A novel type of transverse surface wave propagating in a layered structure consisting of a piezoelectric layer attached to an elastic half-space

The existence and propagation of transverse surface waves in piezoelectric coupled solids is investigated, in which perfect bonding between a metal/dielectric substrate and a piezoelectric layer of finite-thickness is assumed. Dis- persion equations relating phase velocity to material con- stants for the existence of various modes are obtained in a simple mathematical form for a piezoelectric material of class 6mm. It is discovered and proved by numerical examples in this paper that a novel Bleustein-Gulyaev （B-G） type of transverse surface wave can exist in such piezoelectric cou- pled solid media when the bulk-shear-wave velocity in the substrate is less than that in the piezoelectric layer but greater than the corresponding B-G wave velocity in the same pie- zoelectric material with an electroded surface. Such a wave does not exist in such layered structures in the absence of pie- zoelectricity. The mode shapes for displacement and electric potential in the piezoelectric layer are obtained and discussed theoretically. The study extends the regime of transverse sur- face waves and may lead to potential applications to surface acoustic wave devices.

Design and identification of a double-acting piezoelectric-hydraulic hybrid actuator

Traditional single-acting piezoelectric-hydraulic hybrid actuators usually have the problem of inertial force caused by flow pulsation of the liquid,which degrades their output performance.To suppress or solve the associated inertial force and enhance its output capabilities,this paper proposes a new type of double-acting piezoelectric-hydraulic hybrid actuator with four check valves acting as mechanical diodes.The new hybrid actuator was fabricated and its output performance was tested.When the voltage is 700 Vp-pand the bias pressure is 2 MPa,the pulsation ratesδof the new actuator at 400 Hz,500 Hz and 600 Hz are 2.29,2.08 and 1.78,respectively,whileδof the single-acting hybrid actuator under the same conditions are 10.98,11.05 and 17.12.Therefore,the liquid pulsation rate of the new hybrid actuator is significantly reduced,which is beneficial for improving the flow uniformity and weakening the influence of inertial force on the hybrid actuator.This strategy ultimately leads to a maximum no-load velocity of 168.1 mm/s at 600 Hz and a maximum blocking force of 141 N at 450 Hz for the new hybrid actuator.In addition,this strategy has the potential to be used in other electrohydrostatic actuators to improve their performance.

Piezoelectric fbers for fexible and wearable electronics

Flexible and wearable electronics represent paramount technologies ofering revolutionized solutions for medical diagnosis and therapy,nerve and organ interfaces,fabric computation,robot-in-medicine and metaverse.Being ubiquitous in everyday life,piezoelectric materials and devices play a vital role in fexible and wearable electronics with their intriguing functionalities,including energy harvesting,sensing and actuation,personal health care and communications.As a new emerging fexible and wearable technology,fber-shaped piezoelectric devices ofer unique advantages over conventional thin-flm counterparts.In this review,we survey the recent scientifc and technological breakthroughs in thermally drawn piezoelectric fbers and fber-enabled intelligent fabrics.We highlight the fber materials,fber architecture,fabrication,device integration as well as functions that deliver higher forms of unique applications across smart sensing,health care,space security,actuation and energy domains.We conclude with a critical analysis of existing challenges and opportunities that will be important for the continued progress of this feld.

Monolithic piezoceramic actuators with a twist

Designing artificial structures with heterogeneous elements and manipulating their interface coupling ways usually bring in synthetic neo-nature to functional devices.For piezoceramic devices,the deformation response refers to a variety of extensional,contractional,or shear modes of crystals,and also relies on boundary conditions from morphology design.However,to pursue fundamental torsion actuation in an integrated piezoceramic component is still a long-term tough task due to nil twist mode limited by microscopic crystal mirror symmetry.Herein,we demonstrate a design of cofired monolithic actuators to originally overcome this obstacle.The prototype device is composed of two sets of stacked actuation subunits that work on artificially reverse face shear modes,and their chiral stiffness couplings will synergistically contribute to synthetic twist outputs at a broad bandwidth.Finite element simulation reveals twist displacements are highly tunable by manipulating the geometrical dimensions.Transverse deflection measurements manifest the stable and sizeable linear actuation response to applied electric fields(around 3.7μm under 40 V at 1 Hz).Importantly,the design actually introduces a more general route to enable arbitrary modes and actuation states in integrated piezoceramic components.

Piezoelectric pump with flexible venous valves for active cell transmission

The development of organ-on-a-chip systems demands high requirements for adequate micro-pump performance,which needs excellent performance and effective transport of active cells.In this study,we designed a piezoelectric pump with a flexible venous valve inspired by that of humans.Performance test of the proposed pump with deionized water as the transmission medium shows a maximum output flow rate of 14.95 mL/min when the input voltage is 100 V,and the pump can transfer aqueous solutions of glycerol with a viscosity of 10.8 mPa·s.Cell survival rate can reach 97.22%with a yeast cell culture solution as the transmission medium.A computational model of the electric-solid-liquid multi-physical field coupling of the piezoelectric pump with a flexible venous valve is established,and simulation results are consistent with experimental results.The proposed pump can help to construct the circulating organ-on-a-chip system,and the simple structure and portable application can enrich the design of microfluidic systems.In addition,the multi-physical field coupling computational model established for the proposed piezoelectric pump can provide an in-depth study of the characteristics of the flow field,facilitating the optimal design of the micro-pump and providing a reference for the further study of active cell transport in organ-on-a-chip systems.

Piezoelectric-Based Smart Bone Plate for Fracture Healing Progress Monitoring

Fracture healing progress monitoring techniques attract global research attention due to the importance of selecting the timing of removing the fixation device.To this end,in this research,we present a piezoelectric-based smart internal fixation device,in which a piezoelectric sandwich structure is laminated to the surface of a bone plate.In the content,we explain the reasons for utilizing piezoelectric films,elaborate the mechanism of fracture monitoring,and introduce the mechanical parameters of the sensor.The simulation and experimental results show that the electrical output of the device is associated with the elastic modulus of the filler between the tested broken bones when the working load is maintained,indicating that the bone recovery progress could be successfully detected by the developed technique.

Unconventional piezoelectric coefficients in perovskite piezoelectric ceramics

Piezoelectric ceramics exhibit three conventional piezoelectric coefficients,i.e.,d33,d31,d15,due to their∞mm crystal symmetry.Unconventional piezoelectric coefficients,such as d11,d12,d13,d14,d16,etc.,can only be extracted from piezoelectric single crystals of special symmetry with specific cut direction.Here we demonstrate a rotated poling method to realize unconventional piezoelectric coefficients in perovskite piezoelectric ceramics.This method is elaborated in theory and experimentally proven to be effective.Full nonzero piezoelectric coefficients in the 36 piezoelectric coefficients matrix can be obtained by combining these“quasi(effective)piezoelectric coefficients”with the conventional piezoelectric coefficients,which would expand applications in a wide variety of piezoelectric devices.