Experimental Investigation On The Rotary Flow Shearing Fabrication And Manipulation Of Nonspherical Liquid Metal Microdroplets

Gallium-based liquid metals can flow naturally at room temperature,which exhibits low viscosity,high biocompatibility,high thermal and electrical conductivities.These emerging materials have great potential in the fields of biomedicine,flexible electronics,and robotics.It is particularly important to disperse liquid metals into micronano scale droplets,which can be used as core units to build engineering devices and advanced functional materials.Nonspherical liquid metal droplets can often achieve more functions in specific complex environments due to their advantages in anisotropic structure.In this thesis,rotary flow shearing(RFS),a simple and open microfluidic method was introduced for the one-step fabrication of liquid metal droplets.Based on the RFS method,an experimental study is performed for the droplets generation,including formation mechanism,morphology features,parameter influence,and preliminary manipulation.The main contents are briefly given as follows:1.Inspired by shearing-mixing and microfluidic methods,we firstly propose the RFS method.During the RFS process,a high-speed viscous shearing flow is provided by two counter-rotating rotors in the carrier fluid,forcing the dispersed phase to break up.A crucial rotary shearing module is well designed and assembled,which consists of a motor,a gear set,and rotors.On this basis,a complete experimental platform is constructed by an additional parameter control module and an image collection module.2.Nonspherical liquid metal microdroplets are fabricated in 500 cSt silicone oil by the RFS device.The effects of oxygen and viscosity synergy of silicone oil for the formation of nonspherical microdroplets are verified experimentally.According to the morphology of formed droplets,three different formation modes and corresponding parameter regions are identified.The morphology of liquid metal droplets in silicone oil and air were characterized by the optical camera and scanning electron microscope(SEM)respectively.In addition,the existence of oxide film on the droplet surface is demonstrated by the energy-dispersive X-ray energy spectrum(EDS).The non-spherical droplets transform into spherical droplets rapidly in contact with acid,proving the mechanical stability of the oxide film.The morphology and size of the liquid metal droplet can be well controlled by adjusting rotor rotational rate and liquid metal flow rate.3.As a preliminary demonstration for potential applications in novel micromotors and soft electronics,the manipulations of nonspherical microdroplets are performed,including translation,rotation,reciprocation,static and dynamic self-assembly.In this paper,the nonspherical liquid metal droplets were prepared by the RFS technique in one step,and the control of the droplets was also realized,providing a new direction for the application research of liquid metal.