Study On The Structure And Properties Of Spherical Micromotors

In 2016,the Nobel Prize in Chemistry was awarded to three scientists who studied the design and synthesis of molecular machines;In 2018.the Nobel Prize in Physics was awarded to the three inventors of the "Optical Tweezer".These two awards all work on micro machines or the control of microparticles,which demonstrates the great significant of using appropriate controls to manipulate micro machines.Nano/micromotors are of nano/micro scale and mainly achieve movement in a liquid environment by converting external energy into kinetic energy.Although research on micromotors has made great pro gress in material selection,fabrication methods,driving mechanisms and applications,the current research on micromotors mainly uses solid materials and few studies have used liquids to construct micromotors.Moreover,the fabrication process is complicated and usually requires expensive large equipment.For the motion mechanism,most of them study the motion behavior of a single micromotor,and there are few studies on the control of aggregation of micromotors.In terms of applications,the development of multifunctional micromotors remains a major challenge.In this paper,the main work includes the following three parts:1.Unlike previous micromotors based on solid materials,relied on the shear forces generated by high-speed stirring of the oil,we have fabricated a white light-driven liquid(water,serum,urine,etc.)micromotor that can move in oil solution.Interestingly,based on the photochromic and thermal effects of spiropyrans in oil solution,liquid micromotors are capable of exhibiting both positive and negative phototaxis.Furthermore,light shows great versatility in controlling the liquid micromotor so that it can move in a desired fashion.In addition,we have demonstrated that liquid micromotors offer significant advantages over solid micromotors.It not only enables fusion and reaction between different reactant-loaded liquid micromotors based on the combined positive and negative phototaxis,but also allows controlled cargo capture and transportation.2.Using polycaprolactone(PCL)and magnesium particles,a PCL/Mg Janus micromotor can be fabricated by an emulsion solvent evaporation technique.Due to the displacement reaction between Mg and noble metal ions,the PCL/Mg Janus micromotor can move in hydrogen peroxide solution containing noble metal ions.Since the speed of motion is highly dependent on the ion species and its concentrations,the PCL/Mg Janus micromotor may function as a motion-based metal ion sensor with good selectivity and sensitivity.In addition,since Mg alone is capable of propelling the whole structure in the presence of chloride ion(Cl-),the water-driven PCL/Mg micromotor exhibits higher efficiency when utilized in noble metal removal and recycling as compared to that of the stationary one.Thus,the PCL/Mg Janus micromotor is a multifunctional micromotor,which allows not only the precious metal ion sensing,but also removal and recycling.3.By coating a polystyrene microsphere with a layer of polydopamine(PDPM),a PDPM micromotor can be prepared.Under infrared light,the PDPM micromotors move toward the spot and aggregate here.The mechanism may due to that when the PDPM micromotors are irradiated with infrared light,the local thermal convection takes place caused by the local temperature rise,resulting from the photothermal effect of the PDPM.As a result,the moving liquid drives the micromotors deposited on the substrate move toward the spot.Under the action of convection and gravity,the micromotors aggregate at the spot.Interestingly,when the path of the spot is changed,the aggregate also moves with the spot.Based on this phenomenon,by changing the path of the spot,various patterns can be obtained,such as Chinese words,and even animal pictures.