Actuation schemes

Several new surface micromachining processes utilize the thick-fihn polymer SU-8 for fabrication of channels, wells, and other passive microfluidics that are integrated with electronics or optical detection devices. The development of actuation schemes and interconnect technologies may make integrated polymer microfluidic systems more attractive, although more research is needed for these components as well as the integration of the polymers with other materials to realize truly integrated systems. 

Schmid P, et al. Diamond switch using new thermal actuation scheme. Diamond Relat Mater 2003. 

Mechanical pumping Micromechanical pumps are usually based on the movement of a membrane, which results in periodic delivery of a fluid. The actuation schemes utilized for moving the membrane of a pump include piezoelectric, electrostatic, thermopneumatic, pneumatic, and electromagnetic devices, and shape memory alloys and electro wetting. The resulting fluid motion is pulsed, not continuous. The rotary displacement micropump is an example of a mechanical pump not based on membrane movement. External syringe... 

Fig. 2.10. Actuation schemes for the reduction of beam-bending oscillations in consideration of aerodynamic forces in a rotating environment.

An outline of various actuation schemes has been given in Figure 2.10. On account of the efficiency with regard to the helicopter application, we will here focus the derivation of an analytic solution on the variants of twist actuation. This requires the coupled consideration of extension and torsion as well as warping and torsion of the beam. The prior is represented by the stiffness coefficient Pu in the constitutive relation and the latter by the equilibrium of Eq. (8.37a). To ease the solution, shear and bending of the beam will only be coupled with each other. This comprises the stiffness coefficients P25 and P36... 

Table 10.2. Actuation schemes with layup and polarization configuration for the...

With regard to the actuation capabilities, the solution to the beam torsion problem, as given by Eq. (9.4), contains two different parts indicated by the constants twist and gwarp- The prior is in charge of direct and extension-coupled twist, schemes / and II of Table 10.2, and the latter of warping-coupled twist, scheme III of Table 10.2. The influence of the overall beam geometry on the efficiency of the actuation schemes will be analyzed on this basis. 

Remark 10.9. Optimize the box-beam configuration with the objective of attaining maximum tip twist in consideration of the different actuation schemes while satisfying the stiffness and geometry constraints of Section 10.2.2. 

The basis of these examinations are the set-up of walls and the associated actuation schemes as described in Sections 10.1.2 and 10.1.1, respectively. The variables of the optimization problem at hand are the layer orientation angles ol and 02, the relative thickness h of the central, lengthwise oriented fiber layer, and the fiber volume fraction v. The effects of the relative sign of electric field strength and polarization, being allowed to change between layers as well as between sectors, are represented in a discrete manner by the actuation schemes of Table 10.2. 

The behavior represented by Eq. (10.27) is visualized for a fixed fiber volume fraction in Figure 10.7. It may be recognized that not all angular combinations are permissible, as the layer thickness ratio h must not become negative. Since no adaptive properties have been involved so far, these findings are valid for all actuation schemes. The use of Eq. (10.27) for substitution into... 

The objective function of this optimization problem is the evaluation of the twist solution, being given by Eq. (10.19) in conjunction with Eqs. (10.17) and (10.18), at the free end of the beam. For the constitutive coefficients appearing in the respective ratios, the relative layer thickness h of Eq. (10.27) is required besides the material properties and the particular actuation scheme configuration from Table 10.2. After introduction of the geometry constraints, specified in Eqs. (10.22) and (10.24), the tip twist may be found for any combination of the variables oi, 02, and u ... 

The behavior represented by Eq. (10.28) is exemplarily visualized for the cases of direct twist actuation (scheme / of Table 10.2) in Figure 10.8 and combined actuation of coupled extension and twist (scheme Ilh of Table 10.2) in Figure 10.9 for a fixed fiber volume fraction. 

Table 10.4. Maximum tip twist for the different actuation schemes and a fiber volume fraction v = 0.475.

By far the best result is achieved by the direct twist actuation (scheme I) without utilization of anisotropic couplings. Regarding those schemes using such couplings between torsion and extension, the one with the combined actu-... 

---