current, preferably that the criteria for a low voltage according to the Low Voltage Directive (2014/35/EU) and IEC 60449 are met.

6. Actuator element according to one of the preceding claims 3 to 5, characterized in that the coating (11a, 11b, 11c, 11d, 11e, 11f) is annular in the form of a plurality of coating rings (11a, 11b, 11 c, 11 d, 11 e, 11 f) is formed with a segment length between 5 and 20 mm along a longitudinal extent of the actuator material strand (6), in particular that the coating rings (11 a, 11 b, 11 c, 11 d, 11 e , 11f) are arranged along the longitudinal extent of the actuator material strand (6) in order to achieve a defined temperature profile along the actuator material strand (6).

7. Actuator element according to one of the preceding claims, characterized in that the gap (7) between the inside of the guide sleeve (5) and the outside of the actuator material strand (6) is 1 pm - 150 pm, preferably 50 pm - 100 pm.

8. Actuator element according to one of the preceding claims, characterized in that the gap (7) between the inside of the guide sleeve (5) and the outside of the actuator material strand (6) with a gas and / or a fluid, preferably with air or an oil, is filled.

9. Actuator assembly for controlling medical instruments with at least one actuator element (3) according to one of the preceding claims, with the following features: the actuator composite (1) comprises a support structure (2) made of a polymer, the support structure (2) is formed with channels (9a, 9b, 10) and/or grooves (8a, 8b, 8c, 8d) at least along a longitudinal axis of the actuator composite , wherein at least the actuator element is guided in one of the channels (9a, 9b, 10) and / or grooves (8a, 8b, 8c, 8d), and the actuator composite (1) is formed with a casing (4), the casing (4) encloses at least the support structure (2) and the at least one actuator element (3).

10. Actuator assembly according to claim 9, characterized in that a cooling system is provided for a cooling fluid which is in the support structure (2), preferably in the channels (9a, 9b, 10) and / or grooves (8a, 8b, 8c, 8d ) of the support structure (2), particularly preferably at a distance of at least 5 pm from the actuator material strand and the cooling flow is positioned radially at a greater distance from the geometric central axis, and / or that at least one hose is provided for the cooling fluid and that a closed fluid circuit is provided for the cooling fluid or the cooling fluid exits at defined points of the actuator network.

11 .Actuator composite according to claim 9 or 10, characterized in that the channels (9a, 9b, 10) and / or grooves (8a, 8b, 8c, 8d) are designed to accommodate medical tools and / or that the channels (9a, 9b, 10) and/or grooves (8a, 8b, 8c, 8d) are designed for the transmission of data and/or energy.

12. Actuator composite according to one of claims 9 to 11, characterized in that the support structure (2) is designed to be pressure-resistant and flexible, preferably by embedding a metallic or polymer spring in the support structure (2).

13. Actuator assembly according to one of claims 9 to 12, characterized in that the casing (4) is designed to be pressure-resistant and flexible, preferably by embedding a metallic or polymer spring in the casing (4).

14. Invasive medical instrument, preferably endoscope, laparoscope; Bronchoscope, intravascular catheter or arthroscope, with an actuator element (3) and/or an actuator assembly (1) according to one of the preceding claims.

15. Method for operating an actuator assembly (1) and/or a medical instrument according to one of the preceding claims, characterized in that a cooling fluid circulates in the support structure.

16. A method for operating an actuator assembly (1) and / or a medical instrument according to claim 14, characterized in that the cooling fluid has a flow temperature, preferably between 20 ° C and 37 ° C, preferably ° 25 ° C and / or that Cooling fluid circulates at a flow rate of 100 - 500ml / hour.

17. A method for operating an actuator assembly (1) and / or a medical instrument according to claim 16 or 16, characterized in that a flow rate of the cooling fluid and / or a temperature of the cooling fluid is regulated such that a temperature on a surface of the actuator assembly ( 1) does not exceed a limit according to IEC60601-1, preferably a limit of 45°C, in particular that a stable thermal operating point can be set.

18. A method for operating an actuator assembly (1) and/or a medical instrument according to one of claims 15 to 17, characterized in that a closed fluid circuit is provided for the cooling fluid and the cooling fluid circulates in the fluid circuit without loss.

19. Manufacturing process for an actuator element (1) with an actuator material strand (6) made of a shape memory alloy and a guide sleeve (5) made of a polymer material by means of an extrusion process, characterized in that in the extrusion process there is a gap between the actuator material strand (6) and the guide sleeve (5). (7) is formed by introducing a supporting gas, preferably air or nitrogen.

20. Manufacturing process for an actuator composite (1) with a support structure (2), at least one actuator element (3) and a casing (4), wherein at least the support structure (2) is produced by means of an extrusion process and in a process step downstream of the extrusion process at least an actuator element (3) according to one of the preceding claims 1 to 7 is introduced into grooves (8a, 8b, 8c, 8d) of the support structure (2).