Magnetic Printing Research Articles

Study of Magnetic Hydrogel 4D Printability and Smart Self‐Folding Structure

4D printing technology offers the potential to create smart structures that respond to external stimuli. This study focuses on a novel magnetic hydrogel with promising applications in 4D printing, particularly for medical devices such as guidewire robots, drug delivery systems, and vascular stents. Magnetic‐responsive hydrogels suitable for 4D printing are scarce, and their complex rheological properties pose challenges for printing. The study investigates these properties and optimizes them through adjustments in ink composition and the application of an external magnetic field, improving printability. Using the direct writing (DLP) method, which allows magnetic programming of individual strands, the study achieves greater flexibility compared to the traditional SLA method. Optimized printing parameters and material ratios produced high‐quality single strands, grids, and sheet‐like structures, demonstrating responsiveness to varying magnetic fields. Results confirm that DLP can be effectively applied to hydrogel 4D printing, achieving flexible structures with tunable mechanical properties. Additionally, magnetic‐responsive, self‐folding hydrogel structures were created, with a response speed of 180 ms under a magnetic field. This research establishes a foundation for magnetic hydrogel 4D printing and offers insights for the development of future smart medical devices.

4D printing of the ferrite permanent magnet BaFe12O19 and its intelligent shape memory effect

4D printing of the barium ferrite permanent magnets provides new opportunities for intelligent structure and process innovation of permanent magnets. In this paper, the preparation, filament manufacture, and intelligent printing methods with shape memory/recovery effect are studied for the barium ferrite permanent magnet. Firstly, the PLA/TPU/BaFe12O19 composite materials are developed by adding different contents of ferrite permanent magnet BaFe12O19 powders into the PLA/TPU (polylactic acid/thermoplastic polyurethane) matrix. The weight percentage of the BaFe12O19 is 10–40 wt% with an interval of 10 wt%. Secondly, the composites are pelletized and further extruded to manufacture composite filaments with different BaFe12O19 contents. Scanning electron microscope (SEM) is used for the microstructural analysis. The BaFe12O19 particles are uniformly distributed in the PLA/TPU matrix, and the slight particle agglomeration phenomenon occurs in the composite filaments with 30 and 40 wt% BaFe12O19. The thermal properties of PLA/TPU/BaFe12O19 composite filaments are analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). After adding the barium ferrite particles, the glass transition temperature of the composite filaments changes within a small range from 53.5 °C to 55 °C. Thirdly, the filaments are successfully manufactured to magnet parts by the fused deposition modeling (FDM) 3D printing for the tests of mechanical, magnetic, and shape recovery properties. With the increase of the barium ferrite content, the magnetic properties show a rising trend, proving the feasibility of using 3D printing technology to make magnets. The shape memory effects of the printed parts are excellent and the shape recovery ratios show a rising trend, from 85.6 % to 88.9 % under heat contact stimulus and from 88.9 % to 97.8 % under electromagnetic induction non-contact stimulus. Relatively, the parts hold fast response speed due to direct contact with the heat source under the heat stimulus, and the parts hold higher shape recovery ratios due to more heats produced under the electromagnetic induction stimulus. The addition of magnetic particles is helpful to improve the heat transfer ability and provide the possibility of non-contact heat transfer. The magnetic parts with complex structure and intelligent shape memory/recovery effect can be achieved for special application requirements. As a result, the research of this paper expands preparation methods of new magnetic composite materials, explores the manufacture process for intelligent magnets and lays a solid foundation for the development of new permanent magnet devices.

Sensitivity‐Adjustable Flexible Conductors Based on Liquid Metals via Magnetic Printing

AbstractThe ability to shape and pattern conductors has been indispensable for manufacturing functional devices. Herein, a series of patterned liquid metals–based flexible electronics are fabricated via magnetic printing. The combination of highly conductive liquid metals and flexible photosensitive resins endows the as‐prepared devices with excellent electrical and mechanical properties, such as high electric conductivity (8 × 104 S m−1), low detection hysteresis, good durability, and environmental stability. What's more, strain‐insensitive flexible electronics can be achieved by designing the structure of liquid metal‐based conductors, and the resistance is only increased 0.13 Ω at 100% strain. Therefore, the as‐prepared liquid metals‐based flexible electronics have promising applications in stretchable conductors.

Development of a patient specific cartilage graft using magnetic resonance imaging and 3D printing

ObjectivesThe goal of this project was to develop and validate a patient-specific, anatomically correct graft for cartilage restoration using magnetic resonance imaging (MRI) data and 3-dimensional (3D) printing technology. The specific aim was to test the accuracy of a novel method for 3D printing and implanting individualized, anatomically shaped bio-scaffolds to treat cartilage defects in a human cadaveric model. We hypothesized that an individualized, anatomic 3D-printed scaffold designed from MRI data would provide a more optimal fill for a large cartilage defect compared to a generic flat scaffold. MethodsFour focal cartilage defects (FCDs) were created in paired human cadaver knees, age <40 years, in the weight-bearing surfaces of the medial femoral condyle (MFC), lateral femoral condyle (LFC), patella, and trochlea of each knee. MRIs were obtained, anatomic grafts were designed and 3D printed for the left knee as an experimental group, and generic flat grafts for the right knee as a control group. Grafts were implanted into corresponding defects and fixed using tissue adhesive. Repeat post-implant MRIs were obtained. Graft step-off was measured as the distance in mm between the surface of the graft and the native cartilage surface in a direction perpendicular to the subchondral bone. Graft contour was measured as the gap between the undersurface of the graft and the subchondral bone in a direction perpendicular to the joint surface. ResultsGraft step-off was statistically significantly better for the anatomic grafts compared to the generic grafts in the MFC (0.0 ​± ​0.2 ​mm vs. 0.7 ​± ​0.5 ​mm, p ​< ​0.001), LFC (0.1 ​± ​0.3 ​mm vs. 1.0 ​± ​0.2 ​mm, p ​< ​0.001), patella (−0.2 ​± ​0.3 ​mm vs. −1.2 ​± ​0.4 ​mm, p ​< ​0.001), and trochlea (−0.4 ​± ​0.3 vs. 0.4 ​± ​0.7, p ​= ​0.003). Graft contour was statistically significantly better for the anatomic grafts in the LFC (0.0 ​± ​0.0 ​mm vs. 0.2 ​± ​0.4 ​mm, p ​= ​0.022) and trochlea (0.0 ​± ​0.0 ​mm vs. 1.4 ​± ​0.7 ​mm, p ​< ​0.001). The anatomic grafts had an observed maximum step-off of −0.9 ​mm and a maximum contour mismatch of 0.8 ​mm. ConclusionThis study validates a process designed to fabricate anatomically accurate cartilage grafts using MRI and 3D printing technology. Anatomic grafts demonstrated superior fit compared to generic flat grafts. Level of evidenceLevel IV.

Soft Robots with Plant-Inspired Gravitropism Based on Fluidic Liquid Metal.

Plants can autonomously adjust their growth direction based on the gravitropic response to maximize energy acquisition, despite lacking nerves and muscles. Endowing soft robots with gravitropism may facilitate the development of self-regulating systems free of electronics, but remains elusive. Herein, acceleration-regulated soft actuators are described that can respond to the gravitational field by leveraging the unique fluidity of liquid metal in its self-limiting oxide skin. The soft actuator is obtained by magnetic printing of the fluidic liquid metal heater circuit on a thermoresponsive liquid crystal elastomer. The Joule heat of the liquid metal circuit with gravity-regulated resistance can be programmed by changing the actuator's pose to induce the flow of liquid metal. The actuator can autonomously adjust its bending degree by the dynamic interaction between its thermomechanical response and gravity. A gravity-interactive soft gripper is also created with controllable grasping and releasing by rotating the actuator. Moreover, it is demonstrated that self-regulated oscillation motion can be achieved by interfacing the actuator with a monostable tape spring, allowing the electronics-free control of a bionic walker. This work paves the avenue for the development of liquid metal-based reconfigurable electronics and electronics-free soft robots that can perceive gravity or acceleration.

Magnetic printing characteristics of burst signals by using double magnet master media

In this study, the magnetic printing characteristics of burst signals with double magnet master (DMM) media, which consists of hard and soft magnet patterns corresponding to the burst signals, onto energy-assisted magnetic recording (EAMR) media was investigated by the micromagnetic simulation. For comparison, the magnetic printing characteristics with the conventional master media, which includes only soft magnet patterns, was also calculated. The magnetic film patterns of each master media transfer automatic-gain-control (AGC) and burst parts to the recording medium. The burst signals was amplitude AB-burst patterns, which consists of the repeated pattern region and blank area without burst patterns. Two possible master media structures of DMM media were considered, which are herein called positive- and negative- DMM media. By utilizing the positive-DMM, which spatially divides soft magnets, the AGC and the burst signals can be clearly printed, comparing with the conventional master media. While the negative-DMM is insufficient to print burst signals because the blank area without burst patterns has some non-recorded clusters. Thus, the positive-DMM are feasible for the magnetic printing of burst signals. The clear printing onto EAMR media is expected to be obtained by the optimum non-magnetic separator thickness and the optimum printing field. Therefore, the magnetic printing with positive DMM master is promising onto EAMR media.

3-D Printing of Multipolar Bonded SmCo Permanent Magnets

3-D Printing of Multipolar Bonded SmCo Permanent Magnets

Alignment of Fe3O4/CNT electrodes via magnetic blade printing for wireless stress-direction-recognizing strain sensor

Alignment of Fe3O4/CNT electrodes via magnetic blade printing for wireless stress-direction-recognizing strain sensor

4D Printing Technology Based on Magnetic Intelligent Materials: Materials, Processing Processes, and Application.

4D printing technology refers to the manufacturing of products using 3D printing techniques that are capable of changing shape or structure in response to external stimuli. Compared with traditional 3D printing, the additional dimension is manifested in the time dimension. Facilitated by the advancement of magnetic smart materials and 3D printing technology, magnetically controlled 4D printing technology has a wide range of application prospects in many fields such as medical treatment, electronic flexible devices, and industrial manufacturing. Magnetically controlled 4D printing technology is a new scientific research field in the 21st century, which includes but is not limited to the following disciplines: mechanics, materials, dynamics, physics, thermodynamics, and electromagnetism. It involves many fields and needs to be summarized systematically. First, this article introduces various magnetic intelligent materials, which are suitable for magnetically controlled 4D printing, and discusses their programmability. Second, regarding the printing process, the article introduces how to preset the material distribution as well as the research progress about the optimization of magnetically controlled 4D printing platforms and the distribution of magnetic field profiles. Third, the article also makes a brief introduction to the applications of magnetically controlled 4D printing technology in medical, electronic flexible devices, and industrial manufacturing fields.

Low-cost and Non-visual Labels Using Magnetic Printing

This paper presents MagCode, a new type of barcode. MagCode label is printed with magnetic ink through ordinary printers and stores data in the magnetic field. By swiping a magnetometer over it, the stored data can be extracted. Thus, unlike ordinary barcodes, MagCode does not rely on visual channels to decode, implying untapped interaction opportunities when decoding ordinary visual code is not preferred or not possible. Its application cases include an unobstructed and low-cost input interface for wearables, whose visual sensing capabilities are usually limited. Further, MagCode's patterns can be designed to be visually-undecodable and our evaluation shows that accessing its magnetic signal requires very close approximation. These properties allow for using MagCode labels to convey covert and sensitive information, such as Easter eggs in games and payment credentials in daily life.

Development of a Patient Specific Cartilage Graft Using Magnetic Resonance Imaging and 3D Printing

Development of a Patient Specific Cartilage Graft Using Magnetic Resonance Imaging and 3D Printing

Combinatorial dependence of magnetic printing characteristics in double magnet master media for energy-assisted magnetic recording

In this study, the combinatorial dependence in double magnet master for energy-assisted magnetic recording was investigated by the micromagnetic framework. Four kinds of master media, which are soft single magnet (SSM), hard single magnet (HSM), soft double magnet (SDM) and hard double magnet (HDM), were compared. Comparing single magnet and double magnet master media, more adequate combination of double magnet master media was discussed. The HSM, SDM, and HDM master media can write line/space (L/S) pattern with bit length of 20 nm, while the double magnet master media can clearly print L/S patterns comparing with single magnet in case of 10 nm. For higher coercivity EAMR media, the larger printing field causes larger recording field difference by utilizing SDM master media while in case of HDM the recording field difference is almost constant even if the printing field increases. As a result, since the recording field difference of SDM becomes larger than that of HDM as the printing field strengthens, thus, SDM master media can write the servo signals onto higher coercivity EAMR media. It was concluded that it is important for the low coercivity parts of double magnet master media to have a larger saturation magnetization due to enhancement of large recording field difference.

Surface-Embedded Liquid Metal Electrodes with Abrasion Resistance via Direct Magnetic Printing.

Gallium-based liquid metals (LMs) featuring both high conductivity and fluidity are ideal conductors for soft and stretchable electronics. However, their liquid nature is a double-edged sword in many key applications since LMs are inherently prone to mechanical damage. Although additional encapsulation is frequently used for the protection of delicate LM electrodes, it hinders the electrical interfacing with other objects for interconnection, sensing, and stimulation. Here, different from conventional patterning methods that deposit LM on or inside substrates, we for the first time report a simple strategy to create surface-embedded LM of eutectic gallium-indium (EGaIn) circuits with mechanical damage endurance. This was achieved by using direct magnetic printing to overcome the high surface tension of LM, allowing it to be passively filled into the laser-patterned microgrooves on soft substrates. We show that the surface-embedded LM circuits are resistant to mechanical erasure, washing, and peeling. We also show the applications of our surface-embedded LM electrodes in respiration monitoring and electrical stimulation of nerves. This work provides a simple and efficient way to create mechanically reliable LM microelectrodes, holding great promise for wearable and implantable bioelectronics.

Vertically-aligned boron nitride composite as a highly thermally conductive material using magnetic field-assisted three-dimensional printing

With the development of electronic devices, the efficient thermal management of electronic devices has attracted increasing attention. In this study, we fabricated a composite that exhibited effective thermal conductivity by vertically aligning fillers using a generated vertical magnetic field in a three-dimensional (3D) printer. To this end, magnets were placed in the printer such that the same poles faced each other. Consequently, the magnets repelled each other and formed a vertical magnetic field, which enabled the vertical placement of Fe3O4-decorated BN in UV resin. UV resin is a mixture of 1,6-hexanediol diacrylate, diurethane dimethacrylate, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide in a mass ratio of 69 : 30: 1. Owing to the effective transfer of heat in the vertical direction, the printed composite achieved a thermal conductivity value of 1.36 W m−1 K−1 at a filler content of 17.5 vol%. This result demonstrate the effectiveness of this method for aligning fillers on a slurry within a 3D printer, and we believe that it will provide a new paradigm for composite printing.

Master Structure Dependence of Double Magnet Master on Performance of Magnetic Printing Onto Energy-Assisted Magnetic Recording Media

The dependence of double magnet master (DMM) printing characteristics on master thickness and non-magnetic separator (NMS) thickness is investigated using micromagnetic simulation. It is found that the recording field difference saturates when the master thickness reaches the bit length. The NMS, which separates the two magnetic materials of the DMM, shifts the maximum points of the recording field distribution into the softer magnet regions, decreasing the island-like non-reversed regions, thus enhancing the printing performance. The effective switching field is important for understanding magnetic printing characteristics. The printed magnetization distributions are in accordance with the switching field distribution of the recording field generated by the DMM. Therefore, optimizing the master thickness and NMS thickness effectively improves the DMM printing characteristics for various servo patterns.

3D printed personalized, heparinized and biodegradable coronary artery stents for rabbit abdominal aorta implantation

Biodegradable stents have become the focus of attention in the field of interventional medicine. Compared to non-biodegradable stents, these stents are designed to degrade, leaving behind regenerating healthy arteries. In addition to biodegradability, customizability and anticoagulation are also important for stent treatments. The combination of magnetic resonance angiography (MRA) and 3D printing can customize coronary stents according to different vascular geometries of patients. Therefore, this work focused on the rapid fabrication of stents composed of polycaprolactone (PCL) by 3D printing and then functionalized the stents with heparin via covalent grafting. The 3D printed stents were implanted into the abdominal aorta of rabbits to evaluate the feasibility of implantation and biocompatibility. Mechanical tests showed that 3D printed stents have good mechanical properties. In vitro data demonstrated that the stents had excellent blood compatibility and cytocompatibility. The heparinized PCL(PCL-NH2-Hep) stent can promote the adhesion, spreading and proliferation of human umbilical vein endothelial cells (HUVECs) and inhibit the excessive proliferation of smooth muscle cells (SMCs). Presently, there is insufficient study about 3D printed stent implantation in rabbit arteries. Hence, personalized stents were prepared via MRA and 3D printing, which tailored to the patient's unique anatomy. A 3D printed stent-balloon delivery system was employed to deliver stents to the abdominal aorta. At 3-month follow-up, the PCL-NH2-Hep stent maintained good vascular patency. Moreover, the heparinized stents showed rapid endothelialization and prevention of neointimal restenosis in vivo. This study demonstrated that personalized PCL-NH2-Hep stent may have the potential in the field of biodegradable coronary artery stents.

Patterned Magnetofluids via Magnetic Printing and Photopolymerization for Multifunctional Flexible Electronic Sensors.

Liquid conductor-based flexible sensors with high mechanical deformability and reliable electrical reversibility have aroused great interest in electronic skin, soft robotics, environmental monitoring, and other fields. Herein, we develop a novel strategy to fabricate liquid conductor-based flexible sensors by combining ionic liquid-based magnetofluids (IL-MFs), magnetic printing, and photopolymerization techniques. The as-prepared sensors exhibit excellent electromechanical properties, such as a wide detection range, low hysteresis, fast response time, good durability, etc. Moreover, the gauge factors (GFs) of the sensor could be easily adjusted by changing the modulators with different line widths or patterns, and the strain sensors can also be designed for anisotropic monitoring. Apart from serving as strain sensors, the magnetofluid-based flexible sensors can be used to detect external pressure, human activities, and changes in temperature, illumination, and magnetic field as well. This work provides a facile strategy to fabricate liquid conductor-based multifunctional sensors. Such a magnetofluid-based sensor has a great promising future.

A Rare Case of Concordant Atrioventricular Connection to L-Looped Ventricles in Situs Solitus: 4-Dimensional Magnetic Resonance Imaging and 3D Printing

An infant male presented with the rare anatomy consisting of situs solitus, concordant atrioventricular connections to L-looped ventricles, double outlet right ventricle (DORV), and hypoplastic aortic arch. 6 months after neonatal aortic arch repair, the morphologic right ventricle function deteriorated, and surgical evaluation was undertaken to determine if either biventricular repair with a systemic morphologic left ventricle or right ventricular exclusion was possible. After initial echocardiography, magnetic resonance imaging (MRI) was used to create detailed axial and 4-dimensional (4D) images and 3-dimensional (3D) printed models. The detailed anatomy of this rare, complex case and its use in pre-surgical planning is presented.

Printing toner used as carrier for immobilization of laccase

The search for seeking novel immobilized enzyme carriers is a hot topic in the field of enzyme engineering . As a kind of common office consumable, magnetic printing toner has been terribly wasted, leading to potential harm to the environment. We try to use printing toner as carrier for enzyme immobilization to realize waste reuse. In this paper, the laccase extracted from Agaricus bisporus was successfully immobilized on chitosan coated magnetic printing toner by glutaraldehyde linking. The use of printing toner is proved to be feasible. The results show that the optimal temperature of immobilized laccase is 40 °C, and the optimal pH is 3.0. Compared with free laccase, the optimal temperature and optimal pH have been obviously changed after immobilization. And the pH tolerance has been significantly improved, which can remain 53% activity after 5 cycles. Because of the use of magnetic printing toner, it is more convenient to recycle the immobilized enzyme. In this study, printing toner was used as carrier for the immobilization of enzyme and the discarded printing toner recycling was realized. • The immobilized enzyme carrier with printing toner as the main body was successfully constructed. • Laccase was successfully immobilized with the new carrier. • The new carrier uses discarded print toner to reduce environmental pollution.

Visualizing MRI Deep Learning Segmentation Algorithms using 3D Printing

As the capabilities and roles of Artificial Intelligence (AI) in the medical field are continually expanded, new potential uses, and combinations of technology become viable. This paper highlights a methodology for utilizing AI Magnetic Resonance Imaging (MRI) segmentation networks and 3D printing processes in conjunction for medical diagnosis, planning, and visualization of medical images. We also include promising benefits and potential medical offerings made possible by this system. By training a "U- Net" on the 2019 BraTS dataset, we base our research on an MRI brain lesion segmentation dataset with sustaining performance and world recognition. This network automatically segments novel MRI scans into lesion and non-lesion regions. We pair this network with a 3D printing process that enables us to print fully segmented, 1:1 scale, patient organs aided by AI techniques to better explain cases, test models, and plan for operations. In addition to a clearly outlined process that enables these offerings, we establish a potential trajectory for how these combined tools will continue to revolutionize the ways healthcare professionals interact with patients and their data.