Bioinspired Metaskin Patterning
In article number 2203109, Long Meng, Hairong Zheng, Xue‐Feng Zhu, and co‐workers report a reconfigurable acoustic meta‐skin with selective superhydrophobic decoration on a metal surface, which can be utilized for generating different structured ultrasounds and have potential applications in biological low‐intensity ultrasound stimulation of living organisms for the study of behavioral response and contactless control.
Well‐defined azide polymers are successfully synthesized by visible‐light‐induced metal‐free electron transfer–atom transfer radical polymerization (PET‐ATRP) at room temperature. This technique uses Eosin Y/Et3N as the reductive quenching photocatalyst system, which can effectively prevent the destruction of the azide group in polymerization. Four kinds of azide‐derived monomers participate well in this reaction and obtain satisfactory results. The kinetic behavior, “ON/OFF” experiment, and chain‐extension experiment confirm the living feature of this visible light controlled polymerization. Moreover, random copolymers obtained by this protocol can be used as surface modifier which further demonstrates the utility and reliability of this method.
Metasurfaces of the subwavelength thicknesses provide a distinctive route for acoustic wave manipulation. Based on the advanced 3D printing, those judiciously designed 2D metamaterials enable intriguing effects such as abnormal reflection, transmission, and absorption. However, acoustic metasurfaces, with strong wave–structure interactions in subwavelength scales, have encountered a big challenge of being acoustically transparent due to the insufficient impedance mismatch underwater. Here, reconfigurable bioinspired metaskin patterning for generating multistructured waterborne ultrasound is proposed. The nanostructured metaskin exhibits the “lotus effect,” with the thickness of only 70 μm (≈1/20 wavelength at 1 MHz) and a tremendous impedance mismatch (≈0.0001 transmission) for ultrasound. By depositing the strippable metaskins via self‐assembly into different patterns, the focusing, the vortex, and the Talbot structured ultrasound beams are implemented, respectively. The multistructured ultrasound has the patterned intensity fields of energy redistribution, where even weak field enhancement at low frequencies can activate the living organisms directly without using microbubbles, which enables low‐threshold and contactless behavior control via the mechanical stimulus.
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