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Advanced functional materials: tadpole like microrotors with silver nanowires as tails

wallpapers Cruise 2020-10-02
Since the last century

has been a dream for scientists to let micro even nano sized robots freely walk through the human body deliver drugs treat diseases. In the 21st century with the rapid development of nanotechnology micro nano robots emerge as the times require. The characteristics of autonomous motion give the micro nano robot broad application prospects in drug transportation biological diagnosis other fields also cause great interest in the research of micro nano robot. As a kind of micro or nano drilling machine the stirrer can not only be used as the "ideal" model of micro nano fluid but also can be used as the "ideal" model of micro nano fluid. At present

are mainly driven by external field chemical drive. Compared with field driving chemical driven micro rotor can move independently without complex field equipment so it is more competitive in application. However the fabrication of chemically driven micro rotors is very limited most of them are focused on lithography physical vapor deposition electrochemical deposition. These processes are often complex expensive so they are not suitable for large-scale fabrication. Therefore it is of great significance to find a rapid efficient preparation method for the research of micro rotor. In this work Wang Wei's research group sputtered a layer of platinum (PT) on polystyrene (PS) microspheres to prepare PS Pt spheres. Then the PS Pt spheres were placed in the mixed solution of silver nitrate hydrogen peroxide (H2O2) with a certain concentration. After reaction at room temperature for about 10 min more than 30 μ m silver nanowire tails could be grown on the PT side (as shown in Fig. 1). The microsphere with a silver tail is similar to a tadpole so it is called tadpole like microtrochanter.

Fig. 1 Preparation of tadpole like PS Pt silver nanowire microrotor In view of this experimental phenomenon they proposed the electrochemical growth mechanism of silver nanowires: the Pt layer of physical sputtering is uneven in thickness so there is a difference in the catalytic rate of H2O2 resulting in an electron flow from the pole to the equator. The electrons obtained by Ag at the equator are reduced then grow into silver nanowires. This mechanism is also applicable to the photocatalytic system of titanium dioxide (TiO2). On this basis they realized the photo controlled growth of silver nanowires on TiO2 Pt spheres (Fig. 2).

Fig.2 growth mechanism of silver nanowires photo controlled growth of

The results show that the angular velocity of the silver tadpole increases with the increase of nanometric curvature then decreases with the increase of nanometric curvature.

Fig. 3 dynamic behavior of tadpole like microrotors with different lengths of silver nanowires

finally they pointed out that although this study has made substantial progress in the preparation of such tadpole like microrotors the shape controllability of silver nanowires the uniformity of tadpole like microrotors still need to be improved. At the same time the silver nanowires prepared by this method also have great potential in the fields of sensors flexible electronics because they have no surfactant residues.

are published in advanced functional materials( DOI:10.1002/adfm.202004858 )The first author of this article is LV Xianglong a master's degree student in the school of materials of Harbin Institute of Technology (Shenzhen) the co corresponding authors are Professor Wang Wei Professor Ma Xing from the flexible electronics center of Harbin Institute of Technology (Shenzhen).


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