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Self-propelled swimmers using ultrasonic transducers have been proposed and studied. The screw and bionic propulsion systems have dominated underwater robots. However, the complex structures make miniaturization difficult. The swimmers with ultrasonic transducers have no moving parts such as fins or propellers and can be driven by the nanomechanical-vibration in the surface of the transducer. Simple structure and high driving frequency make it easy to miniaturize. A 36° Y-cut lithium niobate (LN) thickness-vibration-mode transducer is used to investigate an underwater acoustic propulsion system. LN transducers are manufactured to 10 × 10 mm, 7 × 7 mm, and 4 × 4 mm square plates. The zero-speed propulsion and no-load speed are investigated to evaluate the swimmer performance. A mm-order swimmer is studied with a 4 × 4 mm LN transducer. At last, the multi-degrees-of-freedom swimmer driven by three 7 × 7 mm LN transducers is demonstrated with the advance and sway locomotion. In the future, a small-scale and agile self-propelled swimmer with an acoustic propulsion system can be expected for narrow and complex environment tasks, such as seagrass-prone areas and narrow pipelines. [Display omitted] • At 10 W, the zero-speed propulsions of LN and PZT transducer are 7.8 mN and 4.9 mN. The zero-speed propulsion of LN transducer is 1.6 times greater. • A mm-order miniaturized swimmer with 4 × 4 × 0.35 mm LN transducer is realized. • A triangle multi-degree-of-freedom swimmer with three 7 × 7 mm LN transducers is designed and fabricated. [ABSTRACT FROM AUTHOR]

As the rapid development of the Internet of Things (IoT), the demand for the self-powered sensors and devices has become urgent. In this work, we present a self-powered magnetic field sensor based on a biomimetic dragonfly-wings like magnetoelectric (DWL-ME) laminated cantilever. The two pairs of wings in DWL-ME cantilever operating in anti-phase vibration modal has shown a strong magnetoelectric coupling for converting magnetic field energy into electric energy with an energy harvesting density of as high as 100 µWOe−2cm−3. It also shows a linear response to an alternating magnetic field (H AC) with a high detectability of 2.7 nT at 60 Hz. Compared to traditional cantilever beam ME sensors, its vibration noise is also effectively decreased by more than 30 dB due to the anti-phase vibration modal of two pairs of wings. The proposed biomimetic design strategy has inspirational significance for future sustainable, self-powered intelligent sensor networks. [Display omitted] • A self-powered biomimetic dragonfly-wings like magnetic field sensor has been developed. • The vibration noise was decreased by 30 dB compared to traditional cantilever beam ME sensors. • The energy harvesting density of 100 µW Oe-2 cm-3 and a detectability of 2.7 nT for AC magnetic field was obtained. [ABSTRACT FROM AUTHOR]

The development of piezoelectric ceramics with large piezoelectric coefficient (d 33), high Curie temperature (T c) and high mechanical quality factor (Q m) is still a key challenge for practical application for high-power device. Herein, a series of Sm3+ and Mn2+ ions co-doped 0.15Pb(Mg1/3Nb2/3)O 3 -(0.85-x)PbZrO 3 -xPbTiO 3 ceramics were prepared by the solid-state sintering method. The optimum piezoelectric properties were achieved at x = 0.435 mol% with a large d 33 ∼ 450 pC/N and a high Q m ∼ 1968 near the morphotropic phase boundary (MPB), and with high T c ∼ 296 °C. The origin of this excellent piezoelectric properties was explained by the phase structure, piezoelectric and dielectric analysis. The composition near MPB region and the appearance of defect dipoles leaded to final excellent piezoelectric properties, and made a harmonization between d 33 , T c and Q m. This work demonstrated a rational strategy to obtain large d 33 , high T c and high Q m for high-power piezoceramics. [Display omitted] [ABSTRACT FROM AUTHOR]

Electromechanical coupling coefficient (k t) of piezoelectric composite is the core indicator for medical ultrasonic, nondestructive testing and underwater acoustic transducers applications. Generally, the k t of piezoelectric composite is susceptible to be interfered by its structure parameter and spurious modes. In this work, we figured out the effect of the polymer on the vibration mode by fixing the size of the piezoelectric rod and changing the content of different softness polymer. The spurious modes were related with resonant standing wave caused by classical Bragg scattering in periodic structures. The propagation of spurious mode vibration can be cut off by soft polymer. The maximum k t of 69% was obtained at a Pb(Zr,Ti)O 3 (PZT4) ceramic volume fraction of 24.5%. The k t was 5% ∼ 10% higher than that of other reported PZT4 ceramic composites and comparable to PZT5 ceramic composites. This work presented a paradigm for vibration modes modulation by changing the polymers ratio, which providing ideas for excellent performance acoustic transducer designing. [Display omitted] • By fixing the volume fraction and thickness of the piezoelectric phase, the thickness vibration resonance peak was basically unchanged. Along with increase of soft polymer, the frequency of the lateral vibration shifted and was close to the thickness vibration. And with the further increase of soft polymer, the propagate of transverse vibration could be cut off. • A high k t of 69% was achieved at a low ceramic volume fraction of 24.5%, which was 5 ∼ 10% higher than other reported PZT4 composites and comparable to other reported PZT5 composites, even larger PZT5 volume fraction composites. [ABSTRACT FROM AUTHOR]

• The circumferential modes excited acoustically in a cylindrical-shell system are used effectively for liquid sensing. • The operating conditions of the cylindrical-shell sensor are optimized analytically for better sensitivity. • The cylindrical-shell sensor is theoretically and experimentally evaluated using different concentrations of sodium iodide (NaI) and water mixtures. • The proposed cylindrical-shell sensor is easily integrated with lab-on-a-chip devices for various microfluidic sensing applications. Liquid sensing is achieved by using a resonant cylindrical shell. The sensing mechanism is based on the fact that the localized circumferential waves confined around the cylindrical shell interact intensively with the liquid sample inside the shell, with the resonant transmission of the cylindrical shell being strongly dependent on the acoustic properties of the liquid in the shell, especially the density of the liquid. Numerical simulations and experimental measurements show that the transmission dip varies with the concentration of a sodium iodide (NaI) and water mixture in the shell. The advantages of a liquid sensor based on the circumferential modes of a cylindrical shell are numerous. For example, a minimal liquid sample is required, the cylindrical shell is disposable, and the sensor is compatible with other microfluidic components, thereby allowing the liquid sensor to be integrated with lab-on-a-chip devices for various microfluidic sensing applications. [ABSTRACT FROM AUTHOR]

An autonomous swimmer with the acoustic propulsion system is proposed and evaluated in novel area of acoustofluidic actuation. The ultrasonic transducer has the same or higher propulsion power with the nanometer/micrometer vibration amplitude and the MHz/kHz frequency, compared with the locomotion of jellyfish body. The sound pressure and flow velocity measurements demonstrate the higher-pressure gradient and fluid downstream to investigate the acoustic propulsion force generated by pushing the surrounding water rearward. The performance of acoustic propulsion system is thus evaluated based on the sound pressure and flow velocity measurements equivalently. The vibration distributions in the transducer surface exhibit a ripple effect and gradually decayed from the center to the edge. The radial distributions of the sound pressure and flow velocity in water match the surface vibration amplitudes for thickness-vibration-mode. Based on the investigation of two thickness-vibration-mode PZT disc transducers, the longitudinal sound pressure and flow velocity in the normal direction result in ZSP force. The power radiated by the longitudinal vibration on the surface of the transducer is shown to be the main cause of the propulsion power. The propulsion calculation with vibration velocity is studied to evaluate the propulsion force. For an input power, the acoustic propulsion system with a higher Q-factor transducer has better performance. Autonomous underwater acoustic propulsion systems have a small size, high power density, and a simple structure, making them suitable for pipeline robots, endovascular microrobots, and underwater drones. [Display omitted] • Mechanism of underwater acoustic propulsion system is illustrated in terms of the bio-inspired and biomimetic engineering. • The sound pressure and flow velocity measurements demonstrate the higher-pressure gradient and fluid downstream to investigate the acoustic propulsion force. • The power radiated by the longitudinal vibration on the surface of the transducer is shown to be the main cause of the propulsion power. [ABSTRACT FROM AUTHOR]

• Bending-bending mode piezoelectric actuator with crystal stacks are proposed and evaluated. • Ultrahigh piezoelectric coefficient d 33 of ~10,800 pC/N are achieved in actuation crystal stacks. • Due to high piezoelectricity and bending mode, max velocity is 3.28 mm/s under 130 V pp. • Minimum step resolution of 0.35 µm is demonstrated under 25 V pp driving voltage. [Display omitted] Piezoelectric actuators are important elements for compact actuations with high precision; however, driving voltage reduction is demanding for integration and minimization of precision actuations. In this work, we proposed a bending-bending mode piezoelectric actuator based on multilayered Pb(In 1/2 Nb 1/2)O 3 -Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PIN-PMN-PT) single crystals. Ultrahigh apparent piezoelectric coefficient d 33 of ~10,800 pC/N is achieved in four crystal stacks. The crystal stacks are used to fabricate bending-bending mode piezoelectric actuators to reduce driving voltage. Experimental results show that it can produce a maximum traveling velocity of 3.28 mm/s under the driving voltage of 130 V pp at 1000 Hz and minimum step resolution of 0.35 µm with 25 V pp driving voltage. Conventional piezoelectric actuators require driving voltage of ~300 V pp for similar motion velocity. This work demonstrates advantages of crystal stacks in piezoelectric actuators and potential applications in low-voltage precise actuations. [ABSTRACT FROM AUTHOR]