Patterning Of Liquid Metal Using Magnetic Field And Its Applications

Gallium-based liquid metals(LMs)with both fluidity and conductivity not only have many unique and interesting physical and chemical properties,but also show great potential in various cutting-edge areas,such as flexible electronics,soft robots,flexible human-machine interfaces,biomedical devices,etc.How to efficiently pattern this liquid conductor is an essential step towards its practical applications.However,the high surface tension of LM and its surface oxide make it difficult to achieve direct patterning of LM.The existing liquid metal patterning techniques not only suffer poor universality,but also often involve complicated and tedious processing steps and the use of expensive equipment.Therefore,the development of a simple,efficient and universal LM patterning technique is highly desirable to expand the range and depth of its application.To achieve this goal,this paper innovatively proposes the use of magnetic field manipulation for rapid and efficient patterning of LM,and a series of applications have been developed based on this new method.The main research contents are as follows:1.We verified the feasibility of using magnetic field to pattern LM.The magnetic field was used to drive the magnetic microparticles inside the LM droplets to move on the substrate,and the droplets can be spread out on the substrate to achieve the direct patterning.This method did not require any pretreatment of the substrate surface,and is applicable for any substrate.The line width can be adjusted by changing the concentration of magnetic microparticles or the volume of LM droplets.In addition,the magnetic field can also enhance the adhesion between the LM and the substrate,making it possible to directly pattern LM on supermetallophobic substrates.Benefiting from the non-contact nature of magnetic manipulation,this method can also achieve threedimensional patterning of LM on nonplanar surfaces in a near closed space.In addition,based on the new patterning technique,a series of flexible functional devices have been constructed,such as flexible heart rate sensors,flexible light-emitting devices,paperbased flexible LM antennas,and wearable strain sensors.2.Combining magnetic patterning of LM and digital laser processing technology,high-resolution patterning of LM was realized for the first time on hydrogel substrates with a minimum line width of 85 micrometers.The LM-hydrogel flexible electronics exhibited excellent electrical conductivity and high stretchability,which were used for the fabrication of miniature electronic skins to realize the sensing of physiological signals.The high-resolution LM pattern also endowed the hydrogel devices with richer functions,such as radio frequency identification and thermal deformation.In addition,mechanical and electrical self?healing are achieved simultaneously by taking advantage of the self-healing characteristics of polyvinyl alcohol hydrogel and LM.This work provides a new route for preparation of multifunctional hydrogel-based flexible electronics.3.Patterned LM circuits were used for soft robots sensing and actuation.A thermally responsive liquid crystal elastomer(LCE)was prepared as the soft actuator body.The LM circuit patterned on the LCE surface can not only realize the electrothermal deformation of LCE,but also achieve proprioception based on the resistance change of the LM circuit.By optimizing the heating circuit pattern,the LM-LCE actuator can achieve biomimetic autonomous deformation feedback to mechanical stimuli(pressure or strain),without any mechatronic control unit.Moreover,the intrinsic stretchability of LM and the polydomain LCE allows to create 3D spring-like actuators via a simple strain-induced 3D structure formation step,and complex helical motions can be obtained upon electrothermal stimulation.The work provides a simple and efficient way for the development of autonomous soft robots and intelligent human-machine interaction interfaces.