The dynamics of the piezo inkjet printhead operation

Internal strain amplification can be utilized in piezoelectric ceramics to obtain relatively large displacements. The monomorph described in the present work is a bending bar made from a single piece of material into which a smooth gradient of piezoelectric activity is introduced. The application of a voltage then causes the bar to bend due to the differential stresses that are induced. These are relatively uniformly distributed and do not peak in the center as in a conventional bimorph. Significantly increased life and reliability can then be achieved.

Piezoelectric Ceramics with Functional Gradients: A New Application in Material Design

Materials issues in design and performance of piezoelectric actuators: an overview

Analysis of out-of-plane displacement and stress field in a piezocomposite plate with functionally graded microstructure

Piezoelectric actuators with functionally graded microstructure (FGM) are designed with the aim of reducing the stress concentration at the middle interface that exists in the standard bimorph actuators while maintaining high bending displacement. A FGM piezoelectric laminate consists of a number laminae, which are composite materials with electroelastic properties varied through the laminate thickness. The electroelastic behavior of piezo-actuators with laminated composite is studied by two-stage hierarchical model, the first based on the Eshelby’s model for predictions of the electroelastic properties of each lamina, the second based on classical lamination theory (CLT). The in-plane stresses and out-of-plane displacements are obtained by the CLT for both standard and FGM piezoelectric bimorph actuators under the assumption of cylindrical bending. The microstructure of the FGM biomorph actuator is optimized by using CLT model to achieve the best performance of the FGM piezoelectric actuator, i.e. large bending displacement while minimizing the induced stress field. Based on the optimized microstructure of the FGM bimorph actuators by the CLT model, we processed the FGM bimorph actuator that is composed of six laminae, and also the standard bimorph actuator. The bending displacements of these actuators are then measured by a laser displacement measurement apparatus as a function of applied voltage. The measured data of the bending displacements versus applied voltage are compared with the predictions by the CLT, resulting in a good agreement. © 2003 Published by Elsevier B.V.

Design of bimorph piezo-composite actuators with functionally graded microstructure

A new type of bending actuator, "monomorph", is proposed by using a single plate of semiconductive piezoelectric ceramics. The principle of bending originates from the nonuniform distribution of the electric field in a single plate caused by the semiconductor–metal electrode contact. Monomorph characteristics are exemplified in lead zirconate based and barium titanate ceramics. A bend curvature comparable to that of conventional piezoelectric "bimorphs" can be obtained.

Monomorph actuators using semiconductive ferroelectrics

A New actuator device is proposed using semiconductive ferroelectric ceramics. This device is a single-plate actuator capable of bending equivalently to a bimorph. A significant difference is simple structure named as a “monomorph” as compared with a multi-stacked type in the bimorph. The bend in the monomorph device is realized by non-uniform electric field distribution in the piezoelectric ceramics, through the semiconductor-metal contact effect (Schottky barrier). The monomorph has been demonstrated in the solid solutions PbZrO3-(K1/2Bi1/2)ZrO3 and BaTiO3-Dy2O3. Both systems reveal the tip deflectionof several hundred micrometers in a 0.5mm thick plate.

https://www.jstage.jst.go.jp/article/jcersj1950/95/1103/95_1103_722/_pdf

New monolithic actuators, 'monomorphs', using semiconductive ferroelectrics.

A “Monomorph” is a new type of actuator, composed of a single ceramic plate which is driven in a bending mode similar to the “Bimorph.” It has been observed that humidity influences the bending displacement, electric resistance and electrostatic capacitance of a porous Nb-doped PZT “Monomorph.” A proton conductivity model is proposed to describe the humidity sensitive characteristics of this material. The model assumes a double layer capacitance is formed at the electrode-bulk interface under an applied electric field which plays an important role in the nonuniform distribution of the electric field. This “active layer” on and inside the surface brings about the bending displacement. This “Monomorph” has potential as a new piezoelectric humidity sensor.

Hiroshi Asakura

Papers

Monomorph actuators using semiconductive ferroelectrics

New monolithic actuators, 'monomorphs', using semiconductive ferroelectrics.

Humidity sensitive actuator