Piezocomposite ultrasonic transducers (PUTs) are extensively used in diverse technological fields, however, PUTs based on conventional 1-3 piezocomposite containing only one type of piezo pillars have met a bottleneck in further performance enhancement. Herein, based on the [011]-oriented relaxor ferroelectric Pb(In1/3Nb2/3)O-3-Pb(Mg1/3Nb2/3)O-3-PbTiO3 (PIN-PMN-PT) crystal, a novel (1(A),1(B))-3 piezocomposite structure containing two types of single-crystal pillars- high d(33), k(t) pillars with square cross-section (termed as 1(A)) and high dhgh pillars with rectangular cross-section (termed as 1(B)), alternately arranging in epoxy resin and forming a 5 x 9 array are reported. The combination effect and synergistic action of two different piezo-pillars in the piezocomposite notably broaden the working bandwidth, improve the sound sensitivity, and also produce a suppression effect to undesirable transverse vibration modes. Experimental results validate the performance enhancements of (1(A),1(B))-3 composite-based PUT: the increases in -3 dB transmitting, receiving bandwidth, and receiving sensitivity are 71.4%, 28.6%, and 26.6%, respectively, in comparison to conventional 13 single-crystal composite-based PUT. Moreover, its hydrostatic figure of merit (HFOM) dhgh (=4084.9 x 10(-15) m(2) N-1) is 177.3% higher than that of commercial single crystal 13 piezocomposites. The proposed design strategy represents a promising development direction of next-generation bandwidth and high-sensitivity ultrasonic transducers.

Piezoelectric poly(vinylidene fluoride) (PVDF) polymer exhibits the flexible characteristic, however, a piezo-generator based on the PVDF polymer normally shows low power density because of its low piezoelectric coefficient. Here, we report a fundamental synergistic strategy to prepare PVDF polymer nanocomposite for enhancing electromechanical coupling performance and improving its energy density, including (i) the mechanically directional stress field (MDSF) fabrication of PVDF nanocomposite doped with polar Pb(Zr,Ti)O3 (PZT) ceramic nanoparticles via high-energy ball milling, (ii) introduction of micro-cavities holding polar nanoparticles, and (iii) floating electrode (Ag) films spaced uniformly inside the polymer nanocomposite. The investigations reveal that the MDSF fabrication can induce ordered, chain-shape nanocrystalline fibers with a high β-crystal phase, which makes 42% contribution to the piezoelectricity; while the micro-cavities and floating electrode films after poling exhibit a strong electret effect, which further make 18% and 27% contributions, respectively, to the piezoelectricity. This multiple-mechanism synergistic effect results in a much higher piezoelectric coefficient d33 increased from 4 pC N-1 for a pure PVDF (without bearing a uniaxial stretching) to 33 pC N-1 for the nanocomposite. It further dramatically increases to 228 pC N-1, a giant apparent piezoelectric charge coefficient d33*, for a 3D-printed 7-layer nanocomposite with 360 μm in thickness. An energy harvester (EH) based on the PVDF nanocomposite generates a record high peak power density of 13.2mWcm-2 and the load power density of 5.46mWcm-2 under a dynamic pressure of 255 kPa at the frequency of 5Hz, which is near two orders of magnitude higher than that of a conventional PVDF polymer EHs. The fabricated flexible EH can even directly light up 46 LEDs in real-time or power a blind-man reading system when touching it. This work is of great significance in enlightening future flexible piezoelectronic designs.

Powerful tactile perception is keystone for robots to achieve human-like dexterous manipulation. However, endowing robots with tactile perception capabilities that approach or even surpass those of humans is a challenge. Organisms can perceive complex environments rapidly, and almost all perception is related to the directional transport of ions. Inspired by this mechanism, we design a flexible dual-responsive skin (FDRS) based on ions migration for proximity and tactile somatosensation, which is consisting of single-electrode triboelectric nanogenerator and iontronic sensor, achieving surpassing-skin capabilities. The single-electrode triboelectric nanogenerator can encode the proximity information of approaching targets into a series of voltage pulses with fast response time (100 mu s). The iontronic tactile unit based on the hierarchical micro-hemispherical gel layer achieves high linearity (R-2 = 0.998) over a broad range of 0-700 kPa. We demonstrate the applications of FDRS for three-dimensional object recognition and robotic control. These capabilities of the multilayer integrated FDRS provide new perspectives for the future development of human-like dexterous robotic manipulation.

We present a T-shaped MME-EH that enables collaborative twisting or bending operation modes for tridimensional responses. The device produces a peak–peak output power of 98.5 mW at 60 Hz, which is 262% higher than the state-of-the-art results.

Conventionally, to produce a linear motion, one motor’s stator is employed to drive one runner moving forward or backward. So far, there is almost no report of one electromechanical motor or piezoelectric ultrasonic motor that can directly generate two symmetrical linear motions, while this function is desired for precise scissoring and grasping in the minimally invasive surgery field. Herein, we report a brand-new symmetric-actuating linear piezoceramic ultrasonic motor capable of generating symmetrical linear motions of two outputs directly without additional mechanical transmission mechanisms. The key component of the motor is an (2 × 3) arrayed piezoceramic bar stator operating in the coupled resonant mode of the first longitudinal (L1) and third bending (B3) modes, leading to symmetric elliptical vibration trajectories at its two ends. A pair of microsurgical scissors is used as the end-effector, demonstrating a very promising future for high-precision microsurgical operations. The sliders of the prototype show the following features: (a) symmetrical, fast relative moving velocity (~1 m/s) outward or inward simultaneously; (b) high step resolution (40 nm); and (c) high power density (405.4 mW/cm3) and high efficiency (22.1%) that are double those of typical piezoceramic ultrasonic motors, indicating the full capacity of symmetric-actuating linear piezoceramic ultrasonic motor working in symmetric operation principle. This work also has enlightening significance for future symmetric-actuating device designs.

The flexible electronics is a fast-moving, emerging interdisciplinary research that involves the use of organic/inorganic functional materials, electronic component designs, and their integration fabrication. Here, we review recent advancements in flexible piezoelectronics and 3D printing preparation, including (i) flexible piezoelectric materials suitable for 3D printing, their piezoelectric properties, and a comparison among them, (ii) 3D-printed flexible piezoelectronics with increasing capabilities in sensing, energy harvesting, and electronic display, and (iii) 3D printing technology and preparation methods, such as inkjet printing, thermal or laser-assisted direct writing printing (DIW), and fused deposition molding (FDM), which enable rapid design and manufacture of new flexible electronic devices. We also summarize the design methods of flexible piezoelectric devices based on 3D printing technology, and discuss their extensive applications in smart wearable electronics, flexible circuits, the Internet of Things, and software robots. Flexible piezoelectronics is a rapidly advancing field that is poised to have a significant impact on the modern industrial structure and human life. Finally, we prospect for the future development of 3D printing flexible piezoelectronics and the challenges that researchers may encounter.

In this work, we report a cofired-12-layer ceramic based standing-wave linear piezoelectric ultrasonic micromotor (SW-LPUM) with a high-load-density using LiCO3 doped 0.05Pb(Mn1/3Sb2/3)O3-0.47PbZrO3-0.48PbTiO3 (PMnS-PZT) material. The proposed SW-LPUM features a miniaturized structure (12.45 × 5.3 × 3.5 mm3) and excellent comprehensive actuation performances, such as fast response time (0.05 ms), high resolution (50 nm), and broad adjustable velocity range (from 0.01 to 123.7 mm s−1). Specifically, its high load density (11.0 mN mm−3) under a single-phase voltage drive is higher than that of most reported LPUMs. The elaborate multilayer structure based on hard-type PMnS-PZT ceramic enables the micromotor to continuously operate without obvious temperature rise, showing its practical value for high-precision positioning.

It is desired to obtain a piezoceramic with a high piezoelectric coefficient and low dielectric loss simultaneously for energy harvester application. Herein, it is reported that the 0.025Pb(Mn 1/3 Nb 2/3 )O 3 ‐0.525Pb(Ni 1/3 Nb 2/3 )O 3 ‐0.135PbZrO 3 ‐0.315PbTiO 3 (PMNN‐PZT) ceramic exhibits superior piezoelectric charge parameter e 33 of 37.74 pC m −2 and low dielectric loss tanδ of 0.45%. Furthermore, a PMNN‐PZT ceramic‐based magneto‐mechano‐electric coupled energy harvester (MMEC‐EH) with a varying‐stiffness cantilever is designed and fabricated, which shows the strong self‐resonance effect in response to a random, transient impulse vibration or magnetic field stimulus. The investigations show that under a 0.6 s pulse vibration stimulus, the MMEC‐EH can tune itself into self‐resonance damping oscillation lasting for six seconds at its resonance frequency of 16 Hz, and the produced maximum power is 1.96 mW RMS . Under both weak magnetic field and force‐field dual‐stimulus ( H ac = 0.5 Oe and a = 0.05 g), the generated power density is about 60 mW RMS Oe −2 g −2 cm −3 , which is one to two orders of magnitude higher than those previously reported MMEC‐EHs. Finally, the MMEC‐EH is successfully demonstrated to power temperature/humidity sensors, indicating its potential for harvesting both weak vibration and magnetic field energy from environments for self‐powered sensor application.

It is well known that Poly(vinylidene fluoride) (PVDF) polymer and its composites exhibit limited piezoelectricity only after strong electric field poling (SEFP) to align randomly oriented molecular dipoles inside. Here, we report that a (Pb, Zr)TiO3 (PZT) particles doped PVDF-polymer nanocomposite shows a large poling-free piezoelectric (PFP) coefficient and strong electromechanical coupling after experiencing mechanically directional stress field (MDSF). Analyses based on WAXD, FTIR, and HRTEM reveal that the MDSF actives and then induces a crystal phase transformation (CPT) from disordered star-shape nanocrystals to ordered, self-poled chain-shape high-beta nanocrystalline fibers. PFM scanning images further show the existence of well-defined polarization. Furthermore, a 7-layer series-connected, self-powered circular pressure sensor was fabricated using multi-material 3D printing technology, which exhibits a high sensitivity of 235 mV/kPa and a high-power density of 0.9 mW/cm(2) under a dynamic pressure of 255 kPa, and it is near 8 times higher than that of a conventional, poled single-layer PVDF sensor. Finally, a (3 x 3) real-time lighting tactile sensor array is 3D printed, confirming its feasibility for practical application. The MDSF-induced CPT and large PFP effect are significant because it may open a way to fabricate piezopolymer integrated devices without SEFP.

It is well known that Poly(vinylidene fluoride) (PVDF) polymer and its composites exhibit limited piezoelectricity only after strong electric field poling (SEFP) to align randomly oriented molecular dipoles inside. Here, we report that a (Pb, Zr)TiO 3 (PZT) particles doped PVDF-polymer nanocomposite shows a large poling-free piezoelectric (PFP) coefficient and strong electromechanical coupling after experiencing mechanically directional stress field (MDSF). Analyses based on WAXD, FTIR, and HRTEM reveal that the MDSF actives and then induces a crystal phase transformation (CPT) from disordered star-shape nanocrystals to ordered, self-poled chain-shape high-β nanocrystalline fibers. PFM scanning images further show the existence of well-defined polarization. Furthermore, a 7-layer series-connected, self-powered circular pressure sensor was fabricated using multi-material 3D-printing technology, which exhibits a high sensitivity of 235 mV/kPa and a high-power density of 0.9 mW/cm 2 under a dynamic pressure of 255 kPa, and it is near 8 times higher than that of a conventional, poled single-layer PVDF sensor. Finally, a (3 × 3) real-time lighting tactile sensor array is 3D printed, confirming its feasibility for practical application. The MDSF induced CPT and large PFP effect is significant because it may open a way to fabricate piezopolymer integrated devices without SEFP.

Ferroelectric memories show great potential in applications of portable electronics due to low power con-sumption, high reliability and fast response speed. Therefore, non-destructive readout of ferroelectric memories using the ferroelectric photovoltaic effect attracted tremendous research attention. In this investigation, flexoelectric-enhanced photovoltaic effect (FPV effect) were systematically investigated in curved 3D-printed BaTiO3/PVDF composite films. In the bending process, a strain gradient field was formed between the BaTiO3 (BTO) particles, which led to a relatively large flexoelectric effect. Compared with that of pristine PVDF, the flexoelectric coefficient of BTO/PVDF-15 (15% BTO) was increased 3.7-fold to 2.65 x 10-9 C/m. Furthermore, we found that the photovoltaic current Ipv of the BTO/PVDF-15 (15% BTO) composite film increased by 3.4 times compared with the pristine PVDF film at the same curvature. This is mainly attributed to the FPV effect. In addition, "polarization channels" were found for the first time inside nanocomposite materials using the flex-oelectricity effect through 2D phase-field simulations, and the channels can be artificially controlled by simply bending the film. Most importantly, the BTO/PVDF-based composite film was designed as flexible ferroelectric memories. We demonstrated for the first time that the intensity difference of the signal for 0 and 1 of the BTO/ PVDF-based memories were more than 10 times, which can be read directly using a laser. This investigation shows great promise that flexoelectricity in piezoelectric polymer nanocomposite can greatly benefit the nondestructive readout of ferroelectric memory devices.

In this work, we report an enhanced magneto-mechano-electric (MME) coupling in Ni/Pb(Zr,Ti)O3 (PZT) ceramic composited ladder-type cantilever attached with a tip mass of NdFeB magnet, which simultaneously exhibits the magnetic flux concentration effect and the stress concentration effect, and therefore, it shows an enhanced extremely weak-field (EWF) coupling ability. Investigations show that the proposed MME energy harvester (EH) can generate an output power density of 7.16 μW Hz−1 Oe−2 cm−3, which is the highest value compared to the state of the art MME energy harvesters. Under an EWF of even as low as Hac = 0.1 Oe (about half level of the geomagnetic field), the proposed MME-EH can still produce a peak–peak output power of 23.5 μW, which is enough power to light up 4 LEDs in real time. Furthermore, it can drive a wireless sensor communication system in real time under a weak Hac = 0.75 Oe excitation, demonstrating it has potential to serve as a micro-energy source of wireless sensor networks in EWF circumstance. This work is not only beneficial but has also inspired future multi-function-integrated material and smart electronic device designs in Internet of Things in EWF circumstance.

This work reports a 3D-printed PVDF-TrFE piezoelectric film (PF) coated with one pair of dislocated interdigital electrode (ID) to produce multiple, alternatively tilt-polarized regions in the cross-sectional area, which exhibits quite high sensitivity to an external stress stimulation. The theoretical analysis further reveals that the enhanced piezoelectric effect of the film can be attributed to the larger electric dipole moment due to tilt dipole orientation in PVDF-TrFE polymer. The experimental measurements show that the ID tilt-polarized PVDF-TrFE film (IDTPPF) can produce a stable peak voltage of 73.5 V under dynamic compression stress of 50 kPa at 1 Hz, corresponding to a pressure sensitivity of 1.47 V/kPa, which are 14.7 times and 3.6 times those of a PVDF-TrFE film with conventional thickness-polarization and in-plane polarization, respectively. Correspondingly, the peak power density of ID-TPPF is as high as 478 mu W/cm2, while at a load of 3 MO, the load power is still 207 mu W/cm2, which even instantly lights up eight LEDs connected in series without using any charging capacitor. This work confirms that the 3D-printed ID-TPPF shows great potential in self-powered tactile sensors and artificial skin applications in the future.

Piezo-polymer is widely used for pressure sensors or electromechanical transducers; and normally, it is simply designed and prepared into thin film as a force-sensing element integrated in smart structures or robots. In this paper, we report a flexible, three-dimensional multilayer composite grid complex structure containing inside electrode layers prepared totally based on direct-writing 3D printing method. The composite material is composed of a polydimethylsiloxane (PDMS) elastomer matrix and 0.55Pb (Ni1/3Nb2/3) O-3-0.135PbZrO(3)-0.315PbTiO(3) (PNN-PZT) piezoelectric ceramic particles coated with Ag and multi-walled carbon nanotubes (1 wt% of the Ag@PNN-PZT ceramic powders). The 3D-printed composite grid exhibits both large piezoelectric effect (with an effect piezoelectric coefficient (d(33)) of 21 pC/N) and qualified mechanical performances, such as a large failure tensile strain of 150% and tensile stress of 2.2 MPa. Under a dynamic compression stress of 0.125 MPa at 3.5 Hz, a 3D-printed 7-layer composite grid (550 mu m in thickness) with internal electrode layers inside could produce output voltage peak of 3 V accompanying with a peak current of 0.7 mu A. In comparison with a single layer composite grid, its peak output current shows a 7-time increase, although its peak output voltage keeps unchanged under the same compression stress. This work shows that the 3D-printed multilayer composite grid exhibits the integrated structural-self-sensing function, which will bring great benefits to future artificial muscle in robots and other flexible intelligent structures. (C) 2021 Elsevier B.V. All rights reserved.

Additive manufacturing technology has promoted the development of piezoelectric devices, from the one-step moulding of micro-miniature devices to large-scale devices.

Piezoelectric actuators are unique driving force-generation devices, which can transfer input electric energy into force, displacement, or movement outputs efficiently and precisely via piezoelectric effect-based electromechanical coupling instead of electromagnetic induction. In comparison with traditional electromagnetic actuators, the most important features of the piezoelectric actuators are their compact size, flexible design, and ability to provide nanometer or sub-micrometer positioning. Here, recent progress in nonresonance piezoelectric actuators including multilayer ceramic actuators, step motors, inertial motors, and resonance ultrasonic motors, such as linear motors, rotary motors, multidegree of freedom motors, and microelectromechanical system actuators, is comprehensively presented. The working principles and properties of these actuators are explained, and the piezoelectric materials and configurations, fabrication, and applications are provided. Furthermore, from the aspects of materials, designs and applications, challenges and outlooks for future developments of piezoelectric actuators and motors are also discussed.

In this work, we report a magneto-mechano-electric (MME) energy harvester with a rectangular cymbal structure consisting of a piezoelectric ceramic plate and magnetostrictive alloy (Metglass) foils. The magnetic field induced voltage was then predicted by using finite element analysis. Experimental results show that under a magnetic field excitation of 8 Oe at 180 Hz (resonance frequency), the MME energy harvester can generate a peak-peak output power of 5.7 mW and peak-peak current of 2.3 mA, respectively, for a load resistance of 5.6 k Omega, which allow to drive 10 LEDs lighting directly and stably. Correspondingly, its power density is 5.1 mW cm(-3) at H-ac=7 Oe, which is comparable with previous reports about traditional cantilever structure MME energy harvester using a piezoelectric single crystal. This work confirms that the MME energy harvester is a promising candidate for powering wireless sensors and other microenergy smart electronics using the stray magnetic field, or even mechanical vibration energy in environment. (C) 2020 Elsevier B.V. All rights reserved.

Piezoelectric ceramic materials such as Pb(Zr,Ti)O-3 (PZT) based ceramics have excellent electromechanical energy conversion ability, however, their rigid and undeformed characters are not suitable for flexible electronics application. Here, we report the design of flexible (0-3) connection ceramic-polymer composite made of poly-dimethylsiloxane (PDMS) elastomeric matrix doped with Ag-coated PNN-PZT (0.55Pb(Ni1/3Nb2/3)O-3-0.135PbZrO(3)-0.315PbTiO(3)) ceramic heterojunction particles, and the 3D printing method for fabricating complex three-dimensional grid architectures. It was found that the 3D-printing, non-stereolithographic grid-composite exhibits a greater flexible character after doping ceramic particles and also excellent electromechanical coupling with a piezoelectric voltage coefficient g(33) as high as 400 x 10(-3) m V N-1, which is one order of magnitude higher than that of PZT based ceramics. Under drop hammer (similar to 20 N) impact, it can instantly drive over 20 commercial red-LEDs lighting directly without using a charge storage capacitor. This work shows that 3D-printed flexible ceramic-polymer composite has potential to replace brittle piezoceramics for electromechanical energy conversion and touching force sensor applications, such as soft robotics, artificial muscles and biology signal identification.

A 3D-printed multilayer copolymer rugby ball-structured energy harvester is prepared, and a high peak output power of 16.4 mW cm−2 is obtained.