Actuation shear mode

FIGURE 4.1.21 3D positioning multilayer actuator. Notice that the x- andy-stacks are using shear mode with the spontaneous polarization perpendicular to the applied electric field direction. 

Retroactive Effects on the Power Electronics. The operating modes of electrorheological actuators are classified into three types flow mode (or valve mode), shear mode and squeeze mode. The former two modes do not exhibit any retroactive effects, whereas the squeeze mode can generate high voltages when the distance between the capacitor plates are altered quickly. When an actuator is operated in squeeze mode, extra precautions must be taken to protect the amplifier from damage. 

Martin SJ, Frye GC, Wessendorf KO (1994) Scaising liquid properties with thickness-shear mode resonators. Sens Actuat A Phys 44 3) 209-218... 

Weber J, Albers WM, Tuppurainen J, Link M, Gabl R, Wersing W, Schreiter M (2006) Shear mode FBARs as highly sensitive liquid biosensors. Sens Actuators A 128 84-88 Wohltjen H (1984) Chemical microsensors and microinstrumentation. Anal Chem 56 87A-103A... 

Electrostatic field components transverse to the direction of polarization induce shear mode actuation, see Eq. (4.20). The particular shear strains or... 

In Section 2.5.1, the various beam actuation concepts are presented using the classification illustrated in Figure 2.10. Analogously applying to sensing, we distinguish between normal (lengthwise) and shear mode actuation in the plane of the wall as well as between its consistent and sectorial application across the plane of the cross-section. 

Finally, the QCM can not only be used in a sensory mode but also as an actuator. It has been recently shown by Dultsev and coworkers [57] that virus particles deposited on the resonator surface may be displaced by increasing the shear amplitude of the resonator. Thus, it seems plausible that the resistance of cell-substrate interactions to lateral shear forces may be inferred from QCM measurements when the shear amplitude is increased to invasive magnitudes. The ease of the measurement, which can be automated and multiplexed, the rather simple experimental design, as well as the unique experimental access to the interface between living cells and technical substrates is very likely to create growing interest within the cell culture community for these new experimental options. 

To facilitate this simple design procedure, and for other reasons, the shear stress and shear rate in a valve should generally be quoted in flow-mode-derived characteristics. Again, the pump actuator and load characteristics and the elasticity of the fluid may have a significant effect on the time response of the system to a change of input voltage signal [105], especially under extreme conditions of operation. 

Figure 13.14 Stress normalized to the shear modulus as a function of the extension for a dielectric elastomer. E = 0 indicates the rubber elasticity theoiy when no external electric field is applied. EMI, EB and indicate, respectively, the pull-in, the electric breakdown and the overstretching failure modes that can occur in a dielectric elastomer actuator. The dashed lines represent the maximum isotonic (constant stress) aetu-ation strokes at three different starting prestrains longer lines indicate higher strokes.

When shear appears in the planes with corresponding piezoelectric coupling, as shown in Figure 4.6, in addition to the intended normal mode actuation or sensing, then it needs to be examined with regard to the electric boundary conditions. At first, the complications induced by electrodes on surfaces other than those associated with the individual shear case will be ignored. Therefore, the theoretically possible electric boundary conditions have the following implications, which correlate with the above assumptions ... 

An alternative to the thiekness-mode and stack actuators has recently been demonstrated (Fig. 7). An array of pivoting pins provides electrical isolation between the skin and a matrix of polymer aetuators (Fig. 7, black traces at bottom). The actuators don t lower the pins, but instead, shift the bases of the pins laterally. The transmission ratio can be adjusted to match skin stiffness by varying the pin lengths above and below the gimbal. Although the skin is stiffer in shear than indentation, smaller displacements suffice to create the same sensation level (Knoop and Rossiter 2014). 

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