Bimorph actuators

Lu, L., et al., Highly stable air working bimorph actuator based on a graphene nanosheet/carbon nanotube hybrid electrode. Advanced Materials, 2012. 24(31) p. 4317-4321. 

Various types of the so-called magnetostrictive inchworm type of motor have been proposed and built. A two-leg travelling machine using a magnetostrictive bimorph actuator with 7.5 /zm-thick polyimtde is shown in fig. 86b (Honda et al. 1994 Arai and Honda 1996). In an alternating magnetic field, it can travel in one direction. The maximum speed of approximately 5 mm/s was obtained around the mechanical resonant frequency... 

Piezoelectric Actuation in Multiphase Microfluidics, Fig. 1 (a) Schematics of a microfluidic chip for drop-on-demand dispensing. The bottom chamber is filled with an aqueous reagent A piezoelectric bimorph actuator glued to the chamber allows the release of an aqueous drop on demand in the horizontal channel filled with an immiscible fiuid. (b) Description of the experimental setup. The... 

Thermomechanical Valves, Fig. 7 Schematic of a nonnally closed thennal bimorph-actuated valve... 

Thermomechanical Valves, Fig. 10 A Si — Ni bimorph-actuated microvalve with thermal isolation comb regions, (a) Thermal isolation comb regions (b) photograph of the microvalve... 

Apart from polyaniline, other condncting polymers that are being studied for electrolytic expansion include polypyrrole [11, 15-17], poly(alkylthiophene) [26] and carbon nanotubes [5]. For example, electrochemically prepared polypyrrole films were used to study the qualitative movement of electrolytic expansion by fabricating a bimorph actuator. The movement of bending and stretching of the actuator was demonstrated in electrolyte solution [15]. Actuators fabricated by electrodeposition on gold-coated polyethylene films were studied [11] for the evaluation of expansion ratio and response time. Also, a microactuator of several tens of microns made from two layers of gold and... 

FIGURE 8.81 Schematic representation of three states during the electromechanical cycle of a rocking-chair-type, bimorph actuator. Both electrodes have the same concentration of dopant (K ) when the cantilever is undistorted, and electrochemical transfer of dopant between electrodes causes bending either to the right or to the left. (From Baughman, R.H., Synth. Met, 78, 339, 1996. With permission.)... 

Ataka, M., A. Omodaka, N. Takeshima, and H. Fujita. 1993. Fabrication and operation of poly-imide bimorph actuators for a ciliary motion system. / Microelectromech Syst 2 146. 

Comparison of response surface and kriging models for multidisciplinary design optimization Design of a PZT bimorph actuator using a metamodel-based approach... 

FIGURE 4.1.29 Camera shutter mechanism using a piezoelectric bimorph actuator. 

Thermal bimorph actuators consist of deformable microstructures that curl into and out of the substrate plane. 

Fig. 27 Schematic representation of the bhnorph piezoelectric actuator where PEDOT/PSS (DMSO) electrodes are used to activate the bimorph actuator (Lee et al. 2005)...

To measure electrodeformation there is a technique that builds a bimorph actuator and calculates the deformation ratio Ifom the curvature [101]. As this method exaggerates even a 1% strain, it is effective for qualitative... 

Thermal actuation makes use of the thermal expansion of solids as they are heated, or the differences in the rates of thermal expansion between different materials as in a bimorph actuator. Relative to electrostatic... 

A thermal bimorph actuator is comprised of two materials with different coefficients of thermal expansion that are bonded together, as shown in Figure 5.12. As the materials heat up they expand at different rates, causing the actuator to deflect toward the side that expands the least. 

We can use this temperature distribution to find the deflection of a bimorph actuator. In one dimension the change in length of a cantilever beam would be... 

For a bimorph actuator comprised of two layers with different coefficients of thermal expansion, y and yj, the temperature change causes a strain mismatch between the layers, leading to curvature of the bimorph ... 

For a bimorph made out of films with different thicknesses and Young s moduli, we can estimate the bending of the bimorph actuator using Stoney s formula modified for a bimorph ... 

When silicon is in contact with a metal, a low-temperature liquid eutectic can be formed, far below the melting temperature of either silicon or the metal. For example, the eutectic temperature for silicon and gold occurs around 370°C for 30% silicon. In contrast, the melting point for pure gold is 1064°C, and the melting point for pure silicon is 1410°C [5]. Aluminum and silicon can form a eutectic around 577°C at around 12% silicon. In designing thermal actuators, such as gold/silicon thermal bimorph actuators or suspended heaters with metal wires and contacts, the metal should not be used in the proximity of any silicon that is heated unless the temperature is kept below the eutectic point. 

Fig. 21-2 Proposed use of paired bimorph actuators as microelectrochemical tweezers. (P), represents any CP, e.g. P(Py). Electrochemical transfer of dopant from the outer layer to the inner layer of each bimorph causes the opening of the tweezers. After Reference [726], reproduced with permission.

The polymer PVDF is to be used in a beam-type bimorph actuator as shown in Figure 16.10. The bottom layer is a permalloy, a nonpiezoelectric soft magnetic material (Ni8oFe2o). The metal alloy adds some stiffness to the bimorph, and being a magnetic material it can be used to add additional force to the actuator if needed. (The electrode layers are a... 

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