Radio-frequency actuated polymer-based phononic meta-materials for control of ultrasonic waves

Abstract

Radio-frequency (RF) control of an ultrasonic phononic crystal was achieved by encapsulating it in a composite of high k-10% KF-doped BaTiO 3 dielectric nanoparticles with poly(N-isopropylacrylamide) (PNIPAm)-based hydrogel. The combination of the nanoparticles and hydrogel produced a composite with elastic properties susceptible to RF actuation. The novel acoustic meta-material enables the regulation of sound waves by electromagnetic waves, which is not possible in a conventional medium as elasto-mechanical waves, and electromagnetic waves do not directly couple. Compared with light waves, radio waves can penetrate deeper into bulk structures and enable the control of propagation of ultrasonic waves through a macroscale phononic crystal. An RF antenna emitting at 318.6 and 422.5 kHz was used to modulate the device in water and ambient air, respectively. An increased transparency of the ultrasonic wave in the material was observed due to an increase in the bandwidth of the modulated device exceeding 8 kHz with a 30-fold increase in the signal modulation at select frequencies. The radio waves induced changes in the transmission and demonstrated the control of ultrasound with applied RF. The synthetic acoustic properties in the resultant meta-material device were actively manipulated through the interaction of electromagnetic waves with the material.

Synergistic Enhancement of Thermal Conductivity and Dielectric Properties in Al2O3/BaTiO3/PP Composites

“…The experimental results could enhance the high temperature tolerance of PP dielectric materials in energy storage and in a supercapacitor, and revealed a novel approach for the preparation of organic/inorganic polymer composites with multi-function or -phase, which is crucial for the design of modern function composites, integrated electronic systems, and metamaterials [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. The corresponding structure design and device will be further discussed and prepared in future.…”

“…In addition, BaTiO 3 and Al 2 O 3 composites and devices have recently been reported as novel metamaterials [ 34 , 35 , 36 , 37 , 38 ], which can be applied in optical cloaking [ 39 ] and biochemical sensing [ 36 , 40 , 41 , 42 , 43 , 44 ] and detection [ 41 , 42 ], protein analysis [ 45 ], food quality analysis, and telecommunication [ 46 ], etc. They can also be used in tumor treatment, and radar cross-section reduction [ 46 , 47 ] as a therapeutic tool or a polarization conversion device due to their unique dielectric and electromagnetic properties [ 48 ]. This paper is focused on the enhancement of both the thermal conductivity and dielectric properties in series of alumina/barium titanate/polypropylene (Al 2 O 3 /BT/PP) composites with various volume ratios of Al 2 O 3 and BT.…”

Tunable photo-responsive elastic metamaterials

“…In comparison to other tuning approaches recently reported (e.g., 50 min in ref. 34 ) the time delay for the BG variation appears minimal (an~30 fold reduction for a full cycle).…”

“…For example, in ref. 34 , the authors show the reversible opening of a transparency window obtained after RF irradiation lasting several tens of minutes. The use of electromagnetic (EM) radiation is very attractive as it can be provided in a contactless fashion, with arbitrary intensity, frequency and polarization state patterns.…”

Modeling Bloch Waves in Prestressed Phononic Crystal Plates

“…To achieve this goal, several approaches have been proposed and explored so far. They include active systems, such as piezoelectric materials (Casadei et al, 2010;Bergamini et al, 2014;Kherraz et al, 2016), temperature (Jim et al, 2009;Airoldi et al, 2011;Cheng et al, 2011;Wu et al, 2018) and magneto-based techniques (Robillard et al, 2009;Matar et al, 2012;Guo and Wei, 2016;, actuated polymers via electromagnetic waves (Walker et al, 2014(Walker et al, , 2017 as well as the application of an external mechanical load. Among them, the latter has shown to be particularly promising to achieve tunable dispersive properties.…”