Amazing stuff! The first article below seems to be short summary of recent developments.
"For the first time, researchers have created micromotors that can move through the air in a controlled way powered only by light.
The findings pave the way for new microscale technologies that transport nanoparticles through the air for applications in catalysis and the environment.
The spiky, pollen-like zinc oxide microparticles are coated with gold nanoparticles which heat up when exposed to near-infrared light.
Researchers can control the temperature gradient in the micromotor by changing the direction of the incoming light. This creates gentle convection currents that lift and push the micromotor into the air in a steerable way.
Micromotors are materials inspired by nature that move in controlled ways in response to chemical reactions or other external stimuli.
These tiny moving motors work well in liquid environments where fluid supports the particles while facilitating heat dissipation and convective motion. But flying micromotors through the air, where the force of gravity works against them, has remained a major challenge. ..."
"... researchers has developed the first micromotors capable of moving through the air using only light as their power source. These tiny, pollen-shaped particles measure about 12 microns wide — roughly one-tenth the thickness of a human hair. Made of zinc oxide and coated with gold, they use heat from near-infrared light to lift and propel themselves without any fuel or batteries.
When a beam of light strikes the micromotors, the gold absorbs energy and heats the surrounding air. This heat creates gentle convection currents — like rising warm air — that push the particles upward and allow them to move in controlled directions. By adjusting the position of the light, the researchers can steer their motion. ..."
From the abstract:
"Micromotors are an attractive cutting-edge technology that exhibit controllable motion in response to chemical reactions or external stimuli.
These nature-inspired materials are widely explored for use in environmental remediation, and drug delivery, other emerging applications.
Until now, the micromotors field is restricted to applications in aqueous environments, as achieving controllable motion in air while overcoming gravity remains a significant challenge.
Herein, for the first time, to our knowledge, we introduce a system capable of overcoming gravity to achieve light-induced thermal convective motion in air, driven by near-infrared light excitation.
The micromotors are composed of spiky, pollen-like ZnO microparticles coated with gold nanoparticles, which interact photothermally with the NIR light, generating a thermal gradient that induces propulsion of the micromotor system. Lanthanide-doped upconverting nanoparticles are deposited onto the micromotor surface to enable nanothermometric monitoring of surface temperature, providing critical information needed to describe the system's thermal behavior in air. This micromotor platform provides a versatile approach to overcome gravity and induce a controllable movement in a gaseous matrix, opening new opportunities to develop proof-of-concepts and applications using this aerodynamic micromotor approach."
Concordia researchers develop light-powered micromotors that move through air (original news release) "Tiny, gold-coated particles can lift and steer themselves using heat from near-infrared light"
Fig. 1 A) Scheme illustrating i) micromotor assembly, and ii) NIR-light driven motion of micromotors in air by induced photophoresis.
B) SEM micrographs of ZnO─Au─UCNPs micromotors with their corresponding EDS elemental mapping images for Zn, O, Au, and Gd. Scale bar is 10 µm. Schematic was created using BioRender.
Fig. 3 Motion mechanism determination of the micromotors in air under 808 nm excitation.
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