Abstract
Self-propelled micro/nanomotors possess tremendous exciting promise in diverse fields. We describe an asymmetric, fuel-free and near-infrared light-powered torpedo micromotor, which is constructed by using a porous membrane-assisted layer-by-layer sol-gel method to form silica multilayer inside the pores, following by the deposition of gold nanoparticles on one end of the pores. In the absence of chemical fuels, the high propulsion of microtorpedoes under illumination of near-infrared light is owing to the photo-thermal effect of gold clusters, generating a thermal gradient inside the microtorpedoes. The speed of microtorpedoes is dependent on the laser powers and media. More interestingly, such fuel free-powered microtorpedoes could explode triggered by higher laser power at the predefined site and thus provide a new platform for future biomedical applications.
Highlights
The development of artificial micro/nanomotors launched a new horizon in the field of nanotechnology as their potential promises for environmental remediation, dynamic assembly of intelligent materials, precise disease treatment, and lab-on-chip devices[1,2,3,4,5,6,7,8,9,10,11,12,13,14]
We demonstrate the successful construction of gold-functionalized torpedo micromotors based on a porous membrane-assisted layer-by-layer sol-gel method, following the assembly of gold clusters in the big opening of the microtorpedoes
The computational simulation reveals that the near infra-red light (NIR) irradiation onto the torpedo rapidly increase the temperature, leading to intensive evaporation inside the torpedo micromotor and the following explosion of the torpedo
Summary
The time-lapse images in Fig. 3a captured from Supplementary Video 1, illustrate a nearly linear trajectory of the torpedoes under the NIR irradiation with a power of 5.5 J cm−2 as indicated by the red line. Upon the irradiation of NIR laser, the temperature of the AuNPs clusters rapidly arises owing to photo-thermal effect, while the temperature of the uncovered remains a relative low temperature In this case, a heated area expands its volume since the water brings the heat away through the convective flow (Fig. 6d, right scheme). The SEM image of the exploded torpedo fragments reveals the highly inhomogeneous distribution of AuNPs clusters on the inner wall of torpedo (Fig. 7b) It means that the explosive position of the torpedoes could be tuned by assembling AuNPs in a controlled manner. Such free-fuel torpedoes provide a path to develop a biocompatible synthetic motor for biomedical application
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