Self-Healing Liquid Metal Magnetic Hydrogels for Smart Feedback Sensors and High-Performance Electromagnetic Shielding

Hydrogels exhibit potential applications in smart wearable devices because of their exceptional sensitivity to various external stimuli.However,their applications are limited by challenges in terms of issues in biocompatibility,custom shape,and self-healing.Herein,a conductive,stretchable,adaptable,self-healing,and biocompatible liquid metal GaInSn/Ni-based composite hydrogel is developed by incorporating a magnetic liquid metal into the hydrogel framework through crosslinking polyvinyl alcohol(PVA)with sodium tetraborate.The excellent stretchability and fast self-healing capability of the PVA/liquid metal hydrogel are derived from its abundant hydrogen binding sites and liquid metal fusion.Significantly,owing to the magnetic constituent,the PVA/liquid metal hydrogel can be guided remotely using an external magnetic field to a specific position to repair the broken wires with no need for manual operation.The composite hydrogel also exhibits sensitive deformation responses and can be used as a strain sensor to monitor various body motions.Additionally,the multifunctional hydrogel displays absorption-dominated electromagnetic interference(EMI)shielding properties.The total shielding performance of the composite hydrogel increases to~62.5 dB from~31.8 dB of the pure PVA hydrogel at the thickness of 3.0 mm.The proposed bioinspired multifunctional magnetic hydrogel demonstrates substantial application potential in the field of intelligent wearable devices.

Influence of Alternating and Static Magnetic Fields on Drug Release from Hybrid Hydrogels Containing Magnetic Nanoparticles

Hybrid hydrogels of carboxymethylcellulose (CMC), containing two different amounts of CoFe2O4 magnetic nanoparticles (50% and 70% in relation to the quantity of the polymer) as crosslinkers, were prepared. The hybrid hydrogels were chemically and morphologically characterized and their viscoelastic properties and swelling degrees were analyzed. The hydrogels were tested as controlled drug delivery systems by applying one static and two different alternating magnetic fields. The application of the two alternating magnetic fields (AMF) to the hybrid hydrogels induced a higher release of methylene blue (MB), used as a model drug, than without the application of any magnetic field, especially at low frequency (4 Hz) and high magnetic intensity (0.5 T). In contrast, when the hybrid hydrogels were exposed to a static magnetic field (SMF) the release of MB was slowed down. Furthermore the two different amounts of magnetic nanoparticles induce different responses to the magnetic field. The greater number of nanoparticles in the CMC-NP-70 hydrogel leads to the formation of some NPs clusters limiting the drug release;conversely, the CMC-NP-50 hydrogel, containing a lower amount of nanoparticles, shows a higher release of MB vs. time. In conclusion, we were able to get a potential system for modulation of the drug delivery: the release behaviour of hybrid hydrogels can be modulated by applying alternating and static magnetic fields cyclically. A possible explanation for the release mechanism is about the structural modification of the polymeric chains that occurs when the hybrid hydrogels are exposed to the magnetic fields.

THE EFFECTS OF MAGNETIC FIELD ON GRAFT COPOLYMERIZATION OF METHYL METHACRYLATE ONTO POLYVINYL ALCOHOL IN THE PRESENCE OF BENZOPHENONE DURING UV IRRADIATION

The effects of magnetic field on the graft ratio and stereoregularity of grafts of PVA-g-MMA in the presence ofbenzophenone during UV irradiation are discussed. By means of IR, it was found that the graft ratio was increased with the increment of magnetic field strength. Furthermore, application of relative weak magnetic field of 0.4 Tesla had been shown to substantially enhance the stereo-regularity of graft copolymer. The maximum stereo-regularity appeared when the graft ratio approached to 85% with the magnetic field of 1.2 Tesla (T). The resistance to moisture and heat resistance of the grafted copolymer in the presence of magnetic field were also improved.

Influence of vacuum annealing and irradiation on magnetic properties of Fe-3% Y_2O_3 films

Yttria （Y） dispersed ferrum （Fe） films were prepared by a double-target magnetron co-sputtering method. Vacuum annealing and xenon ion irradiation were conducted to investigate the influence on the magnetic and mechanical properties of the films. The crystal grain growth mechanism and second phase precipitation mechanism were conducted simultaneously in the vacuum annealing process. These two effects led to an opposite variation of nano-hardness and coercivity in the films. Xenon ion irradiation played a role in rapid annealing, which also affected the magnetic performance of the yttria dispersed ferrum films.

<i>γ</i>-Ray Irradiation Effect on MCF Rubber Solar Cells with both Photovoltaics and Sensing Involving Semiconductors Fabricated under Magnetic and Electric Fields

For cases in which a robot with installed solar cells and a sensor operates in a nuclear reactor building or in space for extravehicular activity, we require elastic and extensible solar cells. More than two different types of sensing are also required, minimally with photovoltaics and built-in electricity. Magnetic compound fluid (MCF) rubber solar cells are made of rubber, so they are elastic and extensible as well as sensitive. To achieve flexibility and an effective photovoltaic effect, MCF rubber solar cells must include both soluble and insoluble rubbers, Fe3O4, TiO2, Na2WO4∙2H2O, etc. On the basis of this constitution, we propose a consummate fabrication process for MCF rubber solar cells. The characteristics of these cells result from the semiconductor-like role of the molecules of TiO2, Fe3O4, Ni, Na2WO4∙2H2O, polydimethylsiloxane (PDMS), natural rubber (NR), oleic acid, polyvinyl alcohol (PVA), water and magnetic cluster involved in the MCF rubber. Their tendencies can be deduced by synthesizing knowledge about the enhancement of the reverse-bias saturation current IS and the diode ideality factor N, with conventional knowledge about the semiconductor affected by γ-irradiation and the attenuation of the photon energy of γ-rays.

Autophagy inhibition mediated via an injectable and NO-releasing hydrogelfor amplifying the antitumor efficacy of mild magnetic hyperthermia

While mild hyperthermia holds great potential in the treatment of solid tumors, the thermal stress-triggered selfrepairingautophagy significantly compromises its efficacy. To circumvent this obstacle, an injectable hydrogel(NO-Gel) composed of thermosensitive poly(ethylene glycol)-polypeptide copolymers modified with abundantNO donors on their side chains is developed. Meanwhile, ferrimagnetic Zn0.5Fe2.5O4 magnetic nanoparticles(MNPs) with high magnetic-heat conversion efficiency are synthesized and loaded into NO-Gel to obtainMNPs@NO-Gel. The MNPs@NO-Gel system exhibits a sol-gel transition upon heating, and has the ability toperform multiple magnetic hyperthermia therapy (MHT) after only one administration due to the even distributionand strong immobilization of MNPs in NO-Gel. NO can be continuously liberated from NO-Gel and thisprocess is markedly accelerated by MHT. Additionally, MNPs@NO-Gel maintains its integrity in vivo for over onemonth and the released MNPs are metabolized by the spleen. After a single administration of MNPs@NO-Gel atthe tumor site, three mild MHT treatments with similar effects are fulfilled, and the sufficient supply of NOeffectively inhibits MHT-induced autophagic flux via blocking the formation of autophagosomes and synchronouslydestroying lysosomes, thereby substantially boosting the efficacy of mild MHT. As a consequence, CT-26colon tumors are completely eliminated without causing severe side-effects.

Self-sensing magnetic actuators of bilayer hydrogels

Hard magnetic soft robots have been widely used in biomedical engineering.In these applications,it is crucial to sense the movement of soft robots and their interaction with target objects.Here,we propose a strategy to fabricate a self-sensing bilayer actuator by combining magnetic and ionic conductive hydrogels.The magnetic hydrogel containing NdFeB particles exhibits rapid response to magnetic field and achieve bending deformation.Meanwhile,the polyacrylamide(PAAm)hydrogel with lithium chloride(LiCl)allows for the sensing of deformation.The bending behavior of the bilayer under magnetic field is well captured by theoretical and simulated models.Additionally,the bilayer strain sensor shows good sensitivity,stability and can endure a wide-range cyclic stretching(0-300%).These merits qualify the self-sensing actuator to monitor the motion signals,such as bending of fingers and grasping process of an intelligent gripper.When subject to an external magnetic field,the gripper can grab a cube and sense the resistance change simultaneously to detect the object size.This work may provide a versatile strategy to integrate actuating and self-sensing ability in soft robots.

Electron-Irradiation Induced Nanocrystallization of Pb（ll） in Silica Gels Prepared in High Magnetic Field

In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical resistance, we show here their possibility of medium in materials processing. In this direction, for example, silica hydrogels have so far been used as media of crystal growth. In this paper, as opposed to the soft-wet state, dried silica gels have been investigated. We have found that lead （II） nanocrystallites were formed induced by electron irradiation to lead （ll）-doped dried Hydrogels made from a sodium metasilicate solution doped with silica gels prepared in a high magnetic field such as B = 10 T. lead （II） acetate were prepared. The dried specimens were irradiated by electrons in a transmission electron microscope environment. Electron diffraction patterns indicated the crystallinity of lead （II） nanocrystallites depending on B. An advantage of this processing technique is that the crystallinity can be controlled through the strength of magnetic field B applied during gel preparation. Specific skills are not required to control the strength of magnetic field.

Development of Magnetic Compound Fluid Rubber Sensor for Practical Usage on &gamma;-Irradiation and Energy Harvesting for Broad-Band Electromagnetic Waves

We have performed sequential studies on new types of soft rubber for their application as artificial skin in robots and haptic sensors. Based on a proposed electrolytic polymerization method and novel adhesion technique for rubber and a metal that utilizes a metal complex hydrate, we have developed an MCF rubber sensor. This sensor uses a magnetic compound fluid (MCF), natural rubber (NR-latex) or chloroprene rubber latex (CR-latex), and requires the application of a magnetic field. The potential application of the developed sensor in various engineering scenarios and our daily lives is significant. In this regard, we investigated the effects of &gamma;-irradiation, infrared radiation, microwaves, and a thermal source on the MCF rubber sensor. We established that the MCF rubber is effective enough to be used for power generation of broadband electro-magnetic waves from &gamma;-rays to microwaves, including the range of the solar spectrum, which is the typical characteristic obtained in the present investigation. The remarkable attribute is that the MCF rubber sensor dose is not degraded by &gamma;-irradiation. We also demonstrated the effectiveness of the MCF rubber sensor in energy harvesting.

RF magnetron sputtering induced the perpendicular magnetic anisotropy modification in Pt/Co based multilayers

We demonstrate that radio frequency(RF)magnetron sputtering technique can modify the perpendicular magnetic anisotropy(PMA)of Pt/Co/normal metal(NM)thin films.Influence of ion irradiation during RF magnetron sputtering should not be neglected and it can weaken PMA of the deposited magnetic films.The magnitude of this influence can be controlled by tuning RF magnetron sputtering deposition conditions and the upper NM layer thickness.According to the stopping and range of ions in matter(SRIM)simulation results,defects such as displacement atoms and vacancies in the deposited film will increase after the RF magnetron sputtering,which can account for the weakness of PMA.The amplitude changes of the Hall resistance and the threshold current intensity of spin orbit torque(SOT)induced magnetization switching also can be modified.Our study could be useful for controlling magnetic properties of PMA films and designing new type of SOT-based spintronic devices.

PVA/PEG Hybrid Hydrogels Prepared by Freeze-thawing and High Energy Electron Beam Irradiation

In this paper, poly（vinyl alcohol）（PVA） and PVA/poly（ethylene glycol）（PEG） hybrid hydrogels were synthesized by freeze-thawing or freeze-thawing followed by high energy electron beam irradiation. The influence of PEG molecular weight, mass ratios of PVA to PEG, thawing temperature and number of freeze-thawing（FT） cycles on the mechanical strength of PVA/PEG hydrogel was investigated. Also, the thermal behaviors were examined by differential scanning calorimetry（DSC） and the microstructttres were observed with scanning electron microscopy（SEM）. The results suggest that the addition of PEG improves the mechanical strength of PVA hydrogel and the irradiation reduces both the strength of PVA/PEG hydrogel slightly and the degree of crystallinity. The improved properties suggest that PVA/PEG hydrogel can be a good candidate for the application in the biomedical.

EFFECT OF MOLECULAR WEIGHT OF PEO ON THE STRUCTURE AND PROPERTIES OF PDMAEMA/PEO HYDROGELS

A new kind of binary hydrogels composed of poly（dimethylaminoethylmethacrylate） （PDMAEMA） and poly（ethylene oxide） （PEO） with varying weight average molecular weights （M^-w = 5 × 10^4, 1 × 10^5 and 2.5 × 10^6） were prepared by У-irradiation technology. The properties of PDMAEMA/PEO hydrogels obtained were evaluated in terms of gel fraction, gel strength, thermal characterization and swelling behavior. The gel strength and swelling degree of the hydrogels could be improved obviously after adding PEO into the PDMAEMA system, while the degree of improvement decreased with increasing M^-w of PEO. The temperature sensitivity of PDMAEMA/PEO was retained only in the sample with PEO of M^-w = 5 × 10^4, and the pH sensitivity was retained in samples with PEO of M^-w = 5 × 10^4 and 1 × 10^5. When DMAEMA/PEO mixtures containing PEO of M^-w = 5 × 10^4 were irradiated, the main reaction could be the cross-linking of DMAEMA, and the linear PEO molecular chains could penetrate into the cross-linked network of PDMAEMA. With increasing M^-w of PEO, some side reactions were induced, such as grafting of DMAEMA onto PEO molecules, the scission or cross-linking of PEO.

The Magnetic Order in Ion Irradiated Graphite

The magnetism of highly oriented pyrolytic graphite （HOPG） induced by ion implantation is investigated with electron spin resonance （ESR） spectroscopy and magnetization measurements. The results indicate that the ESR spectra of the HOPG sample correlate with ion species, incident energy and dose of implantation. The correlation of the ESR spectra and magnetism of the HOPG sample with ：2C＋ ion implantation and H＋ ion implantation are studied in detail. The ferromagnetism of the HOPG sample is likely related to the asymmetric L1 line, which may be attributed to the interaction between localized defects and itinerant electrons occupied in the ＇impurity＇ band induced by ion implantation.

Characterization of Some Hydrogels Used in Water Purification: Correlation of Swelling and Free-Volume Properties

In this study, the main objective is to develop a good chelation and ion exchange hydrogel. This hydrogel is obtained by polymerization of dimethyl amino ethyl methacrylate (DMAEMA) and acrylic acid (AAc) by gamma irradiation, for the purpose of separation of some heavy and toxic metals from water. UV spectroscopy is applied to determine the metal ion concentration before and after treatment. The FTIR spectral analysis has identified the bond structure of PAAc, DMAEMA and P (DMAEMA/AAc) hydrogels. Microstructure and nanostructure are investigated by means of SEM and positron annihilation lifetime spectroscopy (PALS) respectively. A maximum swelling percent is found for 80/20 DMAEMA/AAc at free-volume hole size and fraction of 97?3 and 3.4% respectively. The P (DMAEMA/AAc) and PAAc hydrogels have been applied for Cu+2, Co+2 and Ni+2 removals from aqueous solutions, and the factors affecting the adsorption capacity are determined. The adsorption capacity of P (DMAEMA/AAc) is found to be higher than the corresponding ones PAAc. Its experimental results showed that, the maximum adsorption of P (DMAEMA/AAc) after 24 h occurs at pH 7 with concentration of 250 ppm for Ni+2 ions and at pH 5 with concentration of 40 ppm for Cu+2 and Co+2 ions. The adsorption affinity of P (DMAEMA/AAc) hydrogel at different treatment contact times is in the following order Ni > Cu > Co. However, the order becomes Co > Ni > Cu by the variation of the pH of the metal ion solution;the variation of its concentration leads to a different order of Cu > Co > Ni.

A Novel Regenerated Silk Fibroin-based Hydrogels with Magnetic and Catalytic Activities

A simple and facile synthetic methodology for fabricating the regenerated silk fibroin （RSF）-based hydrogel which consisted of the in situ generated magnetic ferriferous oxide （Fe304） was developed. Using the co-precipitation of Fe2＋ and Fe3＋ within the RSF-based hydrogel with 90% RSF and 10% HPMC （hydroxypropyl methyl cellulose）, the as-prepared RSF/Fe304 hydrogel not only showed high strength of saturation magnetization, but also exhibited excellent catalytic activities. For example, with the assistant of 3,3＇,5,5＇-tetramethylbenzidine （TMB）, the RSF/Fe304 hydrogel could detect H202 at a concentration as low as 1 x 10-6 mol.L-1 In addition, the catalytic activities were able to be maintained for a long term under various conditions. These findings suggest that the RSF-based materials can be endowed with interesting properties, and have great potential for the applications in the fields of biotechnology and environmental chemistry.

Effect of Ar ion irradiation on the room temperature ferromagnetism of undoped and Cu-doped rutile TiO_2 single crystals

Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals（SCs）.To tune their magnetism,Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively.The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2.Meanwhile,a new CuO-like species present in the sample was found to be dissolved after the post-irradiation.Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions,while these ions are directly involved in boosting the absorption in the visible region.

Neutron Irradiation of Electronic Materials at HANARO

HANARO, a 30 MW open-pool type multipurpose research reactor, has been operated as a platform for nuclear researches in Korea, and irradiation facilities have been mainly utilized for various nuclear material irradiation tests requested by users. Although most irradiation tests have been related to national R&D relevant to nuclear power, demand for neutron irradiation of electro-magnetic materials is increasing rapidly at HANARO. Another research reactor, which is named the KIJANG research reactor (KJRR), is under construction in Korea. KJRR is dedicated to increasing the national radio-isotopes supply capacity and to the irradiation facilities including Neutron Transmutation Doping (NTD) facilities for power semiconductor production in a large scale and fast neutron irradiation (FNI) facility for fast neutron irradiation. The NTD and FNI facilities in the KJRR reactor can be effectively utilized on the study of separated effect of thermal and fast neutron irradiations on the properties of electro-magnetic materials. HANARO will also specialize more on irradiation research, including neutron irradiation of electronic materials. The research status and possibility of new electro-magnetic materials using neutron irradiation at HANARO are surveyed to ascertain the utilization of neutron irradiation technology in electro-magnetic material researches.

Engineering neuroregenerative microenvironment via aligned hydrogel-assisted magnetic stimulation for complete spinal cord injury repair

Utilizing biomaterials in tissue engineering has shown considerable promise for tissue regeneration,particularly through delivering multimodel cell-regulatory signals,including the material-related signals and extrinsic stimuli.In this research,we developed a magnetic-responsive aligned nanofiber fibrin hydrogel(MAFG),integrating the structured alignment of nanofibers and the pliability of fibrin hydrogel with an external magnetic field.This design aimed to enhance the regenerative response in spinal cord injury treatment.A medium-strength magnetic field,aligned with the spinal cord,was applied to aid motor function recovery in rats with spinal cord injuries.The use of MAFG in this context not only intensified the effect of the magnetic field but also encouraged the activation and differentiation of native neural stem cells.Furthermore,this method effectively steered macrophage polarization towards a beneficial M2 phenotype,addressing immune dysregulation at the injury site.The parallel application of magnetic field stimulation through MAFG in a spinal cord injury model contributed to the concurrent promotion of neurogenesis,angiogenesis,and immunomodulation,resulting in marked improvement in motor function in rats.This investigation underscores the therapeutic potential of magnetic field stimulation and highlights how aligning this stimulation with the spinal cord can significantly enhance the regenerative milieu at the injury site.