Magnetic and conductive liquid metal gel.

Liquid metals are fast becoming a new class of universal and frictionless additives for the development of multifunctional soft and flexible materials. Here, nano-droplets of eutectic gallium-indium alloy, liquid at room temperature, were used as a platform for the formulation of electrically conductive and magnetically responsive gels with the incorporation of Fe3O4 nanoparticles. The nano-additives were prepared in-situ within a water-based solution of polyvinyl alcohol. A borax cross-linking reaction was then performed to yield multifunctional flexible and self-healing gels. The physico-chemical properties and changes of the nano-additives at each step of the gel preparation method were characterized. Oxidation and complexation reactions between the liquid metal and iron oxide nano-additives were observed. A mix of nano-sized functional magnetic Fe3O4/Fe2O3 and In-Fe oxide complexes was found to enable the magnetic susceptibility of the gels. The mechanical and self-healing properties of the gels were assessed, and finally, this flexible and multifunctional material was used as an electronic switch via remote magnetic actuation. The developed conductive and magnetic gels demonstrate great potential for the design of soft electronic systems.

[1]  LuNanshu,et al.  Flexible and Stretchable Electronics Paving the Way for Soft Robotics , 2014 .

[2]  Kai Xu,et al.  Atomically Thin Ga2S3 from Skin of Liquid Metals for Electrical, Optical, and Sensing Applications , 2019, ACS Applied Nano Materials.

[3]  G. Whitesides,et al.  Eutectic gallium-indium (EGaIn): a moldable liquid metal for electrical characterization of self-assembled monolayers. , 2008, Angewandte Chemie.

[4]  Jing Liu,et al.  Vascularized liquid metal cooling for thermal management of kW high power laser diode array , 2019, Applied Thermal Engineering.

[5]  R. Amal,et al.  Catalytic Metal Foam by Chemical Melting and Sintering of Liquid Metal Nanoparticles , 2019, Advanced Functional Materials.

[6]  R. K. Tubbs.  Sequence distribution of partially hydrolyzed poly(vinyl acetate) , 1966 .

[7]  B. Sreedhar,et al.  Thermal, mechanical, and surface characterization of starch–poly(vinyl alcohol) blends and borax‐crosslinked films , 2005 .

[8]  Barbara D Boyan,et al.  A review of polyvinyl alcohol and its uses in cartilage and orthopedic applications. , 2012, Journal of biomedical materials research. Part B, Applied biomaterials.

[9]  Yuanhua Lin,et al.  Magnetic biodegradable Fe3O4/CS/PVA nanofibrous membranes for bone regeneration , 2011, Biomedical materials.

[10]  Jukka Seppälä,et al.  Stable, self-healing hydrogels from nanofibrillated cellulose, poly(vinyl alcohol) and borax via reversible crosslinking , 2014 .

[11]  Hao Chang,et al.  Soft Liquid Metal Nanoparticles Achieve Reduced Crystal Nucleation and Ultrarapid Rewarming for Human Bone Marrow Stromal Cell and Blood Vessel Cryopreservation. , 2019, Acta biomaterialia.

[12]  Jing Liu,et al.  Experimental and numerical analysis on a compact liquid metal blade heat dissipator with twin stage electromagnetic pumps , 2019, International Communications in Heat and Mass Transfer.

[13]  Arnan Mitchell,et al.  Hydrodynamic directional control of liquid metal droplets within a microfluidic flow focusing system , 2016 .

[14]  Shan Jiang,et al.  PVA hydrogel properties for biomedical application. , 2011, Journal of the mechanical behavior of biomedical materials.

[15]  O. Tretinnikov,et al.  Determination of the degree of crystallinity of poly(vinyl alcohol) by FTIR spectroscopy , 2012 .

[16]  Naresh Pillai,et al.  2D SnO/In2O3 van der Waals Heterostructure Photodetector Based on Printed Oxide Skin of Liquid Metals , 2019, Advanced Materials Interfaces.

[17]  H. Dinç,et al.  Preparation and characterization of polyvinyl borate/polyvinyl alcohol (PVB/PVA) blend nanofibers , 2012 .

[18]  Arnan Mitchell,et al.  Liquid metal enabled microfluidics. , 2017, Lab on a chip.

[19]  J. Church,et al.  Preparation and characterization of silica coated iron oxide magnetic nano-particles. , 2010, Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.

[20]  Chengwu Yang,et al.  Structural Evolution of α-Fe2O3(0001) Surfaces Under Reduction Conditions Monitored by Infrared Spectroscopy , 2019, Front. Chem..

[21]  Weihua Li,et al.  Functional Liquid Metal Nanoparticles Produced by Liquid‐Based Nebulization , 2018, Advanced Materials Technologies.

[22]  Hui Yang,et al.  Highly Stretchable, Elastic, and Ionic Conductive Hydrogel for Artificial Soft Electronics , 2018, Advanced Functional Materials.

[23]  M. Dong,et al.  Combustion assisted preparation of high coercivity Sm–Co hard magnet with stable single-domain size , 2020 .

[24]  B. Forbes,et al.  The synthesis of high molecular weight partially hydrolysed poly(vinyl alcohol) grades suitable for nanoparticle fabrication. , 2008, Journal of Nanoscience and Nanotechnology.

[25]  S. Basavaraja,et al.  Solvothermal synthesis and characterization of acicular α-Fe2O3 nanoparticles , 2011 .

[26]  R. Oréfice,et al.  FTIR and UV‒vis study of chemically engineered biomaterial surfaces for protein immobilization , 2002 .

[27]  Qinmin Pan,et al.  A self-healable polyvinyl alcohol-based hydrogel electrolyte for smart electrochemical capacitors , 2016 .

[28]  M. Panigrahi,et al.  Effect of capping and particle size on Raman laser-induced degradation of γ-Fe2O3 nanoparticles , 2004 .

[29]  K. Nishida,et al.  Structure and dynamics of poly(vinyl alcohol) gels in mixtures of dimethyl sulfoxide and water , 2012 .

[30]  Benjamin J. Carey,et al.  Green Synthesis of Low‐Dimensional Aluminum Oxide Hydroxide and Oxide Using Liquid Metal Reaction Media: Ultrahigh Flux Membranes , 2018, Advanced Functional Materials.

[31]  I. T. Garcia,et al.  Insulating characteristics of polyvinyl alcohol for integrated electronics , 2014 .

[32]  Xiasheng Guo,et al.  On-Chip Production of Size-Controllable Liquid Metal Microdroplets Using Acoustic Waves. , 2016, Small.

[33]  A. Dufresne,et al.  Cellulose whiskers reinforced polyvinyl alcohol copolymers nanocomposites , 2008 .

[34]  Khashayar Khoshmanesh,et al.  Inertial Microfluidics with Integrated Vortex Generators Using Liquid Metal Droplets as Fugitive Ink , 2019, Advanced Functional Materials.

[35]  Xuechang Zhou,et al.  Liquid Metal‐Based Transient Circuits for Flexible and Recyclable Electronics , 2019, Advanced Functional Materials.

[36]  Haiping Du,et al.  Liquid metal-filled magnetorheological elastomer with positive piezoconductivity , 2019, Nature Communications.

[37]  K. Kalantar-zadeh,et al.  Self‐Limiting Galvanic Growth of MnO2 Monolayers on a Liquid Metal—Applied to Photocatalysis , 2019, Advanced Functional Materials.

[38]  K. Khoshmanesh,et al.  Liquid metals: fundamentals and applications in chemistry. , 2018, Chemical Society reviews.

[39]  J. Church,et al.  Infrared and Raman spectroscopic studies on iron oxide magnetic nano-particles and their surface modifications , 2012 .

[40]  Kune-Woo Lee,et al.  Polyvinyl alcohol-borate hydrogel containing Prussian blue for surface decontamination , 2018, Journal of Radioanalytical and Nuclear Chemistry.

[41]  Liqun Zhang,et al.  A Polyvinyl Alcohol Stabilized Liquid Metal Hydrogel for Wearable Transient Epidermal Sensors. , 2019, ACS applied materials & interfaces.

[42]  Weihua Li,et al.  Sonication-enabled rapid production of stable liquid metal nanoparticles grafted with poly(1-octadecene-alt-maleic anhydride) in aqueous solutions. , 2018, Nanoscale.

[43]  Ying-Jie Zhu,et al.  Monodisperse Fe3O4 and γ-Fe2O3 magnetic mesoporous microspheres as anode materials for lithium-ion batteries. , 2012, ACS applied materials & interfaces.

[44]  Jing Liu,et al.  Semi-liquid metal and adhesion-selection enabled rolling and transfer (SMART) printing: A general method towards fast fabrication of flexible electronics , 2019, Science China Materials.

[45]  Jiupeng Zhao,et al.  Structural evolution and characteristics of the phase transformations between α-Fe2O3, Fe3O4 and γ-Fe2O3 nanoparticles under reducing and oxidizing atmospheres , 2013 .

[46]  Jiuyang Zhang,et al.  Ultra-stretchable hydrogels with reactive liquid metals as asymmetric force-sensors , 2019, Materials Horizons.

[47]  MajidiCarmel,et al.  Soft Robotics: A Perspective—Current Trends and Prospects for the Future , 2014 .

[48]  G. Whitesides,et al.  Eutectic Gallium‐Indium (EGaIn): A Liquid Metal Alloy for the Formation of Stable Structures in Microchannels at Room Temperature , 2008 .

[49]  S. Patil,et al.  Borax mediated layer-by-layer self-assembly of neutral poly(vinyl alcohol) and chitosan. , 2009, The journal of physical chemistry. B.

[50]  Jing Liu,et al.  Magnetic Liquid Metal (Fe‐EGaIn) Based Multifunctional Electronics for Remote Self‐Healing Materials, Degradable Electronics, and Thermal Transfer Printing , 2019, Advanced science.

[51]  B. Reeja‐Jayan,et al.  Rechargeable Soft‐Matter EGaIn‐MnO2 Battery for Stretchable Electronics , 2019, Advanced Energy Materials.

[52]  W. Rao,et al.  Recoverable Liquid Metal paste with Reversible Rheological Characteristic for Electronics Printing. , 2020, ACS applied materials & interfaces.

[53]  Kourosh Kalantar-Zadeh,et al.  Liquid Metal Droplet and Graphene Co-Fillers for Electrically Conductive Flexible Composites. , 2020, Small.

[54]  Lei Jiang,et al.  Hydrogel with Ultrafast Self-Healing Property Both in Air and Underwater. , 2018, ACS applied materials & interfaces.

[55]  C. Majidi,et al.  Solution processable liquid metal nanodroplets by surface-initiated atom transfer radical polymerization , 2019, Nature Nanotechnology.

[56]  V. Purushothaman,et al.  The effect of nitridation temperature on the structural, optical and electrical properties of GaN nanoparticles , 2014 .

[57]  Mohammad H. Malakooti,et al.  Liquid Metal Supercooling for Low‐Temperature Thermoelectric Wearables , 2019, Advanced Functional Materials.

[58]  K. Kalantar-zadeh,et al.  Liquid metal core–shell structures functionalised via mechanical agitation: the example of Field's metal , 2019, Journal of Materials Chemistry A.

[59]  Hui Peng,et al.  A flexible and self-healing hydrogel electrolyte for smart supercapacitor , 2019, Journal of Power Sources.

[60]  S. Kanagesan,et al.  Synthesis, Characterization and Effects of Citric Acid and PVA on Magnetic Properties of CoFe2O4 , 2013, Journal of Inorganic and Organometallic Polymers and Materials.

[61]  Ryosuke Matsuzaki,et al.  Highly Stretchable, Global, and Distributed Local Strain Sensing Line Using GaInSn Electrodes for Wearable Electronics , 2015 .