Discussion of Antiplane Singularities of Piezoelectric–Dielectric and Piezoelectric–Conductor Wedges

This technical note deals with two special topics from our previous paper (Chue and Chen in Arch Appl Mech 72 673–685, 2003) in Archive of Applied Mechanics: the effects of electrical conditions imposed on the edges and bonded interfaces of piezoelectric–dielectric and piezoelectric–conductor wedges on antiplane problems. After employing relatively realistic electrical conditions, we found that stress and electric displacement singularities are altered when boundary conditions and/or continuity conditions are changed, and we compared the results with those of previous studies.     

Griffith crack moving in a piezoelectric strip

Summary  The dynamic problem of an impermeable crack of constant length 2a propagating along a piezoelectric ceramic strip is considered under the action of uniform anti-plane shear stress and uniform electric field. The integral transform technique is employed to reduce the mixed-boundary-value problem to a singular integral equation. For the case of a crack moving in the mid-plane, explicit analytic expressions for the electroelastic field and the field intensity factors are obtained, while for an eccentric crack moving along a piezoelectric strip, numerical results are determined via the Lobatto–Chebyshev collocation method for solving a resulting singular integral equation. The results reveal that the electric-displacement intensity factor is independent of the crack velocity, while other field intensity factors depend on the crack velocity when referred to the moving coordinate system. If the crack velocity vanishes, the present results reduce to those for a stationary crack in a piezoelectric strip. In contrast to the results for a stationary crack, applied stress gives rise to a singular electric field and applied electric field results in a singular stress for a moving crack in a piezoelectric strip. Received 14 August 2001; accepted for publication 24 September 2002 The author is indebted to the AAM Reviewers for their helpful suggestions for improving this paper. The work was supported by the National Natural Science Foundation of China under Grant 70272043.     

Design of a Beam with Controllable Force Elements

A method for solving the problem of design of an intellectual structure formulated for the pair optimal position of actuators, optimal control of actuators is developed. In the method proposed, physical and logical objects are treated as equivalent.     

Modeling and control of a piezoelectric microactuator with proprioceptive sensing capabilities

In this paper, modeling and control strategies for a new observability-optimized piezoelectric microactuator are presented. The targeted applications mainly concern the design of microgripper for micromanipulation tasks. The device has been designed using a topological optimization method, which takes into account the optimal full integration of piezoelectric actuating and sensing elements within the device. It is achieved in link with modal controllability and observability considerations. The vibrational modes that govern the tip deflection of the monolithic compliant structure are proved to be fully observable by the integrated sensing area of the device. The proposed control strategy permits to simply reconstruct the deflection using electric charges measurement and modal state observer. Finally, the vibrations that are naturally induced by the flexible structure are successfully damped using robust and low order controller.     

Piezoelectric linear motor using resonant-type clamping based on harmonic vibration synthesis

A piezoelectric linear motor (PLM), which has a mechanism based on synchronized switching control, is composed mainly of a driving unit and a clamping unit. A resonant-type clamping (RTC) unit is developed to increase the working frequency of the motor. The developed RTC unit is a three-layer tuning fork structure with ten pieces of single-layer piezoelectric sheets as driving elements. The RTC unit was designed to have a resonant frequency ratio of 1:3:5 by deliberate design of the lengths and widths of each layer. A resonant-type quasi-square-shaped mechanical wave was obtained combined with the three vibration modes of those layers. A PLM prototype that utilized the developed RTC unit was fabricated and tested. The moving speed of the slider can reach up to 78.3 mm/s at a driving voltage of 240 V_p–p.     

Optical and electrochemical DNA nanobiosensors

In the past two decades, nanoscale advanced materials have been explored for biosensing molecules, so new horizons have opened up for identifying and quantifying biomolecules, and possible early diagnosis of diseases.DNA nanobiosensors show promise. This article provides an overview on their optical and electrochemical aspects. We discuss recent progress in this field, describing basic concepts of molecular beacons and quantum dots as optical nano-imaging systems. Also, carbon nanotubes provide a platform for development and advancement of electrochemical DNA nanobiosensors, which are increasingly being implemented as robust tools for detection in biomedical sciences.     

A novel piezoelectric immunosensor for the detection of malarial Plasmodium falciparum histidine rich protein-2 antigen

A novel piezoelectric (PZ) immunosensor for the direct detection of malarial Plasmodium falciparum histidine rich protein-2 (PfHRP-2) antigen was developed. The mixed self-assembled monolayers (SAMs) of thioctic acid and 1-dodecanethiol were formed on gold surface of quartz crystal. Cyclic voltammetry, electrochemical impedance spectroscopy and surface Raman spectroscopy techniques were used to characterize the mixed SAMs. The rabbit anti-PfHRP-2 antibodies were coupled on mixed SAM modified gold surface of quartz crystal via NHS/EDC activation method. The PZ immunosensor was applied to detect PfHRP-2 in the linear range of 15-60 ng/ml with a detection limit of 12 ng/ml. It was also found that even after 14 days of storage, 50% of the activity still remained. Clinical human serum samples were tested with this method, and the results were in agreement with those obtained from commercially available ICT kit (NOW^® Malaria).     

Effects of electric and mechanical loads on the morphological evolution of a void in piezoelectric films

This paper reports the result of an investigation into the effect of electric and mechanical loads on the morphological evolution of a void in piezoelectric materials based on a model for the morphological evolution of a void, the thermodynamics potential and energy principle. Thus, the path and the bifurcation condition of the morphological evolution of the void in piezoelectric materials are described, which gives some insight into the reliability of piezoelectric films under electric and mechanical loads.     

Characteristics of wave propagation in piezoelectric bent rods with arbitrary curvature

The wave propagation in the piezoelectric bend rods with arbitrary curvature is studied in this paper. Basic three-dimensional equations in an orthogonal curvilinear coordinate system (r, θ, s) are established. The Bessel functions in radial co-ordinate and triangle series in the angular co-ordinate are used to describe the displacements and electrical potential. Characteristics of dispersion, distributions of displacements and electrical potential over the cross section are calculated, respectively. In the numerical examples, the effects of the ratio of the two ellipse axes on the dispersion relations of the first three modes are observed. The characteristics of the distribution of displacements and electric potential in the cross section, along the radial and s direction are investigated.     

Artificial Cilia: Generation of Magnetic Actuators in Microfluidic Systems

Magnetic artificial cilia are fabricated from photoreactive copolymer precursors filled with magnetic nanoparticles by a new photolithographic process. Two different crosslinkers and UV‐radiation of two different wavelengths are used to generate arrays of planar magnetically actuatable rubber flaps. The cilia are integrated into a microfluidic channel and operated in water using a rotating permanent magnet.