Spiral micro-robot based on shape memory polymer and preparation method of spiral micro-robot

Abstract

The invention discloses a spiral micro-robot based on a shape memory polymer and a preparation method of the spiral micro-robot, and relates to the field of micro-nano robots. The problem that a traditional hard non-deformable magnetic drive micro-robot is limited in the aspects of active operation capacity and adaptability is solved. According to the spiral micro-robot based on the shape memory polymer, the spiral micro-robot body is made of the shape memory polymer. A preparation method of a spiral micro-robot based on a shape memory polymer comprises the steps that shape memory fibers are wound into a spiral shape, and the spiral shape memory fibers are subjected to heat treatment and cooling, so that internal stress generated in the winding process of the shape memory fibers is released; and the wound shape memory fiber is unfolded into a straight line, then the linear shape memory fiber is wound into a spiral shape again, the spiral shape memory fiber is heated to the transformation temperature and then cooled, stress caused by the difference between the current shape and the permanent shape of the shape memory fiber is reserved, and the spiral micro-robot is obtained.

Description

Technical Field

[0001] The invention belongs to the field of micro-nano robots. Background Art

[0002] Micro-nano robots have been widely studied due to their controlled motion capabilities and tiny size, and have been applied to targeted drug delivery, minimally invasive surgery, cell manipulation, detection and diagnosis, etc. At present, the energy of micro-nano robots mainly comes from their internal biochemical reactions and external energy fields, such as magnetic fields, electric fields, and light fields. Magnetic field drive is favored due to its advantages such as strong penetration, good biocompatibility, and easy control.

[0003] The helical microrobot is a typical design of magnetically driven micro-nano robots, which is inspired by the flagellar motion of bacteria in nature and can generate highly efficient three-dimensional propulsion motion in a low Reynolds number liquid environment driven by a low-intensity rotating magnetic field. However, traditional hard, non-deformable magnetically driven microrobots have limitations in terms of active operation capabilities and adaptability. Summary of the invention

[0004] The present invention aims to solve the problem that traditional hard non-deformable magnetically driven microrobots have limitations in active operation capability and adaptability, and now provides a spiral microrobot based on shape memory polymer and a preparation method thereof.

[0005] A spiral microrobot based on shape memory polymer comprises a spiral microrobot body 1 and at least one magnetic unit 2 located inside or on the surface of the spiral microrobot body 1. The material of the spiral microrobot body 1 comprises shape memory polymer.

[0006] Furthermore, the magnetic unit 2 includes magnetic powder or magnetic components.

[0007] A method for preparing a spiral microrobot based on a shape memory polymer, comprising:

[0008] Winding the shape memory fiber into a spiral shape, heat treating and cooling the spiral shape memory fiber, so that the internal stress generated by the shape memory fiber during winding is released;

[0009] The wound shape memory fiber is unfolded into a straight line, and then the straight shape memory fiber is wound into a spiral shape again and heated to a transition temperature and then cooled, so that the stress caused by the difference between the current shape and the permanent shape of the shape memory fiber is retained, thereby obtaining a spiral microrobot.

[0010] Furthermore, the method for preparing the shape memory fiber comprises:

[0011] The molten thermoplastic shape memory polymer is extruded from a spinneret hole by a heating extrusion device and is rotationally wound around the outside of a collecting cylinder to form a shape memory fiber.

[0012] Furthermore, in the process of preparing the shape memory fiber, the magnetic unit 2 is mixed into the molten shape memory polymer to obtain the magnetic shape memory fiber.

[0013] Furthermore, the following processing steps are included before the shape memory fiber is wound for the first time:

[0014] The shape memory fiber is straightened and fixed on a glass substrate, a photosensitive resin mixed with magnetic microparticles is dripped on the glass substrate, and a glass slide is covered on the shape memory fiber so that the photosensitive resin forms a liquid film on the shape memory fiber;

[0015] The shape memory fiber is irradiated with an ultraviolet laser passing through a mask, so that a magnetic unit 2 is attached to the shape memory fiber.

[0016] Furthermore, a radial magnetic field is applied to the spiral microrobot to complete the magnetization of the magnetic unit 2 in the spiral microrobot.

[0017] Furthermore, the shape memory polymer is polylactic acid.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention provides a spiral microrobot based on shape memory polymer, which consists of a spiral microrobot body containing shape memory polymer material and a magnetic unit. Shape memory polymer materials generally have low modulus and good biocompatibility, and some shape memory polymers are biodegradable, so they can be safely used in biomedicine and other fields.

[0020] 2. The spiral microrobot body of the present invention has a spiral shape, which can convert rotational motion into axial propulsion motion, so that the microrobot can swim freely in a three-dimensional liquid environment under the drive of an external rotating magnetic field, and achieve high-efficiency driving and precise navigation. At the same time, the spiral microrobot body contains shape memory polymer materials, so that the microrobot can respond to external thermal stimulation at any time, produce pre-programmed shape changes, adjust its own shape size and motion performance, or complete operations such as grasping and releasing.

[0021] 3. The present invention provides a method for preparing a spiral microrobot based on a shape memory polymer, which firstly forms a shape memory polymer into fibers by melt spinning, and processes the fibers to install a magnetic unit. The permanent and temporary shapes of the spiral microrobot body are determined by secondary winding and heat treatment of the fibers, and the spiral microrobot is obtained after cutting and magnetization, and a spiral microrobot with a size of 1.5 to 0.5 mm can be prepared.

[0022] 4. The present invention provides a method for preparing a spiral microrobot based on a shape memory polymer, which can complete the shape memory training of the microrobot during preparation. When subjected to thermal stimulation, the microrobot will return from a temporary shape to a memorized permanent shape. By designing different spiral shapes, the length, diameter, taper and other parameters of the spiral microrobot body can be quantitatively changed, so that the microrobot can be applied to complex and diverse tasks.

[0023] 5. In the present invention, the microrobot has precise navigation capability and stimulus-responsive programmable deformation capability, which enables it to have the functions of active connection, active separation and performance adjustment. The microrobot can use programmable deformation capability to actively grasp the target object, anchor at the target position in the body, actively release the payload, or change its own shape and size to adapt to the environment, so that it can be better applied to micro-manipulation, targeted drug delivery, minimally invasive surgery and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the spiral microrobot in the present invention;

[0025] Figure 2 Schematic diagram of the preparation method of the spiral microrobot, (a) is a schematic diagram of the preparation of the fiber, (b) is a schematic diagram of the marking treatment of the fiber, (c) is a schematic diagram of the first winding and heat treatment, the fiber unfolding, and the secondary winding heat treatment, (d) is a schematic diagram of the cutting and magnetization treatment;

[0026] Figure 3 Schematic diagram of the spiral microrobot actively grasping the target object;

[0027] Figure 4 Schematic diagram of the spiral microrobot anchoring at the target position;

[0028] Figure 5 Schematic diagram of active release of the embedded payload in the spiral microrobot;

[0029] Figure 6 Schematic diagram of the spiral microrobot adapting to the staged task requirements in minimally invasive injection. (a) shows the state of the small-diameter microrobot deployed in the injection needle before deformation, and (b) shows the process of the microrobot returning to shape after being injected into the body.

[0030] Marking instructions in the figure: 1 spiral microrobot body, 2 magnetic unit. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0032] Specific implementation method 1: Shape memory polymers (SMPs), as a type of smart material, have attracted much attention due to their ability to actively deform under external stimuli. This type of material can recover from a temporary shape to a pre-programmed permanent shape through stimuli such as heat, light, magnetism, electricity, and solutions. In particular, some shape memory polymers are also biocompatible and biodegradable. The above advantages make shape memory polymers an ideal choice for the development of new magnetically driven microrobots, which can greatly enhance the active operation capabilities and adaptability of magnetically driven microrobots in complex environments. Therefore, this implementation method applies shape memory polymers to spiral microrobots to realize the design of microrobots.

[0033] Reference Figure 1 Specifically describing this embodiment, a spiral microrobot based on shape memory polymer described in this embodiment includes a spiral microrobot body 1 and at least one magnetic unit 2 located inside or on the surface thereof, and the material of the spiral microrobot body 1 includes shape memory polymer. The magnetic unit 2 includes magnetic powder or magnetic components. The magnetic unit is used to drive the movement of the spiral microrobot under the action of an external magnetic field, and the movement of the spiral microrobot can be controlled by adjusting the external rotating magnetic field strength, frequency, and rotation axis direction.

[0034] The spiral microrobot based on shape memory polymer described in this embodiment has the following characteristics: 1. The material is / or contains shape memory polymer, which provides the ability to change shape under external stimulation; 2. The shape is spiral, which provides the ability to propel movement under magnetic field drive; 3. The size is small and can be adapted to different applications. The spiral microrobot based on shape memory polymer described in this embodiment can achieve precise navigation under magnetic field drive, can achieve precise shape change and action execution under external stimulation, such as thermal stimulation, and can meet the application needs in the fields of micro-manipulation, biomedicine, etc.

[0035] Specific implementation method 2: refer to Figure 2Specifically describing this embodiment, a method for preparing a spiral microrobot based on a shape memory polymer described in this embodiment includes:

[0036] 1. Preparation of shape memory fibers, that is, thermoplastic shape memory polymers (such as polylactic acid) are made into shape memory fibers through melt spinning technology.

[0037] The molten shape memory polymer is extruded from the spinneret using a heated extruder, and the extruded fibers are collected by winding with a rotating collecting cylinder to form shape memory fibers. During this process, the shape memory polymer is stretched and cooled, and the diameter is reduced to form fibers. The fiber diameter is controlled by adjusting process parameters such as spinneret diameter, extrusion speed, collection cylinder rotation speed, polymer temperature, etc.

[0038] In practical applications, magnetic units (magnetic particles) can be mixed into the molten shape memory polymer before spinning to obtain magnetic fibers. Alternatively, magnetic units are not mixed in first, and non-magnetic fibers are obtained.

[0039] 2. Processing of shape memory fibers.

[0040] The purpose of this step is twofold: one is to install the magnetic unit on the non-magnetic fiber, and the other is to mark the length of the fiber involved in the winding. First, the non-magnetic fiber is straightened and fixed on a glass substrate, and then a photosensitive resin is dripped on the glass substrate, in which magnetic microparticles are mixed. Then a cover glass is covered to form a liquid film of the resin. The gap between the two glass sheets is adjusted by a gasket. The ultraviolet laser light path passing through the mask is aligned with the non-magnetic fiber. After timed exposure, the magnetic unit can be polymerized on the non-magnetic fiber. Two magnetic units with a certain spacing can mark the length of the fiber involved in the winding. Finally, the fiber is cleaned with anhydrous ethanol to remove the residual photosensitive resin. Remove the magnetic fiber from the glass substrate for use.

[0041] 3. Initial winding and heat treatment.

[0042] The shape memory fiber is wound around the microshaft to obtain a designed spiral structure. The spiral structure is subjected to high temperature heat treatment and cooled to release the internal stress generated by the winding. This shape is fixed as the permanent shape of the shape memory polymer.

[0043] In the winding process of shape memory fibers, the shape parameters of the spiral microstructure can be controlled by adjusting the process parameters such as the micro-axis diameter, micro-axis taper, winding starting point, winding angle, etc. to obtain the designed spiral shape. The winding starting point is the initial position where the fiber contacts the axis during winding, and the winding angle is the angle between the fiber and the winding axis during winding.

[0044] 4. Expand the spiral microstructure.

[0045] Through the reverse motion of winding, the helical microstructure in the permanent shape is unfolded into a straight line.

[0046] 5. Secondary winding and heat treatment.

[0047] The shape memory fiber is wound around the micro-axis again to obtain a designed spiral structure. The spiral structure is heated to the transition temperature of the shape memory polymer and then cooled. The stress caused by the difference between the current shape and the permanent shape is stored after cooling. This shape is fixed as the temporary shape of the shape memory polymer.

[0048] 6. Cutting and magnetization.

[0049] Cut the fibers at both ends of the spiral microstructure, remove the spiral microstructure from the microshaft, cut off the excess fiber segments at both ends of the spiral microstructure, and cut the spiral microstructure into appropriate lengths. Then perform magnetization: use an electromagnetic coil or a permanent magnet to generate a magnetic field along the radial direction of the spiral microstructure to complete the magnetization of the magnetic unit in the spiral microrobot.

[0050] This embodiment integrates the shape change programming process into the preparation process of the microrobot, and completes the shape memory training of the microrobot during preparation. The prepared spiral microrobot not only has the current temporary shape, but also remembers the pre-programmed permanent shape, and both shapes can be quantitatively controlled. In actual application, a thermal stimulus is applied to the spiral microrobot so that its temperature reaches the transition temperature of the shape memory polymer, and the spiral microrobot will return from the temporary shape to the memorized permanent shape. By designing different spiral shapes, quantitative changes in parameters such as the length, diameter, and taper of the spiral microrobot body can be achieved.

[0051] In the preparation process of the spiral microrobot, it is necessary to use a fiber with a ribbon-shaped cross section to ensure that the fiber has a consistent bending direction in the two windings. The ribbon-shaped cross-section fiber is a fiber whose cross-sectional width is significantly greater than its thickness, which can be obtained by using a spinneret with a significant aspect ratio in the spinning process.

[0052] The method described in this embodiment can complete the shape change programming of the microrobot while preparing it, and can prepare a spiral microrobot with a size of 1.5 to 0.5 mm, and can achieve quantitative control of parameters such as length, diameter, and taper.

[0053] Specific implementation method three: refer to Figure 2 Specifically describing this embodiment, a method for preparing a spiral microrobot based on a shape memory polymer described in this embodiment includes:

[0054] (1) The polymer fibers were produced by melt spinning technology. The melt spinning device included a melt extrusion device, a winding collection device and a temperature control system. Polylactic acid consumables for 3D printing were selected. Magnequench produced MQFP-15-7 grade NdFeB particles with an average diameter of 5 μm. Non-magnetic fibers were prepared from pure polylactic acid. The polymer was heated by a heating plate, and magnetic particles were mixed into the molten polymer. The resulting composite was used to prepare magnetic fibers. A 0.3×0.8 mm ribbon-shaped cross-section spinneret was selected to prepare ribbon-shaped cross-section fibers. The heated extrusion device included a heating block, a spinneret, an electric moving platform and a metal plunger. The polymer was melted by a heating block, and the metal plunger was pushed by an electric moving platform to extrude the polymer from the spinneret. The polymer was wound and collected by a rotating collecting drum. During this period, the polymer was cooled and stretched to obtain polymer fibers.

[0055] (2) It is necessary to install a magnetic component on the non-magnetic fiber, or mark the fiber segment involved in the winding. In this embodiment, a planar photolithography method is used to manufacture and install the magnetic component. First, the fiber is straightened and fixed on a glass substrate, and a flexible photosensitive resin for 3D printing is dripped on the glass substrate. Magnetic microparticles are mixed in the photosensitive resin. Then a cover glass is covered to form a liquid film of the resin. The gap between the two glass sheets is adjusted by a gasket to adjust the thickness of the liquid film. An ultraviolet laser is used to emit an ultraviolet laser through a mask plate with a characteristic shape of light-transmitting holes to irradiate the fiber and the photosensitive resin. After timed exposure, the photosensitive resin containing magnetic particles can be polymerized on the polymer fiber as a magnetic unit. A precision displacement platform is used to translate the position of the laser and the mask plate to expose and polymerize another magnetic unit. Two magnetic units with a certain spacing can mark the fiber segment involved in the winding. Finally, anhydrous ethanol is used to clean the fiber to remove the residual photosensitive resin. The polymer fiber is removed from the glass substrate for use.

[0056] (3) Winding polymer fibers on a metal shaft to obtain a spiral microstructure. In this embodiment, the metal shaft is a cylindrical shaft and a conical shaft with a taper, which is fixed on a rotating platform and can rotate along the axis. One end of the fiber is fixed to the cantilever of the rotating platform, and the other end is connected to a counterweight through a constraint hole on the mobile platform. When the platform rotates, the fiber is wound on the metal shaft to form a spiral microstructure. Before winding, the starting position of the winding can be adjusted by adjusting the axial position of the metal shaft. During winding, the angle between the fiber and the shaft can be controlled by moving the constraint hole through the electric mobile platform, and the spiral angle of the spiral microstructure can be further controlled.

[0057] (4) After winding is completed, the metal shaft is heated by a heating sheet, and the heat is transferred to the spiral microstructure to achieve heat treatment. The temperature of the metal shaft and the spiral microstructure is detected by a micro thermocouple. The polylactic acid spiral microstructure is heated to 90°C and then cooled to room temperature to eliminate the stress generated by winding.

[0058] (5) Through the reverse motion of the winding device, the helical microstructure is unfolded from a three-dimensional structure to a one-dimensional fiber.

[0059] (6) Perform a second winding to obtain a temporary shape of the spiral microrobot. Perform a second heat treatment, the spiral microstructure is heated to above 55°C and then cooled to fix the current shape into a temporary shape.

[0060] (7) After the spiral microstructure is cooled, the fibers at both ends are cut off and removed from the metal shaft. The spiral microstructure is then adhered to a micro-adjustment platform. The spiral microstructure is adjusted to align radially with the axis of the magnetometer coil by rotating the platform. The magnetometer releases a high-intensity magnetic field to complete the magnetization of the spiral microstructure. Finally, the excess fiber segments on the spiral microstructure are cut off to obtain a spiral microrobot.

[0061] Specific implementation method 4: refer to Figure 3-6 The present embodiment is described in detail. The present embodiment describes a method for micromanipulation and medical applications of a spiral microrobot based on a shape memory polymer, including active connection, active separation and performance adjustment.

[0062] (1) The active connection function is used to actively grasp the target object, such as Figure 3 As shown: First, the magnetic field drive system is used to control the automatic docking of the spiral microrobot with the conical target object. Then, through the pre-programmed diameter contraction deformation mode, the spiral microrobot is wound to grab the target object and complete the connection with the target object. Finally, under the control of the magnetic field drive system, the spiral microrobot carries the target object back to the desired recovery position.

[0063] (2) The active connection function is used for target location anchoring, such as Figure 4 As shown: The programmed spiral microrobot has a diameter growth mode, the temporary shape has a diameter of about 270μm, the permanent shape has a diameter of about 720μm, and the anchoring object is a glass tube with an inner diameter of 0.5mm. The spiral microrobot can swim quickly in the glass tube driven by a magnetic field and accurately reach the target position. Under thermal stimulation, the diameter of the spiral microrobot increases and completes the anchoring in the glass tube. The syringe is pushed evenly and quickly to inject a high-speed liquid flow into the glass tube. The spiral microstructure anchored in the glass tube can withstand a water flow of about 1.0 to 1.4m / s at most, and has a certain impact resistance.

[0064] (3) Active separation function is used for active release of embedded cargo, such as Figure 5As shown: The columnar carrier is inserted into the spiral microrobot with an expandable deformation mode, and the carrier inside is clamped by the elastic force generated by the deformation of the microstructure. Under the control of magnetic field drive, the spiral microrobot swims from the chamber on the left side of the U-shaped flow channel to the chamber on the right side of the U-shaped flow channel. Under thermal stimulation, the spiral microrobot unfolds and the clamping force acting on the carrier is cancelled. Under the action of the magnetic field, the spiral microrobot shakes to complete the separation from the carrier and swims upward to leave the target position.

[0065] (4) The performance adjustment function is used to adapt to the staged task requirements in minimally invasive injection, such as Figure 6 As shown: In medical applications, microrobots need to use medical equipment when entering the body environment. The smaller diameter of the spiral microrobot can reduce the required injection needle or catheter diameter to reduce damage to the human body. The spiral microrobot can be programmed to have a temporary shape close to a straight line and be placed in a small diameter injection needle. In the experiment, the spiral microrobot can be injected into a closed chamber by the injection needle and restore the spiral shape through thermal stimulation. The spiral microrobot after the shape change can produce controlled movement under the drive of a magnetic field.

[0066] In summary, the spiral microrobot based on shape memory polymer described in the present invention has a lower modulus and better biocompatibility compared with the prior art, and can be more safely applied in the fields of biomedicine and the like. The present invention also provides a method for preparing the spiral microrobot, which can complete the programming of its shape change while preparing the microrobot, and can prepare a spiral microrobot with a size of 1.5 to 0.5 mm, and can achieve quantitative control of parameters such as length, diameter, and taper. The present invention utilizes the functions of active connection, active separation, and performance adjustment derived from the shape change of the microrobot to realize the applications of active grasping, target position anchoring, active release of carriers, minimally invasive injection, etc. of the microrobot. The microrobot can be applied to the fields of micromanipulation, targeted drug delivery, minimally invasive surgery, etc.

[0067] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A spiral microrobot based on a shape memory polymer, comprising a spiral microrobot body (1) and at least one magnetic unit (2) located inside or on the surface of the spiral microrobot, characterized in that: The material of the spiral microrobot body (1) includes shape memory polymer.

2. The spiral microrobot based on shape memory polymer according to claim 1, characterized in that: The magnetic unit (2) comprises magnetic powder or magnetic components.

3. A method for preparing a spiral microrobot based on a shape memory polymer according to claim 1 or 2, characterized in that: include: Winding the shape memory fiber into a spiral shape, heat treating and cooling the spiral shape memory fiber, so that the internal stress generated by the shape memory fiber during winding is released; The wound shape memory fiber is unfolded into a straight line, and then the straight shape memory fiber is wound into a spiral shape again and heated to a transition temperature and then cooled, so that the stress caused by the difference between the current shape and the permanent shape of the shape memory fiber is retained, thereby obtaining a spiral microrobot.

4. The method for preparing a spiral microrobot based on a shape memory polymer according to claim 3, characterized in that: The method for preparing the shape memory fiber comprises: The molten thermoplastic shape memory polymer is extruded from a spinneret hole by a heating extrusion device and is rotationally wound around the outside of a collecting cylinder to form a shape memory fiber.

5. The method for preparing a spiral microrobot based on a shape memory polymer according to claim 4, characterized in that: In the process of preparing the shape memory fiber, the magnetic unit (2) is mixed into the molten shape memory polymer to obtain the magnetic shape memory fiber.

6. The method for preparing a spiral microrobot based on a shape memory polymer according to claim 4, characterized in that: The following processing steps are included before the shape memory fiber is wound for the first time: The shape memory fiber is straightened and fixed on a glass substrate, a photosensitive resin mixed with magnetic microparticles is dripped on the glass substrate, and a glass slide is covered on the shape memory fiber so that the photosensitive resin forms a liquid film on the shape memory fiber; and the shape memory fiber is irradiated with an ultraviolet laser passing through a mask so that a magnetic unit (2) is attached to the shape memory fiber.

7. The method for preparing a spiral microrobot based on a shape memory polymer according to claim 5 or 6, characterized in that: A radial magnetic field is applied to the spiral microrobot to complete the magnetization of the magnetic unit (2) in the spiral microrobot.

8. The method for preparing a spiral microrobot based on a shape memory polymer according to claim 4, characterized in that: The shape memory polymer is polylactic acid.

Images