Research On The Interface Of Gallium-based Liquid Metal And Its Application

Gallium-based liquid metals possess many exceptional properties,such as low toxicity,high surface tension,high electrical and thermal conductivity while being soft and deformable.As we know,liquid metals are of importance in the fields of soft electronics,such as electronic skin,controllable electronic switch,soft robot and energy equipment.Researches on liquid metal droplets and their controlled movement are important branches of liquid metal researches,enabling diverse applications.However,directed movement of liquid metal droplets is challenging due to the peculiar wettability and adhesion of liquid metal and the generation of the passivated oxide skin surrounding the liquid metal.In this paper,we studied the movement of liquid metal driven by electric field as well as hydrogen chloride vapor by regulating the surface tension of liquid metal.Meanwhile,we obtained liquid metal droplet with performances of non-viscous,non-corrosive,highly conductive and magnetism by surface modification of liquid metal droplet.The main research contents are as follows:First,the interfacial tension changes of liquid metal droplets in acidic,alkaline and acidified salt solutions were studied,a nd the principle of movement liquid metals droplets driven by electric field in solution was explored.The results showed that in acidic solution,the interfacial tension of liquid metal droplets changed little with the increase of concentration of hydrochloric acid.When the concentration of hydrochloric acid increased from 0.1 mol/L to 2 mol/L,the interfacial tension of liquid metal droplets decreased from 455 m N/m to 442 m N/m.In alkaline solution,the interfacial tension of liquid metal droplets changed significantly with the increase of the concentration of sodium hydroxide.When the concentration increased from0.01 mol/L to 10 mol/L,the interfacial tension decreased from 439±4.2 m N/m to352±1.3 m N/m.In acidified salt solutio n,the increase of positive ion concentration has little influence on interfacial tension,while the increase of negative ion concentration has significant influence on interfacial tension.According to the change of the interfacial tension in the solution,we explored movement behavior of the liquid metal droplets driven by electric field with diameter of 2 mm in acidified 0.5 mol/L KBr,acidified 1.5 mol/L KBr solution and 1 mol/L Na OH solution,respectively.And we found that the driving voltage corresponding to maximum velocity of the droplets are 9.0 V,7.5 V,6.0 V,respectively.The uncovered principles of controlled movement of liquid metal droplets are expected to be used in controllable electric switches.Second,the transition of the interfacial tension driven by hydrogen chloride vapor was exploited to change the shape of liquid metal pattern,which overcame the challenge of liquid metal droplet movement in air.It was found that the time for contraction of liquid metal pattern is related to the concentration of HC l solution,the volume of container and the substrate material in contact with the liquid metal.As 38wt%HC l solution is employed,the contraction time of liquid metal pattern was reduced to 2 min.Similarly,by reducing the volume of container from 1900 cm³ to240 cm³,the contraction time was shortened from 105 s to 8.5 s.Both influences,the acid concentration and volume of the container,are related to the rapid saturation of hydrogen chloride vapor.Furthermore,the contraction time of liquid metal pattern on different substrates was investigated.It was found that the contraction time of the liquid metal pattern on the Si O₂ substrate was the shortest with around 60 s.Then the contact angle of the liquid metal droplet treated with hydrogen chloride vapor was measured.The contact angle was found to vary little within 30 min,indicating that the liquid metal droplet treated with hydrogen chloride vapor exhibits good stability.Based on this phenomenon,we have fabricated a liquid metal array with high resolution.And with the help of gravity,a controllable electronic switch was designed.Third,a non-viscous,non-corrosive,highly conductive and magnetic nickel-coated liquid metal(N i LM)droplet was obtained by rolling the liquid metal droplet in nickel particles.We found that the measured contact angles of N i LM droplets were more than 140°on Ag,Cu,Al substrates.And the roll angles of N i LM droplets on Ag,Cu,Al,N i and PTFE substrates ranged from 5.1°to 8.9°.It showed that N i LM droplets are non-viscous and mobile.In addition,N i LM droplets do not corrode the metal substrates because the nickel powder effectively impedes direct contact between N i LM droplets and metal substrates.In addition,N i LM droplets exhibit excellent electrical conductivity.With gradual increase of contact area from0.05 mm²to 2 mm²,the contact resistance was reduced from 12?to 1.8?.Based on excellent performance of N i LM droplet,they were employed as floating electrodes,soft contact points and magnetic controllable electronic switchs.Finally,N i LM droplets can be recycled,and the recovery rate of liquid metal can reach 90%.