Method for manufacturing a programmable and / or reprogrammable magnetic soft device, an untethered programmable and / or reprogrammable, particularly 3D, magnetic soft device, a method for encoding a programmable and / or reprogrammable magnetic soft device, and use of a programmable and / or reprogrammable magnetic soft device

Abstract

The present invention relates to a method for manufacturing a programmable and / or reprogrammable soft magnetic device, in which a portion of the device has a Young's modulus of less than 500 MPa.The present invention further relates to an untethered programmable and / or reprogrammable soft magnetic device, in particular a 3D soft magnetic device, having a portion with a Young's modulus of less than 500 MPa, a method for encoding the programmable and / or reprogrammable soft magnetic device, and uses of the programmable and / or reprogrammable soft magnetic device.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a programmable and / or reprogrammable magnetic soft device having a Young's modulus of less than 500 MPa in one or more parts of the device. The present invention further relates to an untethered programmable and / or reprogrammable, particularly 3D, magnetic soft device having a portion with a Young's modulus of less than 500 MP, a method for encoding a programmable and / or reprogrammable magnetic soft device, and the use of a programmable and / or reprogrammable magnetic soft device. [Background technology]

[0002] Shape-changing active materials that can be activated by external stimuli such as light, temperature, humidity, pH, acoustics, electric fields, and magnetic fields are of paramount importance for future applications in minimally invasive medicine, implantable and wearable devices, soft robotics, and micromachines. Magnetically responsive soft matter with programmable shape deformation is particularly promising for the rapid, reversible, and complex morphing of flexible structures for untethered devices.

[0003] Shape-programmable magnetic soft matter, consisting of magnetic micro / nanoparticles embedded in soft polymers, shows promise for the development of untethered (wireless) devices or robots with complex deformation and kinetic capabilities that can operate on a small scale.

[0004] A magnetic field generates torque in a magnetic soft material until the magnetization direction of all magnetic domains aligns with the direction of the applied magnetic field. Therefore, forming a spatial distribution of magnetization directions in a magnetic soft material enables programmable shape deformation under a magnetic field. Current three-dimensional (3D) discrete magnetic programming methods rely on adjusting the physical orientation of ferromagnetic particles during curing or the alignment of superparamagnetic particles within the polymer matrix, which hinders reprogramming after manufacturing. [Overview of the project] [Problems that the invention aims to solve]

[0005] An object of the present invention is to make available a device that overcomes the shortcomings of the prior art. Another object of the present invention is to make available a device that can be used in multiple applications and uses. [Means for solving the problem]

[0006] This objective is satisfied by a method for manufacturing a programmable and / or reprogrammable magnetic soft device in which the Young's modulus in part of the device is less than 500 MPa, and this method is - The step of forming a composite of a substrate and magnetic elements dispersed within the substrate, - A step of molding the composite to have a desired final shape, - A step of heating the composite while a magnetic field is applied to it, or while a magnetic field is not applied to it, - The process includes the step of cooling the complex while applying a magnetic field to it, The heating step includes heating the composite to a temperature close to or exceeding the Curie temperature of the magnetic element.

[0007] In this regard, it should be noted that temperatures close to the Curie temperature (Tc) can be used for partial magnetization; that is, if the sample is already demagnetized, simply heating it to a temperature below the Curie temperature can magnetize the magnetic element material to half the intensity of its full magnetization.

[0008] In this regard, the temperature of the magnetic element that is close to or above the Curie temperature is selected from a range of less than 25% below the Curie temperature to 25% above the Curie temperature, more specifically, from less than 10% below the Curie temperature to 10% above the Curie temperature, most preferably from less than 5% below the Curie temperature to 5% above the Curie temperature. In such a temperature range, partial magnetization of 25% to 100% of the maximum magnetization intensity of a material that has already been demagnetized at such a temperature can be achieved, thus enabling partial magnetization of each material.

[0009] For example, the Curie temperature of cobalt is 1126°C, while the Curie temperature of CrO2 is 120°C. Depending on whether the material should be partially magnetized, it can be heated within a range of 25% of the Curie temperature, i.e., from temperatures 250°C below the Curie temperature of cobalt to temperatures 250°C above it. Considering CrO2, this partially magnetized state is already achievable in the range of 110-115°C, which is 110°C for the magnetic element material, and more specifically, 5-10% below the Curie temperature of CrO2.

[0010] Preferably, the heating step is carried out to a temperature below the melting point of each composite of the substrate, preferably to a temperature 5°C below the melting point of each composite of the substrate.

[0011] Therefore, the present invention utilizes thermal-assisted magnetic programming of soft materials by heating magnetic elements present in a device to a temperature exceeding the Curie temperature of ferromagnetic particles, thereby enabling the reorientation of magnetic domains of the magnetic elements using an external magnetic field during cooling. For example, sequential thermal-assisted magnetization across the entire magnetic soft body can discretely encode 3D shape change commands and reprogram them on demand.

[0012] Therefore, the present invention makes available a versatile method for encoding reprogrammable shape change commands into soft materials by encoding the three-dimensional magnetization profiles of planar and three-dimensional structures.

[0013] This programming method is based on heating the magnetic soft material of the composite to a temperature above the Curie temperature of the ferromagnetic particles and reorienting their magnetic domains by applying an external magnetic field during cooling.

[0014] Using thermally assisted magnetic programming, it is possible to construct a large number of flexible structures, including "dragonflies," "stick figures," magnetic leaves attached to non-magnetic tree branches, and micro-scale "petals," and it has been demonstrated that discrete three-dimensional reprogrammable magnetization of three-dimensional structures can be performed with high spatiotemporal resolution (currently about 38 μm).

[0015] Below, we can demonstrate how the reprogrammable magnetization capabilities of the presented method can be used to describe the reconfigurable mechanical behavior of authentic metamaterial structures, the adjustable motion patterns of surface-walking soft robots, and the adaptive gripping behavior of soft grippers.

[0016] Thermally assisted magnetic programming enables even higher throughput magnetic coding via contact transfer of dispersed magnetization profiles from a master, allowing up to 10 samples per minute using a single master. The thermally assisted magnetic programming method described here establishes ample design space and one-shot mass production capabilities for the development of multi-scale, reprogrammable software systems and robots with unprecedented shape morphing capabilities.

[0017] By making programmable and reprogrammable devices available, magnetic devices are provided that can be programmed to perform specific tasks and that can be reprogrammed if it is found that fine-tuning of parts of the device is necessary to achieve improved or different functions of the device. This was previously impossible because devices of the prior art were not reprogrammable.

[0018] In this regard, it should be noted that a magnetic soft device is a device comprising one or more parts with a Young's modulus of less than 500 MPa, some of which may have a Young's modulus of less than 100 MPa and some of which may have a Young's modulus of less than 10 MPa in some cases.

[0019] It should also be noted that in this regard, the average Young's modulus of a magnetic soft device or part of a device can be less than 500 MPa, particularly less than 100 MPa.

[0020] This means that this device is more flexible than, for example, a device made of a pure metal or a hard plastic such as polyamide (PA), polytetrafluoroethylene (PTFE), or high-density polyethylene (HDPE).

[0021] It should be noted that in this regard, the magnetic element can be at least one of particles, rods, cubes, wires, disks, ellipsoids of revolution, whiskers, irregular particles, Janus particles, and combinations of the foregoing.

[0022] The heating step can be carried out before, after, and / or during the forming step of the composite. In this way, the method can be adapted as required to various methods of manufacturing materials and composites.

[0023] The forming step and the heating step may be carried out simultaneously. In this way, the production time of the device can be effectively shortened.

[0024] The magnetic field applied during the heating and / or cooling step may be less than the diamagnetic field of the magnetic element at room temperature. In this way, magnetization in undesirable regions is prevented.

[0025] In this regard, it should be noted that the applied magnetic field should be selected to be within the range of 1-99.9% of the coaxial magnetic field of the magnetic element at room temperature, and in particular, within the range of 5-50% of the coaxial magnetic field of the magnetic element at room temperature. In this regard, it should be further noted that the applied magnetic field can be at least 1 mT.

[0026] The steps for forming the composite may include, namely, a step of forming the composite in one mold of a predetermined shape and size; a step of forming one or more parts of the composite in one or more molds of the same shape and size; a step of forming the composite in one or more molds of different shapes and sizes; a step of photolithography the composite; a step of photolithography one or more parts of the composite; a step of stereolithography the composite; a step of stereolithography one or more parts of the composite; a step of 3D printing the composite; a step of 3D printing one or more parts of the composite; a step of combining parts of the composite; a step of cutting out sections of material from the composite; a step of cutting out sections of material from parts of the composite; and at least one combination of the foregoing.

[0027] In this regard, it should be noted that various parts of a device can be manufactured separately from each other, and then these different parts can be joined together. For example, a device can be molded into eight separate parts, and then these eight parts can be joined together. In such a case, all eight parts can be magnetized separately from each other. Furthermore, some parts may be made of non-magnetic materials without introduced magnetic elements, harder or softer materials (in terms of Young's modulus), some parts may be made of materials with different types of magnetic elements incorporated, some parts may include conductive and / or non-conductive materials, piezoelectric materials, magnetocaloric materials, magnetostrictive materials, photovoltaic materials, optoelectronic materials, photogravity materials, thermoelectric materials, and biomaterials with or without cultured cells, and some parts may include combinations of the aforementioned.

[0028] These parts can be incorporated into the device during the molding or printing stage, or they can be manufactured separately and then joined together after each manufacturing process.

[0029] In this regard, it is possible to form the composite such that different parts of the composite have magnetizations of different magnitudes in addition to different magnetization orientations, by including magnetic elements of higher density in those parts.

[0030] The melting temperature of the substrate may be higher than the maximum temperature applied to the magnetic composite during the heating step. In this way, melting of the device during programming or reprogramming of the device is avoided. For example, the melting temperature of the substrate is at least 5°C, preferably at least 10°C, and most preferably at least 20°C higher than the maximum temperature applied to the magnetic composite during the heating step.

[0031] The heating and cooling steps of the composite may be performed sequentially multiple times over different regions of the composite. In this way, within a single device, the same heating device and magnetic field generating device can be used to scan the entirety of various regions of the device, thereby imparting a specific magnetization profile to each region. Preferably, each region is scanned only once during the sequential scanning of multiple regions.

[0032] In this regard, when a magnetic master is used, the heating and cooling steps of the composite can be performed only once during the process of manufacturing a programmable and / or reprogrammable magnetic soft device, and these steps are performed in a so-called one-shot manner. The magnetic master can be configured to generate any magnetic field in adjacent sections and placed near the sample to be magnetized. Then, all sections of the sample are heated, making magnetization possible. The magnetic master should have a Curie temperature higher than the temperature reached in the heating step in this process.

[0033] In this way, programmable and / or reprogrammable magnetic soft devices having sizes selected within the range of 1 μm to 1 m, particularly 20 μm to 30 cm, can be manufactured. Such devices can be used as small cargo delivery devices, such as drug delivery devices, or for transporting parcels using, for example, drones.

[0034] The magnetization step can be performed for each cooling step for each region of the composite, such that each region has its own magnetization direction. In this way, within a single device, the same heating device and magnetic field generating device can scan across various regions of the device and impart a specific magnetization profile to each region.

[0035] The heating step of the composite may be carried out using a tunable light source, such as a parallel laser. The tunable light source provides a predetermined heating function that can be configured to reliably and repeatedly work with the magnetic elements present in the composite material forming the device. The heating step of the composite can also be carried out using ultrasound, radio frequency electrical / electromagnetic radiation, and alternating magnetic fields.

[0036] The heating step of the complex can be carried out using one of the following: a convection oven, a hot plate, or a heat gun. Such equipment can be reliably used to heat the device locally or completely during programming and reprogramming of the device.

[0037] The heating and cooling steps of the composite can be performed once for the entire composite over different regions, and the magnetization step, in particular, may be performed once for each region of the composite during cooling by using a magnetic master configured to produce a desired magnetization profile such that each region has its own magnetization direction.

[0038] In this regard, it should be noted that, apart from the use of lasers, localized and sequential heating steps can also be performed using contact-based devices such as soldering iron tips or other heating devices.

[0039] The magnetic field application step may be carried out using a magnetic field having a magnitude selected within the range of 1 mT to 10 T. Such magnetic field strengths allow for efficient programming and reprogramming of each region.

[0040] In this regard, it should be noted that the maximum applicable magnetic field depends on the antimagnetic field of the selected magnetic material.

[0041] In a further embodiment, the present invention relates to an untethered programmable and / or reprogrammable 3D magnetic soft device having one or more portions with a Young's modulus of less than 500 MPa, wherein the programmable and / or reprogrammable 3D magnetic soft device comprises a body formed of a composite material, the composite material comprising a substrate and magnetic elements dispersed within the substrate, the body having an arbitrary magnetization profile, the body having different magnetization profiles, and the information encoded in the programmable and / or reprogrammable 3D magnetic soft device includes shape change commands for changing the shape of at least some of the regions of the body relative to each other when an external field is applied.

[0042] The advantage that can be achieved using such a device is that it provides a programmable and reprogrammable magnetic device that can be programmed to perform a specific task, and that can be reprogrammed if it is found that fine-tuning of parts of the device is necessary to achieve improved or different functions of the device. This was previously impossible because the device was not reprogrammable.

[0043] The base materials include elastomers, thermoplastic elastomers, rubber, duroplastics, thermoplastic resins, such as polydimethylsiloxane, aliphatic aromatic copolyester or modified polyester, or modified copolyester, polyurethane elastomers, silicone rubber, natural rubber, latex, styrene-ethylenebutylene styrene, butyl rubber, fluorosilicone rubber, polyester, nylon, thermoplastic polyurethane; biodegradable synthetic materials, such as polyglycolide, polylactide, poly(caprolactone), poly(dioxanone), poly(ethylene glycol) diacrylate, poly(N-iso The members may be selected from the group consisting of: propyl acrylamide; biomaterials, such as gelatin, chitosan, alginates, agarose, hyaluronic acid derivatives, fibrin glue, elastin, cellulose, methylcellulose, fibronectin, collagen, silk; hydrogels; ionic gels; liquid crystal polymers, elastomers or gels; shape memory polymers; photoresist polymers, such as SU-8; biological proteins, such as the annular teeth proteins in squid suckers; fabric materials; nonmagnetic metals; silicon; silica; glass; wood; carbon fiber; and derivatives and combinations of the foregoing. Using such materials, flexible devices can be provided compared to rigid devices.

[0044] The magnetic elements may be selected from a group of members consisting of chromium dioxide (CrO2), samarium cobalt (SmCo), neodymium-iron-boron (NdFeB), cobalt (Co), ferrite, permalloy (NiFe), carbon steel, tungsten steel, alnico, iron, stainless steel, nickel (Ni), iron-platinum (FePt), iron oxide (Fe2O3), barium ferrite, magnetite; or combinations, alloys, or composites of the aforementioned. Such materials can be programmed and reprogrammed by heating them above the Curie temperature.

[0045] In a further aspect, the present invention relates to a method for encoding a programmable and / or reprogrammable magnetic soft device as described herein, the method being - A step of heating the composite material to a temperature close to or exceeding the Curie temperature of the magnetic elements dispersed therein, - A step of cooling the composite material, - The process includes the step of reorienting the magnetic domains of a magnetic element by applying an external magnetic field during cooling, or during both heating and cooling.

[0046] Magnetic elements, such as particles, only realign after reaching the Curie temperature. Once the Curie temperature is reached and the magnetic elements have realigned, an external magnetic field can be used to program the magnetic elements, i.e., the particles, to create a desired new arrangement of magnetic domains, i.e., programming.

[0047] The magnetic field may be applied during the heating step, but in either case, it must be applied during the cooling step to allow the magnetic domains of the magnetic element to be reoriented.

[0048] The heating and cooling steps of the composite can be performed sequentially by sequentially focusing a tunable light source, i.e., a parallel laser, onto the region of the composite and optionally cooling that region before moving to further regions of the composite. In this way, a unique magnetization profile can be programmed for each region of the device.

[0049] The heating and cooling steps of the composite can be carried out entirely by using a convection oven for the composite and cooling the composite using a magnetic master placed adjacent to the composite. Such assemblies can be effectively used for batch processing of devices of the same type.

[0050] The reprogramming step can also be achieved, for example, by using a magnetic master comprising a jig and a magnetic field generating device, or simply a magnetic field generating device that generates a magnetic field of a predetermined orientation and magnitude, and heating everything together in a single shot. The magnetic master can be configured to generate any magnetic field in adjacent sections and placed near the sample to be magnetized. Once all sections of the sample are heated, magnetization becomes possible. The magnetic master should have a Curie temperature that exceeds the heat added in this process.

[0051] The magnetic field application step may be carried out for each cooling cycle using a magnetic field of a magnitude selected in the range of 1 mT to 10 T, particularly in the range of 15 mT to 3 T, in order to orient each region of the composite using its own magnetic magnetization profile.

[0052] This magnetization profile may be different from or the same as the magnetization profiles of other regions of the complex. In this way, different magnetization profiles can be programmed into different parts of the device so that each part of the device can perform one or more specific types of motion.

[0053] In a further aspect, the present invention relates to the use of manufactured programmable and / or reprogrammable magnetic soft devices, and / or reconfigurable grippers, programmable and / or reconfigurable acoustic guides, programmable and / or reprogrammable electronic circuits, programmable and / or reprogrammable antennas, programmable and / or reprogrammable mechanical metamaterials, programmable and / or reprogrammable wearable devices, adaptive medical robots, and untethered programmable and / or reprogrammable 3D magnetic soft devices as a combination of the foregoing.

[0054] The present invention will be described in detail with reference to the following drawings. The following is shown. [Brief explanation of the drawing]

[0055] [Figure 1a-1i] Steps performed for untethered programmable and / or reprogrammable 3D magnetic soft devices, and for thermally assisted 3D magnetic programming and reprogramming of magnetoactive soft matter in sample devices. [Figure 2a-2p] Various reprogrammable magnetic soft devices, and the response of these devices to the application of an external magnetic field after initial programming and after reprogramming. [Figure 3a-3h] Various types of structures of magnetic soft devices before and after reprogramming of magnetization. [Figure 4a-4j] An example of thermally assisted magnetic programming of magnetic soft matter at the microscale. [Figures 5a-5c] Mechanical properties of magnetic soft elastomers. [Figures 6a-6d] The magnetic properties of the device. [Figures 7a-7c] Photothermal response of magnetic soft elastomers forming part of a composite. [Figures 8a-8d] Discrete 3D magnetization of magnetically active soft matter forming part of a complex. [Figures 9a-9g] Two stacked hemispherical structures form a device that transforms into a perfect sphere when magnetically activated. [Figures 10a-10j] Reprogrammable magnetization of a device. [Figures 11a-11b] Reprogrammable magnetization of flexible magnetic leaves as a device. [Figure 12] Performance comparison between previous magnetic soft material programming methods and current research. [Figures 13a-13f] Computational modeling and verification of device shape deformation. [Figure 14a] Heat-assisted magnetization and magnetic actuation device. [Figures 15a-15b] Photomask design and limit dimensions used in the fabrication of (a) micropatterned polyurethane NdFeB magnets for laser heating and (b) contact transfer of magnetic profiles. [Modes for carrying out the invention]

[0056] Figure 1 shows the steps performed for heat-assisted 3D magnetic programming and reprogramming of magnetoactive soft matter in an untethered programmable and / or reprogrammable 3D magnetic soft device 10. The 3D magnetic soft device 10 has one or more parts and / or regions with a Young's modulus of less than 500 MPa. The programmable and / or reprogrammable 3D magnetic soft device 10 comprises a body 14 formed from a composite 12. In Figure 1a, the body has a rod shape, but in Figures 1d to 1i, the body 14 generally has a dragonfly shape with several leg-shaped parts 16, wing-shaped parts 18, and tail-shaped parts 19 extending from the body 14. Furthermore, in Figures 1h and 1i, the body has leg-shaped parts 16 and wing-shaped parts 18 extending from there.

[0057] The legs 16, wings 18, and tail 19 can be formed from the same composite 12 as the main body 14, or from further composites 12 with different material composition and / or material properties such as hardness, rigidity, and magnetization profile. Parts or regions of the main body 14 may include materials in which magnetic elements are not embedded. Each composite 12 having a non-zero magnetization profile includes a substrate and magnetic elements dispersed within the substrate.

[0058] The body 14, legs 16, wings 18, tail 19, and any further shapes or sections 20 (see, for example, Figure 8) or fingers 34 (see Figures 3e to 3h) of the 3D magnetic soft device 10 have arbitrary profiles, and different regions of the 3D magnetic soft device 10, i.e., the body 14, legs 16, wings 18, tail 19, sections 20, and / or fingers 34, have different magnetization profiles. The information encoded in the programmable and / or reprogrammable 3D magnetic soft device 10 includes shape change commands to change the shapes of at least some of the regions of the 3D magnetic soft device 10, i.e., the body 14, legs 16, wings 18, tail 19, and sections 20, relative to each other when an external magnetic field is applied.

[0059] In connection therewith, the substrates used to form the various parts of the programmable and / or reprogrammable 3D magnetic soft device 10, namely the body 14, legs 16, wings 18, tail 19, section 20, fingers 34, etc., are elastomers, thermoplastic elastomers, rubber, duroplastics, thermoplastic resins, for example, polydimethylsiloxane, aliphatic aromatic copolyester or modified polyester, or modified copolyester, polyurethane elastomer, silicone rubber, natural rubber, latex, styrene-ethylene-butylene-styrene, butyl rubber, fluorosilicone rubber, polyester, nylon, thermoplastic polyurethane, biodegradable synthetic materials, for example, polyglycolide polylactide The members may be selected from the group consisting of poly(caprolactone), poly(dioxanone), poly(ethylene glycol) diacrylate, poly(N-isopropylacrylamide); biomaterials, e.g., gelatin, chitosan, alginates, agarose, hyaluronic acid derivatives, fibrin glue, elastin, cellulose, methylcellulose, fibronectin, collagen, silk; hydrogels; ionic gels; liquid crystal polymers, elastomers or gels; shape memory polymers; photoresist polymers, e.g., SU-8; biological proteins, e.g., the proteins of the annular teeth in the suckers of squid; fabric materials; nonmagnetic metals; silicon; silica; glass; wood; carbon fiber; and derivatives and combinations of the foregoing.

[0060] In this regard, it should be noted that the magnetic elements used in various parts of the programmable and / or reprogrammable 3D magnetic soft device 10, namely the body 14, legs 16, wings 18, tail 19, section 20, and fingers 34, etc., may be selected from a group of members consisting of chromium dioxide, samarium cobalt, neodymium-iron-boron, cobalt, ferrite, permalloy, carbon steel, tungsten steel, alnico, iron, stainless steel, nickel, iron-platinum, iron oxide, barium ferrite, magnetite; or combinations, alloys, or composites of the aforementioned.

[0061] In this regard, it should be further noted that magnetic elements can exist in the form of particles, rods, wires, disks, ellipsoids, whiskers, disordered particles, Janus particles, and combinations thereof.

[0062] In the example shown in Figure 1a, the rod-shaped body 14 of the 3D magnetic soft device 10 is formed from a magnetic soft elastomer composed of magnetic CrO2 particles embedded in polydimethylsiloxane (PDMS). The following steps are performed to form the 3D magnetic soft device 10: - The composite 12 of the substrate and magnetic elements dispersed within the substrate is formed, for example, by simply mixing the magnetic elements, such as magnetic CrO2 particles, with a relatively soft material such as PDMS. - The composite 12 is then molded to have the desired final shape. In the example of Figure 1a, the desired shape is a rod shape which can be formed, for example, by pouring the still-unsolidified composite material into a mold and allowing it to solidify. Other forms of manufacturing the complete 3D magnetic soft device 10 may include 3D printing of parts, injection molding of parts, cutting of parts from bulk material, and so on. - After molding at least a portion of the 3D magnetic soft device 10, namely the body 14, legs 16, wings 18, tail 19, section 20 and / or fingers 34, the 3D magnetic soft device 10 is heated, either partially or completely. A magnetic field may or may not be applied to the composite 12 during the heating step of the composite 12. - Subsequently, the composite 12 is cooled while a magnetic field is applied to it. The heating step 12 heats the composite 12 to a temperature close to or above the Curie temperature of the magnetic element, i.e., a temperature in the range of 10% below the Curie temperature, preferably a temperature up to 10°C, particularly 5°C below the Curie temperature, when CrO2 is the magnetic element, and a temperature up to 5°C below the melting point of the substrate, in order to prevent the substrate from melting.

[0063] In this regard, it should be noted that the heating step may be performed before, after, and / or during the molding step of the composite.

[0064] In this regard, it should be further noted that the molding step and the heating step may be performed simultaneously.

[0065] In this regard, it should be further noted that the magnetic field applied during the heating and / or cooling steps is lower than the coaxial magnetic field of the magnetic element at room temperature, i.e., generally speaking, 25-99% lower than the coaxial magnetic field of the magnetic element. For example, in the case of CrO2, the magnetic field applied during the heating and / or cooling steps may be 50-95% lower than the coaxial magnetic field of the magnetic element.

[0066] The molding step of the composite 12 may include at least one of the following steps: molding the composite 12 in one mold of a predetermined shape and size; molding one or more parts of the composite 12 in one or more molds of the same shape and size; molding the composite in one or more molds of different shapes and sizes; 3D printing the composite 12; 3D printing one or more parts of the composite 12; combining the parts of the composite 12; cutting out sections of material from the composite 12; cutting out sections of material from the parts of the composite 12; and any combination thereof.

[0067] The melting temperature of the substrate may be higher than the maximum temperature applied to the magnetic composite 12 during the heating step in order to prevent a phase change in the substrate.

[0068] The heating step and cooling step of the composite 12 may be performed sequentially multiple times on different regions 22 of the composite 12. Alternatively, the heating step and cooling step of the composite 12 may be performed once on the entire 3D magnetic soft device 10.

[0069] The magnetization step may be performed for each cooling step for each region 22 of the composite 12, such that each region 22 has its own magnetization direction. Alternatively, the magnetization step of the composite 12 may be performed once for the complete 3D magnetic soft device 10, if the moving shape of the complete 3D magnetic soft device 10 is predefined using a jig 26 (see Figures 14e and 14f), etc.

[0070] As shown in Figure 1a, the heating step of the composite 12 can be performed using a tunable laser 24. This is done to locally heat different regions 22 (see excerpt in Figure 1a) and then locally apply a magnetic field to program the region of interest 22 with its own magnetization profile. Different regions can be magnetized with different magnetization profiles, or the same or similar magnetization profiles (including, for example, the direction and magnitude of magnetization), as shown in various excerpts.

[0071] In this regard, it should be noted that the average diameter and average width of each region 22 can be selected within the range of 1 μm to 100 mm, particularly within the range of 20 μm to 50 mm, depending on the heating device and its optical components used to heat a particular region 22.

[0072] The magnetic field application step may be carried out using a magnetic field having a magnitude selected within the range of 1 mT to 10 T. In the example of Figure 1a, the magnetic field is applied using a permanent magnet 30, and other magnetic field sources may be used to magnetize the region 22 of the 3D magnetic soft device 10.

[0073] When region 22 is locally heated by the laser 24 to a temperature close to, preferably above, the Curie temperature of the particles, the magnetic elements, such as particles, lose their permanent magnetization, and the magnetization direction of the magnetic elements is reoriented by applying an external magnetic field during the cooling step.

[0074] Figure 1b shows the heating and cooling curves of the magnetic soft elastomer, i.e., composite 12, when composite 12 is heated to a temperature above the Curie temperature of CrO2 particles (118°C) in 1.7 seconds and cooled to half this temperature in 4 seconds.

[0075] Figure 1c shows that the magnetic soft elastomer, i.e., composite 12, is magnetized with 90% efficiency by heat-assisted magnetization and demagnetized simply by heating to a temperature above the Curie temperature without an external magnetic field, with error bars representing the standard deviation from the mean.

[0076] Figures 1d-1g show examples of the 3D magnetic soft device 10, cut into the shapes of the tail section 19, wing section 18 (Figure 1d), and the main body of the six legs 16 (Figure 1e), along with the corresponding magnetization direction (indicated by arrows) and out-of-plane magnetic flux profile measurement results. The inset shows the magnetic flux density intensity, and the scale bar is 2 mm.

[0077] Figures 1f and 1g show that when the 3D magnetic soft device 10 in Figures 1d and 1e is magnetically activated, the individual parts 16, 18, and 19 (legs 16, wings 18, and tail 19) change shape according to the programmed magnetization direction, and the inset shows the initial shape of the structure when there is no magnetic field.

[0078] Figures 1h and 1i show a 3D magnetic soft device 10 having stacked wing sections 18 and leg sections 16 to generate a 3D hierarchical "dragonfly" structure when magnetically actuated. The scale bar is 2 mm. The 3D magnetic soft device 10 is actuated by applying a magnetic field of 60 mT in the direction indicated by the arrow.

[0079] Figure 2a shows the dispersed 3D magnetization, out-of-plane magnetic flux density profile measurements, finite element simulations, and experimental shape changes of the "stick figure" structure during magnetic operation.

[0080] Figures 2b and 2c show how the dispersed magnetization direction of the magnetic soft device 10 in the form of a stick figure structure in Figure 2a can be reprogrammed to reconfigure the shape change so that the stick figure structure 10 can change its shape in different ways after reprogramming. Arrows indicate local magnetization directions. Magnetic flux density and total deformation are also shown, and the scale bar is 1 mm.

[0081] Figures 2d-2j illustrate how the mechanical behavior of the authentic metamaterial can be tuned by reprogramming the dispersed magnetization profiles of individual units, i.e., device 10. The overall length and width of structure 10 are shown by a and b, respectively.

[0082] Figures 2e to 2g show that the flexible oustic structure expands and compresses in both length and width depending on the magnetic operating direction, and that device 10 has a negative Poisson's ratio.

[0083] Figures 2h–2j show how the magnetization profiles of the three central units can be reprogrammed to expand the width while minimizing the change in length, regardless of the magnetic operating direction. The arrows indicate the local magnetization direction. Box 32 shows the reprogrammed region 22 of the magnetic soft device 10, with the scale bar being 5 mm. The structure is operated by applying a uniform magnetic field of 60 mT in the direction indicated by the arrow below B, which indicates the magnetic field.

[0084] Figures 2k to 2p show how the magnetization profile of a four-legged flexible robot 10 can be reprogrammed to achieve adjustable motion patterns. Figures 2k and 2n show how the magnetization direction of the legs 16 is programmed to generate different deformation configurations, with arrows passing through the legs 16 indicating local magnetization directions. Figures 2l and 2o show how the legs 16 deform according to their magnetization direction during magnetic action (20mT) indicated by the arrow below B, with the scale bar being 1mm.

[0085] Figures 2m and 2p show the flexible robot, i.e., device 10, where different magnetization profiles generate different motion patterns through rotational magnetic action. The scale bar is 5 mm.

[0086] Figures 3a-3d show the reprogrammable magnetization of flexible magnetic leaves as magnetic soft devices 10 dispersed on a 3D printed non-magnetic material.

[0087] Figures 3b and 3c show how the magnetization direction of individual leaves is programmed by localized laser heating using laser 24. Figure 3d shows that the magnetization direction of half of the leaves, indicated by the dashed line, is reprogrammed in the opposite direction, with the scale bar being 5 mm. Figures 3e–3h show a 4-finger 34 adaptive soft gripper as a magnetic soft device 10, which can be realized by reprogramming the magnetization profile of the fingers.

[0088] Figures 3f-3h show that the shape deformation of finger 34 is reprogrammed to grip objects of different shapes, including a sphere (3 mm in diameter) (see Figure 3f), a rod (4 mm in diameter and 4 mm in height) (see Figure 3g), and a car representing a complex shape (10.6 mm in length, 3 mm in width, and 1.75 mm in height) (see Figure 3h). The arrows indicate the local magnetization direction, and the scale bar is 2 mm. The structure is operated by applying a uniform magnetic field of 60 mT in the direction indicated by the arrow below B.

[0089] Figure 4a shows scanning of a region 22 of a magnetic soft elastomer (MSE) as a magnetic soft device 10 with a focused laser spot from a laser 24, which results in precisely controlled local heating of the desired region 22. Laser scanning of the device 10 in a desired pattern is used to program the magnetization profile of the material.

[0090] Figures 4b and 4c show an exemplary soft structure, namely a magnetic soft device 10 having six petals (fingers 34) (150 μm wide, 500 μm long, and 30 μm thick) placed on a micropost. The red arrows indicate the magnetization direction of the petals. The petals were deformed in the opposite direction by magnetic action (60 mT). Figure 4d shows how a collimated laser 34 can heat the target magnetic soft elastomer, i.e., the desired shape on region 22, in a single shot via a mask containing a micropattern of the desired shape.

[0091] Figures 4e and 4f show the results of magnetic flux density measurements of an exemplary magnetically programmed sample 10 using such micropatterned laser heating. The smallest magnetic pattern has a width of 80 μm, and the scale bar is 250 μm.

[0092] Figure 4g shows the contact transfer of the desired magnetic profile in a single shot via overall heating. The magnetic soft elastomer, i.e., composite 12, is positioned in direct contact with an NdFeB magnet, which is heated to a temperature above the Curie temperature of CrO2, arranged in a different configuration with a higher Curie temperature. The magnetization direction of the NdFeB magnet is transferred to the magnetic soft elastomer during cooling.

[0093] Figures 4h and 4i show the magnetic flux density measurement results of NDFeB masters and magnetic soft elastomer slaves of various shapes and configurations, with scale bars of 500 μm and 1 mm, respectively. Figure 4j shows the contact transfer of a complex magnetization profile in the geometric pattern of "Minerva". The inset shows a magnified view of the magnetic flux density profile of the magnetic soft elastomer slave. The smallest magnetic pattern has a width of 38 μm. The bars indicate magnetic flux density intensity, with scale bars of 1 mm and 250 μm, respectively.

[0094] Figure 5a shows how the film thickness of the fabricated magnetic soft elastomer forming part of the composite 12 of the device 10 is controlled by varying the mold depth between 25 μm and 200 μm.

[0095] Figures 5b and 5c show the elastic modulus (E) and tensile strain of the magnetic soft elastomer forming part of the composite 12 of device 10 before and after laser heating above 150°C. Error bars represent the standard deviation from the mean.

[0096] Figure 6a shows the hysteresis loop of CrO2 at room temperature. The remanent magnetization of CrO2 particles (M r The magnetic field strength is 109 kA / m, and the coercivity is 67 mT. Figure 6b shows the effect of the applied magnetic field strength during cooling on the magnetization efficiency, and Figure 6c shows the heat-assisted magnetization efficiency and heat-assisted demagnetization in directions parallel and perpendicular to the magnetization direction. The magnetization value of the sample magnetized under a uniform 1.8 T magnetic field was considered to be 100%. Error bars represent the standard deviation from the mean. Figure 6d shows the measured out-of-plane magnetic flux density profiles of rectangular magnetic soft elastomer samples magnetized in various directions.

[0097] Figure 7a shows the effect of laser output on the average temperature of the magnetic soft elastomer forming part of the composite 12 of device 10. Figure 7b shows the heating and cooling duration of the magnetic soft elastomer forming part of the composite 12 of device 10. Figure 7c shows the effect of laser output on the spot diameter heated to a temperature above the Curie temperature of CrO2.

[0098] Figures 8a–8d show the dispersed 3D magnetization, out-of-plane magnetic flux density profile measurements, finite element simulations, and experimental shape changes during magnetic operation of a 4-segment ring (Figure 8a), an 8-segment ring (Figure 8b), a hemisphere (Figure 8c), and a cubic structure (Figure 8d). The scale bar is 1 mm, and operation was performed by applying a magnetic field of 60 mT in the direction indicated by the black arrow.

[0099] Figures 9a and 9b show the magnetization directions of sections 20 of the two hemispherical structures that form device 10. Figure 9c shows the manual assembly of the two hemispherical structures, which is achieved by bonding corresponding hexagonal sections around the periphery to form device 10, as shown in the inset. Figures 9d-9f show the out-of-plane compression and formation of the closed spherical structure under magnetic action (60 mT) in the direction indicated by the arrow below B. Figure 9g shows rotational magnetic action that rotates the spherical structure while maintaining a closed structure. The scale bar is 1 mm.

[0100] Figures 10a–10d illustrate how reprogramming the magnetization profile of a single device 10 within an authentic metamaterial induces non-uniform deformation within the structure. Arrows indicate local magnetization directions. The solid box 32 shows the reprogrammed region 22. The scale bar is 5 mm.

[0101] Figures 10a to 10g show the out-of-plane magnetic flux density profile measurement results for the authentic metamaterials shown in Figures 2e(e), 10b(f), and 2h(g). The bars indicate magnetic flux density intensity.

[0102] Figures 10h–10j show that adjustable motion patterns can be achieved by reprogramming the magnetization profile of a four-legged flexible robot, and Figures 10h–10i show how the legs deform according to their magnetization direction when magnetically actuated (20mT), indicated by the arrows. The scale bar is 1mm. Figure 10j shows the motion of the four-legged flexible robot 10 in a linear trajectory under rotating magnetic field operation. The scale bar is 5mm.

[0103] Figures 11a and 11b show the reprogrammable magnetization of flexible magnetic leaves as device 10. The magnetization directions of two leaves (indicated by arrows) have been reprogrammed in the opposite direction to that of the remaining leaves. Figures 10a and 10b show how magnetic action (60 mT in the direction indicated by the arrow below B) resulted in the two leaves undergoing opposite deformation compared to the others. The scale bar is 5 mm.

[0104] Figure 12 shows a performance comparison between previous magnetic soft material programming methods and the current research. The results of the previous research are described in the following literature. Hu,W.,Lum,GZ,Mastrangeli,M.&Sitti,M.Small-scale soft-bodied robots with multimodal locomotion.Nature 554,81-85,(2018),Xu,T.,Zhang,J.,Salehizadeh,M.,Onaizah,O.&Diller,E.,Millimeter-scale flexible robots with programmable three-dimensional magnetization and motions.Science Robotics 4,eaav4494,(2019), Cui,J.et al.Nanomagnetic encoding of shape-morphing micromachines.Nature 575,164-168,(2019), and Kim,Y.,Yuk,H.,Zhao,R.,Chester,SA,& Zhao.X.,Printing ferromagnetic domains for untethered fast-transforming soft materialsNature 558, 274-279, (2018).

[0105] This specification compares the magnetization capabilities and associated manufacturing capabilities of the heat-assisted magnetic programming methods presented herein with those of existing magnetic programming techniques for soft materials in the literature. Magnetization dimension indicates the degrees of freedom available for magnetization, where 3D refers to the ability to magnetize in any direction. Continuous magnetization prevents abrupt changes between adjacent sections, while discrete magnetization allows for independent magnetization of adjacent sections. In terms of reprogrammability, limitations refer to reprogramming in specified directions during manufacturing and techniques that are technically difficult on a small scale. Activated structure refers to the dimensions of the soft system demonstrated in various methods. In magnetic programming and manufacturing, coupling refers to magnetic programming during the manufacturing process, while separation refers to magnetic programming after manufacturing. In mass production, limitations refer to the limited high-throughput production capacity compared to lithography and roll-to-roll methods.

[0106] Figure 13a shows the sample beam structure with a net magnetic moment m. Figure 13b shows the beam structure with a net magnetic moment m. x d y , and d z The predetermined length and the net magnetic moment m i It has to be divided into smaller subsections indicated by "i". Figure 13c shows a free-form diagram of the subsections.

number

[0107] Figure 13d shows magnetic torque.

number

number

[0108] Figures 14a and 14b show how the magnetization mechanism 36 consists of an electric stage 38, a 360° rotatable NdFeB permanent magnet 30, a 3D magnetic Hall effect sensor 40, and an adjustable-output fiber-coupled NIR laser 34 having a collimator 42. (c) In the case of magnetic actuation, a disc-shaped magnet 44 (60 mm in diameter and 10 mm thick) was moved or rotated vertically or horizontally below the actuation platform 46. Figure 14d shows that a Halbach array 48 consisting of 16 permanent magnets 50 (10 mm × 10 mm × 10 mm) arranged as shown was used to generate a uniform magnetic field for magnetic actuation.

[0109] Figures 14e and 14f show a jig 26 that can be used to program a device 10, for example, a rod-shaped device 10. The jig comprises an upper half 28 and a lower half 28' that are clamped around the device 10 to be programmed and / or reprogrammed. Once the device 10 is heated to a temperature close to or above the Curie temperature of the magnetic elements of the device 10, a magnetic field B can be applied, as shown in Figure 14e, to magnetize different regions 22 of the device 10 in different orientations, the different orientations depending on the shape of the internal structure of the jig 26.

[0110] Figures 15a and 15b show the designs and limiting dimensions of various photomasks 52 used in the fabrication of polyurethane NdFeB magnets for micropatterned laser heating (see Figure 15a) and contact transfer of magnetic profiles (see Figure 15b). The scale bar is 500 μm.

[0111] The device 10 described above discloses a programmable magnetic soft matter device 10 in which magnetic micro / nanoparticles are embedded in a soft polymer. Such a device 10 is promising for the development of untethered (wireless) devices or robots with complex deformation and motion capabilities that can operate on a small scale. The magnetic field generates torque on the magnetic soft material until the magnetization direction of all magnetic domains aligns with the direction of the applied magnetic field. Thus, forming a spatial distribution of magnetization directions in the magnetic soft material enables programmable shape deformation under a magnetic field. Current three-dimensional (3D) discrete magnetic programming methods rely on adjusting the physical orientation of ferromagnetic particles during curing or the alignment of superparamagnetic particles in the polymer matrix, thereby hindering reprogramming after manufacturing. This work uses thermal-assisted magnetic programming of soft materials by heating the ferromagnetic particles to a temperature above the Curie temperature and reorienting the magnetic domains of the ferromagnetic particles using an external magnetic field during cooling (Figure 1a). Sequential thermal-assisted magnetization throughout the magnetic soft body allows for the discrete encoding of 3D shape change commands, which can then be reprogrammed on demand.

[0112] The presented magnetic soft elastomer consists of chromium dioxide (CrO2) nanoparticles with an average diameter of 10 μm embedded in a polydimethylsiloxane (PDMS) elastomer. CrO2 is a ferromagnetic material (Figure 6a) with a Curie temperature of 118°C, enabling heat-assisted magnetic (re)programming within the operating temperature range of most elastomers.

[0113] CrO2 / PDMS magnetic soft elastomer composite sheets are fabricated by curing a mixture of CrO2 particles and PDMS in molds of different thicknesses, yielding magnetorheological films with a thickness in the range of 25 to 200 μm (Figure 5a).

[0114] In this regard, it should be noted that device 10 may have a device thickness of at least some portion of the device selected within the range of 25 to 200 μm. It is also conceivable that device 10 may have a device thickness of at least some portion of the device selected within the range of 10 μm to 10 mm.

[0115] A collimated near-infrared (NIR) laser with adjustable power is used to locally and precisely heat magnetic soft elastomers with controlled temperature, heating / cooling time, and heating spot size (Figures 1b and 7). The shortest heating / cooling cycle for a 1.3 mm diameter heating spot is achieved in 5.7 seconds (Figure 1b). The laser-heated magnetic soft elastomer spot is magnetized by an external magnetic field exceeding 15 mT, resulting in a magnetization efficiency 90% higher compared to the maximum magnetization achievable under a 1.8 T magnetic field (Figure 5b).

[0116] Such high magnetization efficiency indicates that magnetic domains are almost completely reoriented in the desired direction, while undesirable magnetization in other directions is minimized. The same material can then be locally or completely demagnetized by reheating it to a temperature above the Curie temperature of CrO2 particles in the absence of a magnetic field (Figures 1c and 5c). The applied temperature is well within the curing and operating temperature range of the PDMS, enabling non-invasive magnetic programming and reprogramming, thus limiting the impact of instantaneous heating on the mechanical properties of the magnetic soft elastomer (Figures 6b, c).

[0117] To illustrate the thermally assisted magnetic programming of a soft material embedded with CrO2 particles, a planar magnetic soft elastomer film is shown, cut into the shapes of a body with a tail and wings, and a body with six legs (Figures 1d-h). The body and limbs are discretely magnetized in various 3D directions (Figures 1d, e), and the magnetization direction is verified by measuring the out-of-plane component of the magnetic flux density of the body and limbs, as shown in the insets of Figures 1d, e.

[0118] When a 60mT magnetic field perpendicular to the plane is applied, the magnetic torque on components with different magnetization directions attempts to align the components with the direction of the external field, causing 3D deformation of the structure (Figures 1f, g). Furthermore, as shown in Figure 1h, a multi-component 3D structure can be formed by stacking the individual components. During magnetic operation, the main body with legs and wings is stacked, forming a multi-component 3D "dragonfly" structure (Figure 1i).

[0119] Figure 8 shows a series of structures with various 3D magnetization profiles that can be transformed into complex 3D structures under a magnetic field. To predict complex 3D shape transformations using the designed magnetization profiles, a computational model was developed that takes into account the magnetization direction, external magnetic field, and mechanical deformation (Figure 8).

[0120] A ring structure with a 4-segment alternating magnetization profile generates a vertically rising profile when magnetically actuated (Figure 8a), while a ring of the same size with an 8-segment alternating magnetization profile yields a undulating edge (Figure 8b). A 3D hemispherical structure is formed by radially symmetrical magnetization of a planar structure composed of hexagonal and pentagonal units connected via hinges (Figure 8c). Furthermore, stacking two of these structures that complement the magnetization profiles allows for the formation of a closed 3D sphere, which can also be rotated on a plane by applying a rotating magnetic field (Figure 9). In addition to manual assembly, complex 3D structures can be manufactured from the magnetic soft elastomer of the present invention using molding or 3D printing techniques. The formation of closed structures can also be achieved by complementary 3D magnetization, and therefore deformation, of connected segments, as shown in Figure 1c. Planar segments connected via hinges are magnetized both in-plane and out-of-plane to form a closed cube under a magnetic field of 60 mT (Figure 8d).

[0121] In the field, specifically in the laboratory, magnetic reprogramming of soft systems is essential for optimization, multi-functional operation, and adaptation to dynamic environments. The heat-assisted magnetization method allows for easy magnetic reprogramming of soft structures as needed.

[0122] Figure 2a presents a "stick figure" structure with 3D magnetization profiles encoded in the body, shoulders, arms, and head, which undergoes complex 3D shape transformations during magnetic operation. By reprogramming the magnetization profiles of the stick figure structure, the bending of the head and arms can be reconfigured as shown in Figures 2b and 2c. Locally reprogramming the behavior of the internal material also enables the design and optimization of highly active metamaterials.

[0123] Figure 2d presents an auxetic mechanical metamaterial structure composed of eight units. When the units are magnetically programmed, as shown in Figure 2e, the entire structure is simultaneously expanded and compressed in both length and width, thus exhibiting a negative Poisson's ratio depending on the magnetic operating direction (Figures 2f, g). Using a heat-assisted magnetic reprogramming technique, the magnetization profiles of individual units, and therefore the mechanical behavior of individual units, can be reprogrammed (Figures 10a-g). Reprogramming multiple units in the central section of the structure expands the width while minimizing changes in length, regardless of the magnetic operating direction (Figures 2h-j).

[0124] To further emphasize the importance of easy reprogramming, a four-legged flexible robot with a specific magnetization direction assigned to each leg is shown (Figures 2k-p and 10h-j). Asymmetric magnetization of the legs on two sides results in greater deformation of the right leg during magnetic operation, generating a circular trajectory (Figures 2k-m). Reprogramming the soft robot's magnetization profile to be bilaterally symmetric and anteriorly symmetric results in bilaterally symmetrical leg deformation during magnetic operation, generating a linear trajectory (Figures 2n-p). These results demonstrate that remote, non-invasive reprogramming can be used for experimental optimization of material behavior, such as mechanical and acoustic metamaterials, and for tuning the motion performance and characteristics of soft robots.

[0125] Heat-assisted magnetization can also be extended to program complex 3D structures. Figure 3a presents a 3D-printed non-magnetic tree body with magnetic leaves assembled at the tips of branches. The magnetization direction of the leaves is programmed by laser-based heating while applying a magnetic field in the desired direction, so that only the programmed leaves deform when magnetically activated (Figure 3b).

[0126] When all magnetic leaves are sequentially programmed in the same direction, all leaves operate synchronously in the same direction (Figure 3c). Furthermore, the magnetization direction of individual leaves can be reprogrammed as needed to generate various configurations (Figures 3d and 11), making it possible to control shape deformation commands distributed across a complex 3D structure. Magnetic reprogramming of 3D structures enables the development of reconfigurable soft machines for adaptive interaction with objects of any shape.

[0127] As an example, an adaptive soft gripper (Figure 3e) consisting of four fingers made of magnetic soft elastomer was assembled. Out-of-plane magnetization of the fingers creates maximum deflection at the fingertips, allowing a spherical object (3 mm in diameter) to be compressed downwards around its circumference (Figure 3f a). On the other hand, a vertically positioned cylindrical object (4 mm in diameter, 4 mm in height) requires a larger contact area with the gripping fingers, which is achieved by the concave deflection of the fingers via the magnetization profile shown in Figure 3g. The operation of grasping a more complex example, such as an automobile-like object (10.6 mm in length, 3 mm in width, 1.75 mm in height) with an internal cavity and a gap at the bottom due to the wheels, is achieved by outward deformation of the fingers within the internal cavity and inward deformation of the fingers on the sides (Figure 3h). Compared with existing methods, the laser-based heat-assisted magnetization method of the present invention enables on-demand local reprogramming of 3D magnetic structures with arbitrary magnetization profiles.

[0128] Microscale robots and machines have remarkable potential for manipulating the microscopic world, ranging from biotechnology to minimally invasive medicine. Magnetically programmed shape deformation enables a new type of microsystem with advanced kinetic and manipulative capabilities. The heat-assisted magnetization technique described herein can be scaled down to magnetically program microstructures with a spatial resolution of 38 μm (Figure 4).

[0129] One method for downscaling is to narrow the size of the NIR laser beam to less than 200 μm by using a microscope objective lens (Figure 4a). By using focused laser heating, a soft structure with six petals (150 μm wide, 500 μm long, and 30 μm thick) is magnetized in complementary directions, causing the petals to deform synchronously in opposite directions (Figures 4b, c). Microscale magnetic programming can also be achieved by placing a photomask on a magnetic soft elastomer (Figures 4d-f). The photomask allows the laser to pass through micropatterned areas of different sizes with a minimum dimension of 65 μm (Figure 15a), thus reducing the area of ​​the heated area relative to the patterned area. By using photomask-compatible micropatterned laser heating, the letters "MPI" are magnetically programmed in the magnetic soft elastomer in different magnetization directions at different sizes, as indicated by the measured magnetic flux density profiles (Figures 4e-f).

[0130] In addition to laser-based sequential heating and magnetization, magnetic programming can also be achieved by generating a desired magnetic pattern (master) in close proximity to a magnetic soft elastomer (slave), and then heating the entire system to enable one-shot magnetization of the entire sample (Figure 4g). When fabricating a magnetic master, polyurethane neodymium-iron-boron (NdFeB) composite magnets, which have a higher Curie temperature than CrO2 and vary in size, shape, and polarity in different configurations, are manually positioned (Figures 4h, i). Magnetic one-shot pattern transfer is achieved by directly contacting the magnetic soft elastomer slave with the magnetic master and heating the entire system to 150°C (Figures 4h, i). Magnetic masters with complex "Minerva" symbols (Figures 4j and 15b) were also fabricated. By contact magnetic transfer, the magnetic profile of the magnetic master is copied to a magnetic soft elastomer slave with a minimum dimension of 38 μm (Figure 4j). High-resolution 2D magnetic programming has already been demonstrated in rigid panels connected via flexible hinges, but the heat-assisted magnetization method described here enables 3D magnetic programming with equivalent resolution (Figure 12).

[0131] The heat-assisted magnetic programming method described here is essentially separate from the manufacturing methods of magnetic soft elastomers, enabling a non-invasive, non-surgical, and non-destructive means of reprogramming the shape deformation encoded in the material with high spatial resolution. Easy and non-invasive magnetic reprogramming allows for rapid database optimization of the performance and behavior of soft systems such as mechanical and optical soft metamaterials and cut-paper-compatible structures. The resolution and speed of heat-assisted magnetic programming can be further scaled down using established magneto-optical recording technologies used in the data storage industry. Furthermore, the heat-assisted magnetic contact transfer shown in Figures 4g-j can be adapted for high-throughput magnetic encoding using a magnetic master and a 3-axis stage, enabling programming of 10 samples per minute. High-throughput magnetic contact transfer can be further combined with multiple masters of desired magnetic profiles and a mechanical puncher to cut magnetic soft elastomer samples into desired shapes, paving the way for future continuous roll-to-roll mass production of magnetic soft machines (Figure 12).

[0132] Material performance can be improved by using other magnetic particles with a Curie temperature designed low enough to maintain the polymer's operating temperature, and other polymers or gels with softer material properties. While this description primarily focuses on a laser 24 for heating a soft magnetic elastomer, remote selective heating can also be achieved by remote power transmission to a thin receiver coil mounted on the elastomer. The application of an AC magnetic field, along with a spatially patterned DC magnetic field for programming the magnetic soft elastomer, can also be used for overall heating. Remote magnetic programming and reprogramming can enable adaptive operation of soft untethered systems in closed and restricted dynamic environments. Magnetically responsive multiscale soft systems with reprogrammable complex shape transformation capabilities have diverse applications in medical robotics, wearable healthcare devices, and biomimetic microrobots.

[0133] The following steps can be taken to prepare the complex.

[0134] Preparation of composite 12 formed by magnetic elastomer: CrO2 powder (Sigma-Aldrich, St. Louis, MO) was heated in an oven at 300°C for 3 hours. 22 g of calcined CrO2 particles were dispersed in a solution of 250 mL of sodium bisulfite (NaHSO3) solution (from https: / / www.sigmaaldrich.com / catalog / product / sigald / 243973?lang=de®ion=DE) mixed with deionized (DI) water (50 g / L, Sigma-Aldrich, St. Louis, MO), and the mixture was held at 65°C for 16 hours with occasional stirring. The particles were then washed five times with 1 L of DI water and filtered using a test sieve with a mesh size of 20 μm. The remaining CrO2 particles were left in a fume hood for 2 days to remove residual water. The resulting film was scraped and ground using a mortar and pestle to obtain the final dried and stabilized CrO2 particles.

[0135] A CrO2 / PDMS magnetic soft elastomer composite was prepared by adding dried and stabilized CrO2 particles to a siloxane base (Dow Corning, Midland, MI) in a mass ratio of 1:2 (CrO2:siloxane base) and shear mixing for 5 minutes using a Pasteur pipette. Next, a crosslinking agent was added to the prepolymer mixture in a mass ratio of crosslinking agent to mixture of 1:10 and shear mixing was performed for another 5 minutes. The mixture was then poured into a mold consisting of two tapes of desired thickness (25 μm to 200 μm) attached to a flat glass substrate and cured at 90°C for 4 hours. The desired shape was cut from the magnetic elastomer film using a UV laser system (LPKF ProtoLaser U3, Garbsen, Germany). The thickness of the magnetic elastomer film was measured using an optical profiler (VK-X250, Keyence, Osaka, Japan). 0.005s -1The elastic modulus (E) and strain of magnetic elastomers were experimentally characterized by uniaxial tensile tests of unheated and heated dogbone-shaped samples at strain rates (Instron 5942, Instron, Norwood, MA).

[0136] After the magnetic soft device 10 is formed, heat-assisted magnetic (re)programming can be initiated.

[0137] Local heating of a CrO2 elastomer film, i.e., region 22 of device 10, was achieved using an adjustable-power fiber-coupled NIR laser equipped with a collimator (808 nm, 133-457 mW, Edmund Optics, Barrington, NJ). The temperature and heating spot size of the magnetic elastomer film were measured using an infrared thermal camera (ETS320, Wilsonville, OR) from a distance of 7 cm. The heating and cooling times of the magnetic soft elastomer were measured by heating the sample for 100 seconds. The sample was placed on an automated stage (Axidraw v3, Evil Mad Scientist, Sunnyvale, CA), and a 360° rotatable NdFeB magnet (20 mm diameter and 20 mm thickness, Supermagnete, Gottmadingen, Germany) was placed below the magnetic soft elastomer during heating and cooling to align the magnetization direction of the CrO2 particles (Figure 14a, b).

[0138] The magnitude and direction of the applied magnetic field were continuously monitored using a 3D magnetic Hall sensor (TLE493D-W2B6, Infineon Technologies, Munich, Germany) and adjusted according to the desired magnetization direction.

[0139] The magnetization of magnetic soft elastomers was measured using a vibrating sample magnetometer (VSM; MicroSense, Lowell, MA). A 1 mm diameter circular sample was placed on a sample holder, and the hysteresis loop of CrO2 was acquired in an external field ranging from 1.5 T to -1.5 T (Figure 5a). By dividing the remanent magnetization by the sample volume, the magnetization of the magnetic soft elastomer as device 10 was calculated to be 9.8 kA / m. The magnetization efficiency was determined in the VSM as the ratio of the magnetization of the thermomagnetized sample to that of the sample magnetized under a 1.8 T magnetic field. The magnetization profile of the magnetically programmed sample was characterized by measuring the magnetic flux density at the sample surface via a magneto-optical sensor (MagViewS, Matesy, Jena, Germany).

[0140] Device 10 was designed, and then computational modeling of shape deformation was performed to compare the design with the developed model. For this purpose, finite element analysis was used for predictive modeling of shape changes under magnetic operation (Figure 13).

[0141] Link the COMSOL Structural Mechanics module (COMSOL, Burlington, MA) to a custom MATLAB script (MathWorks, Natick, MA) via "LiveLink". Divide the sample geometry into smaller subsections with predetermined magnetization profiles, use the MATLAB script to calculate magnetic forces and torques, and resolve mechanical deformations in COMSOL.

[0142] In each iteration, the magnetic force and torque were recalculated according to the updated magnetization direction vector of each subsection until a quasi-static equilibrium state was reached in 3D. For all simulations, experimentally measured values ​​of 200 kPa and 9.8 kA / m were used for E and magnetization. The density of the magnetic soft elastomer was 3.89 g / cm³. 3 This was the calculation. We assume Poisson's ratio is 0.49.

[0143] A cylindrical NdFeB magnet 44 (60 mm in diameter, 10 mm thick, Supermagnete, Gottmadingen, Germany) was used to magnetically actuate the formed device 10. For magnetic actuation, the magnet 44 was guided vertically or horizontally toward the device 10 placed on the platform 46 (Figure 14c). For magnetic actuation under a uniform field, a Halbach array 48 consisting of 16 permanent magnets 50 (10 mm × 10 mm × 10 mm) was used (Figure 14d). For dynamic actuation, the Halbach array 48 was rotated to rotate the sample.

[0144] Once device 10 is programmed, magnetic (re)programming can be performed at the micron scale. Three different methods were employed for micron-scale magnetic (re)programming: focused laser heating, photomask-compatible micropatterned laser heating, and contact magnetic transfer by overall heating. Focused laser heating was achieved by placing a microscope objective lens (20×, NA0.5, Carl Zeiss, Oberkochen, Germany) in the laser beam path and reducing the beam size to less than 200 microns.

[0145] In photomask-compatible micropatterned laser heating, a photomask containing a microscale pattern (Figure 15a) was placed on the sample with a 20 μm gap. The sample was locally heated in the shape of the pattern available on the photomask when exposed to a laser beam that could pass only through the micropatterned areas.

[0146] For contact transfer of magnetic profiles, polyurethane NdFeB magnetic composites of different shapes were used. First, SU-8 positive templates of the desired shape were fabricated on silicon wafers by photolithography and wet chemical development. In the fabrication of the positive templates, SU-8 100 (Microchem Inc., Newton, MA) was placed on a silicon wafer, spin-coated at 2500 rpm for 45 seconds, pre-baked on a hot plate at 95°C for 30 minutes, and cooled to room temperature. Next, the fabricated templates were subjected to UV light (365 nm, 13 mW / cm²). 2 A photoresist-coated wafer was loaded into a mask aligner (MJB4 Mask Aligner, SUSS MicroTec, Garching, Germany) having a photomask containing the desired pattern to be exposed to 15 seconds. The photoresist-coated wafer was then baked at 95°C for 10 minutes, cooled to room temperature, immersed in a chemical developer (mr-600, micro resist technology, Berlin, Germany) with slight agitation for about 10 minutes, and then rinsed with IPA for about 2 minutes. Finally, the microfabricated template was baked on a hot plate at 100°C for 30 minutes. Silicone rubber (Mold Max 20, Smooth-On, Macungie, PA) was then poured onto the positive template, cured at room temperature for 4 hours, and peeled off to obtain a negative template. Subsequently, a mixture of polyurethane prepolymer (Smooth-Cast 310 / 1, Smooth-On, Macungie, PA) and NdFeB powder (MQFP-15-7, Magnequench, Toronto, Canada) was molded into a negative template in a 1:1 mass ratio, cured at room temperature for 4 hours, and then peeled off.

[0147] The prepared polyurethane NdFeB magnets were pre-magnetized. The magnetic field generated by the polyurethane NdFeB magnets was less than the coercivity of the magnetic soft elastomer. Modular polyurethane magnets were manually arranged in the desired configurations, but configurations with complex shapes were used as monolithic units. Finally, for contact magnetic transfer, the magnetic soft elastomer was placed on top of the polyurethane NdFeB magnets and placed in an oven at 150°C for 5 minutes, then allowed to cool to room temperature while in contact.

[0148] In this way, a method for encoding a programmable and / or reprogrammable magnetic soft device 10 becomes available, and this method is - A step of heating the composite to a temperature above the Curie temperature of the magnetic elements dispersed therein, - A step of cooling the composite, - The process includes the step of reorienting the magnetic domains of a magnetic element by applying an external magnetic field during cooling.

[0149] The heating step and the cooling step of the composite can be carried out sequentially by sequentially focusing the tunable laser 24 onto the region of the composite material and optionally cooling the region before moving to a further region of the composite material. Alternatively, the heating step and the cooling step may be carried out only once using a master, for example, as described above.

[0150] The magnetic field application step may be performed for each cooling cycle using a magnetic field of a magnitude selected in the range of 1 mT to 10 T, particularly in order to orient each region of the composite 12 using its own magnetic magnetization profile.

[0151] In the design of the magnetic soft structure 10, both the shape and the magnetization profile are taken into account to control the shape change. An intuitive design can be used for simple shape changes under an external magnetic field, but a prediction model is required for more demanding and complex deformations. Therefore, a prediction model has been developed to obtain the solution for the quasi-static state of the magnetic soft structure using COMSOL and custom MATLAB scripts.

[0152] This prediction model is based on the following assumptions. The magnetic soft structure 10 is subjected to magnetic force (f), magnetic torque (τ), and gravity (mg), thereby generating stress on the soft body 10 and causing the soft body 10 to deform to minimize the total magnetic potential energy and elastic potential energy. Furthermore, the directions of the magnetic force and torque change along with the magnetization direction during deformation, resulting in a non-uniform response distributed with respect to the external magnetic field across the structure. To capture this non-uniform response, each sample shape is divided into smaller subsections labeled with "i" having predefined dimensions of d x d y d z and magnetic moment of m i (Figs. 13a, b). The magnetic force and torque of each subsection are calculated in a custom MATLAB script according to the applied magnetic field (B) and magnetic moment of each subsection. Then, the calculated magnetic force (f i = ▽(m i B)) is applied to the subsection as a directional force. On the other hand, the magnetic torque (τ i = m i × B) is distributed as a force on the facets of the subsection. To achieve this, the magnetic torque (τ i ) is separated into the orthogonal components of the magnetic torque with respect to the selected Cartesian reference frame

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[0153] The model is validated using a beam structure with dimensions of 10 mm in length, 1 mm in width, and 0.17 mm in thickness. The beam is magnetized along its long axis and fixed at 1.25 mm from one end. A magnetic field in the range of 0 to 56 mT is then applied perpendicular to the magnetization direction of the beam. Both experimental and simulation results are obtained under the same conditions (Figure 13e). The deflection angle θ is calculated and compared for both the experimental and simulation results (Figure 13f). The developed calculation method captures the deformation characteristics and agrees well with the experimental results. [Explanation of Symbols]

[0154] List of reference numbers 10 devices 12 complex 14 Main unit 16 Legs 18 Wings 19 Tail 20 sections 22 areas 24 lasers 26 jigs 28, 28' Upper half of 26, Lower half of 26 30 permanent magnets 32 boxes 34 Fingers 36 Magnetization mechanism 38 Electric Stage 40 Hall effect sensors 42 Collimator 44 Magnets 46 Operating Platforms 48 Halbach sequence 50 magnets 52 Photomasks

Claims

1. A method for manufacturing a magnetic soft device (10), wherein the Young's modulus in one or more parts of the device (10) is less than 500 MPa, and the method is - A step of forming a composite (12) of a substrate and magnetic elements dispersed within the substrate, - A step of molding the composite (12) to have a desired final shape, - A step of heating the composite (12) while a magnetic field is applied to it or while a magnetic field is not applied to it, wherein the heating step is a step of heating the composite (12) to a temperature close to or above the Curie temperature of the magnetic element, A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) such that it undergoes magnetically programmed shape deformation, comprising the steps of: - Cooling the composite (12) while applying a magnetic field to the composite (12).

2. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to claim 1, wherein the heating step is performed before and / or after and / or during the molding step of the composite (12).

3. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to claim 1 or 2, wherein the molding step and the heating step are performed simultaneously.

4. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to any one of claims 1 to 3, wherein the magnetic field applied during the heating and / or cooling step is lower than the coaxial magnetic field of the magnetic element at room temperature.

5. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to any one of claims 1 to 4, wherein the molding step of the composite (12) includes at least one of the following steps: molding the composite (12) in one mold of a predetermined shape and size; molding one or more parts of the composite (12) in one or more molds of the same shape and size; molding the composite (12) in one or more molds of different shapes and sizes; photolithography of the composite (12); photolithography of one or more parts of the composite (12); stereolithography of the composite (12); stereolithography of one or more parts of the composite (12); 3D printing of the composite (12); 3D printing of one or more parts of the composite (12); combining parts of the composite (12); cutting out sections of material from the composite (12); cutting out sections of material from parts of the composite (12); and a combination of the above.

6. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to any one of claims 1 to 5, wherein the melting temperature of the substrate is higher than the maximum temperature applied to the magnetic composite (12) during the heating step.

7. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to any one of claims 1 to 6, wherein the heating step and the cooling step of the composite (12) are performed sequentially multiple times on different regions of the composite (12).

8. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to claim 7, wherein the magnetization step is performed for each cooling step with respect to each region of the composite (12) such that each region of the composite (12) has its own magnetization direction.

9. The heating step of the composite (12) is carried out using a light source, or A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to any one of claims 1 to 8, wherein the heating step of the composite (12) is carried out using one of a convection oven, a hot plate, and a heat gun.

10. The heating step and the cooling step of the composite (12) are performed once in total on different regions of the composite (12). The magnetization step is performed once during the cooling of each region of the composite (12) by using a magnetic master configured to generate a desired magnetization profile such that each region has its own magnetization direction, and / or A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to any one of claims 1 to 9, wherein the magnetic field applied during the heating and / or cooling step is performed using a magnetic field having a magnitude selected in the range of 1 mT to 10 T.

11. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to claim 1, wherein the device (10) includes a body (14) formed from the composite (12), the body (14) having an arbitrary magnetization profile, different regions of the body (14) having different magnetization profiles, and the information encoded in the device (10) includes shape change commands for changing the shape of at least some of the regions of the body (14) relative to each other when an external field is applied.

12. A method for producing a programmable and / or reprogrammable magnetic soft device (10) according to claim 11, wherein the substrate is selected from the group of members consisting of elastomers, thermoplastic elastomers, rubber, duroplastics, thermoplastic resins, biodegradable synthetic materials; biomaterials; hydrogels; ionic gels; liquid crystal polymers, elastomers or gels; shape memory polymers; photoresist polymers, biological proteins, fabric materials; nonmagnetic metals; silicon; silica; glass; wood; carbon fiber; and derivatives and combinations thereof.

13. A method for manufacturing a programmable and / or reprogrammable magnetic soft device (10) according to claim 11 or 12, wherein the magnetic element is selected from the group of members consisting of chromium dioxide, samarium cobalt, neodymium iron boron, cobalt, ferrite, permalloy, carbon steel, tungsten steel, alnico, iron, stainless steel, nickel, platinum iron, iron oxide, barium ferrite, magnetite, combinations of the aforementioned, alloys, or composites.

14. A method for encoding shape change commands to change the shape of a programmable and / or reprogrammable magnetic soft device (10) manufactured according to any one of claims 1 to 13 when an external magnetic field is applied to the device (10), - The step of heating the composite (12) to a temperature close to or exceeding the Curie temperature of the magnetic elements dispersed therein, - A step of cooling the composite (12), A method for encoding a programmable and / or reprogrammable magnetic soft device (10), comprising the step of reorienting the magnetic domains of the magnetic element by applying an external magnetic field during cooling, or during both heating and cooling.

15. A method for encoding a programmable and / or reprogrammable magnetic soft device (10) according to claim 14, wherein the step of reorienting the magnetic domains is performed for each cooling cycle using a magnetic field having a magnitude selected in the range of 1 mT to 10 T in order to orient each region of the composite (12) using its own magnetic magnetization profile.

16. Manufacturing a programmable and / or reprogrammable magnetic soft device (10) in accordance with any one of claims 1 to 13, for use as a reconfigurable gripper, a programmable and / or reprogrammable acoustic guide, a programmable and / or reprogrammable electronic circuit, a programmable and / or reprogrammable antenna, a programmable and / or reprogrammable mechanical metamaterial, a programmable and / or reprogrammable wearable device, an adaptive medical robot, and at least one combination thereof.

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